Use ifunc to resolve context switching mode on amd64.

[FreeBSD/FreeBSD.git] / sys / amd64 / amd64 / pmap.c

/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 1991 Regents of the University of California.
 * All rights reserved.
 * Copyright (c) 1994 John S. Dyson
 * All rights reserved.
 * Copyright (c) 1994 David Greenman
 * All rights reserved.
 * Copyright (c) 2003 Peter Wemm
 * All rights reserved.
 * Copyright (c) 2005-2010 Alan L. Cox <alc@cs.rice.edu>
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department and William Jolitz of UUNET Technologies Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from:   @(#)pmap.c      7.7 (Berkeley)  5/12/91
 */
/*-
 * Copyright (c) 2003 Networks Associates Technology, Inc.
 * Copyright (c) 2014-2018 The FreeBSD Foundation
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by Jake Burkholder,
 * Safeport Network Services, and Network Associates Laboratories, the
 * Security Research Division of Network Associates, Inc. under
 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA
 * CHATS research program.
 *
 * Portions of this software were developed by
 * Konstantin Belousov <kib@FreeBSD.org> under sponsorship from
 * the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#define AMD64_NPT_AWARE

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 *      Manages physical address maps.
 *
 *      Since the information managed by this module is
 *      also stored by the logical address mapping module,
 *      this module may throw away valid virtual-to-physical
 *      mappings at almost any time.  However, invalidations
 *      of virtual-to-physical mappings must be done as
 *      requested.
 *
 *      In order to cope with hardware architectures which
 *      make virtual-to-physical map invalidates expensive,
 *      this module may delay invalidate or reduced protection
 *      operations until such time as they are actually
 *      necessary.  This module is given full information as
 *      to which processors are currently using which maps,
 *      and to when physical maps must be made correct.
 */

#include "opt_pmap.h"
#include "opt_vm.h"

#include <sys/param.h>
#include <sys/bitstring.h>
#include <sys/bus.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/sx.h>
#include <sys/turnstile.h>
#include <sys/vmem.h>
#include <sys/vmmeter.h>
#include <sys/sched.h>
#include <sys/sysctl.h>
#include <sys/smp.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/vm_phys.h>
#include <vm/vm_radix.h>
#include <vm/vm_reserv.h>
#include <vm/uma.h>

#include <machine/intr_machdep.h>
#include <x86/apicvar.h>
#include <x86/ifunc.h>
#include <machine/cpu.h>
#include <machine/cputypes.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/specialreg.h>
#ifdef SMP
#include <machine/smp.h>
#endif
#include <machine/tss.h>

static __inline boolean_t
pmap_type_guest(pmap_t pmap)
{

        return ((pmap->pm_type == PT_EPT) || (pmap->pm_type == PT_RVI));
}

static __inline boolean_t
pmap_emulate_ad_bits(pmap_t pmap)
{

        return ((pmap->pm_flags & PMAP_EMULATE_AD_BITS) != 0);
}

static __inline pt_entry_t
pmap_valid_bit(pmap_t pmap)
{
        pt_entry_t mask;

        switch (pmap->pm_type) {
        case PT_X86:
        case PT_RVI:
                mask = X86_PG_V;
                break;
        case PT_EPT:
                if (pmap_emulate_ad_bits(pmap))
                        mask = EPT_PG_EMUL_V;
                else
                        mask = EPT_PG_READ;
                break;
        default:
                panic("pmap_valid_bit: invalid pm_type %d", pmap->pm_type);
        }

        return (mask);
}

static __inline pt_entry_t
pmap_rw_bit(pmap_t pmap)
{
        pt_entry_t mask;

        switch (pmap->pm_type) {
        case PT_X86:
        case PT_RVI:
                mask = X86_PG_RW;
                break;
        case PT_EPT:
                if (pmap_emulate_ad_bits(pmap))
                        mask = EPT_PG_EMUL_RW;
                else
                        mask = EPT_PG_WRITE;
                break;
        default:
                panic("pmap_rw_bit: invalid pm_type %d", pmap->pm_type);
        }

        return (mask);
}

static pt_entry_t pg_g;

static __inline pt_entry_t
pmap_global_bit(pmap_t pmap)
{
        pt_entry_t mask;

        switch (pmap->pm_type) {
        case PT_X86:
                mask = pg_g;
                break;
        case PT_RVI:
        case PT_EPT:
                mask = 0;
                break;
        default:
                panic("pmap_global_bit: invalid pm_type %d", pmap->pm_type);
        }

        return (mask);
}

static __inline pt_entry_t
pmap_accessed_bit(pmap_t pmap)
{
        pt_entry_t mask;

        switch (pmap->pm_type) {
        case PT_X86:
        case PT_RVI:
                mask = X86_PG_A;
                break;
        case PT_EPT:
                if (pmap_emulate_ad_bits(pmap))
                        mask = EPT_PG_READ;
                else
                        mask = EPT_PG_A;
                break;
        default:
                panic("pmap_accessed_bit: invalid pm_type %d", pmap->pm_type);
        }

        return (mask);
}

static __inline pt_entry_t
pmap_modified_bit(pmap_t pmap)
{
        pt_entry_t mask;

        switch (pmap->pm_type) {
        case PT_X86:
        case PT_RVI:
                mask = X86_PG_M;
                break;
        case PT_EPT:
                if (pmap_emulate_ad_bits(pmap))
                        mask = EPT_PG_WRITE;
                else
                        mask = EPT_PG_M;
                break;
        default:
                panic("pmap_modified_bit: invalid pm_type %d", pmap->pm_type);
        }

        return (mask);
}

#if !defined(DIAGNOSTIC)
#ifdef __GNUC_GNU_INLINE__
#define PMAP_INLINE     __attribute__((__gnu_inline__)) inline
#else
#define PMAP_INLINE     extern inline
#endif
#else
#define PMAP_INLINE
#endif

#ifdef PV_STATS
#define PV_STAT(x)      do { x ; } while (0)
#else
#define PV_STAT(x)      do { } while (0)
#endif

#define pa_index(pa)    ((pa) >> PDRSHIFT)
#define pa_to_pvh(pa)   (&pv_table[pa_index(pa)])

#define NPV_LIST_LOCKS  MAXCPU

#define PHYS_TO_PV_LIST_LOCK(pa)        \
                        (&pv_list_locks[pa_index(pa) % NPV_LIST_LOCKS])

#define CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa)  do {    \
        struct rwlock **_lockp = (lockp);               \
        struct rwlock *_new_lock;                       \
                                                        \
        _new_lock = PHYS_TO_PV_LIST_LOCK(pa);           \
        if (_new_lock != *_lockp) {                     \
                if (*_lockp != NULL)                    \
                        rw_wunlock(*_lockp);            \
                *_lockp = _new_lock;                    \
                rw_wlock(*_lockp);                      \
        }                                               \
} while (0)

#define CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m)        \
                        CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, VM_PAGE_TO_PHYS(m))

#define RELEASE_PV_LIST_LOCK(lockp)             do {    \
        struct rwlock **_lockp = (lockp);               \
                                                        \
        if (*_lockp != NULL) {                          \
                rw_wunlock(*_lockp);                    \
                *_lockp = NULL;                         \
        }                                               \
} while (0)

#define VM_PAGE_TO_PV_LIST_LOCK(m)      \
                        PHYS_TO_PV_LIST_LOCK(VM_PAGE_TO_PHYS(m))

struct pmap kernel_pmap_store;

vm_offset_t virtual_avail;      /* VA of first avail page (after kernel bss) */
vm_offset_t virtual_end;        /* VA of last avail page (end of kernel AS) */

int nkpt;
SYSCTL_INT(_machdep, OID_AUTO, nkpt, CTLFLAG_RD, &nkpt, 0,
    "Number of kernel page table pages allocated on bootup");

static int ndmpdp;
vm_paddr_t dmaplimit;
vm_offset_t kernel_vm_end = VM_MIN_KERNEL_ADDRESS;
pt_entry_t pg_nx;

static SYSCTL_NODE(_vm, OID_AUTO, pmap, CTLFLAG_RD, 0, "VM/pmap parameters");

static int pat_works = 1;
SYSCTL_INT(_vm_pmap, OID_AUTO, pat_works, CTLFLAG_RD, &pat_works, 1,
    "Is page attribute table fully functional?");

static int pg_ps_enabled = 1;
SYSCTL_INT(_vm_pmap, OID_AUTO, pg_ps_enabled, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
    &pg_ps_enabled, 0, "Are large page mappings enabled?");

#define PAT_INDEX_SIZE  8
static int pat_index[PAT_INDEX_SIZE];   /* cache mode to PAT index conversion */

static u_int64_t        KPTphys;        /* phys addr of kernel level 1 */
static u_int64_t        KPDphys;        /* phys addr of kernel level 2 */
u_int64_t               KPDPphys;       /* phys addr of kernel level 3 */
u_int64_t               KPML4phys;      /* phys addr of kernel level 4 */

static u_int64_t        DMPDphys;       /* phys addr of direct mapped level 2 */
static u_int64_t        DMPDPphys;      /* phys addr of direct mapped level 3 */
static int              ndmpdpphys;     /* number of DMPDPphys pages */

static vm_paddr_t       KERNend;        /* phys addr of end of bootstrap data */

/*
 * pmap_mapdev support pre initialization (i.e. console)
 */
#define PMAP_PREINIT_MAPPING_COUNT      8
static struct pmap_preinit_mapping {
        vm_paddr_t      pa;
        vm_offset_t     va;
        vm_size_t       sz;
        int             mode;
} pmap_preinit_mapping[PMAP_PREINIT_MAPPING_COUNT];
static int pmap_initialized;

/*
 * Data for the pv entry allocation mechanism.
 * Updates to pv_invl_gen are protected by the pv_list_locks[]
 * elements, but reads are not.
 */
static TAILQ_HEAD(pch, pv_chunk) pv_chunks = TAILQ_HEAD_INITIALIZER(pv_chunks);
static struct mtx __exclusive_cache_line pv_chunks_mutex;
static struct rwlock __exclusive_cache_line pv_list_locks[NPV_LIST_LOCKS];
static u_long pv_invl_gen[NPV_LIST_LOCKS];
static struct md_page *pv_table;
static struct md_page pv_dummy;

/*
 * All those kernel PT submaps that BSD is so fond of
 */
pt_entry_t *CMAP1 = NULL;
caddr_t CADDR1 = 0;
static vm_offset_t qframe = 0;
static struct mtx qframe_mtx;

static int pmap_flags = PMAP_PDE_SUPERPAGE;     /* flags for x86 pmaps */

int pmap_pcid_enabled = 1;
SYSCTL_INT(_vm_pmap, OID_AUTO, pcid_enabled, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
    &pmap_pcid_enabled, 0, "Is TLB Context ID enabled ?");
int invpcid_works = 0;
SYSCTL_INT(_vm_pmap, OID_AUTO, invpcid_works, CTLFLAG_RD, &invpcid_works, 0,
    "Is the invpcid instruction available ?");

int __read_frequently pti = 0;
SYSCTL_INT(_vm_pmap, OID_AUTO, pti, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
    &pti, 0,
    "Page Table Isolation enabled");
static vm_object_t pti_obj;
static pml4_entry_t *pti_pml4;
static vm_pindex_t pti_pg_idx;
static bool pti_finalized;

static int
pmap_pcid_save_cnt_proc(SYSCTL_HANDLER_ARGS)
{
        int i;
        uint64_t res;

        res = 0;
        CPU_FOREACH(i) {
                res += cpuid_to_pcpu[i]->pc_pm_save_cnt;
        }
        return (sysctl_handle_64(oidp, &res, 0, req));
}
SYSCTL_PROC(_vm_pmap, OID_AUTO, pcid_save_cnt, CTLTYPE_U64 | CTLFLAG_RW |
    CTLFLAG_MPSAFE, NULL, 0, pmap_pcid_save_cnt_proc, "QU",
    "Count of saved TLB context on switch");

static LIST_HEAD(, pmap_invl_gen) pmap_invl_gen_tracker =
    LIST_HEAD_INITIALIZER(&pmap_invl_gen_tracker);
static struct mtx invl_gen_mtx;
static u_long pmap_invl_gen = 0;
/* Fake lock object to satisfy turnstiles interface. */
static struct lock_object invl_gen_ts = {
        .lo_name = "invlts",
};

static bool
pmap_not_in_di(void)
{

        return (curthread->td_md.md_invl_gen.gen == 0);
}

#define PMAP_ASSERT_NOT_IN_DI() \
    KASSERT(pmap_not_in_di(), ("DI already started"))

/*
 * Start a new Delayed Invalidation (DI) block of code, executed by
 * the current thread.  Within a DI block, the current thread may
 * destroy both the page table and PV list entries for a mapping and
 * then release the corresponding PV list lock before ensuring that
 * the mapping is flushed from the TLBs of any processors with the
 * pmap active.
 */
static void
pmap_delayed_invl_started(void)
{
        struct pmap_invl_gen *invl_gen;
        u_long currgen;

        invl_gen = &curthread->td_md.md_invl_gen;
        PMAP_ASSERT_NOT_IN_DI();
        mtx_lock(&invl_gen_mtx);
        if (LIST_EMPTY(&pmap_invl_gen_tracker))
                currgen = pmap_invl_gen;
        else
                currgen = LIST_FIRST(&pmap_invl_gen_tracker)->gen;
        invl_gen->gen = currgen + 1;
        LIST_INSERT_HEAD(&pmap_invl_gen_tracker, invl_gen, link);
        mtx_unlock(&invl_gen_mtx);
}

/*
 * Finish the DI block, previously started by the current thread.  All
 * required TLB flushes for the pages marked by
 * pmap_delayed_invl_page() must be finished before this function is
 * called.
 *
 * This function works by bumping the global DI generation number to
 * the generation number of the current thread's DI, unless there is a
 * pending DI that started earlier.  In the latter case, bumping the
 * global DI generation number would incorrectly signal that the
 * earlier DI had finished.  Instead, this function bumps the earlier
 * DI's generation number to match the generation number of the
 * current thread's DI.
 */
static void
pmap_delayed_invl_finished(void)
{
        struct pmap_invl_gen *invl_gen, *next;
        struct turnstile *ts;

        invl_gen = &curthread->td_md.md_invl_gen;
        KASSERT(invl_gen->gen != 0, ("missed invl_started"));
        mtx_lock(&invl_gen_mtx);
        next = LIST_NEXT(invl_gen, link);
        if (next == NULL) {
                turnstile_chain_lock(&invl_gen_ts);
                ts = turnstile_lookup(&invl_gen_ts);
                pmap_invl_gen = invl_gen->gen;
                if (ts != NULL) {
                        turnstile_broadcast(ts, TS_SHARED_QUEUE);
                        turnstile_unpend(ts);
                }
                turnstile_chain_unlock(&invl_gen_ts);
        } else {
                next->gen = invl_gen->gen;
        }
        LIST_REMOVE(invl_gen, link);
        mtx_unlock(&invl_gen_mtx);
        invl_gen->gen = 0;
}

#ifdef PV_STATS
static long invl_wait;
SYSCTL_LONG(_vm_pmap, OID_AUTO, invl_wait, CTLFLAG_RD, &invl_wait, 0,
    "Number of times DI invalidation blocked pmap_remove_all/write");
#endif

static u_long *
pmap_delayed_invl_genp(vm_page_t m)
{

        return (&pv_invl_gen[pa_index(VM_PAGE_TO_PHYS(m)) % NPV_LIST_LOCKS]);
}

/*
 * Ensure that all currently executing DI blocks, that need to flush
 * TLB for the given page m, actually flushed the TLB at the time the
 * function returned.  If the page m has an empty PV list and we call
 * pmap_delayed_invl_wait(), upon its return we know that no CPU has a
 * valid mapping for the page m in either its page table or TLB.
 *
 * This function works by blocking until the global DI generation
 * number catches up with the generation number associated with the
 * given page m and its PV list.  Since this function's callers
 * typically own an object lock and sometimes own a page lock, it
 * cannot sleep.  Instead, it blocks on a turnstile to relinquish the
 * processor.
 */
static void
pmap_delayed_invl_wait(vm_page_t m)
{
        struct turnstile *ts;
        u_long *m_gen;
#ifdef PV_STATS
        bool accounted = false;
#endif

        m_gen = pmap_delayed_invl_genp(m);
        while (*m_gen > pmap_invl_gen) {
#ifdef PV_STATS
                if (!accounted) {
                        atomic_add_long(&invl_wait, 1);
                        accounted = true;
                }
#endif
                ts = turnstile_trywait(&invl_gen_ts);
                if (*m_gen > pmap_invl_gen)
                        turnstile_wait(ts, NULL, TS_SHARED_QUEUE);
                else
                        turnstile_cancel(ts);
        }
}

/*
 * Mark the page m's PV list as participating in the current thread's
 * DI block.  Any threads concurrently using m's PV list to remove or
 * restrict all mappings to m will wait for the current thread's DI
 * block to complete before proceeding.
 *
 * The function works by setting the DI generation number for m's PV
 * list to at least the DI generation number of the current thread.
 * This forces a caller of pmap_delayed_invl_wait() to block until
 * current thread calls pmap_delayed_invl_finished().
 */
static void
pmap_delayed_invl_page(vm_page_t m)
{
        u_long gen, *m_gen;

        rw_assert(VM_PAGE_TO_PV_LIST_LOCK(m), RA_WLOCKED);
        gen = curthread->td_md.md_invl_gen.gen;
        if (gen == 0)
                return;
        m_gen = pmap_delayed_invl_genp(m);
        if (*m_gen < gen)
                *m_gen = gen;
}

/*
 * Crashdump maps.
 */
static caddr_t crashdumpmap;

/*
 * Internal flags for pmap_enter()'s helper functions.
 */
#define PMAP_ENTER_NORECLAIM    0x1000000       /* Don't reclaim PV entries. */
#define PMAP_ENTER_NOREPLACE    0x2000000       /* Don't replace mappings. */

static void     free_pv_chunk(struct pv_chunk *pc);
static void     free_pv_entry(pmap_t pmap, pv_entry_t pv);
static pv_entry_t get_pv_entry(pmap_t pmap, struct rwlock **lockp);
static int      popcnt_pc_map_pq(uint64_t *map);
static vm_page_t reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp);
static void     reserve_pv_entries(pmap_t pmap, int needed,
                    struct rwlock **lockp);
static void     pmap_pv_demote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa,
                    struct rwlock **lockp);
static bool     pmap_pv_insert_pde(pmap_t pmap, vm_offset_t va, pd_entry_t pde,
                    u_int flags, struct rwlock **lockp);
#if VM_NRESERVLEVEL > 0
static void     pmap_pv_promote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa,
                    struct rwlock **lockp);
#endif
static void     pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va);
static pv_entry_t pmap_pvh_remove(struct md_page *pvh, pmap_t pmap,
                    vm_offset_t va);

static int pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode);
static boolean_t pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va);
static boolean_t pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde,
    vm_offset_t va, struct rwlock **lockp);
static boolean_t pmap_demote_pdpe(pmap_t pmap, pdp_entry_t *pdpe,
    vm_offset_t va);
static bool     pmap_enter_2mpage(pmap_t pmap, vm_offset_t va, vm_page_t m,
                    vm_prot_t prot, struct rwlock **lockp);
static int      pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t newpde,
                    u_int flags, vm_page_t m, struct rwlock **lockp);
static vm_page_t pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va,
    vm_page_t m, vm_prot_t prot, vm_page_t mpte, struct rwlock **lockp);
static void pmap_fill_ptp(pt_entry_t *firstpte, pt_entry_t newpte);
static int pmap_insert_pt_page(pmap_t pmap, vm_page_t mpte);
static void pmap_invalidate_pde_page(pmap_t pmap, vm_offset_t va,
                    pd_entry_t pde);
static void pmap_kenter_attr(vm_offset_t va, vm_paddr_t pa, int mode);
static void pmap_pde_attr(pd_entry_t *pde, int cache_bits, int mask);
#if VM_NRESERVLEVEL > 0
static void pmap_promote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va,
    struct rwlock **lockp);
#endif
static boolean_t pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t sva,
    vm_prot_t prot);
static void pmap_pte_attr(pt_entry_t *pte, int cache_bits, int mask);
static void pmap_pti_add_kva_locked(vm_offset_t sva, vm_offset_t eva,
    bool exec);
static pdp_entry_t *pmap_pti_pdpe(vm_offset_t va);
static pd_entry_t *pmap_pti_pde(vm_offset_t va);
static void pmap_pti_wire_pte(void *pte);
static int pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
    struct spglist *free, struct rwlock **lockp);
static int pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t sva,
    pd_entry_t ptepde, struct spglist *free, struct rwlock **lockp);
static vm_page_t pmap_remove_pt_page(pmap_t pmap, vm_offset_t va);
static void pmap_remove_page(pmap_t pmap, vm_offset_t va, pd_entry_t *pde,
    struct spglist *free);
static bool     pmap_remove_ptes(pmap_t pmap, vm_offset_t sva, vm_offset_t eva,
                    pd_entry_t *pde, struct spglist *free,
                    struct rwlock **lockp);
static boolean_t pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va,
    vm_page_t m, struct rwlock **lockp);
static void pmap_update_pde(pmap_t pmap, vm_offset_t va, pd_entry_t *pde,
    pd_entry_t newpde);
static void pmap_update_pde_invalidate(pmap_t, vm_offset_t va, pd_entry_t pde);

static vm_page_t _pmap_allocpte(pmap_t pmap, vm_pindex_t ptepindex,
                struct rwlock **lockp);
static vm_page_t pmap_allocpde(pmap_t pmap, vm_offset_t va,
                struct rwlock **lockp);
static vm_page_t pmap_allocpte(pmap_t pmap, vm_offset_t va,
                struct rwlock **lockp);

static void _pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m,
    struct spglist *free);
static int pmap_unuse_pt(pmap_t, vm_offset_t, pd_entry_t, struct spglist *);

/********************/
/* Inline functions */
/********************/

/* Return a non-clipped PD index for a given VA */
static __inline vm_pindex_t
pmap_pde_pindex(vm_offset_t va)
{
        return (va >> PDRSHIFT);
}


/* Return a pointer to the PML4 slot that corresponds to a VA */
static __inline pml4_entry_t *
pmap_pml4e(pmap_t pmap, vm_offset_t va)
{

        return (&pmap->pm_pml4[pmap_pml4e_index(va)]);
}

/* Return a pointer to the PDP slot that corresponds to a VA */
static __inline pdp_entry_t *
pmap_pml4e_to_pdpe(pml4_entry_t *pml4e, vm_offset_t va)
{
        pdp_entry_t *pdpe;

        pdpe = (pdp_entry_t *)PHYS_TO_DMAP(*pml4e & PG_FRAME);
        return (&pdpe[pmap_pdpe_index(va)]);
}

/* Return a pointer to the PDP slot that corresponds to a VA */
static __inline pdp_entry_t *
pmap_pdpe(pmap_t pmap, vm_offset_t va)
{
        pml4_entry_t *pml4e;
        pt_entry_t PG_V;

        PG_V = pmap_valid_bit(pmap);
        pml4e = pmap_pml4e(pmap, va);
        if ((*pml4e & PG_V) == 0)
                return (NULL);
        return (pmap_pml4e_to_pdpe(pml4e, va));
}

/* Return a pointer to the PD slot that corresponds to a VA */
static __inline pd_entry_t *
pmap_pdpe_to_pde(pdp_entry_t *pdpe, vm_offset_t va)
{
        pd_entry_t *pde;

        pde = (pd_entry_t *)PHYS_TO_DMAP(*pdpe & PG_FRAME);
        return (&pde[pmap_pde_index(va)]);
}

/* Return a pointer to the PD slot that corresponds to a VA */
static __inline pd_entry_t *
pmap_pde(pmap_t pmap, vm_offset_t va)
{
        pdp_entry_t *pdpe;
        pt_entry_t PG_V;

        PG_V = pmap_valid_bit(pmap);
        pdpe = pmap_pdpe(pmap, va);
        if (pdpe == NULL || (*pdpe & PG_V) == 0)
                return (NULL);
        return (pmap_pdpe_to_pde(pdpe, va));
}

/* Return a pointer to the PT slot that corresponds to a VA */
static __inline pt_entry_t *
pmap_pde_to_pte(pd_entry_t *pde, vm_offset_t va)
{
        pt_entry_t *pte;

        pte = (pt_entry_t *)PHYS_TO_DMAP(*pde & PG_FRAME);
        return (&pte[pmap_pte_index(va)]);
}

/* Return a pointer to the PT slot that corresponds to a VA */
static __inline pt_entry_t *
pmap_pte(pmap_t pmap, vm_offset_t va)
{
        pd_entry_t *pde;
        pt_entry_t PG_V;

        PG_V = pmap_valid_bit(pmap);
        pde = pmap_pde(pmap, va);
        if (pde == NULL || (*pde & PG_V) == 0)
                return (NULL);
        if ((*pde & PG_PS) != 0)        /* compat with i386 pmap_pte() */
                return ((pt_entry_t *)pde);
        return (pmap_pde_to_pte(pde, va));
}

static __inline void
pmap_resident_count_inc(pmap_t pmap, int count)
{

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        pmap->pm_stats.resident_count += count;
}

static __inline void
pmap_resident_count_dec(pmap_t pmap, int count)
{

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT(pmap->pm_stats.resident_count >= count,
            ("pmap %p resident count underflow %ld %d", pmap,
            pmap->pm_stats.resident_count, count));
        pmap->pm_stats.resident_count -= count;
}

PMAP_INLINE pt_entry_t *
vtopte(vm_offset_t va)
{
        u_int64_t mask = ((1ul << (NPTEPGSHIFT + NPDEPGSHIFT + NPDPEPGSHIFT + NPML4EPGSHIFT)) - 1);

        KASSERT(va >= VM_MAXUSER_ADDRESS, ("vtopte on a uva/gpa 0x%0lx", va));

        return (PTmap + ((va >> PAGE_SHIFT) & mask));
}

static __inline pd_entry_t *
vtopde(vm_offset_t va)
{
        u_int64_t mask = ((1ul << (NPDEPGSHIFT + NPDPEPGSHIFT + NPML4EPGSHIFT)) - 1);

        KASSERT(va >= VM_MAXUSER_ADDRESS, ("vtopde on a uva/gpa 0x%0lx", va));

        return (PDmap + ((va >> PDRSHIFT) & mask));
}

static u_int64_t
allocpages(vm_paddr_t *firstaddr, int n)
{
        u_int64_t ret;

        ret = *firstaddr;
        bzero((void *)ret, n * PAGE_SIZE);
        *firstaddr += n * PAGE_SIZE;
        return (ret);
}

CTASSERT(powerof2(NDMPML4E));

/* number of kernel PDP slots */
#define NKPDPE(ptpgs)           howmany(ptpgs, NPDEPG)

static void
nkpt_init(vm_paddr_t addr)
{
        int pt_pages;
        
#ifdef NKPT
        pt_pages = NKPT;
#else
        pt_pages = howmany(addr, 1 << PDRSHIFT);
        pt_pages += NKPDPE(pt_pages);

        /*
         * Add some slop beyond the bare minimum required for bootstrapping
         * the kernel.
         *
         * This is quite important when allocating KVA for kernel modules.
         * The modules are required to be linked in the negative 2GB of
         * the address space.  If we run out of KVA in this region then
         * pmap_growkernel() will need to allocate page table pages to map
         * the entire 512GB of KVA space which is an unnecessary tax on
         * physical memory.
         *
         * Secondly, device memory mapped as part of setting up the low-
         * level console(s) is taken from KVA, starting at virtual_avail.
         * This is because cninit() is called after pmap_bootstrap() but
         * before vm_init() and pmap_init(). 20MB for a frame buffer is
         * not uncommon.
         */
        pt_pages += 32;         /* 64MB additional slop. */
#endif
        nkpt = pt_pages;
}

/*
 * Returns the proper write/execute permission for a physical page that is
 * part of the initial boot allocations.
 *
 * If the page has kernel text, it is marked as read-only. If the page has
 * kernel read-only data, it is marked as read-only/not-executable. If the
 * page has only read-write data, it is marked as read-write/not-executable.
 * If the page is below/above the kernel range, it is marked as read-write.
 *
 * This function operates on 2M pages, since we map the kernel space that
 * way.
 *
 * Note that this doesn't currently provide any protection for modules.
 */
static inline pt_entry_t
bootaddr_rwx(vm_paddr_t pa)
{

        /*
         * Everything in the same 2M page as the start of the kernel
         * should be static. On the other hand, things in the same 2M
         * page as the end of the kernel could be read-write/executable,
         * as the kernel image is not guaranteed to end on a 2M boundary.
         */
        if (pa < trunc_2mpage(btext - KERNBASE) ||
           pa >= trunc_2mpage(_end - KERNBASE))
                return (X86_PG_RW);
        /*
         * The linker should ensure that the read-only and read-write
         * portions don't share the same 2M page, so this shouldn't
         * impact read-only data. However, in any case, any page with
         * read-write data needs to be read-write.
         */
        if (pa >= trunc_2mpage(brwsection - KERNBASE))
                return (X86_PG_RW | pg_nx);
        /*
         * Mark any 2M page containing kernel text as read-only. Mark
         * other pages with read-only data as read-only and not executable.
         * (It is likely a small portion of the read-only data section will
         * be marked as read-only, but executable. This should be acceptable
         * since the read-only protection will keep the data from changing.)
         * Note that fixups to the .text section will still work until we
         * set CR0.WP.
         */
        if (pa < round_2mpage(etext - KERNBASE))
                return (0);
        return (pg_nx);
}

static void
create_pagetables(vm_paddr_t *firstaddr)
{
        int i, j, ndm1g, nkpdpe, nkdmpde;
        pt_entry_t *pt_p;
        pd_entry_t *pd_p;
        pdp_entry_t *pdp_p;
        pml4_entry_t *p4_p;
        uint64_t DMPDkernphys;

        /* Allocate page table pages for the direct map */
        ndmpdp = howmany(ptoa(Maxmem), NBPDP);
        if (ndmpdp < 4)         /* Minimum 4GB of dirmap */
                ndmpdp = 4;
        ndmpdpphys = howmany(ndmpdp, NPDPEPG);
        if (ndmpdpphys > NDMPML4E) {
                /*
                 * Each NDMPML4E allows 512 GB, so limit to that,
                 * and then readjust ndmpdp and ndmpdpphys.
                 */
                printf("NDMPML4E limits system to %d GB\n", NDMPML4E * 512);
                Maxmem = atop(NDMPML4E * NBPML4);
                ndmpdpphys = NDMPML4E;
                ndmpdp = NDMPML4E * NPDEPG;
        }
        DMPDPphys = allocpages(firstaddr, ndmpdpphys);
        ndm1g = 0;
        if ((amd_feature & AMDID_PAGE1GB) != 0) {
                /*
                 * Calculate the number of 1G pages that will fully fit in
                 * Maxmem.
                 */
                ndm1g = ptoa(Maxmem) >> PDPSHIFT;

                /*
                 * Allocate 2M pages for the kernel. These will be used in
                 * place of the first one or more 1G pages from ndm1g.
                 */
                nkdmpde = howmany((vm_offset_t)(brwsection - KERNBASE), NBPDP);
                DMPDkernphys = allocpages(firstaddr, nkdmpde);
        }
        if (ndm1g < ndmpdp)
                DMPDphys = allocpages(firstaddr, ndmpdp - ndm1g);
        dmaplimit = (vm_paddr_t)ndmpdp << PDPSHIFT;

        /* Allocate pages */
        KPML4phys = allocpages(firstaddr, 1);
        KPDPphys = allocpages(firstaddr, NKPML4E);

        /*
         * Allocate the initial number of kernel page table pages required to
         * bootstrap.  We defer this until after all memory-size dependent
         * allocations are done (e.g. direct map), so that we don't have to
         * build in too much slop in our estimate.
         *
         * Note that when NKPML4E > 1, we have an empty page underneath
         * all but the KPML4I'th one, so we need NKPML4E-1 extra (zeroed)
         * pages.  (pmap_enter requires a PD page to exist for each KPML4E.)
         */
        nkpt_init(*firstaddr);
        nkpdpe = NKPDPE(nkpt);

        KPTphys = allocpages(firstaddr, nkpt);
        KPDphys = allocpages(firstaddr, nkpdpe);

        /* Fill in the underlying page table pages */
        /* XXX not fully used, underneath 2M pages */
        pt_p = (pt_entry_t *)KPTphys;
        for (i = 0; ptoa(i) < *firstaddr; i++)
                pt_p[i] = ptoa(i) | X86_PG_V | pg_g | bootaddr_rwx(ptoa(i));

        /* Now map the page tables at their location within PTmap */
        pd_p = (pd_entry_t *)KPDphys;
        for (i = 0; i < nkpt; i++)
                pd_p[i] = (KPTphys + ptoa(i)) | X86_PG_RW | X86_PG_V;

        /* Map from zero to end of allocations under 2M pages */
        /* This replaces some of the KPTphys entries above */
        for (i = 0; (i << PDRSHIFT) < *firstaddr; i++)
                /* Preset PG_M and PG_A because demotion expects it. */
                pd_p[i] = (i << PDRSHIFT) | X86_PG_V | PG_PS | pg_g |
                    X86_PG_M | X86_PG_A | bootaddr_rwx(i << PDRSHIFT);

        /*
         * Because we map the physical blocks in 2M pages, adjust firstaddr
         * to record the physical blocks we've actually mapped into kernel
         * virtual address space.
         */
        *firstaddr = round_2mpage(*firstaddr);

        /* And connect up the PD to the PDP (leaving room for L4 pages) */
        pdp_p = (pdp_entry_t *)(KPDPphys + ptoa(KPML4I - KPML4BASE));
        for (i = 0; i < nkpdpe; i++)
                pdp_p[i + KPDPI] = (KPDphys + ptoa(i)) | X86_PG_RW | X86_PG_V;

        /*
         * Now, set up the direct map region using 2MB and/or 1GB pages.  If
         * the end of physical memory is not aligned to a 1GB page boundary,
         * then the residual physical memory is mapped with 2MB pages.  Later,
         * if pmap_mapdev{_attr}() uses the direct map for non-write-back
         * memory, pmap_change_attr() will demote any 2MB or 1GB page mappings
         * that are partially used. 
         */
        pd_p = (pd_entry_t *)DMPDphys;
        for (i = NPDEPG * ndm1g, j = 0; i < NPDEPG * ndmpdp; i++, j++) {
                pd_p[j] = (vm_paddr_t)i << PDRSHIFT;
                /* Preset PG_M and PG_A because demotion expects it. */
                pd_p[j] |= X86_PG_RW | X86_PG_V | PG_PS | pg_g |
                    X86_PG_M | X86_PG_A | pg_nx;
        }
        pdp_p = (pdp_entry_t *)DMPDPphys;
        for (i = 0; i < ndm1g; i++) {
                pdp_p[i] = (vm_paddr_t)i << PDPSHIFT;
                /* Preset PG_M and PG_A because demotion expects it. */
                pdp_p[i] |= X86_PG_RW | X86_PG_V | PG_PS | pg_g |
                    X86_PG_M | X86_PG_A | pg_nx;
        }
        for (j = 0; i < ndmpdp; i++, j++) {
                pdp_p[i] = DMPDphys + ptoa(j);
                pdp_p[i] |= X86_PG_RW | X86_PG_V;
        }

        /*
         * Instead of using a 1G page for the memory containing the kernel,
         * use 2M pages with appropriate permissions. (If using 1G pages,
         * this will partially overwrite the PDPEs above.)
         */
        if (ndm1g) {
                pd_p = (pd_entry_t *)DMPDkernphys;
                for (i = 0; i < (NPDEPG * nkdmpde); i++)
                        pd_p[i] = (i << PDRSHIFT) | X86_PG_V | PG_PS | pg_g |
                            X86_PG_M | X86_PG_A | pg_nx |
                            bootaddr_rwx(i << PDRSHIFT);
                for (i = 0; i < nkdmpde; i++)
                        pdp_p[i] = (DMPDkernphys + ptoa(i)) | X86_PG_RW |
                            X86_PG_V;
        }

        /* And recursively map PML4 to itself in order to get PTmap */
        p4_p = (pml4_entry_t *)KPML4phys;
        p4_p[PML4PML4I] = KPML4phys;
        p4_p[PML4PML4I] |= X86_PG_RW | X86_PG_V | pg_nx;

        /* Connect the Direct Map slot(s) up to the PML4. */
        for (i = 0; i < ndmpdpphys; i++) {
                p4_p[DMPML4I + i] = DMPDPphys + ptoa(i);
                p4_p[DMPML4I + i] |= X86_PG_RW | X86_PG_V;
        }

        /* Connect the KVA slots up to the PML4 */
        for (i = 0; i < NKPML4E; i++) {
                p4_p[KPML4BASE + i] = KPDPphys + ptoa(i);
                p4_p[KPML4BASE + i] |= X86_PG_RW | X86_PG_V;
        }
}

/*
 *      Bootstrap the system enough to run with virtual memory.
 *
 *      On amd64 this is called after mapping has already been enabled
 *      and just syncs the pmap module with what has already been done.
 *      [We can't call it easily with mapping off since the kernel is not
 *      mapped with PA == VA, hence we would have to relocate every address
 *      from the linked base (virtual) address "KERNBASE" to the actual
 *      (physical) address starting relative to 0]
 */
void
pmap_bootstrap(vm_paddr_t *firstaddr)
{
        vm_offset_t va;
        pt_entry_t *pte;
        uint64_t cr4;
        int i;

        KERNend = *firstaddr;

        if (!pti)
                pg_g = X86_PG_G;

        /*
         * Create an initial set of page tables to run the kernel in.
         */
        create_pagetables(firstaddr);

        /*
         * Add a physical memory segment (vm_phys_seg) corresponding to the
         * preallocated kernel page table pages so that vm_page structures
         * representing these pages will be created.  The vm_page structures
         * are required for promotion of the corresponding kernel virtual
         * addresses to superpage mappings.
         */
        vm_phys_add_seg(KPTphys, KPTphys + ptoa(nkpt));

        virtual_avail = (vm_offset_t) KERNBASE + *firstaddr;

        virtual_end = VM_MAX_KERNEL_ADDRESS;


        /*
         * Enable PG_G global pages, then switch to the kernel page
         * table from the bootstrap page table.  After the switch, it
         * is possible to enable SMEP and SMAP since PG_U bits are
         * correct now.
         */
        cr4 = rcr4();
        cr4 |= CR4_PGE;
        load_cr4(cr4);
        load_cr3(KPML4phys);
        if (cpu_stdext_feature & CPUID_STDEXT_SMEP)
                cr4 |= CR4_SMEP;
        if (cpu_stdext_feature & CPUID_STDEXT_SMAP)
                cr4 |= CR4_SMAP;
        load_cr4(cr4);

        /*
         * Initialize the kernel pmap (which is statically allocated).
         */
        PMAP_LOCK_INIT(kernel_pmap);
        kernel_pmap->pm_pml4 = (pdp_entry_t *)PHYS_TO_DMAP(KPML4phys);
        kernel_pmap->pm_cr3 = KPML4phys;
        kernel_pmap->pm_ucr3 = PMAP_NO_CR3;
        CPU_FILL(&kernel_pmap->pm_active);      /* don't allow deactivation */
        TAILQ_INIT(&kernel_pmap->pm_pvchunk);
        kernel_pmap->pm_flags = pmap_flags;

        /*
         * Initialize the TLB invalidations generation number lock.
         */
        mtx_init(&invl_gen_mtx, "invlgn", NULL, MTX_DEF);

        /*
         * Reserve some special page table entries/VA space for temporary
         * mapping of pages.
         */
#define SYSMAP(c, p, v, n)      \
        v = (c)va; va += ((n)*PAGE_SIZE); p = pte; pte += (n);

        va = virtual_avail;
        pte = vtopte(va);

        /*
         * Crashdump maps.  The first page is reused as CMAP1 for the
         * memory test.
         */
        SYSMAP(caddr_t, CMAP1, crashdumpmap, MAXDUMPPGS)
        CADDR1 = crashdumpmap;

        virtual_avail = va;

        /*
         * Initialize the PAT MSR.
         * pmap_init_pat() clears and sets CR4_PGE, which, as a
         * side-effect, invalidates stale PG_G TLB entries that might
         * have been created in our pre-boot environment.
         */
        pmap_init_pat();

        /* Initialize TLB Context Id. */
        if (pmap_pcid_enabled) {
                for (i = 0; i < MAXCPU; i++) {
                        kernel_pmap->pm_pcids[i].pm_pcid = PMAP_PCID_KERN;
                        kernel_pmap->pm_pcids[i].pm_gen = 1;
                }

                /*
                 * PMAP_PCID_KERN + 1 is used for initialization of
                 * proc0 pmap.  The pmap' pcid state might be used by
                 * EFIRT entry before first context switch, so it
                 * needs to be valid.
                 */
                PCPU_SET(pcid_next, PMAP_PCID_KERN + 2);
                PCPU_SET(pcid_gen, 1);

                /*
                 * pcpu area for APs is zeroed during AP startup.
                 * pc_pcid_next and pc_pcid_gen are initialized by AP
                 * during pcpu setup.
                 */
                load_cr4(rcr4() | CR4_PCIDE);
        }
}

/*
 * Setup the PAT MSR.
 */
void
pmap_init_pat(void)
{
        int pat_table[PAT_INDEX_SIZE];
        uint64_t pat_msr;
        u_long cr0, cr4;
        int i;

        /* Bail if this CPU doesn't implement PAT. */
        if ((cpu_feature & CPUID_PAT) == 0)
                panic("no PAT??");

        /* Set default PAT index table. */
        for (i = 0; i < PAT_INDEX_SIZE; i++)
                pat_table[i] = -1;
        pat_table[PAT_WRITE_BACK] = 0;
        pat_table[PAT_WRITE_THROUGH] = 1;
        pat_table[PAT_UNCACHEABLE] = 3;
        pat_table[PAT_WRITE_COMBINING] = 3;
        pat_table[PAT_WRITE_PROTECTED] = 3;
        pat_table[PAT_UNCACHED] = 3;

        /* Initialize default PAT entries. */
        pat_msr = PAT_VALUE(0, PAT_WRITE_BACK) |
            PAT_VALUE(1, PAT_WRITE_THROUGH) |
            PAT_VALUE(2, PAT_UNCACHED) |
            PAT_VALUE(3, PAT_UNCACHEABLE) |
            PAT_VALUE(4, PAT_WRITE_BACK) |
            PAT_VALUE(5, PAT_WRITE_THROUGH) |
            PAT_VALUE(6, PAT_UNCACHED) |
            PAT_VALUE(7, PAT_UNCACHEABLE);

        if (pat_works) {
                /*
                 * Leave the indices 0-3 at the default of WB, WT, UC-, and UC.
                 * Program 5 and 6 as WP and WC.
                 * Leave 4 and 7 as WB and UC.
                 */
                pat_msr &= ~(PAT_MASK(5) | PAT_MASK(6));
                pat_msr |= PAT_VALUE(5, PAT_WRITE_PROTECTED) |
                    PAT_VALUE(6, PAT_WRITE_COMBINING);
                pat_table[PAT_UNCACHED] = 2;
                pat_table[PAT_WRITE_PROTECTED] = 5;
                pat_table[PAT_WRITE_COMBINING] = 6;
        } else {
                /*
                 * Just replace PAT Index 2 with WC instead of UC-.
                 */
                pat_msr &= ~PAT_MASK(2);
                pat_msr |= PAT_VALUE(2, PAT_WRITE_COMBINING);
                pat_table[PAT_WRITE_COMBINING] = 2;
        }

        /* Disable PGE. */
        cr4 = rcr4();
        load_cr4(cr4 & ~CR4_PGE);

        /* Disable caches (CD = 1, NW = 0). */
        cr0 = rcr0();
        load_cr0((cr0 & ~CR0_NW) | CR0_CD);

        /* Flushes caches and TLBs. */
        wbinvd();
        invltlb();

        /* Update PAT and index table. */
        wrmsr(MSR_PAT, pat_msr);
        for (i = 0; i < PAT_INDEX_SIZE; i++)
                pat_index[i] = pat_table[i];

        /* Flush caches and TLBs again. */
        wbinvd();
        invltlb();

        /* Restore caches and PGE. */
        load_cr0(cr0);
        load_cr4(cr4);
}

/*
 *      Initialize a vm_page's machine-dependent fields.
 */
void
pmap_page_init(vm_page_t m)
{

        TAILQ_INIT(&m->md.pv_list);
        m->md.pat_mode = PAT_WRITE_BACK;
}

/*
 *      Initialize the pmap module.
 *      Called by vm_init, to initialize any structures that the pmap
 *      system needs to map virtual memory.
 */
void
pmap_init(void)
{
        struct pmap_preinit_mapping *ppim;
        vm_page_t mpte;
        vm_size_t s;
        int error, i, pv_npg, ret, skz63;

        /* L1TF, reserve page @0 unconditionally */
        vm_page_blacklist_add(0, bootverbose);

        /* Detect bare-metal Skylake Server and Skylake-X. */
        if (vm_guest == VM_GUEST_NO && cpu_vendor_id == CPU_VENDOR_INTEL &&
            CPUID_TO_FAMILY(cpu_id) == 0x6 && CPUID_TO_MODEL(cpu_id) == 0x55) {
                /*
                 * Skylake-X errata SKZ63. Processor May Hang When
                 * Executing Code In an HLE Transaction Region between
                 * 40000000H and 403FFFFFH.
                 *
                 * Mark the pages in the range as preallocated.  It
                 * seems to be impossible to distinguish between
                 * Skylake Server and Skylake X.
                 */
                skz63 = 1;
                TUNABLE_INT_FETCH("hw.skz63_enable", &skz63);
                if (skz63 != 0) {
                        if (bootverbose)
                                printf("SKZ63: skipping 4M RAM starting "
                                    "at physical 1G\n");
                        for (i = 0; i < atop(0x400000); i++) {
                                ret = vm_page_blacklist_add(0x40000000 +
                                    ptoa(i), FALSE);
                                if (!ret && bootverbose)
                                        printf("page at %#lx already used\n",
                                            0x40000000 + ptoa(i));
                        }
                }
        }

        /*
         * Initialize the vm page array entries for the kernel pmap's
         * page table pages.
         */ 
        PMAP_LOCK(kernel_pmap);
        for (i = 0; i < nkpt; i++) {
                mpte = PHYS_TO_VM_PAGE(KPTphys + (i << PAGE_SHIFT));
                KASSERT(mpte >= vm_page_array &&
                    mpte < &vm_page_array[vm_page_array_size],
                    ("pmap_init: page table page is out of range"));
                mpte->pindex = pmap_pde_pindex(KERNBASE) + i;
                mpte->phys_addr = KPTphys + (i << PAGE_SHIFT);
                mpte->wire_count = 1;
                if (i << PDRSHIFT < KERNend &&
                    pmap_insert_pt_page(kernel_pmap, mpte))
                        panic("pmap_init: pmap_insert_pt_page failed");
        }
        PMAP_UNLOCK(kernel_pmap);
        vm_wire_add(nkpt);

        /*
         * If the kernel is running on a virtual machine, then it must assume
         * that MCA is enabled by the hypervisor.  Moreover, the kernel must
         * be prepared for the hypervisor changing the vendor and family that
         * are reported by CPUID.  Consequently, the workaround for AMD Family
         * 10h Erratum 383 is enabled if the processor's feature set does not
         * include at least one feature that is only supported by older Intel
         * or newer AMD processors.
         */
        if (vm_guest != VM_GUEST_NO && (cpu_feature & CPUID_SS) == 0 &&
            (cpu_feature2 & (CPUID2_SSSE3 | CPUID2_SSE41 | CPUID2_AESNI |
            CPUID2_AVX | CPUID2_XSAVE)) == 0 && (amd_feature2 & (AMDID2_XOP |
            AMDID2_FMA4)) == 0)
                workaround_erratum383 = 1;

        /*
         * Are large page mappings enabled?
         */
        TUNABLE_INT_FETCH("vm.pmap.pg_ps_enabled", &pg_ps_enabled);
        if (pg_ps_enabled) {
                KASSERT(MAXPAGESIZES > 1 && pagesizes[1] == 0,
                    ("pmap_init: can't assign to pagesizes[1]"));
                pagesizes[1] = NBPDR;
        }

        /*
         * Initialize the pv chunk list mutex.
         */
        mtx_init(&pv_chunks_mutex, "pmap pv chunk list", NULL, MTX_DEF);

        /*
         * Initialize the pool of pv list locks.
         */
        for (i = 0; i < NPV_LIST_LOCKS; i++)
                rw_init(&pv_list_locks[i], "pmap pv list");

        /*
         * Calculate the size of the pv head table for superpages.
         */
        pv_npg = howmany(vm_phys_segs[vm_phys_nsegs - 1].end, NBPDR);

        /*
         * Allocate memory for the pv head table for superpages.
         */
        s = (vm_size_t)(pv_npg * sizeof(struct md_page));
        s = round_page(s);
        pv_table = (struct md_page *)kmem_malloc(s, M_WAITOK | M_ZERO);
        for (i = 0; i < pv_npg; i++)
                TAILQ_INIT(&pv_table[i].pv_list);
        TAILQ_INIT(&pv_dummy.pv_list);

        pmap_initialized = 1;
        for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                ppim = pmap_preinit_mapping + i;
                if (ppim->va == 0)
                        continue;
                /* Make the direct map consistent */
                if (ppim->pa < dmaplimit && ppim->pa + ppim->sz < dmaplimit) {
                        (void)pmap_change_attr(PHYS_TO_DMAP(ppim->pa),
                            ppim->sz, ppim->mode);
                }
                if (!bootverbose)
                        continue;
                printf("PPIM %u: PA=%#lx, VA=%#lx, size=%#lx, mode=%#x\n", i,
                    ppim->pa, ppim->va, ppim->sz, ppim->mode);
        }

        mtx_init(&qframe_mtx, "qfrmlk", NULL, MTX_SPIN);
        error = vmem_alloc(kernel_arena, PAGE_SIZE, M_BESTFIT | M_WAITOK,
            (vmem_addr_t *)&qframe);
        if (error != 0)
                panic("qframe allocation failed");
}

static SYSCTL_NODE(_vm_pmap, OID_AUTO, pde, CTLFLAG_RD, 0,
    "2MB page mapping counters");

static u_long pmap_pde_demotions;
SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, demotions, CTLFLAG_RD,
    &pmap_pde_demotions, 0, "2MB page demotions");

static u_long pmap_pde_mappings;
SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, mappings, CTLFLAG_RD,
    &pmap_pde_mappings, 0, "2MB page mappings");

static u_long pmap_pde_p_failures;
SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, p_failures, CTLFLAG_RD,
    &pmap_pde_p_failures, 0, "2MB page promotion failures");

static u_long pmap_pde_promotions;
SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, promotions, CTLFLAG_RD,
    &pmap_pde_promotions, 0, "2MB page promotions");

static SYSCTL_NODE(_vm_pmap, OID_AUTO, pdpe, CTLFLAG_RD, 0,
    "1GB page mapping counters");

static u_long pmap_pdpe_demotions;
SYSCTL_ULONG(_vm_pmap_pdpe, OID_AUTO, demotions, CTLFLAG_RD,
    &pmap_pdpe_demotions, 0, "1GB page demotions");

/***************************************************
 * Low level helper routines.....
 ***************************************************/

static pt_entry_t
pmap_swap_pat(pmap_t pmap, pt_entry_t entry)
{
        int x86_pat_bits = X86_PG_PTE_PAT | X86_PG_PDE_PAT;

        switch (pmap->pm_type) {
        case PT_X86:
        case PT_RVI:
                /* Verify that both PAT bits are not set at the same time */
                KASSERT((entry & x86_pat_bits) != x86_pat_bits,
                    ("Invalid PAT bits in entry %#lx", entry));

                /* Swap the PAT bits if one of them is set */
                if ((entry & x86_pat_bits) != 0)
                        entry ^= x86_pat_bits;
                break;
        case PT_EPT:
                /*
                 * Nothing to do - the memory attributes are represented
                 * the same way for regular pages and superpages.
                 */
                break;
        default:
                panic("pmap_switch_pat_bits: bad pm_type %d", pmap->pm_type);
        }

        return (entry);
}

boolean_t
pmap_is_valid_memattr(pmap_t pmap __unused, vm_memattr_t mode)
{

        return (mode >= 0 && mode < PAT_INDEX_SIZE &&
            pat_index[(int)mode] >= 0);
}

/*
 * Determine the appropriate bits to set in a PTE or PDE for a specified
 * caching mode.
 */
int
pmap_cache_bits(pmap_t pmap, int mode, boolean_t is_pde)
{
        int cache_bits, pat_flag, pat_idx;

        if (!pmap_is_valid_memattr(pmap, mode))
                panic("Unknown caching mode %d\n", mode);

        switch (pmap->pm_type) {
        case PT_X86:
        case PT_RVI:
                /* The PAT bit is different for PTE's and PDE's. */
                pat_flag = is_pde ? X86_PG_PDE_PAT : X86_PG_PTE_PAT;

                /* Map the caching mode to a PAT index. */
                pat_idx = pat_index[mode];

                /* Map the 3-bit index value into the PAT, PCD, and PWT bits. */
                cache_bits = 0;
                if (pat_idx & 0x4)
                        cache_bits |= pat_flag;
                if (pat_idx & 0x2)
                        cache_bits |= PG_NC_PCD;
                if (pat_idx & 0x1)
                        cache_bits |= PG_NC_PWT;
                break;

        case PT_EPT:
                cache_bits = EPT_PG_IGNORE_PAT | EPT_PG_MEMORY_TYPE(mode);
                break;

        default:
                panic("unsupported pmap type %d", pmap->pm_type);
        }

        return (cache_bits);
}

static int
pmap_cache_mask(pmap_t pmap, boolean_t is_pde)
{
        int mask;

        switch (pmap->pm_type) {
        case PT_X86:
        case PT_RVI:
                mask = is_pde ? X86_PG_PDE_CACHE : X86_PG_PTE_CACHE;
                break;
        case PT_EPT:
                mask = EPT_PG_IGNORE_PAT | EPT_PG_MEMORY_TYPE(0x7);
                break;
        default:
                panic("pmap_cache_mask: invalid pm_type %d", pmap->pm_type);
        }

        return (mask);
}

bool
pmap_ps_enabled(pmap_t pmap)
{

        return (pg_ps_enabled && (pmap->pm_flags & PMAP_PDE_SUPERPAGE) != 0);
}

static void
pmap_update_pde_store(pmap_t pmap, pd_entry_t *pde, pd_entry_t newpde)
{

        switch (pmap->pm_type) {
        case PT_X86:
                break;
        case PT_RVI:
        case PT_EPT:
                /*
                 * XXX
                 * This is a little bogus since the generation number is
                 * supposed to be bumped up when a region of the address
                 * space is invalidated in the page tables.
                 *
                 * In this case the old PDE entry is valid but yet we want
                 * to make sure that any mappings using the old entry are
                 * invalidated in the TLB.
                 *
                 * The reason this works as expected is because we rendezvous
                 * "all" host cpus and force any vcpu context to exit as a
                 * side-effect.
                 */
                atomic_add_acq_long(&pmap->pm_eptgen, 1);
                break;
        default:
                panic("pmap_update_pde_store: bad pm_type %d", pmap->pm_type);
        }
        pde_store(pde, newpde);
}

/*
 * After changing the page size for the specified virtual address in the page
 * table, flush the corresponding entries from the processor's TLB.  Only the
 * calling processor's TLB is affected.
 *
 * The calling thread must be pinned to a processor.
 */
static void
pmap_update_pde_invalidate(pmap_t pmap, vm_offset_t va, pd_entry_t newpde)
{
        pt_entry_t PG_G;

        if (pmap_type_guest(pmap))
                return;

        KASSERT(pmap->pm_type == PT_X86,
            ("pmap_update_pde_invalidate: invalid type %d", pmap->pm_type));

        PG_G = pmap_global_bit(pmap);

        if ((newpde & PG_PS) == 0)
                /* Demotion: flush a specific 2MB page mapping. */
                invlpg(va);
        else if ((newpde & PG_G) == 0)
                /*
                 * Promotion: flush every 4KB page mapping from the TLB
                 * because there are too many to flush individually.
                 */
                invltlb();
        else {
                /*
                 * Promotion: flush every 4KB page mapping from the TLB,
                 * including any global (PG_G) mappings.
                 */
                invltlb_glob();
        }
}
#ifdef SMP

/*
 * For SMP, these functions have to use the IPI mechanism for coherence.
 *
 * N.B.: Before calling any of the following TLB invalidation functions,
 * the calling processor must ensure that all stores updating a non-
 * kernel page table are globally performed.  Otherwise, another
 * processor could cache an old, pre-update entry without being
 * invalidated.  This can happen one of two ways: (1) The pmap becomes
 * active on another processor after its pm_active field is checked by
 * one of the following functions but before a store updating the page
 * table is globally performed. (2) The pmap becomes active on another
 * processor before its pm_active field is checked but due to
 * speculative loads one of the following functions stills reads the
 * pmap as inactive on the other processor.
 * 
 * The kernel page table is exempt because its pm_active field is
 * immutable.  The kernel page table is always active on every
 * processor.
 */

/*
 * Interrupt the cpus that are executing in the guest context.
 * This will force the vcpu to exit and the cached EPT mappings
 * will be invalidated by the host before the next vmresume.
 */
static __inline void
pmap_invalidate_ept(pmap_t pmap)
{
        int ipinum;

        sched_pin();
        KASSERT(!CPU_ISSET(curcpu, &pmap->pm_active),
            ("pmap_invalidate_ept: absurd pm_active"));

        /*
         * The TLB mappings associated with a vcpu context are not
         * flushed each time a different vcpu is chosen to execute.
         *
         * This is in contrast with a process's vtop mappings that
         * are flushed from the TLB on each context switch.
         *
         * Therefore we need to do more than just a TLB shootdown on
         * the active cpus in 'pmap->pm_active'. To do this we keep
         * track of the number of invalidations performed on this pmap.
         *
         * Each vcpu keeps a cache of this counter and compares it
         * just before a vmresume. If the counter is out-of-date an
         * invept will be done to flush stale mappings from the TLB.
         */
        atomic_add_acq_long(&pmap->pm_eptgen, 1);

        /*
         * Force the vcpu to exit and trap back into the hypervisor.
         */
        ipinum = pmap->pm_flags & PMAP_NESTED_IPIMASK;
        ipi_selected(pmap->pm_active, ipinum);
        sched_unpin();
}

void
pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
{
        cpuset_t *mask;
        struct invpcid_descr d;
        uint64_t kcr3, ucr3;
        uint32_t pcid;
        u_int cpuid, i;

        if (pmap_type_guest(pmap)) {
                pmap_invalidate_ept(pmap);
                return;
        }

        KASSERT(pmap->pm_type == PT_X86,
            ("pmap_invalidate_page: invalid type %d", pmap->pm_type));

        sched_pin();
        if (pmap == kernel_pmap) {
                invlpg(va);
                mask = &all_cpus;
        } else {
                cpuid = PCPU_GET(cpuid);
                if (pmap == PCPU_GET(curpmap)) {
                        invlpg(va);
                        if (pmap_pcid_enabled && pmap->pm_ucr3 != PMAP_NO_CR3) {
                                /*
                                 * Disable context switching. pm_pcid
                                 * is recalculated on switch, which
                                 * might make us use wrong pcid below.
                                 */
                                critical_enter();
                                pcid = pmap->pm_pcids[cpuid].pm_pcid;

                                if (invpcid_works) {
                                        d.pcid = pcid | PMAP_PCID_USER_PT;
                                        d.pad = 0;
                                        d.addr = va;
                                        invpcid(&d, INVPCID_ADDR);
                                } else {
                                        kcr3 = pmap->pm_cr3 | pcid |
                                            CR3_PCID_SAVE;
                                        ucr3 = pmap->pm_ucr3 | pcid |
                                            PMAP_PCID_USER_PT | CR3_PCID_SAVE;
                                        pmap_pti_pcid_invlpg(ucr3, kcr3, va);
                                }
                                critical_exit();
                        }
                } else if (pmap_pcid_enabled)
                        pmap->pm_pcids[cpuid].pm_gen = 0;
                if (pmap_pcid_enabled) {
                        CPU_FOREACH(i) {
                                if (cpuid != i)
                                        pmap->pm_pcids[i].pm_gen = 0;
                        }

                        /*
                         * The fence is between stores to pm_gen and the read of
                         * the pm_active mask.  We need to ensure that it is
                         * impossible for us to miss the bit update in pm_active
                         * and simultaneously observe a non-zero pm_gen in
                         * pmap_activate_sw(), otherwise TLB update is missed.
                         * Without the fence, IA32 allows such an outcome.
                         * Note that pm_active is updated by a locked operation,
                         * which provides the reciprocal fence.
                         */
                        atomic_thread_fence_seq_cst();
                }
                mask = &pmap->pm_active;
        }
        smp_masked_invlpg(*mask, va, pmap);
        sched_unpin();
}

/* 4k PTEs -- Chosen to exceed the total size of Broadwell L2 TLB */
#define PMAP_INVLPG_THRESHOLD   (4 * 1024 * PAGE_SIZE)

void
pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        cpuset_t *mask;
        struct invpcid_descr d;
        vm_offset_t addr;
        uint64_t kcr3, ucr3;
        uint32_t pcid;
        u_int cpuid, i;

        if (eva - sva >= PMAP_INVLPG_THRESHOLD) {
                pmap_invalidate_all(pmap);
                return;
        }

        if (pmap_type_guest(pmap)) {
                pmap_invalidate_ept(pmap);
                return;
        }

        KASSERT(pmap->pm_type == PT_X86,
            ("pmap_invalidate_range: invalid type %d", pmap->pm_type));

        sched_pin();
        cpuid = PCPU_GET(cpuid);
        if (pmap == kernel_pmap) {
                for (addr = sva; addr < eva; addr += PAGE_SIZE)
                        invlpg(addr);
                mask = &all_cpus;
        } else {
                if (pmap == PCPU_GET(curpmap)) {
                        for (addr = sva; addr < eva; addr += PAGE_SIZE)
                                invlpg(addr);
                        if (pmap_pcid_enabled && pmap->pm_ucr3 != PMAP_NO_CR3) {
                                critical_enter();
                                pcid = pmap->pm_pcids[cpuid].pm_pcid;
                                if (invpcid_works) {
                                        d.pcid = pcid | PMAP_PCID_USER_PT;
                                        d.pad = 0;
                                        d.addr = sva;
                                        for (; d.addr < eva; d.addr +=
                                            PAGE_SIZE)
                                                invpcid(&d, INVPCID_ADDR);
                                } else {
                                        kcr3 = pmap->pm_cr3 | pcid |
                                            CR3_PCID_SAVE;
                                        ucr3 = pmap->pm_ucr3 | pcid |
                                            PMAP_PCID_USER_PT | CR3_PCID_SAVE;
                                        pmap_pti_pcid_invlrng(ucr3, kcr3, sva,
                                            eva);
                                }
                                critical_exit();
                        }
                } else if (pmap_pcid_enabled) {
                        pmap->pm_pcids[cpuid].pm_gen = 0;
                }
                if (pmap_pcid_enabled) {
                        CPU_FOREACH(i) {
                                if (cpuid != i)
                                        pmap->pm_pcids[i].pm_gen = 0;
                        }
                        /* See the comment in pmap_invalidate_page(). */
                        atomic_thread_fence_seq_cst();
                }
                mask = &pmap->pm_active;
        }
        smp_masked_invlpg_range(*mask, sva, eva, pmap);
        sched_unpin();
}

void
pmap_invalidate_all(pmap_t pmap)
{
        cpuset_t *mask;
        struct invpcid_descr d;
        uint64_t kcr3, ucr3;
        uint32_t pcid;
        u_int cpuid, i;

        if (pmap_type_guest(pmap)) {
                pmap_invalidate_ept(pmap);
                return;
        }

        KASSERT(pmap->pm_type == PT_X86,
            ("pmap_invalidate_all: invalid type %d", pmap->pm_type));

        sched_pin();
        if (pmap == kernel_pmap) {
                if (pmap_pcid_enabled && invpcid_works) {
                        bzero(&d, sizeof(d));
                        invpcid(&d, INVPCID_CTXGLOB);
                } else {
                        invltlb_glob();
                }
                mask = &all_cpus;
        } else {
                cpuid = PCPU_GET(cpuid);
                if (pmap == PCPU_GET(curpmap)) {
                        if (pmap_pcid_enabled) {
                                critical_enter();
                                pcid = pmap->pm_pcids[cpuid].pm_pcid;
                                if (invpcid_works) {
                                        d.pcid = pcid;
                                        d.pad = 0;
                                        d.addr = 0;
                                        invpcid(&d, INVPCID_CTX);
                                        if (pmap->pm_ucr3 != PMAP_NO_CR3) {
                                                d.pcid |= PMAP_PCID_USER_PT;
                                                invpcid(&d, INVPCID_CTX);
                                        }
                                } else {
                                        kcr3 = pmap->pm_cr3 | pcid;
                                        ucr3 = pmap->pm_ucr3;
                                        if (ucr3 != PMAP_NO_CR3) {
                                                ucr3 |= pcid | PMAP_PCID_USER_PT;
                                                pmap_pti_pcid_invalidate(ucr3,
                                                    kcr3);
                                        } else {
                                                load_cr3(kcr3);
                                        }
                                }
                                critical_exit();
                        } else {
                                invltlb();
                        }
                } else if (pmap_pcid_enabled) {
                        pmap->pm_pcids[cpuid].pm_gen = 0;
                }
                if (pmap_pcid_enabled) {
                        CPU_FOREACH(i) {
                                if (cpuid != i)
                                        pmap->pm_pcids[i].pm_gen = 0;
                        }
                        /* See the comment in pmap_invalidate_page(). */
                        atomic_thread_fence_seq_cst();
                }
                mask = &pmap->pm_active;
        }
        smp_masked_invltlb(*mask, pmap);
        sched_unpin();
}

void
pmap_invalidate_cache(void)
{

        sched_pin();
        wbinvd();
        smp_cache_flush();
        sched_unpin();
}

struct pde_action {
        cpuset_t invalidate;    /* processors that invalidate their TLB */
        pmap_t pmap;
        vm_offset_t va;
        pd_entry_t *pde;
        pd_entry_t newpde;
        u_int store;            /* processor that updates the PDE */
};

static void
pmap_update_pde_action(void *arg)
{
        struct pde_action *act = arg;

        if (act->store == PCPU_GET(cpuid))
                pmap_update_pde_store(act->pmap, act->pde, act->newpde);
}

static void
pmap_update_pde_teardown(void *arg)
{
        struct pde_action *act = arg;

        if (CPU_ISSET(PCPU_GET(cpuid), &act->invalidate))
                pmap_update_pde_invalidate(act->pmap, act->va, act->newpde);
}

/*
 * Change the page size for the specified virtual address in a way that
 * prevents any possibility of the TLB ever having two entries that map the
 * same virtual address using different page sizes.  This is the recommended
 * workaround for Erratum 383 on AMD Family 10h processors.  It prevents a
 * machine check exception for a TLB state that is improperly diagnosed as a
 * hardware error.
 */
static void
pmap_update_pde(pmap_t pmap, vm_offset_t va, pd_entry_t *pde, pd_entry_t newpde)
{
        struct pde_action act;
        cpuset_t active, other_cpus;
        u_int cpuid;

        sched_pin();
        cpuid = PCPU_GET(cpuid);
        other_cpus = all_cpus;
        CPU_CLR(cpuid, &other_cpus);
        if (pmap == kernel_pmap || pmap_type_guest(pmap)) 
                active = all_cpus;
        else {
                active = pmap->pm_active;
        }
        if (CPU_OVERLAP(&active, &other_cpus)) { 
                act.store = cpuid;
                act.invalidate = active;
                act.va = va;
                act.pmap = pmap;
                act.pde = pde;
                act.newpde = newpde;
                CPU_SET(cpuid, &active);
                smp_rendezvous_cpus(active,
                    smp_no_rendezvous_barrier, pmap_update_pde_action,
                    pmap_update_pde_teardown, &act);
        } else {
                pmap_update_pde_store(pmap, pde, newpde);
                if (CPU_ISSET(cpuid, &active))
                        pmap_update_pde_invalidate(pmap, va, newpde);
        }
        sched_unpin();
}
#else /* !SMP */
/*
 * Normal, non-SMP, invalidation functions.
 */
void
pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
{
        struct invpcid_descr d;
        uint64_t kcr3, ucr3;
        uint32_t pcid;

        if (pmap->pm_type == PT_RVI || pmap->pm_type == PT_EPT) {
                pmap->pm_eptgen++;
                return;
        }
        KASSERT(pmap->pm_type == PT_X86,
            ("pmap_invalidate_range: unknown type %d", pmap->pm_type));

        if (pmap == kernel_pmap || pmap == PCPU_GET(curpmap)) {
                invlpg(va);
                if (pmap == PCPU_GET(curpmap) && pmap_pcid_enabled &&
                    pmap->pm_ucr3 != PMAP_NO_CR3) {
                        critical_enter();
                        pcid = pmap->pm_pcids[0].pm_pcid;
                        if (invpcid_works) {
                                d.pcid = pcid | PMAP_PCID_USER_PT;
                                d.pad = 0;
                                d.addr = va;
                                invpcid(&d, INVPCID_ADDR);
                        } else {
                                kcr3 = pmap->pm_cr3 | pcid | CR3_PCID_SAVE;
                                ucr3 = pmap->pm_ucr3 | pcid |
                                    PMAP_PCID_USER_PT | CR3_PCID_SAVE;
                                pmap_pti_pcid_invlpg(ucr3, kcr3, va);
                        }
                        critical_exit();
                }
        } else if (pmap_pcid_enabled)
                pmap->pm_pcids[0].pm_gen = 0;
}

void
pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        struct invpcid_descr d;
        vm_offset_t addr;
        uint64_t kcr3, ucr3;

        if (pmap->pm_type == PT_RVI || pmap->pm_type == PT_EPT) {
                pmap->pm_eptgen++;
                return;
        }
        KASSERT(pmap->pm_type == PT_X86,
            ("pmap_invalidate_range: unknown type %d", pmap->pm_type));

        if (pmap == kernel_pmap || pmap == PCPU_GET(curpmap)) {
                for (addr = sva; addr < eva; addr += PAGE_SIZE)
                        invlpg(addr);
                if (pmap == PCPU_GET(curpmap) && pmap_pcid_enabled &&
                    pmap->pm_ucr3 != PMAP_NO_CR3) {
                        critical_enter();
                        if (invpcid_works) {
                                d.pcid = pmap->pm_pcids[0].pm_pcid |
                                    PMAP_PCID_USER_PT;
                                d.pad = 0;
                                d.addr = sva;
                                for (; d.addr < eva; d.addr += PAGE_SIZE)
                                        invpcid(&d, INVPCID_ADDR);
                        } else {
                                kcr3 = pmap->pm_cr3 | pmap->pm_pcids[0].
                                    pm_pcid | CR3_PCID_SAVE;
                                ucr3 = pmap->pm_ucr3 | pmap->pm_pcids[0].
                                    pm_pcid | PMAP_PCID_USER_PT | CR3_PCID_SAVE;
                                pmap_pti_pcid_invlrng(ucr3, kcr3, sva, eva);
                        }
                        critical_exit();
                }
        } else if (pmap_pcid_enabled) {
                pmap->pm_pcids[0].pm_gen = 0;
        }
}

void
pmap_invalidate_all(pmap_t pmap)
{
        struct invpcid_descr d;
        uint64_t kcr3, ucr3;

        if (pmap->pm_type == PT_RVI || pmap->pm_type == PT_EPT) {
                pmap->pm_eptgen++;
                return;
        }
        KASSERT(pmap->pm_type == PT_X86,
            ("pmap_invalidate_all: unknown type %d", pmap->pm_type));

        if (pmap == kernel_pmap) {
                if (pmap_pcid_enabled && invpcid_works) {
                        bzero(&d, sizeof(d));
                        invpcid(&d, INVPCID_CTXGLOB);
                } else {
                        invltlb_glob();
                }
        } else if (pmap == PCPU_GET(curpmap)) {
                if (pmap_pcid_enabled) {
                        critical_enter();
                        if (invpcid_works) {
                                d.pcid = pmap->pm_pcids[0].pm_pcid;
                                d.pad = 0;
                                d.addr = 0;
                                invpcid(&d, INVPCID_CTX);
                                if (pmap->pm_ucr3 != PMAP_NO_CR3) {
                                        d.pcid |= PMAP_PCID_USER_PT;
                                        invpcid(&d, INVPCID_CTX);
                                }
                        } else {
                                kcr3 = pmap->pm_cr3 | pmap->pm_pcids[0].pm_pcid;
                                if (pmap->pm_ucr3 != PMAP_NO_CR3) {
                                        ucr3 = pmap->pm_ucr3 | pmap->pm_pcids[
                                            0].pm_pcid | PMAP_PCID_USER_PT;
                                        pmap_pti_pcid_invalidate(ucr3, kcr3);
                                } else
                                        load_cr3(kcr3);
                        }
                        critical_exit();
                } else {
                        invltlb();
                }
        } else if (pmap_pcid_enabled) {
                pmap->pm_pcids[0].pm_gen = 0;
        }
}

PMAP_INLINE void
pmap_invalidate_cache(void)
{

        wbinvd();
}

static void
pmap_update_pde(pmap_t pmap, vm_offset_t va, pd_entry_t *pde, pd_entry_t newpde)
{

        pmap_update_pde_store(pmap, pde, newpde);
        if (pmap == kernel_pmap || pmap == PCPU_GET(curpmap))
                pmap_update_pde_invalidate(pmap, va, newpde);
        else
                pmap->pm_pcids[0].pm_gen = 0;
}
#endif /* !SMP */

static void
pmap_invalidate_pde_page(pmap_t pmap, vm_offset_t va, pd_entry_t pde)
{

        /*
         * When the PDE has PG_PROMOTED set, the 2MB page mapping was created
         * by a promotion that did not invalidate the 512 4KB page mappings
         * that might exist in the TLB.  Consequently, at this point, the TLB
         * may hold both 4KB and 2MB page mappings for the address range [va,
         * va + NBPDR).  Therefore, the entire range must be invalidated here.
         * In contrast, when PG_PROMOTED is clear, the TLB will not hold any
         * 4KB page mappings for the address range [va, va + NBPDR), and so a
         * single INVLPG suffices to invalidate the 2MB page mapping from the
         * TLB.
         */
        if ((pde & PG_PROMOTED) != 0)
                pmap_invalidate_range(pmap, va, va + NBPDR - 1);
        else
                pmap_invalidate_page(pmap, va);
}

#define PMAP_CLFLUSH_THRESHOLD   (2 * 1024 * 1024)

void
pmap_invalidate_cache_range(vm_offset_t sva, vm_offset_t eva, boolean_t force)
{

        if (force) {
                sva &= ~(vm_offset_t)(cpu_clflush_line_size - 1);
        } else {
                KASSERT((sva & PAGE_MASK) == 0,
                    ("pmap_invalidate_cache_range: sva not page-aligned"));
                KASSERT((eva & PAGE_MASK) == 0,
                    ("pmap_invalidate_cache_range: eva not page-aligned"));
        }

        if ((cpu_feature & CPUID_SS) != 0 && !force)
                ; /* If "Self Snoop" is supported and allowed, do nothing. */
        else if ((cpu_stdext_feature & CPUID_STDEXT_CLFLUSHOPT) != 0 &&
            eva - sva < PMAP_CLFLUSH_THRESHOLD) {
                /*
                 * XXX: Some CPUs fault, hang, or trash the local APIC
                 * registers if we use CLFLUSH on the local APIC
                 * range.  The local APIC is always uncached, so we
                 * don't need to flush for that range anyway.
                 */
                if (pmap_kextract(sva) == lapic_paddr)
                        return;

                /*
                 * Otherwise, do per-cache line flush.  Use the sfence
                 * instruction to insure that previous stores are
                 * included in the write-back.  The processor
                 * propagates flush to other processors in the cache
                 * coherence domain.
                 */
                sfence();
                for (; sva < eva; sva += cpu_clflush_line_size)
                        clflushopt(sva);
                sfence();
        } else if ((cpu_feature & CPUID_CLFSH) != 0 &&
            eva - sva < PMAP_CLFLUSH_THRESHOLD) {
                if (pmap_kextract(sva) == lapic_paddr)
                        return;
                /*
                 * Writes are ordered by CLFLUSH on Intel CPUs.
                 */
                if (cpu_vendor_id != CPU_VENDOR_INTEL)
                        mfence();
                for (; sva < eva; sva += cpu_clflush_line_size)
                        clflush(sva);
                if (cpu_vendor_id != CPU_VENDOR_INTEL)
                        mfence();
        } else {

                /*
                 * No targeted cache flush methods are supported by CPU,
                 * or the supplied range is bigger than 2MB.
                 * Globally invalidate cache.
                 */
                pmap_invalidate_cache();
        }
}

/*
 * Remove the specified set of pages from the data and instruction caches.
 *
 * In contrast to pmap_invalidate_cache_range(), this function does not
 * rely on the CPU's self-snoop feature, because it is intended for use
 * when moving pages into a different cache domain.
 */
void
pmap_invalidate_cache_pages(vm_page_t *pages, int count)
{
        vm_offset_t daddr, eva;
        int i;
        bool useclflushopt;

        useclflushopt = (cpu_stdext_feature & CPUID_STDEXT_CLFLUSHOPT) != 0;
        if (count >= PMAP_CLFLUSH_THRESHOLD / PAGE_SIZE ||
            ((cpu_feature & CPUID_CLFSH) == 0 && !useclflushopt))
                pmap_invalidate_cache();
        else {
                if (useclflushopt)
                        sfence();
                else if (cpu_vendor_id != CPU_VENDOR_INTEL)
                        mfence();
                for (i = 0; i < count; i++) {
                        daddr = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pages[i]));
                        eva = daddr + PAGE_SIZE;
                        for (; daddr < eva; daddr += cpu_clflush_line_size) {
                                if (useclflushopt)
                                        clflushopt(daddr);
                                else
                                        clflush(daddr);
                        }
                }
                if (useclflushopt)
                        sfence();
                else if (cpu_vendor_id != CPU_VENDOR_INTEL)
                        mfence();
        }
}

/*
 *      Routine:        pmap_extract
 *      Function:
 *              Extract the physical page address associated
 *              with the given map/virtual_address pair.
 */
vm_paddr_t 
pmap_extract(pmap_t pmap, vm_offset_t va)
{
        pdp_entry_t *pdpe;
        pd_entry_t *pde;
        pt_entry_t *pte, PG_V;
        vm_paddr_t pa;

        pa = 0;
        PG_V = pmap_valid_bit(pmap);
        PMAP_LOCK(pmap);
        pdpe = pmap_pdpe(pmap, va);
        if (pdpe != NULL && (*pdpe & PG_V) != 0) {
                if ((*pdpe & PG_PS) != 0)
                        pa = (*pdpe & PG_PS_FRAME) | (va & PDPMASK);
                else {
                        pde = pmap_pdpe_to_pde(pdpe, va);
                        if ((*pde & PG_V) != 0) {
                                if ((*pde & PG_PS) != 0) {
                                        pa = (*pde & PG_PS_FRAME) |
                                            (va & PDRMASK);
                                } else {
                                        pte = pmap_pde_to_pte(pde, va);
                                        pa = (*pte & PG_FRAME) |
                                            (va & PAGE_MASK);
                                }
                        }
                }
        }
        PMAP_UNLOCK(pmap);
        return (pa);
}

/*
 *      Routine:        pmap_extract_and_hold
 *      Function:
 *              Atomically extract and hold the physical page
 *              with the given pmap and virtual address pair
 *              if that mapping permits the given protection.
 */
vm_page_t
pmap_extract_and_hold(pmap_t pmap, vm_offset_t va, vm_prot_t prot)
{
        pd_entry_t pde, *pdep;
        pt_entry_t pte, PG_RW, PG_V;
        vm_paddr_t pa;
        vm_page_t m;

        pa = 0;
        m = NULL;
        PG_RW = pmap_rw_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PMAP_LOCK(pmap);
retry:
        pdep = pmap_pde(pmap, va);
        if (pdep != NULL && (pde = *pdep)) {
                if (pde & PG_PS) {
                        if ((pde & PG_RW) || (prot & VM_PROT_WRITE) == 0) {
                                if (vm_page_pa_tryrelock(pmap, (pde &
                                    PG_PS_FRAME) | (va & PDRMASK), &pa))
                                        goto retry;
                                m = PHYS_TO_VM_PAGE(pa);
                        }
                } else {
                        pte = *pmap_pde_to_pte(pdep, va);
                        if ((pte & PG_V) &&
                            ((pte & PG_RW) || (prot & VM_PROT_WRITE) == 0)) {
                                if (vm_page_pa_tryrelock(pmap, pte & PG_FRAME,
                                    &pa))
                                        goto retry;
                                m = PHYS_TO_VM_PAGE(pa);
                        }
                }
                if (m != NULL)
                        vm_page_hold(m);
        }
        PA_UNLOCK_COND(pa);
        PMAP_UNLOCK(pmap);
        return (m);
}

vm_paddr_t
pmap_kextract(vm_offset_t va)
{
        pd_entry_t pde;
        vm_paddr_t pa;

        if (va >= DMAP_MIN_ADDRESS && va < DMAP_MAX_ADDRESS) {
                pa = DMAP_TO_PHYS(va);
        } else {
                pde = *vtopde(va);
                if (pde & PG_PS) {
                        pa = (pde & PG_PS_FRAME) | (va & PDRMASK);
                } else {
                        /*
                         * Beware of a concurrent promotion that changes the
                         * PDE at this point!  For example, vtopte() must not
                         * be used to access the PTE because it would use the
                         * new PDE.  It is, however, safe to use the old PDE
                         * because the page table page is preserved by the
                         * promotion.
                         */
                        pa = *pmap_pde_to_pte(&pde, va);
                        pa = (pa & PG_FRAME) | (va & PAGE_MASK);
                }
        }
        return (pa);
}

/***************************************************
 * Low level mapping routines.....
 ***************************************************/

/*
 * Add a wired page to the kva.
 * Note: not SMP coherent.
 */
PMAP_INLINE void 
pmap_kenter(vm_offset_t va, vm_paddr_t pa)
{
        pt_entry_t *pte;

        pte = vtopte(va);
        pte_store(pte, pa | X86_PG_RW | X86_PG_V | pg_g);
}

static __inline void
pmap_kenter_attr(vm_offset_t va, vm_paddr_t pa, int mode)
{
        pt_entry_t *pte;
        int cache_bits;

        pte = vtopte(va);
        cache_bits = pmap_cache_bits(kernel_pmap, mode, 0);
        pte_store(pte, pa | X86_PG_RW | X86_PG_V | pg_g | cache_bits);
}

/*
 * Remove a page from the kernel pagetables.
 * Note: not SMP coherent.
 */
PMAP_INLINE void
pmap_kremove(vm_offset_t va)
{
        pt_entry_t *pte;

        pte = vtopte(va);
        pte_clear(pte);
}

/*
 *      Used to map a range of physical addresses into kernel
 *      virtual address space.
 *
 *      The value passed in '*virt' is a suggested virtual address for
 *      the mapping. Architectures which can support a direct-mapped
 *      physical to virtual region can return the appropriate address
 *      within that region, leaving '*virt' unchanged. Other
 *      architectures should map the pages starting at '*virt' and
 *      update '*virt' with the first usable address after the mapped
 *      region.
 */
vm_offset_t
pmap_map(vm_offset_t *virt, vm_paddr_t start, vm_paddr_t end, int prot)
{
        return PHYS_TO_DMAP(start);
}


/*
 * Add a list of wired pages to the kva
 * this routine is only used for temporary
 * kernel mappings that do not need to have
 * page modification or references recorded.
 * Note that old mappings are simply written
 * over.  The page *must* be wired.
 * Note: SMP coherent.  Uses a ranged shootdown IPI.
 */
void
pmap_qenter(vm_offset_t sva, vm_page_t *ma, int count)
{
        pt_entry_t *endpte, oldpte, pa, *pte;
        vm_page_t m;
        int cache_bits;

        oldpte = 0;
        pte = vtopte(sva);
        endpte = pte + count;
        while (pte < endpte) {
                m = *ma++;
                cache_bits = pmap_cache_bits(kernel_pmap, m->md.pat_mode, 0);
                pa = VM_PAGE_TO_PHYS(m) | cache_bits;
                if ((*pte & (PG_FRAME | X86_PG_PTE_CACHE)) != pa) {
                        oldpte |= *pte;
                        pte_store(pte, pa | pg_g | pg_nx | X86_PG_RW | X86_PG_V);
                }
                pte++;
        }
        if (__predict_false((oldpte & X86_PG_V) != 0))
                pmap_invalidate_range(kernel_pmap, sva, sva + count *
                    PAGE_SIZE);
}

/*
 * This routine tears out page mappings from the
 * kernel -- it is meant only for temporary mappings.
 * Note: SMP coherent.  Uses a ranged shootdown IPI.
 */
void
pmap_qremove(vm_offset_t sva, int count)
{
        vm_offset_t va;

        va = sva;
        while (count-- > 0) {
                KASSERT(va >= VM_MIN_KERNEL_ADDRESS, ("usermode va %lx", va));
                pmap_kremove(va);
                va += PAGE_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
}

/***************************************************
 * Page table page management routines.....
 ***************************************************/
/*
 * Schedule the specified unused page table page to be freed.  Specifically,
 * add the page to the specified list of pages that will be released to the
 * physical memory manager after the TLB has been updated.
 */
static __inline void
pmap_add_delayed_free_list(vm_page_t m, struct spglist *free,
    boolean_t set_PG_ZERO)
{

        if (set_PG_ZERO)
                m->flags |= PG_ZERO;
        else
                m->flags &= ~PG_ZERO;
        SLIST_INSERT_HEAD(free, m, plinks.s.ss);
}
        
/*
 * Inserts the specified page table page into the specified pmap's collection
 * of idle page table pages.  Each of a pmap's page table pages is responsible
 * for mapping a distinct range of virtual addresses.  The pmap's collection is
 * ordered by this virtual address range.
 */
static __inline int
pmap_insert_pt_page(pmap_t pmap, vm_page_t mpte)
{

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        return (vm_radix_insert(&pmap->pm_root, mpte));
}

/*
 * Removes the page table page mapping the specified virtual address from the
 * specified pmap's collection of idle page table pages, and returns it.
 * Otherwise, returns NULL if there is no page table page corresponding to the
 * specified virtual address.
 */
static __inline vm_page_t
pmap_remove_pt_page(pmap_t pmap, vm_offset_t va)
{

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        return (vm_radix_remove(&pmap->pm_root, pmap_pde_pindex(va)));
}

/*
 * Decrements a page table page's wire count, which is used to record the
 * number of valid page table entries within the page.  If the wire count
 * drops to zero, then the page table page is unmapped.  Returns TRUE if the
 * page table page was unmapped and FALSE otherwise.
 */
static inline boolean_t
pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m, struct spglist *free)
{

        --m->wire_count;
        if (m->wire_count == 0) {
                _pmap_unwire_ptp(pmap, va, m, free);
                return (TRUE);
        } else
                return (FALSE);
}

static void
_pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m, struct spglist *free)
{

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        /*
         * unmap the page table page
         */
        if (m->pindex >= (NUPDE + NUPDPE)) {
                /* PDP page */
                pml4_entry_t *pml4;
                pml4 = pmap_pml4e(pmap, va);
                *pml4 = 0;
                if (pmap->pm_pml4u != NULL && va <= VM_MAXUSER_ADDRESS) {
                        pml4 = &pmap->pm_pml4u[pmap_pml4e_index(va)];
                        *pml4 = 0;
                }
        } else if (m->pindex >= NUPDE) {
                /* PD page */
                pdp_entry_t *pdp;
                pdp = pmap_pdpe(pmap, va);
                *pdp = 0;
        } else {
                /* PTE page */
                pd_entry_t *pd;
                pd = pmap_pde(pmap, va);
                *pd = 0;
        }
        pmap_resident_count_dec(pmap, 1);
        if (m->pindex < NUPDE) {
                /* We just released a PT, unhold the matching PD */
                vm_page_t pdpg;

                pdpg = PHYS_TO_VM_PAGE(*pmap_pdpe(pmap, va) & PG_FRAME);
                pmap_unwire_ptp(pmap, va, pdpg, free);
        }
        if (m->pindex >= NUPDE && m->pindex < (NUPDE + NUPDPE)) {
                /* We just released a PD, unhold the matching PDP */
                vm_page_t pdppg;

                pdppg = PHYS_TO_VM_PAGE(*pmap_pml4e(pmap, va) & PG_FRAME);
                pmap_unwire_ptp(pmap, va, pdppg, free);
        }

        /* 
         * Put page on a list so that it is released after
         * *ALL* TLB shootdown is done
         */
        pmap_add_delayed_free_list(m, free, TRUE);
}

/*
 * After removing a page table entry, this routine is used to
 * conditionally free the page, and manage the hold/wire counts.
 */
static int
pmap_unuse_pt(pmap_t pmap, vm_offset_t va, pd_entry_t ptepde,
    struct spglist *free)
{
        vm_page_t mpte;

        if (va >= VM_MAXUSER_ADDRESS)
                return (0);
        KASSERT(ptepde != 0, ("pmap_unuse_pt: ptepde != 0"));
        mpte = PHYS_TO_VM_PAGE(ptepde & PG_FRAME);
        return (pmap_unwire_ptp(pmap, va, mpte, free));
}

void
pmap_pinit0(pmap_t pmap)
{
        int i;

        PMAP_LOCK_INIT(pmap);
        pmap->pm_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(KPML4phys);
        pmap->pm_pml4u = NULL;
        pmap->pm_cr3 = KPML4phys;
        /* hack to keep pmap_pti_pcid_invalidate() alive */
        pmap->pm_ucr3 = PMAP_NO_CR3;
        pmap->pm_root.rt_root = 0;
        CPU_ZERO(&pmap->pm_active);
        TAILQ_INIT(&pmap->pm_pvchunk);
        bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
        pmap->pm_flags = pmap_flags;
        CPU_FOREACH(i) {
                pmap->pm_pcids[i].pm_pcid = PMAP_PCID_KERN + 1;
                pmap->pm_pcids[i].pm_gen = 1;
        }
        pmap_activate_boot(pmap);
}

void
pmap_pinit_pml4(vm_page_t pml4pg)
{
        pml4_entry_t *pm_pml4;
        int i;

        pm_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pml4pg));

        /* Wire in kernel global address entries. */
        for (i = 0; i < NKPML4E; i++) {
                pm_pml4[KPML4BASE + i] = (KPDPphys + ptoa(i)) | X86_PG_RW |
                    X86_PG_V;
        }
        for (i = 0; i < ndmpdpphys; i++) {
                pm_pml4[DMPML4I + i] = (DMPDPphys + ptoa(i)) | X86_PG_RW |
                    X86_PG_V;
        }

        /* install self-referential address mapping entry(s) */
        pm_pml4[PML4PML4I] = VM_PAGE_TO_PHYS(pml4pg) | X86_PG_V | X86_PG_RW |
            X86_PG_A | X86_PG_M;
}

static void
pmap_pinit_pml4_pti(vm_page_t pml4pg)
{
        pml4_entry_t *pm_pml4;
        int i;

        pm_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pml4pg));
        for (i = 0; i < NPML4EPG; i++)
                pm_pml4[i] = pti_pml4[i];
}

/*
 * Initialize a preallocated and zeroed pmap structure,
 * such as one in a vmspace structure.
 */
int
pmap_pinit_type(pmap_t pmap, enum pmap_type pm_type, int flags)
{
        vm_page_t pml4pg, pml4pgu;
        vm_paddr_t pml4phys;
        int i;

        /*
         * allocate the page directory page
         */
        pml4pg = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
            VM_ALLOC_WIRED | VM_ALLOC_ZERO | VM_ALLOC_WAITOK);

        pml4phys = VM_PAGE_TO_PHYS(pml4pg);
        pmap->pm_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(pml4phys);
        CPU_FOREACH(i) {
                pmap->pm_pcids[i].pm_pcid = PMAP_PCID_NONE;
                pmap->pm_pcids[i].pm_gen = 0;
        }
        pmap->pm_cr3 = PMAP_NO_CR3;     /* initialize to an invalid value */
        pmap->pm_ucr3 = PMAP_NO_CR3;
        pmap->pm_pml4u = NULL;

        pmap->pm_type = pm_type;
        if ((pml4pg->flags & PG_ZERO) == 0)
                pagezero(pmap->pm_pml4);

        /*
         * Do not install the host kernel mappings in the nested page
         * tables. These mappings are meaningless in the guest physical
         * address space.
         * Install minimal kernel mappings in PTI case.
         */
        if (pm_type == PT_X86) {
                pmap->pm_cr3 = pml4phys;
                pmap_pinit_pml4(pml4pg);
                if (pti) {
                        pml4pgu = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
                            VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_WAITOK);
                        pmap->pm_pml4u = (pml4_entry_t *)PHYS_TO_DMAP(
                            VM_PAGE_TO_PHYS(pml4pgu));
                        pmap_pinit_pml4_pti(pml4pgu);
                        pmap->pm_ucr3 = VM_PAGE_TO_PHYS(pml4pgu);
                }
        }

        pmap->pm_root.rt_root = 0;
        CPU_ZERO(&pmap->pm_active);
        TAILQ_INIT(&pmap->pm_pvchunk);
        bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
        pmap->pm_flags = flags;
        pmap->pm_eptgen = 0;

        return (1);
}

int
pmap_pinit(pmap_t pmap)
{

        return (pmap_pinit_type(pmap, PT_X86, pmap_flags));
}

/*
 * This routine is called if the desired page table page does not exist.
 *
 * If page table page allocation fails, this routine may sleep before
 * returning NULL.  It sleeps only if a lock pointer was given.
 *
 * Note: If a page allocation fails at page table level two or three,
 * one or two pages may be held during the wait, only to be released
 * afterwards.  This conservative approach is easily argued to avoid
 * race conditions.
 */
static vm_page_t
_pmap_allocpte(pmap_t pmap, vm_pindex_t ptepindex, struct rwlock **lockp)
{
        vm_page_t m, pdppg, pdpg;
        pt_entry_t PG_A, PG_M, PG_RW, PG_V;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        PG_A = pmap_accessed_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        /*
         * Allocate a page table page.
         */
        if ((m = vm_page_alloc(NULL, ptepindex, VM_ALLOC_NOOBJ |
            VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL) {
                if (lockp != NULL) {
                        RELEASE_PV_LIST_LOCK(lockp);
                        PMAP_UNLOCK(pmap);
                        PMAP_ASSERT_NOT_IN_DI();
                        vm_wait(NULL);
                        PMAP_LOCK(pmap);
                }

                /*
                 * Indicate the need to retry.  While waiting, the page table
                 * page may have been allocated.
                 */
                return (NULL);
        }
        if ((m->flags & PG_ZERO) == 0)
                pmap_zero_page(m);

        /*
         * Map the pagetable page into the process address space, if
         * it isn't already there.
         */

        if (ptepindex >= (NUPDE + NUPDPE)) {
                pml4_entry_t *pml4, *pml4u;
                vm_pindex_t pml4index;

                /* Wire up a new PDPE page */
                pml4index = ptepindex - (NUPDE + NUPDPE);
                pml4 = &pmap->pm_pml4[pml4index];
                *pml4 = VM_PAGE_TO_PHYS(m) | PG_U | PG_RW | PG_V | PG_A | PG_M;
                if (pmap->pm_pml4u != NULL && pml4index < NUPML4E) {
                        /*
                         * PTI: Make all user-space mappings in the
                         * kernel-mode page table no-execute so that
                         * we detect any programming errors that leave
                         * the kernel-mode page table active on return
                         * to user space.
                         */
                        if (pmap->pm_ucr3 != PMAP_NO_CR3)
                                *pml4 |= pg_nx;

                        pml4u = &pmap->pm_pml4u[pml4index];
                        *pml4u = VM_PAGE_TO_PHYS(m) | PG_U | PG_RW | PG_V |
                            PG_A | PG_M;
                }

        } else if (ptepindex >= NUPDE) {
                vm_pindex_t pml4index;
                vm_pindex_t pdpindex;
                pml4_entry_t *pml4;
                pdp_entry_t *pdp;

                /* Wire up a new PDE page */
                pdpindex = ptepindex - NUPDE;
                pml4index = pdpindex >> NPML4EPGSHIFT;

                pml4 = &pmap->pm_pml4[pml4index];
                if ((*pml4 & PG_V) == 0) {
                        /* Have to allocate a new pdp, recurse */
                        if (_pmap_allocpte(pmap, NUPDE + NUPDPE + pml4index,
                            lockp) == NULL) {
                                vm_page_unwire_noq(m);
                                vm_page_free_zero(m);
                                return (NULL);
                        }
                } else {
                        /* Add reference to pdp page */
                        pdppg = PHYS_TO_VM_PAGE(*pml4 & PG_FRAME);
                        pdppg->wire_count++;
                }
                pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & PG_FRAME);

                /* Now find the pdp page */
                pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)];
                *pdp = VM_PAGE_TO_PHYS(m) | PG_U | PG_RW | PG_V | PG_A | PG_M;

        } else {
                vm_pindex_t pml4index;
                vm_pindex_t pdpindex;
                pml4_entry_t *pml4;
                pdp_entry_t *pdp;
                pd_entry_t *pd;

                /* Wire up a new PTE page */
                pdpindex = ptepindex >> NPDPEPGSHIFT;
                pml4index = pdpindex >> NPML4EPGSHIFT;

                /* First, find the pdp and check that its valid. */
                pml4 = &pmap->pm_pml4[pml4index];
                if ((*pml4 & PG_V) == 0) {
                        /* Have to allocate a new pd, recurse */
                        if (_pmap_allocpte(pmap, NUPDE + pdpindex,
                            lockp) == NULL) {
                                vm_page_unwire_noq(m);
                                vm_page_free_zero(m);
                                return (NULL);
                        }
                        pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & PG_FRAME);
                        pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)];
                } else {
                        pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & PG_FRAME);
                        pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)];
                        if ((*pdp & PG_V) == 0) {
                                /* Have to allocate a new pd, recurse */
                                if (_pmap_allocpte(pmap, NUPDE + pdpindex,
                                    lockp) == NULL) {
                                        vm_page_unwire_noq(m);
                                        vm_page_free_zero(m);
                                        return (NULL);
                                }
                        } else {
                                /* Add reference to the pd page */
                                pdpg = PHYS_TO_VM_PAGE(*pdp & PG_FRAME);
                                pdpg->wire_count++;
                        }
                }
                pd = (pd_entry_t *)PHYS_TO_DMAP(*pdp & PG_FRAME);

                /* Now we know where the page directory page is */
                pd = &pd[ptepindex & ((1ul << NPDEPGSHIFT) - 1)];
                *pd = VM_PAGE_TO_PHYS(m) | PG_U | PG_RW | PG_V | PG_A | PG_M;
        }

        pmap_resident_count_inc(pmap, 1);

        return (m);
}

static vm_page_t
pmap_allocpde(pmap_t pmap, vm_offset_t va, struct rwlock **lockp)
{
        vm_pindex_t pdpindex, ptepindex;
        pdp_entry_t *pdpe, PG_V;
        vm_page_t pdpg;

        PG_V = pmap_valid_bit(pmap);

retry:
        pdpe = pmap_pdpe(pmap, va);
        if (pdpe != NULL && (*pdpe & PG_V) != 0) {
                /* Add a reference to the pd page. */
                pdpg = PHYS_TO_VM_PAGE(*pdpe & PG_FRAME);
                pdpg->wire_count++;
        } else {
                /* Allocate a pd page. */
                ptepindex = pmap_pde_pindex(va);
                pdpindex = ptepindex >> NPDPEPGSHIFT;
                pdpg = _pmap_allocpte(pmap, NUPDE + pdpindex, lockp);
                if (pdpg == NULL && lockp != NULL)
                        goto retry;
        }
        return (pdpg);
}

static vm_page_t
pmap_allocpte(pmap_t pmap, vm_offset_t va, struct rwlock **lockp)
{
        vm_pindex_t ptepindex;
        pd_entry_t *pd, PG_V;
        vm_page_t m;

        PG_V = pmap_valid_bit(pmap);

        /*
         * Calculate pagetable page index
         */
        ptepindex = pmap_pde_pindex(va);
retry:
        /*
         * Get the page directory entry
         */
        pd = pmap_pde(pmap, va);

        /*
         * This supports switching from a 2MB page to a
         * normal 4K page.
         */
        if (pd != NULL && (*pd & (PG_PS | PG_V)) == (PG_PS | PG_V)) {
                if (!pmap_demote_pde_locked(pmap, pd, va, lockp)) {
                        /*
                         * Invalidation of the 2MB page mapping may have caused
                         * the deallocation of the underlying PD page.
                         */
                        pd = NULL;
                }
        }

        /*
         * If the page table page is mapped, we just increment the
         * hold count, and activate it.
         */
        if (pd != NULL && (*pd & PG_V) != 0) {
                m = PHYS_TO_VM_PAGE(*pd & PG_FRAME);
                m->wire_count++;
        } else {
                /*
                 * Here if the pte page isn't mapped, or if it has been
                 * deallocated.
                 */
                m = _pmap_allocpte(pmap, ptepindex, lockp);
                if (m == NULL && lockp != NULL)
                        goto retry;
        }
        return (m);
}


/***************************************************
 * Pmap allocation/deallocation routines.
 ***************************************************/

/*
 * Release any resources held by the given physical map.
 * Called when a pmap initialized by pmap_pinit is being released.
 * Should only be called if the map contains no valid mappings.
 */
void
pmap_release(pmap_t pmap)
{
        vm_page_t m;
        int i;

        KASSERT(pmap->pm_stats.resident_count == 0,
            ("pmap_release: pmap resident count %ld != 0",
            pmap->pm_stats.resident_count));
        KASSERT(vm_radix_is_empty(&pmap->pm_root),
            ("pmap_release: pmap has reserved page table page(s)"));
        KASSERT(CPU_EMPTY(&pmap->pm_active),
            ("releasing active pmap %p", pmap));

        m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pmap->pm_pml4));

        for (i = 0; i < NKPML4E; i++)   /* KVA */
                pmap->pm_pml4[KPML4BASE + i] = 0;
        for (i = 0; i < ndmpdpphys; i++)/* Direct Map */
                pmap->pm_pml4[DMPML4I + i] = 0;
        pmap->pm_pml4[PML4PML4I] = 0;   /* Recursive Mapping */

        vm_page_unwire_noq(m);
        vm_page_free_zero(m);

        if (pmap->pm_pml4u != NULL) {
                m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pmap->pm_pml4u));
                vm_page_unwire_noq(m);
                vm_page_free(m);
        }
}

static int
kvm_size(SYSCTL_HANDLER_ARGS)
{
        unsigned long ksize = VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS;

        return sysctl_handle_long(oidp, &ksize, 0, req);
}
SYSCTL_PROC(_vm, OID_AUTO, kvm_size, CTLTYPE_LONG|CTLFLAG_RD, 
    0, 0, kvm_size, "LU", "Size of KVM");

static int
kvm_free(SYSCTL_HANDLER_ARGS)
{
        unsigned long kfree = VM_MAX_KERNEL_ADDRESS - kernel_vm_end;

        return sysctl_handle_long(oidp, &kfree, 0, req);
}
SYSCTL_PROC(_vm, OID_AUTO, kvm_free, CTLTYPE_LONG|CTLFLAG_RD, 
    0, 0, kvm_free, "LU", "Amount of KVM free");

/*
 * grow the number of kernel page table entries, if needed
 */
void
pmap_growkernel(vm_offset_t addr)
{
        vm_paddr_t paddr;
        vm_page_t nkpg;
        pd_entry_t *pde, newpdir;
        pdp_entry_t *pdpe;

        mtx_assert(&kernel_map->system_mtx, MA_OWNED);

        /*
         * Return if "addr" is within the range of kernel page table pages
         * that were preallocated during pmap bootstrap.  Moreover, leave
         * "kernel_vm_end" and the kernel page table as they were.
         *
         * The correctness of this action is based on the following
         * argument: vm_map_insert() allocates contiguous ranges of the
         * kernel virtual address space.  It calls this function if a range
         * ends after "kernel_vm_end".  If the kernel is mapped between
         * "kernel_vm_end" and "addr", then the range cannot begin at
         * "kernel_vm_end".  In fact, its beginning address cannot be less
         * than the kernel.  Thus, there is no immediate need to allocate
         * any new kernel page table pages between "kernel_vm_end" and
         * "KERNBASE".
         */
        if (KERNBASE < addr && addr <= KERNBASE + nkpt * NBPDR)
                return;

        addr = roundup2(addr, NBPDR);
        if (addr - 1 >= vm_map_max(kernel_map))
                addr = vm_map_max(kernel_map);
        while (kernel_vm_end < addr) {
                pdpe = pmap_pdpe(kernel_pmap, kernel_vm_end);
                if ((*pdpe & X86_PG_V) == 0) {
                        /* We need a new PDP entry */
                        nkpg = vm_page_alloc(NULL, kernel_vm_end >> PDPSHIFT,
                            VM_ALLOC_INTERRUPT | VM_ALLOC_NOOBJ |
                            VM_ALLOC_WIRED | VM_ALLOC_ZERO);
                        if (nkpg == NULL)
                                panic("pmap_growkernel: no memory to grow kernel");
                        if ((nkpg->flags & PG_ZERO) == 0)
                                pmap_zero_page(nkpg);
                        paddr = VM_PAGE_TO_PHYS(nkpg);
                        *pdpe = (pdp_entry_t)(paddr | X86_PG_V | X86_PG_RW |
                            X86_PG_A | X86_PG_M);
                        continue; /* try again */
                }
                pde = pmap_pdpe_to_pde(pdpe, kernel_vm_end);
                if ((*pde & X86_PG_V) != 0) {
                        kernel_vm_end = (kernel_vm_end + NBPDR) & ~PDRMASK;
                        if (kernel_vm_end - 1 >= vm_map_max(kernel_map)) {
                                kernel_vm_end = vm_map_max(kernel_map);
                                break;                       
                        }
                        continue;
                }

                nkpg = vm_page_alloc(NULL, pmap_pde_pindex(kernel_vm_end),
                    VM_ALLOC_INTERRUPT | VM_ALLOC_NOOBJ | VM_ALLOC_WIRED |
                    VM_ALLOC_ZERO);
                if (nkpg == NULL)
                        panic("pmap_growkernel: no memory to grow kernel");
                if ((nkpg->flags & PG_ZERO) == 0)
                        pmap_zero_page(nkpg);
                paddr = VM_PAGE_TO_PHYS(nkpg);
                newpdir = paddr | X86_PG_V | X86_PG_RW | X86_PG_A | X86_PG_M;
                pde_store(pde, newpdir);

                kernel_vm_end = (kernel_vm_end + NBPDR) & ~PDRMASK;
                if (kernel_vm_end - 1 >= vm_map_max(kernel_map)) {
                        kernel_vm_end = vm_map_max(kernel_map);
                        break;                       
                }
        }
}


/***************************************************
 * page management routines.
 ***************************************************/

CTASSERT(sizeof(struct pv_chunk) == PAGE_SIZE);
CTASSERT(_NPCM == 3);
CTASSERT(_NPCPV == 168);

static __inline struct pv_chunk *
pv_to_chunk(pv_entry_t pv)
{

        return ((struct pv_chunk *)((uintptr_t)pv & ~(uintptr_t)PAGE_MASK));
}

#define PV_PMAP(pv) (pv_to_chunk(pv)->pc_pmap)

#define PC_FREE0        0xfffffffffffffffful
#define PC_FREE1        0xfffffffffffffffful
#define PC_FREE2        0x000000fffffffffful

static const uint64_t pc_freemask[_NPCM] = { PC_FREE0, PC_FREE1, PC_FREE2 };

#ifdef PV_STATS
static int pc_chunk_count, pc_chunk_allocs, pc_chunk_frees, pc_chunk_tryfail;

SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_count, CTLFLAG_RD, &pc_chunk_count, 0,
        "Current number of pv entry chunks");
SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_allocs, CTLFLAG_RD, &pc_chunk_allocs, 0,
        "Current number of pv entry chunks allocated");
SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_frees, CTLFLAG_RD, &pc_chunk_frees, 0,
        "Current number of pv entry chunks frees");
SYSCTL_INT(_vm_pmap, OID_AUTO, pc_chunk_tryfail, CTLFLAG_RD, &pc_chunk_tryfail, 0,
        "Number of times tried to get a chunk page but failed.");

static long pv_entry_frees, pv_entry_allocs, pv_entry_count;
static int pv_entry_spare;

SYSCTL_LONG(_vm_pmap, OID_AUTO, pv_entry_frees, CTLFLAG_RD, &pv_entry_frees, 0,
        "Current number of pv entry frees");
SYSCTL_LONG(_vm_pmap, OID_AUTO, pv_entry_allocs, CTLFLAG_RD, &pv_entry_allocs, 0,
        "Current number of pv entry allocs");
SYSCTL_LONG(_vm_pmap, OID_AUTO, pv_entry_count, CTLFLAG_RD, &pv_entry_count, 0,
        "Current number of pv entries");
SYSCTL_INT(_vm_pmap, OID_AUTO, pv_entry_spare, CTLFLAG_RD, &pv_entry_spare, 0,
        "Current number of spare pv entries");
#endif

static void
reclaim_pv_chunk_leave_pmap(pmap_t pmap, pmap_t locked_pmap, bool start_di)
{

        if (pmap == NULL)
                return;
        pmap_invalidate_all(pmap);
        if (pmap != locked_pmap)
                PMAP_UNLOCK(pmap);
        if (start_di)
                pmap_delayed_invl_finished();
}

/*
 * We are in a serious low memory condition.  Resort to
 * drastic measures to free some pages so we can allocate
 * another pv entry chunk.
 *
 * Returns NULL if PV entries were reclaimed from the specified pmap.
 *
 * We do not, however, unmap 2mpages because subsequent accesses will
 * allocate per-page pv entries until repromotion occurs, thereby
 * exacerbating the shortage of free pv entries.
 */
static vm_page_t
reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp)
{
        struct pv_chunk *pc, *pc_marker, *pc_marker_end;
        struct pv_chunk_header pc_marker_b, pc_marker_end_b;
        struct md_page *pvh;
        pd_entry_t *pde;
        pmap_t next_pmap, pmap;
        pt_entry_t *pte, tpte;
        pt_entry_t PG_G, PG_A, PG_M, PG_RW;
        pv_entry_t pv;
        vm_offset_t va;
        vm_page_t m, m_pc;
        struct spglist free;
        uint64_t inuse;
        int bit, field, freed;
        bool start_di;
        static int active_reclaims = 0;

        PMAP_LOCK_ASSERT(locked_pmap, MA_OWNED);
        KASSERT(lockp != NULL, ("reclaim_pv_chunk: lockp is NULL"));
        pmap = NULL;
        m_pc = NULL;
        PG_G = PG_A = PG_M = PG_RW = 0;
        SLIST_INIT(&free);
        bzero(&pc_marker_b, sizeof(pc_marker_b));
        bzero(&pc_marker_end_b, sizeof(pc_marker_end_b));
        pc_marker = (struct pv_chunk *)&pc_marker_b;
        pc_marker_end = (struct pv_chunk *)&pc_marker_end_b;

        /*
         * A delayed invalidation block should already be active if
         * pmap_advise() or pmap_remove() called this function by way
         * of pmap_demote_pde_locked().
         */
        start_di = pmap_not_in_di();

        mtx_lock(&pv_chunks_mutex);
        active_reclaims++;
        TAILQ_INSERT_HEAD(&pv_chunks, pc_marker, pc_lru);
        TAILQ_INSERT_TAIL(&pv_chunks, pc_marker_end, pc_lru);
        while ((pc = TAILQ_NEXT(pc_marker, pc_lru)) != pc_marker_end &&
            SLIST_EMPTY(&free)) {
                next_pmap = pc->pc_pmap;
                if (next_pmap == NULL) {
                        /*
                         * The next chunk is a marker.  However, it is
                         * not our marker, so active_reclaims must be
                         * > 1.  Consequently, the next_chunk code
                         * will not rotate the pv_chunks list.
                         */
                        goto next_chunk;
                }
                mtx_unlock(&pv_chunks_mutex);

                /*
                 * A pv_chunk can only be removed from the pc_lru list
                 * when both pc_chunks_mutex is owned and the
                 * corresponding pmap is locked.
                 */
                if (pmap != next_pmap) {
                        reclaim_pv_chunk_leave_pmap(pmap, locked_pmap,
                            start_di);
                        pmap = next_pmap;
                        /* Avoid deadlock and lock recursion. */
                        if (pmap > locked_pmap) {
                                RELEASE_PV_LIST_LOCK(lockp);
                                PMAP_LOCK(pmap);
                                if (start_di)
                                        pmap_delayed_invl_started();
                                mtx_lock(&pv_chunks_mutex);
                                continue;
                        } else if (pmap != locked_pmap) {
                                if (PMAP_TRYLOCK(pmap)) {
                                        if (start_di)
                                                pmap_delayed_invl_started();
                                        mtx_lock(&pv_chunks_mutex);
                                        continue;
                                } else {
                                        pmap = NULL; /* pmap is not locked */
                                        mtx_lock(&pv_chunks_mutex);
                                        pc = TAILQ_NEXT(pc_marker, pc_lru);
                                        if (pc == NULL ||
                                            pc->pc_pmap != next_pmap)
                                                continue;
                                        goto next_chunk;
                                }
                        } else if (start_di)
                                pmap_delayed_invl_started();
                        PG_G = pmap_global_bit(pmap);
                        PG_A = pmap_accessed_bit(pmap);
                        PG_M = pmap_modified_bit(pmap);
                        PG_RW = pmap_rw_bit(pmap);
                }

                /*
                 * Destroy every non-wired, 4 KB page mapping in the chunk.
                 */
                freed = 0;
                for (field = 0; field < _NPCM; field++) {
                        for (inuse = ~pc->pc_map[field] & pc_freemask[field];
                            inuse != 0; inuse &= ~(1UL << bit)) {
                                bit = bsfq(inuse);
                                pv = &pc->pc_pventry[field * 64 + bit];
                                va = pv->pv_va;
                                pde = pmap_pde(pmap, va);
                                if ((*pde & PG_PS) != 0)
                                        continue;
                                pte = pmap_pde_to_pte(pde, va);
                                if ((*pte & PG_W) != 0)
                                        continue;
                                tpte = pte_load_clear(pte);
                                if ((tpte & PG_G) != 0)
                                        pmap_invalidate_page(pmap, va);
                                m = PHYS_TO_VM_PAGE(tpte & PG_FRAME);
                                if ((tpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                                        vm_page_dirty(m);
                                if ((tpte & PG_A) != 0)
                                        vm_page_aflag_set(m, PGA_REFERENCED);
                                CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m);
                                TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                                m->md.pv_gen++;
                                if (TAILQ_EMPTY(&m->md.pv_list) &&
                                    (m->flags & PG_FICTITIOUS) == 0) {
                                        pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                                        if (TAILQ_EMPTY(&pvh->pv_list)) {
                                                vm_page_aflag_clear(m,
                                                    PGA_WRITEABLE);
                                        }
                                }
                                pmap_delayed_invl_page(m);
                                pc->pc_map[field] |= 1UL << bit;
                                pmap_unuse_pt(pmap, va, *pde, &free);
                                freed++;
                        }
                }
                if (freed == 0) {
                        mtx_lock(&pv_chunks_mutex);
                        goto next_chunk;
                }
                /* Every freed mapping is for a 4 KB page. */
                pmap_resident_count_dec(pmap, freed);
                PV_STAT(atomic_add_long(&pv_entry_frees, freed));
                PV_STAT(atomic_add_int(&pv_entry_spare, freed));
                PV_STAT(atomic_subtract_long(&pv_entry_count, freed));
                TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                if (pc->pc_map[0] == PC_FREE0 && pc->pc_map[1] == PC_FREE1 &&
                    pc->pc_map[2] == PC_FREE2) {
                        PV_STAT(atomic_subtract_int(&pv_entry_spare, _NPCPV));
                        PV_STAT(atomic_subtract_int(&pc_chunk_count, 1));
                        PV_STAT(atomic_add_int(&pc_chunk_frees, 1));
                        /* Entire chunk is free; return it. */
                        m_pc = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pc));
                        dump_drop_page(m_pc->phys_addr);
                        mtx_lock(&pv_chunks_mutex);
                        TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
                        break;
                }
                TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
                mtx_lock(&pv_chunks_mutex);
                /* One freed pv entry in locked_pmap is sufficient. */
                if (pmap == locked_pmap)
                        break;
next_chunk:
                TAILQ_REMOVE(&pv_chunks, pc_marker, pc_lru);
                TAILQ_INSERT_AFTER(&pv_chunks, pc, pc_marker, pc_lru);
                if (active_reclaims == 1 && pmap != NULL) {
                        /*
                         * Rotate the pv chunks list so that we do not
                         * scan the same pv chunks that could not be
                         * freed (because they contained a wired
                         * and/or superpage mapping) on every
                         * invocation of reclaim_pv_chunk().
                         */
                        while ((pc = TAILQ_FIRST(&pv_chunks)) != pc_marker) {
                                MPASS(pc->pc_pmap != NULL);
                                TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
                                TAILQ_INSERT_TAIL(&pv_chunks, pc, pc_lru);
                        }
                }
        }
        TAILQ_REMOVE(&pv_chunks, pc_marker, pc_lru);
        TAILQ_REMOVE(&pv_chunks, pc_marker_end, pc_lru);
        active_reclaims--;
        mtx_unlock(&pv_chunks_mutex);
        reclaim_pv_chunk_leave_pmap(pmap, locked_pmap, start_di);
        if (m_pc == NULL && !SLIST_EMPTY(&free)) {
                m_pc = SLIST_FIRST(&free);
                SLIST_REMOVE_HEAD(&free, plinks.s.ss);
                /* Recycle a freed page table page. */
                m_pc->wire_count = 1;
        }
        vm_page_free_pages_toq(&free, true);
        return (m_pc);
}

/*
 * free the pv_entry back to the free list
 */
static void
free_pv_entry(pmap_t pmap, pv_entry_t pv)
{
        struct pv_chunk *pc;
        int idx, field, bit;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PV_STAT(atomic_add_long(&pv_entry_frees, 1));
        PV_STAT(atomic_add_int(&pv_entry_spare, 1));
        PV_STAT(atomic_subtract_long(&pv_entry_count, 1));
        pc = pv_to_chunk(pv);
        idx = pv - &pc->pc_pventry[0];
        field = idx / 64;
        bit = idx % 64;
        pc->pc_map[field] |= 1ul << bit;
        if (pc->pc_map[0] != PC_FREE0 || pc->pc_map[1] != PC_FREE1 ||
            pc->pc_map[2] != PC_FREE2) {
                /* 98% of the time, pc is already at the head of the list. */
                if (__predict_false(pc != TAILQ_FIRST(&pmap->pm_pvchunk))) {
                        TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                        TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
                }
                return;
        }
        TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
        free_pv_chunk(pc);
}

static void
free_pv_chunk(struct pv_chunk *pc)
{
        vm_page_t m;

        mtx_lock(&pv_chunks_mutex);
        TAILQ_REMOVE(&pv_chunks, pc, pc_lru);
        mtx_unlock(&pv_chunks_mutex);
        PV_STAT(atomic_subtract_int(&pv_entry_spare, _NPCPV));
        PV_STAT(atomic_subtract_int(&pc_chunk_count, 1));
        PV_STAT(atomic_add_int(&pc_chunk_frees, 1));
        /* entire chunk is free, return it */
        m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((vm_offset_t)pc));
        dump_drop_page(m->phys_addr);
        vm_page_unwire(m, PQ_NONE);
        vm_page_free(m);
}

/*
 * Returns a new PV entry, allocating a new PV chunk from the system when
 * needed.  If this PV chunk allocation fails and a PV list lock pointer was
 * given, a PV chunk is reclaimed from an arbitrary pmap.  Otherwise, NULL is
 * returned.
 *
 * The given PV list lock may be released.
 */
static pv_entry_t
get_pv_entry(pmap_t pmap, struct rwlock **lockp)
{
        int bit, field;
        pv_entry_t pv;
        struct pv_chunk *pc;
        vm_page_t m;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PV_STAT(atomic_add_long(&pv_entry_allocs, 1));
retry:
        pc = TAILQ_FIRST(&pmap->pm_pvchunk);
        if (pc != NULL) {
                for (field = 0; field < _NPCM; field++) {
                        if (pc->pc_map[field]) {
                                bit = bsfq(pc->pc_map[field]);
                                break;
                        }
                }
                if (field < _NPCM) {
                        pv = &pc->pc_pventry[field * 64 + bit];
                        pc->pc_map[field] &= ~(1ul << bit);
                        /* If this was the last item, move it to tail */
                        if (pc->pc_map[0] == 0 && pc->pc_map[1] == 0 &&
                            pc->pc_map[2] == 0) {
                                TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                                TAILQ_INSERT_TAIL(&pmap->pm_pvchunk, pc,
                                    pc_list);
                        }
                        PV_STAT(atomic_add_long(&pv_entry_count, 1));
                        PV_STAT(atomic_subtract_int(&pv_entry_spare, 1));
                        return (pv);
                }
        }
        /* No free items, allocate another chunk */
        m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
            VM_ALLOC_WIRED);
        if (m == NULL) {
                if (lockp == NULL) {
                        PV_STAT(pc_chunk_tryfail++);
                        return (NULL);
                }
                m = reclaim_pv_chunk(pmap, lockp);
                if (m == NULL)
                        goto retry;
        }
        PV_STAT(atomic_add_int(&pc_chunk_count, 1));
        PV_STAT(atomic_add_int(&pc_chunk_allocs, 1));
        dump_add_page(m->phys_addr);
        pc = (void *)PHYS_TO_DMAP(m->phys_addr);
        pc->pc_pmap = pmap;
        pc->pc_map[0] = PC_FREE0 & ~1ul;        /* preallocated bit 0 */
        pc->pc_map[1] = PC_FREE1;
        pc->pc_map[2] = PC_FREE2;
        mtx_lock(&pv_chunks_mutex);
        TAILQ_INSERT_TAIL(&pv_chunks, pc, pc_lru);
        mtx_unlock(&pv_chunks_mutex);
        pv = &pc->pc_pventry[0];
        TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
        PV_STAT(atomic_add_long(&pv_entry_count, 1));
        PV_STAT(atomic_add_int(&pv_entry_spare, _NPCPV - 1));
        return (pv);
}

/*
 * Returns the number of one bits within the given PV chunk map.
 *
 * The erratas for Intel processors state that "POPCNT Instruction May
 * Take Longer to Execute Than Expected".  It is believed that the
 * issue is the spurious dependency on the destination register.
 * Provide a hint to the register rename logic that the destination
 * value is overwritten, by clearing it, as suggested in the
 * optimization manual.  It should be cheap for unaffected processors
 * as well.
 *
 * Reference numbers for erratas are
 * 4th Gen Core: HSD146
 * 5th Gen Core: BDM85
 * 6th Gen Core: SKL029
 */
static int
popcnt_pc_map_pq(uint64_t *map)
{
        u_long result, tmp;

        __asm __volatile("xorl %k0,%k0;popcntq %2,%0;"
            "xorl %k1,%k1;popcntq %3,%1;addl %k1,%k0;"
            "xorl %k1,%k1;popcntq %4,%1;addl %k1,%k0"
            : "=&r" (result), "=&r" (tmp)
            : "m" (map[0]), "m" (map[1]), "m" (map[2]));
        return (result);
}

/*
 * Ensure that the number of spare PV entries in the specified pmap meets or
 * exceeds the given count, "needed".
 *
 * The given PV list lock may be released.
 */
static void
reserve_pv_entries(pmap_t pmap, int needed, struct rwlock **lockp)
{
        struct pch new_tail;
        struct pv_chunk *pc;
        vm_page_t m;
        int avail, free;
        bool reclaimed;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT(lockp != NULL, ("reserve_pv_entries: lockp is NULL"));

        /*
         * Newly allocated PV chunks must be stored in a private list until
         * the required number of PV chunks have been allocated.  Otherwise,
         * reclaim_pv_chunk() could recycle one of these chunks.  In
         * contrast, these chunks must be added to the pmap upon allocation.
         */
        TAILQ_INIT(&new_tail);
retry:
        avail = 0;
        TAILQ_FOREACH(pc, &pmap->pm_pvchunk, pc_list) {
#ifndef __POPCNT__
                if ((cpu_feature2 & CPUID2_POPCNT) == 0)
                        bit_count((bitstr_t *)pc->pc_map, 0,
                            sizeof(pc->pc_map) * NBBY, &free);
                else
#endif
                free = popcnt_pc_map_pq(pc->pc_map);
                if (free == 0)
                        break;
                avail += free;
                if (avail >= needed)
                        break;
        }
        for (reclaimed = false; avail < needed; avail += _NPCPV) {
                m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ |
                    VM_ALLOC_WIRED);
                if (m == NULL) {
                        m = reclaim_pv_chunk(pmap, lockp);
                        if (m == NULL)
                                goto retry;
                        reclaimed = true;
                }
                PV_STAT(atomic_add_int(&pc_chunk_count, 1));
                PV_STAT(atomic_add_int(&pc_chunk_allocs, 1));
                dump_add_page(m->phys_addr);
                pc = (void *)PHYS_TO_DMAP(m->phys_addr);
                pc->pc_pmap = pmap;
                pc->pc_map[0] = PC_FREE0;
                pc->pc_map[1] = PC_FREE1;
                pc->pc_map[2] = PC_FREE2;
                TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
                TAILQ_INSERT_TAIL(&new_tail, pc, pc_lru);
                PV_STAT(atomic_add_int(&pv_entry_spare, _NPCPV));

                /*
                 * The reclaim might have freed a chunk from the current pmap.
                 * If that chunk contained available entries, we need to
                 * re-count the number of available entries.
                 */
                if (reclaimed)
                        goto retry;
        }
        if (!TAILQ_EMPTY(&new_tail)) {
                mtx_lock(&pv_chunks_mutex);
                TAILQ_CONCAT(&pv_chunks, &new_tail, pc_lru);
                mtx_unlock(&pv_chunks_mutex);
        }
}

/*
 * First find and then remove the pv entry for the specified pmap and virtual
 * address from the specified pv list.  Returns the pv entry if found and NULL
 * otherwise.  This operation can be performed on pv lists for either 4KB or
 * 2MB page mappings.
 */
static __inline pv_entry_t
pmap_pvh_remove(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
{
        pv_entry_t pv;

        TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                if (pmap == PV_PMAP(pv) && va == pv->pv_va) {
                        TAILQ_REMOVE(&pvh->pv_list, pv, pv_next);
                        pvh->pv_gen++;
                        break;
                }
        }
        return (pv);
}

/*
 * After demotion from a 2MB page mapping to 512 4KB page mappings,
 * destroy the pv entry for the 2MB page mapping and reinstantiate the pv
 * entries for each of the 4KB page mappings.
 */
static void
pmap_pv_demote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa,
    struct rwlock **lockp)
{
        struct md_page *pvh;
        struct pv_chunk *pc;
        pv_entry_t pv;
        vm_offset_t va_last;
        vm_page_t m;
        int bit, field;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT((pa & PDRMASK) == 0,
            ("pmap_pv_demote_pde: pa is not 2mpage aligned"));
        CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa);

        /*
         * Transfer the 2mpage's pv entry for this mapping to the first
         * page's pv list.  Once this transfer begins, the pv list lock
         * must not be released until the last pv entry is reinstantiated.
         */
        pvh = pa_to_pvh(pa);
        va = trunc_2mpage(va);
        pv = pmap_pvh_remove(pvh, pmap, va);
        KASSERT(pv != NULL, ("pmap_pv_demote_pde: pv not found"));
        m = PHYS_TO_VM_PAGE(pa);
        TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
        m->md.pv_gen++;
        /* Instantiate the remaining NPTEPG - 1 pv entries. */
        PV_STAT(atomic_add_long(&pv_entry_allocs, NPTEPG - 1));
        va_last = va + NBPDR - PAGE_SIZE;
        for (;;) {
                pc = TAILQ_FIRST(&pmap->pm_pvchunk);
                KASSERT(pc->pc_map[0] != 0 || pc->pc_map[1] != 0 ||
                    pc->pc_map[2] != 0, ("pmap_pv_demote_pde: missing spare"));
                for (field = 0; field < _NPCM; field++) {
                        while (pc->pc_map[field]) {
                                bit = bsfq(pc->pc_map[field]);
                                pc->pc_map[field] &= ~(1ul << bit);
                                pv = &pc->pc_pventry[field * 64 + bit];
                                va += PAGE_SIZE;
                                pv->pv_va = va;
                                m++;
                                KASSERT((m->oflags & VPO_UNMANAGED) == 0,
                            ("pmap_pv_demote_pde: page %p is not managed", m));
                                TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                                m->md.pv_gen++;
                                if (va == va_last)
                                        goto out;
                        }
                }
                TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                TAILQ_INSERT_TAIL(&pmap->pm_pvchunk, pc, pc_list);
        }
out:
        if (pc->pc_map[0] == 0 && pc->pc_map[1] == 0 && pc->pc_map[2] == 0) {
                TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                TAILQ_INSERT_TAIL(&pmap->pm_pvchunk, pc, pc_list);
        }
        PV_STAT(atomic_add_long(&pv_entry_count, NPTEPG - 1));
        PV_STAT(atomic_subtract_int(&pv_entry_spare, NPTEPG - 1));
}

#if VM_NRESERVLEVEL > 0
/*
 * After promotion from 512 4KB page mappings to a single 2MB page mapping,
 * replace the many pv entries for the 4KB page mappings by a single pv entry
 * for the 2MB page mapping.
 */
static void
pmap_pv_promote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa,
    struct rwlock **lockp)
{
        struct md_page *pvh;
        pv_entry_t pv;
        vm_offset_t va_last;
        vm_page_t m;

        KASSERT((pa & PDRMASK) == 0,
            ("pmap_pv_promote_pde: pa is not 2mpage aligned"));
        CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa);

        /*
         * Transfer the first page's pv entry for this mapping to the 2mpage's
         * pv list.  Aside from avoiding the cost of a call to get_pv_entry(),
         * a transfer avoids the possibility that get_pv_entry() calls
         * reclaim_pv_chunk() and that reclaim_pv_chunk() removes one of the
         * mappings that is being promoted.
         */
        m = PHYS_TO_VM_PAGE(pa);
        va = trunc_2mpage(va);
        pv = pmap_pvh_remove(&m->md, pmap, va);
        KASSERT(pv != NULL, ("pmap_pv_promote_pde: pv not found"));
        pvh = pa_to_pvh(pa);
        TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_next);
        pvh->pv_gen++;
        /* Free the remaining NPTEPG - 1 pv entries. */
        va_last = va + NBPDR - PAGE_SIZE;
        do {
                m++;
                va += PAGE_SIZE;
                pmap_pvh_free(&m->md, pmap, va);
        } while (va < va_last);
}
#endif /* VM_NRESERVLEVEL > 0 */

/*
 * First find and then destroy the pv entry for the specified pmap and virtual
 * address.  This operation can be performed on pv lists for either 4KB or 2MB
 * page mappings.
 */
static void
pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
{
        pv_entry_t pv;

        pv = pmap_pvh_remove(pvh, pmap, va);
        KASSERT(pv != NULL, ("pmap_pvh_free: pv not found"));
        free_pv_entry(pmap, pv);
}

/*
 * Conditionally create the PV entry for a 4KB page mapping if the required
 * memory can be allocated without resorting to reclamation.
 */
static boolean_t
pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va, vm_page_t m,
    struct rwlock **lockp)
{
        pv_entry_t pv;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        /* Pass NULL instead of the lock pointer to disable reclamation. */
        if ((pv = get_pv_entry(pmap, NULL)) != NULL) {
                pv->pv_va = va;
                CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m);
                TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                m->md.pv_gen++;
                return (TRUE);
        } else
                return (FALSE);
}

/*
 * Create the PV entry for a 2MB page mapping.  Always returns true unless the
 * flag PMAP_ENTER_NORECLAIM is specified.  If that flag is specified, returns
 * false if the PV entry cannot be allocated without resorting to reclamation.
 */
static bool
pmap_pv_insert_pde(pmap_t pmap, vm_offset_t va, pd_entry_t pde, u_int flags,
    struct rwlock **lockp)
{
        struct md_page *pvh;
        pv_entry_t pv;
        vm_paddr_t pa;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        /* Pass NULL instead of the lock pointer to disable reclamation. */
        if ((pv = get_pv_entry(pmap, (flags & PMAP_ENTER_NORECLAIM) != 0 ?
            NULL : lockp)) == NULL)
                return (false);
        pv->pv_va = va;
        pa = pde & PG_PS_FRAME;
        CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, pa);
        pvh = pa_to_pvh(pa);
        TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_next);
        pvh->pv_gen++;
        return (true);
}

/*
 * Fills a page table page with mappings to consecutive physical pages.
 */
static void
pmap_fill_ptp(pt_entry_t *firstpte, pt_entry_t newpte)
{
        pt_entry_t *pte;

        for (pte = firstpte; pte < firstpte + NPTEPG; pte++) {
                *pte = newpte;
                newpte += PAGE_SIZE;
        }
}

/*
 * Tries to demote a 2MB page mapping.  If demotion fails, the 2MB page
 * mapping is invalidated.
 */
static boolean_t
pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
{
        struct rwlock *lock;
        boolean_t rv;

        lock = NULL;
        rv = pmap_demote_pde_locked(pmap, pde, va, &lock);
        if (lock != NULL)
                rw_wunlock(lock);
        return (rv);
}

static boolean_t
pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde, vm_offset_t va,
    struct rwlock **lockp)
{
        pd_entry_t newpde, oldpde;
        pt_entry_t *firstpte, newpte;
        pt_entry_t PG_A, PG_G, PG_M, PG_RW, PG_V;
        vm_paddr_t mptepa;
        vm_page_t mpte;
        struct spglist free;
        vm_offset_t sva;
        int PG_PTE_CACHE;

        PG_G = pmap_global_bit(pmap);
        PG_A = pmap_accessed_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_PTE_CACHE = pmap_cache_mask(pmap, 0);

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        oldpde = *pde;
        KASSERT((oldpde & (PG_PS | PG_V)) == (PG_PS | PG_V),
            ("pmap_demote_pde: oldpde is missing PG_PS and/or PG_V"));
        if ((oldpde & PG_A) == 0 || (mpte = pmap_remove_pt_page(pmap, va)) ==
            NULL) {
                KASSERT((oldpde & PG_W) == 0,
                    ("pmap_demote_pde: page table page for a wired mapping"
                    " is missing"));

                /*
                 * Invalidate the 2MB page mapping and return "failure" if the
                 * mapping was never accessed or the allocation of the new
                 * page table page fails.  If the 2MB page mapping belongs to
                 * the direct map region of the kernel's address space, then
                 * the page allocation request specifies the highest possible
                 * priority (VM_ALLOC_INTERRUPT).  Otherwise, the priority is
                 * normal.  Page table pages are preallocated for every other
                 * part of the kernel address space, so the direct map region
                 * is the only part of the kernel address space that must be
                 * handled here.
                 */
                if ((oldpde & PG_A) == 0 || (mpte = vm_page_alloc(NULL,
                    pmap_pde_pindex(va), (va >= DMAP_MIN_ADDRESS && va <
                    DMAP_MAX_ADDRESS ? VM_ALLOC_INTERRUPT : VM_ALLOC_NORMAL) |
                    VM_ALLOC_NOOBJ | VM_ALLOC_WIRED)) == NULL) {
                        SLIST_INIT(&free);
                        sva = trunc_2mpage(va);
                        pmap_remove_pde(pmap, pde, sva, &free, lockp);
                        if ((oldpde & PG_G) == 0)
                                pmap_invalidate_pde_page(pmap, sva, oldpde);
                        vm_page_free_pages_toq(&free, true);
                        CTR2(KTR_PMAP, "pmap_demote_pde: failure for va %#lx"
                            " in pmap %p", va, pmap);
                        return (FALSE);
                }
                if (va < VM_MAXUSER_ADDRESS)
                        pmap_resident_count_inc(pmap, 1);
        }
        mptepa = VM_PAGE_TO_PHYS(mpte);
        firstpte = (pt_entry_t *)PHYS_TO_DMAP(mptepa);
        newpde = mptepa | PG_M | PG_A | (oldpde & PG_U) | PG_RW | PG_V;
        KASSERT((oldpde & PG_A) != 0,
            ("pmap_demote_pde: oldpde is missing PG_A"));
        KASSERT((oldpde & (PG_M | PG_RW)) != PG_RW,
            ("pmap_demote_pde: oldpde is missing PG_M"));
        newpte = oldpde & ~PG_PS;
        newpte = pmap_swap_pat(pmap, newpte);

        /*
         * If the page table page is new, initialize it.
         */
        if (mpte->wire_count == 1) {
                mpte->wire_count = NPTEPG;
                pmap_fill_ptp(firstpte, newpte);
        }
        KASSERT((*firstpte & PG_FRAME) == (newpte & PG_FRAME),
            ("pmap_demote_pde: firstpte and newpte map different physical"
            " addresses"));

        /*
         * If the mapping has changed attributes, update the page table
         * entries.
         */
        if ((*firstpte & PG_PTE_PROMOTE) != (newpte & PG_PTE_PROMOTE))
                pmap_fill_ptp(firstpte, newpte);

        /*
         * The spare PV entries must be reserved prior to demoting the
         * mapping, that is, prior to changing the PDE.  Otherwise, the state
         * of the PDE and the PV lists will be inconsistent, which can result
         * in reclaim_pv_chunk() attempting to remove a PV entry from the
         * wrong PV list and pmap_pv_demote_pde() failing to find the expected
         * PV entry for the 2MB page mapping that is being demoted.
         */
        if ((oldpde & PG_MANAGED) != 0)
                reserve_pv_entries(pmap, NPTEPG - 1, lockp);

        /*
         * Demote the mapping.  This pmap is locked.  The old PDE has
         * PG_A set.  If the old PDE has PG_RW set, it also has PG_M
         * set.  Thus, there is no danger of a race with another
         * processor changing the setting of PG_A and/or PG_M between
         * the read above and the store below. 
         */
        if (workaround_erratum383)
                pmap_update_pde(pmap, va, pde, newpde);
        else
                pde_store(pde, newpde);

        /*
         * Invalidate a stale recursive mapping of the page table page.
         */
        if (va >= VM_MAXUSER_ADDRESS)
                pmap_invalidate_page(pmap, (vm_offset_t)vtopte(va));

        /*
         * Demote the PV entry.
         */
        if ((oldpde & PG_MANAGED) != 0)
                pmap_pv_demote_pde(pmap, va, oldpde & PG_PS_FRAME, lockp);

        atomic_add_long(&pmap_pde_demotions, 1);
        CTR2(KTR_PMAP, "pmap_demote_pde: success for va %#lx"
            " in pmap %p", va, pmap);
        return (TRUE);
}

/*
 * pmap_remove_kernel_pde: Remove a kernel superpage mapping.
 */
static void
pmap_remove_kernel_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
{
        pd_entry_t newpde;
        vm_paddr_t mptepa;
        vm_page_t mpte;

        KASSERT(pmap == kernel_pmap, ("pmap %p is not kernel_pmap", pmap));
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        mpte = pmap_remove_pt_page(pmap, va);
        if (mpte == NULL)
                panic("pmap_remove_kernel_pde: Missing pt page.");

        mptepa = VM_PAGE_TO_PHYS(mpte);
        newpde = mptepa | X86_PG_M | X86_PG_A | X86_PG_RW | X86_PG_V;

        /*
         * Initialize the page table page.
         */
        pagezero((void *)PHYS_TO_DMAP(mptepa));

        /*
         * Demote the mapping.
         */
        if (workaround_erratum383)
                pmap_update_pde(pmap, va, pde, newpde);
        else
                pde_store(pde, newpde);

        /*
         * Invalidate a stale recursive mapping of the page table page.
         */
        pmap_invalidate_page(pmap, (vm_offset_t)vtopte(va));
}

/*
 * pmap_remove_pde: do the things to unmap a superpage in a process
 */
static int
pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
    struct spglist *free, struct rwlock **lockp)
{
        struct md_page *pvh;
        pd_entry_t oldpde;
        vm_offset_t eva, va;
        vm_page_t m, mpte;
        pt_entry_t PG_G, PG_A, PG_M, PG_RW;

        PG_G = pmap_global_bit(pmap);
        PG_A = pmap_accessed_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT((sva & PDRMASK) == 0,
            ("pmap_remove_pde: sva is not 2mpage aligned"));
        oldpde = pte_load_clear(pdq);
        if (oldpde & PG_W)
                pmap->pm_stats.wired_count -= NBPDR / PAGE_SIZE;
        if ((oldpde & PG_G) != 0)
                pmap_invalidate_pde_page(kernel_pmap, sva, oldpde);
        pmap_resident_count_dec(pmap, NBPDR / PAGE_SIZE);
        if (oldpde & PG_MANAGED) {
                CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, oldpde & PG_PS_FRAME);
                pvh = pa_to_pvh(oldpde & PG_PS_FRAME);
                pmap_pvh_free(pvh, pmap, sva);
                eva = sva + NBPDR;
                for (va = sva, m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
                    va < eva; va += PAGE_SIZE, m++) {
                        if ((oldpde & (PG_M | PG_RW)) == (PG_M | PG_RW))
                                vm_page_dirty(m);
                        if (oldpde & PG_A)
                                vm_page_aflag_set(m, PGA_REFERENCED);
                        if (TAILQ_EMPTY(&m->md.pv_list) &&
                            TAILQ_EMPTY(&pvh->pv_list))
                                vm_page_aflag_clear(m, PGA_WRITEABLE);
                        pmap_delayed_invl_page(m);
                }
        }
        if (pmap == kernel_pmap) {
                pmap_remove_kernel_pde(pmap, pdq, sva);
        } else {
                mpte = pmap_remove_pt_page(pmap, sva);
                if (mpte != NULL) {
                        pmap_resident_count_dec(pmap, 1);
                        KASSERT(mpte->wire_count == NPTEPG,
                            ("pmap_remove_pde: pte page wire count error"));
                        mpte->wire_count = 0;
                        pmap_add_delayed_free_list(mpte, free, FALSE);
                }
        }
        return (pmap_unuse_pt(pmap, sva, *pmap_pdpe(pmap, sva), free));
}

/*
 * pmap_remove_pte: do the things to unmap a page in a process
 */
static int
pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t va, 
    pd_entry_t ptepde, struct spglist *free, struct rwlock **lockp)
{
        struct md_page *pvh;
        pt_entry_t oldpte, PG_A, PG_M, PG_RW;
        vm_page_t m;

        PG_A = pmap_accessed_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        oldpte = pte_load_clear(ptq);
        if (oldpte & PG_W)
                pmap->pm_stats.wired_count -= 1;
        pmap_resident_count_dec(pmap, 1);
        if (oldpte & PG_MANAGED) {
                m = PHYS_TO_VM_PAGE(oldpte & PG_FRAME);
                if ((oldpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                        vm_page_dirty(m);
                if (oldpte & PG_A)
                        vm_page_aflag_set(m, PGA_REFERENCED);
                CHANGE_PV_LIST_LOCK_TO_VM_PAGE(lockp, m);
                pmap_pvh_free(&m->md, pmap, va);
                if (TAILQ_EMPTY(&m->md.pv_list) &&
                    (m->flags & PG_FICTITIOUS) == 0) {
                        pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                        if (TAILQ_EMPTY(&pvh->pv_list))
                                vm_page_aflag_clear(m, PGA_WRITEABLE);
                }
                pmap_delayed_invl_page(m);
        }
        return (pmap_unuse_pt(pmap, va, ptepde, free));
}

/*
 * Remove a single page from a process address space
 */
static void
pmap_remove_page(pmap_t pmap, vm_offset_t va, pd_entry_t *pde,
    struct spglist *free)
{
        struct rwlock *lock;
        pt_entry_t *pte, PG_V;

        PG_V = pmap_valid_bit(pmap);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        if ((*pde & PG_V) == 0)
                return;
        pte = pmap_pde_to_pte(pde, va);
        if ((*pte & PG_V) == 0)
                return;
        lock = NULL;
        pmap_remove_pte(pmap, pte, va, *pde, free, &lock);
        if (lock != NULL)
                rw_wunlock(lock);
        pmap_invalidate_page(pmap, va);
}

/*
 * Removes the specified range of addresses from the page table page.
 */
static bool
pmap_remove_ptes(pmap_t pmap, vm_offset_t sva, vm_offset_t eva,
    pd_entry_t *pde, struct spglist *free, struct rwlock **lockp)
{
        pt_entry_t PG_G, *pte;
        vm_offset_t va;
        bool anyvalid;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PG_G = pmap_global_bit(pmap);
        anyvalid = false;
        va = eva;
        for (pte = pmap_pde_to_pte(pde, sva); sva != eva; pte++,
            sva += PAGE_SIZE) {
                if (*pte == 0) {
                        if (va != eva) {
                                pmap_invalidate_range(pmap, va, sva);
                                va = eva;
                        }
                        continue;
                }
                if ((*pte & PG_G) == 0)
                        anyvalid = true;
                else if (va == eva)
                        va = sva;
                if (pmap_remove_pte(pmap, pte, sva, *pde, free, lockp)) {
                        sva += PAGE_SIZE;
                        break;
                }
        }
        if (va != eva)
                pmap_invalidate_range(pmap, va, sva);
        return (anyvalid);
}

/*
 *      Remove the given range of addresses from the specified map.
 *
 *      It is assumed that the start and end are properly
 *      rounded to the page size.
 */
void
pmap_remove(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        struct rwlock *lock;
        vm_offset_t va_next;
        pml4_entry_t *pml4e;
        pdp_entry_t *pdpe;
        pd_entry_t ptpaddr, *pde;
        pt_entry_t PG_G, PG_V;
        struct spglist free;
        int anyvalid;

        PG_G = pmap_global_bit(pmap);
        PG_V = pmap_valid_bit(pmap);

        /*
         * Perform an unsynchronized read.  This is, however, safe.
         */
        if (pmap->pm_stats.resident_count == 0)
                return;

        anyvalid = 0;
        SLIST_INIT(&free);

        pmap_delayed_invl_started();
        PMAP_LOCK(pmap);

        /*
         * special handling of removing one page.  a very
         * common operation and easy to short circuit some
         * code.
         */
        if (sva + PAGE_SIZE == eva) {
                pde = pmap_pde(pmap, sva);
                if (pde && (*pde & PG_PS) == 0) {
                        pmap_remove_page(pmap, sva, pde, &free);
                        goto out;
                }
        }

        lock = NULL;
        for (; sva < eva; sva = va_next) {

                if (pmap->pm_stats.resident_count == 0)
                        break;

                pml4e = pmap_pml4e(pmap, sva);
                if ((*pml4e & PG_V) == 0) {
                        va_next = (sva + NBPML4) & ~PML4MASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                pdpe = pmap_pml4e_to_pdpe(pml4e, sva);
                if ((*pdpe & PG_V) == 0) {
                        va_next = (sva + NBPDP) & ~PDPMASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                /*
                 * Calculate index for next page table.
                 */
                va_next = (sva + NBPDR) & ~PDRMASK;
                if (va_next < sva)
                        va_next = eva;

                pde = pmap_pdpe_to_pde(pdpe, sva);
                ptpaddr = *pde;

                /*
                 * Weed out invalid mappings.
                 */
                if (ptpaddr == 0)
                        continue;

                /*
                 * Check for large page.
                 */
                if ((ptpaddr & PG_PS) != 0) {
                        /*
                         * Are we removing the entire large page?  If not,
                         * demote the mapping and fall through.
                         */
                        if (sva + NBPDR == va_next && eva >= va_next) {
                                /*
                                 * The TLB entry for a PG_G mapping is
                                 * invalidated by pmap_remove_pde().
                                 */
                                if ((ptpaddr & PG_G) == 0)
                                        anyvalid = 1;
                                pmap_remove_pde(pmap, pde, sva, &free, &lock);
                                continue;
                        } else if (!pmap_demote_pde_locked(pmap, pde, sva,
                            &lock)) {
                                /* The large page mapping was destroyed. */
                                continue;
                        } else
                                ptpaddr = *pde;
                }

                /*
                 * Limit our scan to either the end of the va represented
                 * by the current page table page, or to the end of the
                 * range being removed.
                 */
                if (va_next > eva)
                        va_next = eva;

                if (pmap_remove_ptes(pmap, sva, va_next, pde, &free, &lock))
                        anyvalid = 1;
        }
        if (lock != NULL)
                rw_wunlock(lock);
out:
        if (anyvalid)
                pmap_invalidate_all(pmap);
        PMAP_UNLOCK(pmap);
        pmap_delayed_invl_finished();
        vm_page_free_pages_toq(&free, true);
}

/*
 *      Routine:        pmap_remove_all
 *      Function:
 *              Removes this physical page from
 *              all physical maps in which it resides.
 *              Reflects back modify bits to the pager.
 *
 *      Notes:
 *              Original versions of this routine were very
 *              inefficient because they iteratively called
 *              pmap_remove (slow...)
 */

void
pmap_remove_all(vm_page_t m)
{
        struct md_page *pvh;
        pv_entry_t pv;
        pmap_t pmap;
        struct rwlock *lock;
        pt_entry_t *pte, tpte, PG_A, PG_M, PG_RW;
        pd_entry_t *pde;
        vm_offset_t va;
        struct spglist free;
        int pvh_gen, md_gen;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_remove_all: page %p is not managed", m));
        SLIST_INIT(&free);
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy :
            pa_to_pvh(VM_PAGE_TO_PHYS(m));
retry:
        rw_wlock(lock);
        while ((pv = TAILQ_FIRST(&pvh->pv_list)) != NULL) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        pvh_gen = pvh->pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (pvh_gen != pvh->pv_gen) {
                                rw_wunlock(lock);
                                PMAP_UNLOCK(pmap);
                                goto retry;
                        }
                }
                va = pv->pv_va;
                pde = pmap_pde(pmap, va);
                (void)pmap_demote_pde_locked(pmap, pde, va, &lock);
                PMAP_UNLOCK(pmap);
        }
        while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        pvh_gen = pvh->pv_gen;
                        md_gen = m->md.pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (pvh_gen != pvh->pv_gen || md_gen != m->md.pv_gen) {
                                rw_wunlock(lock);
                                PMAP_UNLOCK(pmap);
                                goto retry;
                        }
                }
                PG_A = pmap_accessed_bit(pmap);
                PG_M = pmap_modified_bit(pmap);
                PG_RW = pmap_rw_bit(pmap);
                pmap_resident_count_dec(pmap, 1);
                pde = pmap_pde(pmap, pv->pv_va);
                KASSERT((*pde & PG_PS) == 0, ("pmap_remove_all: found"
                    " a 2mpage in page %p's pv list", m));
                pte = pmap_pde_to_pte(pde, pv->pv_va);
                tpte = pte_load_clear(pte);
                if (tpte & PG_W)
                        pmap->pm_stats.wired_count--;
                if (tpte & PG_A)
                        vm_page_aflag_set(m, PGA_REFERENCED);

                /*
                 * Update the vm_page_t clean and reference bits.
                 */
                if ((tpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                        vm_page_dirty(m);
                pmap_unuse_pt(pmap, pv->pv_va, *pde, &free);
                pmap_invalidate_page(pmap, pv->pv_va);
                TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                m->md.pv_gen++;
                free_pv_entry(pmap, pv);
                PMAP_UNLOCK(pmap);
        }
        vm_page_aflag_clear(m, PGA_WRITEABLE);
        rw_wunlock(lock);
        pmap_delayed_invl_wait(m);
        vm_page_free_pages_toq(&free, true);
}

/*
 * pmap_protect_pde: do the things to protect a 2mpage in a process
 */
static boolean_t
pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t sva, vm_prot_t prot)
{
        pd_entry_t newpde, oldpde;
        vm_offset_t eva, va;
        vm_page_t m;
        boolean_t anychanged;
        pt_entry_t PG_G, PG_M, PG_RW;

        PG_G = pmap_global_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT((sva & PDRMASK) == 0,
            ("pmap_protect_pde: sva is not 2mpage aligned"));
        anychanged = FALSE;
retry:
        oldpde = newpde = *pde;
        if ((oldpde & (PG_MANAGED | PG_M | PG_RW)) ==
            (PG_MANAGED | PG_M | PG_RW)) {
                eva = sva + NBPDR;
                for (va = sva, m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
                    va < eva; va += PAGE_SIZE, m++)
                        vm_page_dirty(m);
        }
        if ((prot & VM_PROT_WRITE) == 0)
                newpde &= ~(PG_RW | PG_M);
        if ((prot & VM_PROT_EXECUTE) == 0)
                newpde |= pg_nx;
        if (newpde != oldpde) {
                /*
                 * As an optimization to future operations on this PDE, clear
                 * PG_PROMOTED.  The impending invalidation will remove any
                 * lingering 4KB page mappings from the TLB.
                 */
                if (!atomic_cmpset_long(pde, oldpde, newpde & ~PG_PROMOTED))
                        goto retry;
                if ((oldpde & PG_G) != 0)
                        pmap_invalidate_pde_page(kernel_pmap, sva, oldpde);
                else
                        anychanged = TRUE;
        }
        return (anychanged);
}

/*
 *      Set the physical protection on the
 *      specified range of this map as requested.
 */
void
pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
{
        vm_offset_t va_next;
        pml4_entry_t *pml4e;
        pdp_entry_t *pdpe;
        pd_entry_t ptpaddr, *pde;
        pt_entry_t *pte, PG_G, PG_M, PG_RW, PG_V;
        boolean_t anychanged;

        KASSERT((prot & ~VM_PROT_ALL) == 0, ("invalid prot %x", prot));
        if (prot == VM_PROT_NONE) {
                pmap_remove(pmap, sva, eva);
                return;
        }

        if ((prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) ==
            (VM_PROT_WRITE|VM_PROT_EXECUTE))
                return;

        PG_G = pmap_global_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);
        anychanged = FALSE;

        /*
         * Although this function delays and batches the invalidation
         * of stale TLB entries, it does not need to call
         * pmap_delayed_invl_started() and
         * pmap_delayed_invl_finished(), because it does not
         * ordinarily destroy mappings.  Stale TLB entries from
         * protection-only changes need only be invalidated before the
         * pmap lock is released, because protection-only changes do
         * not destroy PV entries.  Even operations that iterate over
         * a physical page's PV list of mappings, like
         * pmap_remove_write(), acquire the pmap lock for each
         * mapping.  Consequently, for protection-only changes, the
         * pmap lock suffices to synchronize both page table and TLB
         * updates.
         *
         * This function only destroys a mapping if pmap_demote_pde()
         * fails.  In that case, stale TLB entries are immediately
         * invalidated.
         */
        
        PMAP_LOCK(pmap);
        for (; sva < eva; sva = va_next) {

                pml4e = pmap_pml4e(pmap, sva);
                if ((*pml4e & PG_V) == 0) {
                        va_next = (sva + NBPML4) & ~PML4MASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                pdpe = pmap_pml4e_to_pdpe(pml4e, sva);
                if ((*pdpe & PG_V) == 0) {
                        va_next = (sva + NBPDP) & ~PDPMASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                va_next = (sva + NBPDR) & ~PDRMASK;
                if (va_next < sva)
                        va_next = eva;

                pde = pmap_pdpe_to_pde(pdpe, sva);
                ptpaddr = *pde;

                /*
                 * Weed out invalid mappings.
                 */
                if (ptpaddr == 0)
                        continue;

                /*
                 * Check for large page.
                 */
                if ((ptpaddr & PG_PS) != 0) {
                        /*
                         * Are we protecting the entire large page?  If not,
                         * demote the mapping and fall through.
                         */
                        if (sva + NBPDR == va_next && eva >= va_next) {
                                /*
                                 * The TLB entry for a PG_G mapping is
                                 * invalidated by pmap_protect_pde().
                                 */
                                if (pmap_protect_pde(pmap, pde, sva, prot))
                                        anychanged = TRUE;
                                continue;
                        } else if (!pmap_demote_pde(pmap, pde, sva)) {
                                /*
                                 * The large page mapping was destroyed.
                                 */
                                continue;
                        }
                }

                if (va_next > eva)
                        va_next = eva;

                for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
                    sva += PAGE_SIZE) {
                        pt_entry_t obits, pbits;
                        vm_page_t m;

retry:
                        obits = pbits = *pte;
                        if ((pbits & PG_V) == 0)
                                continue;

                        if ((prot & VM_PROT_WRITE) == 0) {
                                if ((pbits & (PG_MANAGED | PG_M | PG_RW)) ==
                                    (PG_MANAGED | PG_M | PG_RW)) {
                                        m = PHYS_TO_VM_PAGE(pbits & PG_FRAME);
                                        vm_page_dirty(m);
                                }
                                pbits &= ~(PG_RW | PG_M);
                        }
                        if ((prot & VM_PROT_EXECUTE) == 0)
                                pbits |= pg_nx;

                        if (pbits != obits) {
                                if (!atomic_cmpset_long(pte, obits, pbits))
                                        goto retry;
                                if (obits & PG_G)
                                        pmap_invalidate_page(pmap, sva);
                                else
                                        anychanged = TRUE;
                        }
                }
        }
        if (anychanged)
                pmap_invalidate_all(pmap);
        PMAP_UNLOCK(pmap);
}

#if VM_NRESERVLEVEL > 0
/*
 * Tries to promote the 512, contiguous 4KB page mappings that are within a
 * single page table page (PTP) to a single 2MB page mapping.  For promotion
 * to occur, two conditions must be met: (1) the 4KB page mappings must map
 * aligned, contiguous physical memory and (2) the 4KB page mappings must have
 * identical characteristics. 
 */
static void
pmap_promote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va,
    struct rwlock **lockp)
{
        pd_entry_t newpde;
        pt_entry_t *firstpte, oldpte, pa, *pte;
        pt_entry_t PG_G, PG_A, PG_M, PG_RW, PG_V;
        vm_page_t mpte;
        int PG_PTE_CACHE;

        PG_A = pmap_accessed_bit(pmap);
        PG_G = pmap_global_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);
        PG_PTE_CACHE = pmap_cache_mask(pmap, 0);

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        /*
         * Examine the first PTE in the specified PTP.  Abort if this PTE is
         * either invalid, unused, or does not map the first 4KB physical page
         * within a 2MB page. 
         */
        firstpte = (pt_entry_t *)PHYS_TO_DMAP(*pde & PG_FRAME);
setpde:
        newpde = *firstpte;
        if ((newpde & ((PG_FRAME & PDRMASK) | PG_A | PG_V)) != (PG_A | PG_V)) {
                atomic_add_long(&pmap_pde_p_failures, 1);
                CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#lx"
                    " in pmap %p", va, pmap);
                return;
        }
        if ((newpde & (PG_M | PG_RW)) == PG_RW) {
                /*
                 * When PG_M is already clear, PG_RW can be cleared without
                 * a TLB invalidation.
                 */
                if (!atomic_cmpset_long(firstpte, newpde, newpde & ~PG_RW))
                        goto setpde;
                newpde &= ~PG_RW;
        }

        /*
         * Examine each of the other PTEs in the specified PTP.  Abort if this
         * PTE maps an unexpected 4KB physical page or does not have identical
         * characteristics to the first PTE.
         */
        pa = (newpde & (PG_PS_FRAME | PG_A | PG_V)) + NBPDR - PAGE_SIZE;
        for (pte = firstpte + NPTEPG - 1; pte > firstpte; pte--) {
setpte:
                oldpte = *pte;
                if ((oldpte & (PG_FRAME | PG_A | PG_V)) != pa) {
                        atomic_add_long(&pmap_pde_p_failures, 1);
                        CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#lx"
                            " in pmap %p", va, pmap);
                        return;
                }
                if ((oldpte & (PG_M | PG_RW)) == PG_RW) {
                        /*
                         * When PG_M is already clear, PG_RW can be cleared
                         * without a TLB invalidation.
                         */
                        if (!atomic_cmpset_long(pte, oldpte, oldpte & ~PG_RW))
                                goto setpte;
                        oldpte &= ~PG_RW;
                        CTR2(KTR_PMAP, "pmap_promote_pde: protect for va %#lx"
                            " in pmap %p", (oldpte & PG_FRAME & PDRMASK) |
                            (va & ~PDRMASK), pmap);
                }
                if ((oldpte & PG_PTE_PROMOTE) != (newpde & PG_PTE_PROMOTE)) {
                        atomic_add_long(&pmap_pde_p_failures, 1);
                        CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#lx"
                            " in pmap %p", va, pmap);
                        return;
                }
                pa -= PAGE_SIZE;
        }

        /*
         * Save the page table page in its current state until the PDE
         * mapping the superpage is demoted by pmap_demote_pde() or
         * destroyed by pmap_remove_pde(). 
         */
        mpte = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
        KASSERT(mpte >= vm_page_array &&
            mpte < &vm_page_array[vm_page_array_size],
            ("pmap_promote_pde: page table page is out of range"));
        KASSERT(mpte->pindex == pmap_pde_pindex(va),
            ("pmap_promote_pde: page table page's pindex is wrong"));
        if (pmap_insert_pt_page(pmap, mpte)) {
                atomic_add_long(&pmap_pde_p_failures, 1);
                CTR2(KTR_PMAP,
                    "pmap_promote_pde: failure for va %#lx in pmap %p", va,
                    pmap);
                return;
        }

        /*
         * Promote the pv entries.
         */
        if ((newpde & PG_MANAGED) != 0)
                pmap_pv_promote_pde(pmap, va, newpde & PG_PS_FRAME, lockp);

        /*
         * Propagate the PAT index to its proper position.
         */
        newpde = pmap_swap_pat(pmap, newpde);

        /*
         * Map the superpage.
         */
        if (workaround_erratum383)
                pmap_update_pde(pmap, va, pde, PG_PS | newpde);
        else
                pde_store(pde, PG_PROMOTED | PG_PS | newpde);

        atomic_add_long(&pmap_pde_promotions, 1);
        CTR2(KTR_PMAP, "pmap_promote_pde: success for va %#lx"
            " in pmap %p", va, pmap);
}
#endif /* VM_NRESERVLEVEL > 0 */

/*
 *      Insert the given physical page (p) at
 *      the specified virtual address (v) in the
 *      target physical map with the protection requested.
 *
 *      If specified, the page will be wired down, meaning
 *      that the related pte can not be reclaimed.
 *
 *      NB:  This is the only routine which MAY NOT lazy-evaluate
 *      or lose information.  That is, this routine must actually
 *      insert this page into the given map NOW.
 *
 *      When destroying both a page table and PV entry, this function
 *      performs the TLB invalidation before releasing the PV list
 *      lock, so we do not need pmap_delayed_invl_page() calls here.
 */
int
pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
    u_int flags, int8_t psind)
{
        struct rwlock *lock;
        pd_entry_t *pde;
        pt_entry_t *pte, PG_G, PG_A, PG_M, PG_RW, PG_V;
        pt_entry_t newpte, origpte;
        pv_entry_t pv;
        vm_paddr_t opa, pa;
        vm_page_t mpte, om;
        int rv;
        boolean_t nosleep;

        PG_A = pmap_accessed_bit(pmap);
        PG_G = pmap_global_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        va = trunc_page(va);
        KASSERT(va <= VM_MAX_KERNEL_ADDRESS, ("pmap_enter: toobig"));
        KASSERT(va < UPT_MIN_ADDRESS || va >= UPT_MAX_ADDRESS,
            ("pmap_enter: invalid to pmap_enter page table pages (va: 0x%lx)",
            va));
        KASSERT((m->oflags & VPO_UNMANAGED) != 0 || va < kmi.clean_sva ||
            va >= kmi.clean_eva,
            ("pmap_enter: managed mapping within the clean submap"));
        if ((m->oflags & VPO_UNMANAGED) == 0 && !vm_page_xbusied(m))
                VM_OBJECT_ASSERT_LOCKED(m->object);
        KASSERT((flags & PMAP_ENTER_RESERVED) == 0,
            ("pmap_enter: flags %u has reserved bits set", flags));
        pa = VM_PAGE_TO_PHYS(m);
        newpte = (pt_entry_t)(pa | PG_A | PG_V);
        if ((flags & VM_PROT_WRITE) != 0)
                newpte |= PG_M;
        if ((prot & VM_PROT_WRITE) != 0)
                newpte |= PG_RW;
        KASSERT((newpte & (PG_M | PG_RW)) != PG_M,
            ("pmap_enter: flags includes VM_PROT_WRITE but prot doesn't"));
        if ((prot & VM_PROT_EXECUTE) == 0)
                newpte |= pg_nx;
        if ((flags & PMAP_ENTER_WIRED) != 0)
                newpte |= PG_W;
        if (va < VM_MAXUSER_ADDRESS)
                newpte |= PG_U;
        if (pmap == kernel_pmap)
                newpte |= PG_G;
        newpte |= pmap_cache_bits(pmap, m->md.pat_mode, psind > 0);

        /*
         * Set modified bit gratuitously for writeable mappings if
         * the page is unmanaged. We do not want to take a fault
         * to do the dirty bit accounting for these mappings.
         */
        if ((m->oflags & VPO_UNMANAGED) != 0) {
                if ((newpte & PG_RW) != 0)
                        newpte |= PG_M;
        } else
                newpte |= PG_MANAGED;

        lock = NULL;
        PMAP_LOCK(pmap);
        if (psind == 1) {
                /* Assert the required virtual and physical alignment. */ 
                KASSERT((va & PDRMASK) == 0, ("pmap_enter: va unaligned"));
                KASSERT(m->psind > 0, ("pmap_enter: m->psind < psind"));
                rv = pmap_enter_pde(pmap, va, newpte | PG_PS, flags, m, &lock);
                goto out;
        }
        mpte = NULL;

        /*
         * In the case that a page table page is not
         * resident, we are creating it here.
         */
retry:
        pde = pmap_pde(pmap, va);
        if (pde != NULL && (*pde & PG_V) != 0 && ((*pde & PG_PS) == 0 ||
            pmap_demote_pde_locked(pmap, pde, va, &lock))) {
                pte = pmap_pde_to_pte(pde, va);
                if (va < VM_MAXUSER_ADDRESS && mpte == NULL) {
                        mpte = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
                        mpte->wire_count++;
                }
        } else if (va < VM_MAXUSER_ADDRESS) {
                /*
                 * Here if the pte page isn't mapped, or if it has been
                 * deallocated.
                 */
                nosleep = (flags & PMAP_ENTER_NOSLEEP) != 0;
                mpte = _pmap_allocpte(pmap, pmap_pde_pindex(va),
                    nosleep ? NULL : &lock);
                if (mpte == NULL && nosleep) {
                        rv = KERN_RESOURCE_SHORTAGE;
                        goto out;
                }
                goto retry;
        } else
                panic("pmap_enter: invalid page directory va=%#lx", va);

        origpte = *pte;
        pv = NULL;

        /*
         * Is the specified virtual address already mapped?
         */
        if ((origpte & PG_V) != 0) {
                /*
                 * Wiring change, just update stats. We don't worry about
                 * wiring PT pages as they remain resident as long as there
                 * are valid mappings in them. Hence, if a user page is wired,
                 * the PT page will be also.
                 */
                if ((newpte & PG_W) != 0 && (origpte & PG_W) == 0)
                        pmap->pm_stats.wired_count++;
                else if ((newpte & PG_W) == 0 && (origpte & PG_W) != 0)
                        pmap->pm_stats.wired_count--;

                /*
                 * Remove the extra PT page reference.
                 */
                if (mpte != NULL) {
                        mpte->wire_count--;
                        KASSERT(mpte->wire_count > 0,
                            ("pmap_enter: missing reference to page table page,"
                             " va: 0x%lx", va));
                }

                /*
                 * Has the physical page changed?
                 */
                opa = origpte & PG_FRAME;
                if (opa == pa) {
                        /*
                         * No, might be a protection or wiring change.
                         */
                        if ((origpte & PG_MANAGED) != 0 &&
                            (newpte & PG_RW) != 0)
                                vm_page_aflag_set(m, PGA_WRITEABLE);
                        if (((origpte ^ newpte) & ~(PG_M | PG_A)) == 0)
                                goto unchanged;
                        goto validate;
                }

                /*
                 * The physical page has changed.  Temporarily invalidate
                 * the mapping.  This ensures that all threads sharing the
                 * pmap keep a consistent view of the mapping, which is
                 * necessary for the correct handling of COW faults.  It
                 * also permits reuse of the old mapping's PV entry,
                 * avoiding an allocation.
                 *
                 * For consistency, handle unmanaged mappings the same way.
                 */
                origpte = pte_load_clear(pte);
                KASSERT((origpte & PG_FRAME) == opa,
                    ("pmap_enter: unexpected pa update for %#lx", va));
                if ((origpte & PG_MANAGED) != 0) {
                        om = PHYS_TO_VM_PAGE(opa);

                        /*
                         * The pmap lock is sufficient to synchronize with
                         * concurrent calls to pmap_page_test_mappings() and
                         * pmap_ts_referenced().
                         */
                        if ((origpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                                vm_page_dirty(om);
                        if ((origpte & PG_A) != 0)
                                vm_page_aflag_set(om, PGA_REFERENCED);
                        CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, opa);
                        pv = pmap_pvh_remove(&om->md, pmap, va);
                        if ((newpte & PG_MANAGED) == 0)
                                free_pv_entry(pmap, pv);
                        if ((om->aflags & PGA_WRITEABLE) != 0 &&
                            TAILQ_EMPTY(&om->md.pv_list) &&
                            ((om->flags & PG_FICTITIOUS) != 0 ||
                            TAILQ_EMPTY(&pa_to_pvh(opa)->pv_list)))
                                vm_page_aflag_clear(om, PGA_WRITEABLE);
                }
                if ((origpte & PG_A) != 0)
                        pmap_invalidate_page(pmap, va);
                origpte = 0;
        } else {
                /*
                 * Increment the counters.
                 */
                if ((newpte & PG_W) != 0)
                        pmap->pm_stats.wired_count++;
                pmap_resident_count_inc(pmap, 1);
        }

        /*
         * Enter on the PV list if part of our managed memory.
         */
        if ((newpte & PG_MANAGED) != 0) {
                if (pv == NULL) {
                        pv = get_pv_entry(pmap, &lock);
                        pv->pv_va = va;
                }
                CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, pa);
                TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                m->md.pv_gen++;
                if ((newpte & PG_RW) != 0)
                        vm_page_aflag_set(m, PGA_WRITEABLE);
        }

        /*
         * Update the PTE.
         */
        if ((origpte & PG_V) != 0) {
validate:
                origpte = pte_load_store(pte, newpte);
                KASSERT((origpte & PG_FRAME) == pa,
                    ("pmap_enter: unexpected pa update for %#lx", va));
                if ((newpte & PG_M) == 0 && (origpte & (PG_M | PG_RW)) ==
                    (PG_M | PG_RW)) {
                        if ((origpte & PG_MANAGED) != 0)
                                vm_page_dirty(m);

                        /*
                         * Although the PTE may still have PG_RW set, TLB
                         * invalidation may nonetheless be required because
                         * the PTE no longer has PG_M set.
                         */
                } else if ((origpte & PG_NX) != 0 || (newpte & PG_NX) == 0) {
                        /*
                         * This PTE change does not require TLB invalidation.
                         */
                        goto unchanged;
                }
                if ((origpte & PG_A) != 0)
                        pmap_invalidate_page(pmap, va);
        } else
                pte_store(pte, newpte);

unchanged:

#if VM_NRESERVLEVEL > 0
        /*
         * If both the page table page and the reservation are fully
         * populated, then attempt promotion.
         */
        if ((mpte == NULL || mpte->wire_count == NPTEPG) &&
            pmap_ps_enabled(pmap) &&
            (m->flags & PG_FICTITIOUS) == 0 &&
            vm_reserv_level_iffullpop(m) == 0)
                pmap_promote_pde(pmap, pde, va, &lock);
#endif

        rv = KERN_SUCCESS;
out:
        if (lock != NULL)
                rw_wunlock(lock);
        PMAP_UNLOCK(pmap);
        return (rv);
}

/*
 * Tries to create a read- and/or execute-only 2MB page mapping.  Returns true
 * if successful.  Returns false if (1) a page table page cannot be allocated
 * without sleeping, (2) a mapping already exists at the specified virtual
 * address, or (3) a PV entry cannot be allocated without reclaiming another
 * PV entry.
 */
static bool
pmap_enter_2mpage(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
    struct rwlock **lockp)
{
        pd_entry_t newpde;
        pt_entry_t PG_V;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PG_V = pmap_valid_bit(pmap);
        newpde = VM_PAGE_TO_PHYS(m) | pmap_cache_bits(pmap, m->md.pat_mode, 1) |
            PG_PS | PG_V;
        if ((m->oflags & VPO_UNMANAGED) == 0)
                newpde |= PG_MANAGED;
        if ((prot & VM_PROT_EXECUTE) == 0)
                newpde |= pg_nx;
        if (va < VM_MAXUSER_ADDRESS)
                newpde |= PG_U;
        return (pmap_enter_pde(pmap, va, newpde, PMAP_ENTER_NOSLEEP |
            PMAP_ENTER_NOREPLACE | PMAP_ENTER_NORECLAIM, NULL, lockp) ==
            KERN_SUCCESS);
}

/*
 * Tries to create the specified 2MB page mapping.  Returns KERN_SUCCESS if
 * the mapping was created, and either KERN_FAILURE or KERN_RESOURCE_SHORTAGE
 * otherwise.  Returns KERN_FAILURE if PMAP_ENTER_NOREPLACE was specified and
 * a mapping already exists at the specified virtual address.  Returns
 * KERN_RESOURCE_SHORTAGE if PMAP_ENTER_NOSLEEP was specified and a page table
 * page allocation failed.  Returns KERN_RESOURCE_SHORTAGE if
 * PMAP_ENTER_NORECLAIM was specified and a PV entry allocation failed.
 *
 * The parameter "m" is only used when creating a managed, writeable mapping.
 */
static int
pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t newpde, u_int flags,
    vm_page_t m, struct rwlock **lockp)
{
        struct spglist free;
        pd_entry_t oldpde, *pde;
        pt_entry_t PG_G, PG_RW, PG_V;
        vm_page_t mt, pdpg;

        PG_G = pmap_global_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);
        KASSERT((newpde & (pmap_modified_bit(pmap) | PG_RW)) != PG_RW,
            ("pmap_enter_pde: newpde is missing PG_M"));
        PG_V = pmap_valid_bit(pmap);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        if ((pdpg = pmap_allocpde(pmap, va, (flags & PMAP_ENTER_NOSLEEP) != 0 ?
            NULL : lockp)) == NULL) {
                CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                    " in pmap %p", va, pmap);
                return (KERN_RESOURCE_SHORTAGE);
        }
        pde = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pdpg));
        pde = &pde[pmap_pde_index(va)];
        oldpde = *pde;
        if ((oldpde & PG_V) != 0) {
                KASSERT(pdpg->wire_count > 1,
                    ("pmap_enter_pde: pdpg's wire count is too low"));
                if ((flags & PMAP_ENTER_NOREPLACE) != 0) {
                        pdpg->wire_count--;
                        CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                            " in pmap %p", va, pmap);
                        return (KERN_FAILURE);
                }
                /* Break the existing mapping(s). */
                SLIST_INIT(&free);
                if ((oldpde & PG_PS) != 0) {
                        /*
                         * The reference to the PD page that was acquired by
                         * pmap_allocpde() ensures that it won't be freed.
                         * However, if the PDE resulted from a promotion, then
                         * a reserved PT page could be freed.
                         */
                        (void)pmap_remove_pde(pmap, pde, va, &free, lockp);
                        if ((oldpde & PG_G) == 0)
                                pmap_invalidate_pde_page(pmap, va, oldpde);
                } else {
                        pmap_delayed_invl_started();
                        if (pmap_remove_ptes(pmap, va, va + NBPDR, pde, &free,
                            lockp))
                               pmap_invalidate_all(pmap);
                        pmap_delayed_invl_finished();
                }
                vm_page_free_pages_toq(&free, true);
                if (va >= VM_MAXUSER_ADDRESS) {
                        mt = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
                        if (pmap_insert_pt_page(pmap, mt)) {
                                /*
                                 * XXX Currently, this can't happen because
                                 * we do not perform pmap_enter(psind == 1)
                                 * on the kernel pmap.
                                 */
                                panic("pmap_enter_pde: trie insert failed");
                        }
                } else
                        KASSERT(*pde == 0, ("pmap_enter_pde: non-zero pde %p",
                            pde));
        }
        if ((newpde & PG_MANAGED) != 0) {
                /*
                 * Abort this mapping if its PV entry could not be created.
                 */
                if (!pmap_pv_insert_pde(pmap, va, newpde, flags, lockp)) {
                        SLIST_INIT(&free);
                        if (pmap_unwire_ptp(pmap, va, pdpg, &free)) {
                                /*
                                 * Although "va" is not mapped, paging-
                                 * structure caches could nonetheless have
                                 * entries that refer to the freed page table
                                 * pages.  Invalidate those entries.
                                 */
                                pmap_invalidate_page(pmap, va);
                                vm_page_free_pages_toq(&free, true);
                        }
                        CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                            " in pmap %p", va, pmap);
                        return (KERN_RESOURCE_SHORTAGE);
                }
                if ((newpde & PG_RW) != 0) {
                        for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                vm_page_aflag_set(mt, PGA_WRITEABLE);
                }
        }

        /*
         * Increment counters.
         */
        if ((newpde & PG_W) != 0)
                pmap->pm_stats.wired_count += NBPDR / PAGE_SIZE;
        pmap_resident_count_inc(pmap, NBPDR / PAGE_SIZE);

        /*
         * Map the superpage.  (This is not a promoted mapping; there will not
         * be any lingering 4KB page mappings in the TLB.)
         */
        pde_store(pde, newpde);

        atomic_add_long(&pmap_pde_mappings, 1);
        CTR2(KTR_PMAP, "pmap_enter_pde: success for va %#lx"
            " in pmap %p", va, pmap);
        return (KERN_SUCCESS);
}

/*
 * Maps a sequence of resident pages belonging to the same object.
 * The sequence begins with the given page m_start.  This page is
 * mapped at the given virtual address start.  Each subsequent page is
 * mapped at a virtual address that is offset from start by the same
 * amount as the page is offset from m_start within the object.  The
 * last page in the sequence is the page with the largest offset from
 * m_start that can be mapped at a virtual address less than the given
 * virtual address end.  Not every virtual page between start and end
 * is mapped; only those for which a resident page exists with the
 * corresponding offset from m_start are mapped.
 */
void
pmap_enter_object(pmap_t pmap, vm_offset_t start, vm_offset_t end,
    vm_page_t m_start, vm_prot_t prot)
{
        struct rwlock *lock;
        vm_offset_t va;
        vm_page_t m, mpte;
        vm_pindex_t diff, psize;

        VM_OBJECT_ASSERT_LOCKED(m_start->object);

        psize = atop(end - start);
        mpte = NULL;
        m = m_start;
        lock = NULL;
        PMAP_LOCK(pmap);
        while (m != NULL && (diff = m->pindex - m_start->pindex) < psize) {
                va = start + ptoa(diff);
                if ((va & PDRMASK) == 0 && va + NBPDR <= end &&
                    m->psind == 1 && pmap_ps_enabled(pmap) &&
                    pmap_enter_2mpage(pmap, va, m, prot, &lock))
                        m = &m[NBPDR / PAGE_SIZE - 1];
                else
                        mpte = pmap_enter_quick_locked(pmap, va, m, prot,
                            mpte, &lock);
                m = TAILQ_NEXT(m, listq);
        }
        if (lock != NULL)
                rw_wunlock(lock);
        PMAP_UNLOCK(pmap);
}

/*
 * this code makes some *MAJOR* assumptions:
 * 1. Current pmap & pmap exists.
 * 2. Not wired.
 * 3. Read access.
 * 4. No page table pages.
 * but is *MUCH* faster than pmap_enter...
 */

void
pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot)
{
        struct rwlock *lock;

        lock = NULL;
        PMAP_LOCK(pmap);
        (void)pmap_enter_quick_locked(pmap, va, m, prot, NULL, &lock);
        if (lock != NULL)
                rw_wunlock(lock);
        PMAP_UNLOCK(pmap);
}

static vm_page_t
pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, vm_page_t m,
    vm_prot_t prot, vm_page_t mpte, struct rwlock **lockp)
{
        struct spglist free;
        pt_entry_t *pte, PG_V;
        vm_paddr_t pa;

        KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva ||
            (m->oflags & VPO_UNMANAGED) != 0,
            ("pmap_enter_quick_locked: managed mapping within the clean submap"));
        PG_V = pmap_valid_bit(pmap);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        /*
         * In the case that a page table page is not
         * resident, we are creating it here.
         */
        if (va < VM_MAXUSER_ADDRESS) {
                vm_pindex_t ptepindex;
                pd_entry_t *ptepa;

                /*
                 * Calculate pagetable page index
                 */
                ptepindex = pmap_pde_pindex(va);
                if (mpte && (mpte->pindex == ptepindex)) {
                        mpte->wire_count++;
                } else {
                        /*
                         * Get the page directory entry
                         */
                        ptepa = pmap_pde(pmap, va);

                        /*
                         * If the page table page is mapped, we just increment
                         * the hold count, and activate it.  Otherwise, we
                         * attempt to allocate a page table page.  If this
                         * attempt fails, we don't retry.  Instead, we give up.
                         */
                        if (ptepa && (*ptepa & PG_V) != 0) {
                                if (*ptepa & PG_PS)
                                        return (NULL);
                                mpte = PHYS_TO_VM_PAGE(*ptepa & PG_FRAME);
                                mpte->wire_count++;
                        } else {
                                /*
                                 * Pass NULL instead of the PV list lock
                                 * pointer, because we don't intend to sleep.
                                 */
                                mpte = _pmap_allocpte(pmap, ptepindex, NULL);
                                if (mpte == NULL)
                                        return (mpte);
                        }
                }
                pte = (pt_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mpte));
                pte = &pte[pmap_pte_index(va)];
        } else {
                mpte = NULL;
                pte = vtopte(va);
        }
        if (*pte) {
                if (mpte != NULL) {
                        mpte->wire_count--;
                        mpte = NULL;
                }
                return (mpte);
        }

        /*
         * Enter on the PV list if part of our managed memory.
         */
        if ((m->oflags & VPO_UNMANAGED) == 0 &&
            !pmap_try_insert_pv_entry(pmap, va, m, lockp)) {
                if (mpte != NULL) {
                        SLIST_INIT(&free);
                        if (pmap_unwire_ptp(pmap, va, mpte, &free)) {
                                /*
                                 * Although "va" is not mapped, paging-
                                 * structure caches could nonetheless have
                                 * entries that refer to the freed page table
                                 * pages.  Invalidate those entries.
                                 */
                                pmap_invalidate_page(pmap, va);
                                vm_page_free_pages_toq(&free, true);
                        }
                        mpte = NULL;
                }
                return (mpte);
        }

        /*
         * Increment counters
         */
        pmap_resident_count_inc(pmap, 1);

        pa = VM_PAGE_TO_PHYS(m) | pmap_cache_bits(pmap, m->md.pat_mode, 0);
        if ((prot & VM_PROT_EXECUTE) == 0)
                pa |= pg_nx;

        /*
         * Now validate mapping with RO protection
         */
        if ((m->oflags & VPO_UNMANAGED) != 0)
                pte_store(pte, pa | PG_V | PG_U);
        else
                pte_store(pte, pa | PG_V | PG_U | PG_MANAGED);
        return (mpte);
}

/*
 * Make a temporary mapping for a physical address.  This is only intended
 * to be used for panic dumps.
 */
void *
pmap_kenter_temporary(vm_paddr_t pa, int i)
{
        vm_offset_t va;

        va = (vm_offset_t)crashdumpmap + (i * PAGE_SIZE);
        pmap_kenter(va, pa);
        invlpg(va);
        return ((void *)crashdumpmap);
}

/*
 * This code maps large physical mmap regions into the
 * processor address space.  Note that some shortcuts
 * are taken, but the code works.
 */
void
pmap_object_init_pt(pmap_t pmap, vm_offset_t addr, vm_object_t object,
    vm_pindex_t pindex, vm_size_t size)
{
        pd_entry_t *pde;
        pt_entry_t PG_A, PG_M, PG_RW, PG_V;
        vm_paddr_t pa, ptepa;
        vm_page_t p, pdpg;
        int pat_mode;

        PG_A = pmap_accessed_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        VM_OBJECT_ASSERT_WLOCKED(object);
        KASSERT(object->type == OBJT_DEVICE || object->type == OBJT_SG,
            ("pmap_object_init_pt: non-device object"));
        if ((addr & (NBPDR - 1)) == 0 && (size & (NBPDR - 1)) == 0) {
                if (!pmap_ps_enabled(pmap))
                        return;
                if (!vm_object_populate(object, pindex, pindex + atop(size)))
                        return;
                p = vm_page_lookup(object, pindex);
                KASSERT(p->valid == VM_PAGE_BITS_ALL,
                    ("pmap_object_init_pt: invalid page %p", p));
                pat_mode = p->md.pat_mode;

                /*
                 * Abort the mapping if the first page is not physically
                 * aligned to a 2MB page boundary.
                 */
                ptepa = VM_PAGE_TO_PHYS(p);
                if (ptepa & (NBPDR - 1))
                        return;

                /*
                 * Skip the first page.  Abort the mapping if the rest of
                 * the pages are not physically contiguous or have differing
                 * memory attributes.
                 */
                p = TAILQ_NEXT(p, listq);
                for (pa = ptepa + PAGE_SIZE; pa < ptepa + size;
                    pa += PAGE_SIZE) {
                        KASSERT(p->valid == VM_PAGE_BITS_ALL,
                            ("pmap_object_init_pt: invalid page %p", p));
                        if (pa != VM_PAGE_TO_PHYS(p) ||
                            pat_mode != p->md.pat_mode)
                                return;
                        p = TAILQ_NEXT(p, listq);
                }

                /*
                 * Map using 2MB pages.  Since "ptepa" is 2M aligned and
                 * "size" is a multiple of 2M, adding the PAT setting to "pa"
                 * will not affect the termination of this loop.
                 */ 
                PMAP_LOCK(pmap);
                for (pa = ptepa | pmap_cache_bits(pmap, pat_mode, 1);
                    pa < ptepa + size; pa += NBPDR) {
                        pdpg = pmap_allocpde(pmap, addr, NULL);
                        if (pdpg == NULL) {
                                /*
                                 * The creation of mappings below is only an
                                 * optimization.  If a page directory page
                                 * cannot be allocated without blocking,
                                 * continue on to the next mapping rather than
                                 * blocking.
                                 */
                                addr += NBPDR;
                                continue;
                        }
                        pde = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pdpg));
                        pde = &pde[pmap_pde_index(addr)];
                        if ((*pde & PG_V) == 0) {
                                pde_store(pde, pa | PG_PS | PG_M | PG_A |
                                    PG_U | PG_RW | PG_V);
                                pmap_resident_count_inc(pmap, NBPDR / PAGE_SIZE);
                                atomic_add_long(&pmap_pde_mappings, 1);
                        } else {
                                /* Continue on if the PDE is already valid. */
                                pdpg->wire_count--;
                                KASSERT(pdpg->wire_count > 0,
                                    ("pmap_object_init_pt: missing reference "
                                    "to page directory page, va: 0x%lx", addr));
                        }
                        addr += NBPDR;
                }
                PMAP_UNLOCK(pmap);
        }
}

/*
 *      Clear the wired attribute from the mappings for the specified range of
 *      addresses in the given pmap.  Every valid mapping within that range
 *      must have the wired attribute set.  In contrast, invalid mappings
 *      cannot have the wired attribute set, so they are ignored.
 *
 *      The wired attribute of the page table entry is not a hardware
 *      feature, so there is no need to invalidate any TLB entries.
 *      Since pmap_demote_pde() for the wired entry must never fail,
 *      pmap_delayed_invl_started()/finished() calls around the
 *      function are not needed.
 */
void
pmap_unwire(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        vm_offset_t va_next;
        pml4_entry_t *pml4e;
        pdp_entry_t *pdpe;
        pd_entry_t *pde;
        pt_entry_t *pte, PG_V;

        PG_V = pmap_valid_bit(pmap);
        PMAP_LOCK(pmap);
        for (; sva < eva; sva = va_next) {
                pml4e = pmap_pml4e(pmap, sva);
                if ((*pml4e & PG_V) == 0) {
                        va_next = (sva + NBPML4) & ~PML4MASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }
                pdpe = pmap_pml4e_to_pdpe(pml4e, sva);
                if ((*pdpe & PG_V) == 0) {
                        va_next = (sva + NBPDP) & ~PDPMASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }
                va_next = (sva + NBPDR) & ~PDRMASK;
                if (va_next < sva)
                        va_next = eva;
                pde = pmap_pdpe_to_pde(pdpe, sva);
                if ((*pde & PG_V) == 0)
                        continue;
                if ((*pde & PG_PS) != 0) {
                        if ((*pde & PG_W) == 0)
                                panic("pmap_unwire: pde %#jx is missing PG_W",
                                    (uintmax_t)*pde);

                        /*
                         * Are we unwiring the entire large page?  If not,
                         * demote the mapping and fall through.
                         */
                        if (sva + NBPDR == va_next && eva >= va_next) {
                                atomic_clear_long(pde, PG_W);
                                pmap->pm_stats.wired_count -= NBPDR /
                                    PAGE_SIZE;
                                continue;
                        } else if (!pmap_demote_pde(pmap, pde, sva))
                                panic("pmap_unwire: demotion failed");
                }
                if (va_next > eva)
                        va_next = eva;
                for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
                    sva += PAGE_SIZE) {
                        if ((*pte & PG_V) == 0)
                                continue;
                        if ((*pte & PG_W) == 0)
                                panic("pmap_unwire: pte %#jx is missing PG_W",
                                    (uintmax_t)*pte);

                        /*
                         * PG_W must be cleared atomically.  Although the pmap
                         * lock synchronizes access to PG_W, another processor
                         * could be setting PG_M and/or PG_A concurrently.
                         */
                        atomic_clear_long(pte, PG_W);
                        pmap->pm_stats.wired_count--;
                }
        }
        PMAP_UNLOCK(pmap);
}

/*
 *      Copy the range specified by src_addr/len
 *      from the source map to the range dst_addr/len
 *      in the destination map.
 *
 *      This routine is only advisory and need not do anything.
 */

void
pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr, vm_size_t len,
    vm_offset_t src_addr)
{
        struct rwlock *lock;
        struct spglist free;
        vm_offset_t addr;
        vm_offset_t end_addr = src_addr + len;
        vm_offset_t va_next;
        vm_page_t dst_pdpg, dstmpte, srcmpte;
        pt_entry_t PG_A, PG_M, PG_V;

        if (dst_addr != src_addr)
                return;

        if (dst_pmap->pm_type != src_pmap->pm_type)
                return;

        /*
         * EPT page table entries that require emulation of A/D bits are
         * sensitive to clearing the PG_A bit (aka EPT_PG_READ). Although
         * we clear PG_M (aka EPT_PG_WRITE) concomitantly, the PG_U bit
         * (aka EPT_PG_EXECUTE) could still be set. Since some EPT
         * implementations flag an EPT misconfiguration for exec-only
         * mappings we skip this function entirely for emulated pmaps.
         */
        if (pmap_emulate_ad_bits(dst_pmap))
                return;

        lock = NULL;
        if (dst_pmap < src_pmap) {
                PMAP_LOCK(dst_pmap);
                PMAP_LOCK(src_pmap);
        } else {
                PMAP_LOCK(src_pmap);
                PMAP_LOCK(dst_pmap);
        }

        PG_A = pmap_accessed_bit(dst_pmap);
        PG_M = pmap_modified_bit(dst_pmap);
        PG_V = pmap_valid_bit(dst_pmap);

        for (addr = src_addr; addr < end_addr; addr = va_next) {
                pt_entry_t *src_pte, *dst_pte;
                pml4_entry_t *pml4e;
                pdp_entry_t *pdpe;
                pd_entry_t srcptepaddr, *pde;

                KASSERT(addr < UPT_MIN_ADDRESS,
                    ("pmap_copy: invalid to pmap_copy page tables"));

                pml4e = pmap_pml4e(src_pmap, addr);
                if ((*pml4e & PG_V) == 0) {
                        va_next = (addr + NBPML4) & ~PML4MASK;
                        if (va_next < addr)
                                va_next = end_addr;
                        continue;
                }

                pdpe = pmap_pml4e_to_pdpe(pml4e, addr);
                if ((*pdpe & PG_V) == 0) {
                        va_next = (addr + NBPDP) & ~PDPMASK;
                        if (va_next < addr)
                                va_next = end_addr;
                        continue;
                }

                va_next = (addr + NBPDR) & ~PDRMASK;
                if (va_next < addr)
                        va_next = end_addr;

                pde = pmap_pdpe_to_pde(pdpe, addr);
                srcptepaddr = *pde;
                if (srcptepaddr == 0)
                        continue;
                        
                if (srcptepaddr & PG_PS) {
                        if ((addr & PDRMASK) != 0 || addr + NBPDR > end_addr)
                                continue;
                        dst_pdpg = pmap_allocpde(dst_pmap, addr, NULL);
                        if (dst_pdpg == NULL)
                                break;
                        pde = (pd_entry_t *)
                            PHYS_TO_DMAP(VM_PAGE_TO_PHYS(dst_pdpg));
                        pde = &pde[pmap_pde_index(addr)];
                        if (*pde == 0 && ((srcptepaddr & PG_MANAGED) == 0 ||
                            pmap_pv_insert_pde(dst_pmap, addr, srcptepaddr,
                            PMAP_ENTER_NORECLAIM, &lock))) {
                                *pde = srcptepaddr & ~PG_W;
                                pmap_resident_count_inc(dst_pmap, NBPDR / PAGE_SIZE);
                                atomic_add_long(&pmap_pde_mappings, 1);
                        } else
                                dst_pdpg->wire_count--;
                        continue;
                }

                srcptepaddr &= PG_FRAME;
                srcmpte = PHYS_TO_VM_PAGE(srcptepaddr);
                KASSERT(srcmpte->wire_count > 0,
                    ("pmap_copy: source page table page is unused"));

                if (va_next > end_addr)
                        va_next = end_addr;

                src_pte = (pt_entry_t *)PHYS_TO_DMAP(srcptepaddr);
                src_pte = &src_pte[pmap_pte_index(addr)];
                dstmpte = NULL;
                while (addr < va_next) {
                        pt_entry_t ptetemp;
                        ptetemp = *src_pte;
                        /*
                         * we only virtual copy managed pages
                         */
                        if ((ptetemp & PG_MANAGED) != 0) {
                                if (dstmpte != NULL &&
                                    dstmpte->pindex == pmap_pde_pindex(addr))
                                        dstmpte->wire_count++;
                                else if ((dstmpte = pmap_allocpte(dst_pmap,
                                    addr, NULL)) == NULL)
                                        goto out;
                                dst_pte = (pt_entry_t *)
                                    PHYS_TO_DMAP(VM_PAGE_TO_PHYS(dstmpte));
                                dst_pte = &dst_pte[pmap_pte_index(addr)];
                                if (*dst_pte == 0 &&
                                    pmap_try_insert_pv_entry(dst_pmap, addr,
                                    PHYS_TO_VM_PAGE(ptetemp & PG_FRAME),
                                    &lock)) {
                                        /*
                                         * Clear the wired, modified, and
                                         * accessed (referenced) bits
                                         * during the copy.
                                         */
                                        *dst_pte = ptetemp & ~(PG_W | PG_M |
                                            PG_A);
                                        pmap_resident_count_inc(dst_pmap, 1);
                                } else {
                                        SLIST_INIT(&free);
                                        if (pmap_unwire_ptp(dst_pmap, addr,
                                            dstmpte, &free)) {
                                                /*
                                                 * Although "addr" is not
                                                 * mapped, paging-structure
                                                 * caches could nonetheless
                                                 * have entries that refer to
                                                 * the freed page table pages.
                                                 * Invalidate those entries.
                                                 */
                                                pmap_invalidate_page(dst_pmap,
                                                    addr);
                                                vm_page_free_pages_toq(&free,
                                                    true);
                                        }
                                        goto out;
                                }
                                if (dstmpte->wire_count >= srcmpte->wire_count)
                                        break;
                        }
                        addr += PAGE_SIZE;
                        src_pte++;
                }
        }
out:
        if (lock != NULL)
                rw_wunlock(lock);
        PMAP_UNLOCK(src_pmap);
        PMAP_UNLOCK(dst_pmap);
}

/*
 * Zero the specified hardware page.
 */
void
pmap_zero_page(vm_page_t m)
{
        vm_offset_t va = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));

        pagezero((void *)va);
}

/*
 * Zero an an area within a single hardware page.  off and size must not
 * cover an area beyond a single hardware page.
 */
void
pmap_zero_page_area(vm_page_t m, int off, int size)
{
        vm_offset_t va = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));

        if (off == 0 && size == PAGE_SIZE)
                pagezero((void *)va);
        else
                bzero((char *)va + off, size);
}

/*
 * Copy 1 specified hardware page to another.
 */
void
pmap_copy_page(vm_page_t msrc, vm_page_t mdst)
{
        vm_offset_t src = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(msrc));
        vm_offset_t dst = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mdst));

        pagecopy((void *)src, (void *)dst);
}

int unmapped_buf_allowed = 1;

void
pmap_copy_pages(vm_page_t ma[], vm_offset_t a_offset, vm_page_t mb[],
    vm_offset_t b_offset, int xfersize)
{
        void *a_cp, *b_cp;
        vm_page_t pages[2];
        vm_offset_t vaddr[2], a_pg_offset, b_pg_offset;
        int cnt;
        boolean_t mapped;

        while (xfersize > 0) {
                a_pg_offset = a_offset & PAGE_MASK;
                pages[0] = ma[a_offset >> PAGE_SHIFT];
                b_pg_offset = b_offset & PAGE_MASK;
                pages[1] = mb[b_offset >> PAGE_SHIFT];
                cnt = min(xfersize, PAGE_SIZE - a_pg_offset);
                cnt = min(cnt, PAGE_SIZE - b_pg_offset);
                mapped = pmap_map_io_transient(pages, vaddr, 2, FALSE);
                a_cp = (char *)vaddr[0] + a_pg_offset;
                b_cp = (char *)vaddr[1] + b_pg_offset;
                bcopy(a_cp, b_cp, cnt);
                if (__predict_false(mapped))
                        pmap_unmap_io_transient(pages, vaddr, 2, FALSE);
                a_offset += cnt;
                b_offset += cnt;
                xfersize -= cnt;
        }
}

/*
 * Returns true if the pmap's pv is one of the first
 * 16 pvs linked to from this page.  This count may
 * be changed upwards or downwards in the future; it
 * is only necessary that true be returned for a small
 * subset of pmaps for proper page aging.
 */
boolean_t
pmap_page_exists_quick(pmap_t pmap, vm_page_t m)
{
        struct md_page *pvh;
        struct rwlock *lock;
        pv_entry_t pv;
        int loops = 0;
        boolean_t rv;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_page_exists_quick: page %p is not managed", m));
        rv = FALSE;
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        rw_rlock(lock);
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                if (PV_PMAP(pv) == pmap) {
                        rv = TRUE;
                        break;
                }
                loops++;
                if (loops >= 16)
                        break;
        }
        if (!rv && loops < 16 && (m->flags & PG_FICTITIOUS) == 0) {
                pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                        if (PV_PMAP(pv) == pmap) {
                                rv = TRUE;
                                break;
                        }
                        loops++;
                        if (loops >= 16)
                                break;
                }
        }
        rw_runlock(lock);
        return (rv);
}

/*
 *      pmap_page_wired_mappings:
 *
 *      Return the number of managed mappings to the given physical page
 *      that are wired.
 */
int
pmap_page_wired_mappings(vm_page_t m)
{
        struct rwlock *lock;
        struct md_page *pvh;
        pmap_t pmap;
        pt_entry_t *pte;
        pv_entry_t pv;
        int count, md_gen, pvh_gen;

        if ((m->oflags & VPO_UNMANAGED) != 0)
                return (0);
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        rw_rlock(lock);
restart:
        count = 0;
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        md_gen = m->md.pv_gen;
                        rw_runlock(lock);
                        PMAP_LOCK(pmap);
                        rw_rlock(lock);
                        if (md_gen != m->md.pv_gen) {
                                PMAP_UNLOCK(pmap);
                                goto restart;
                        }
                }
                pte = pmap_pte(pmap, pv->pv_va);
                if ((*pte & PG_W) != 0)
                        count++;
                PMAP_UNLOCK(pmap);
        }
        if ((m->flags & PG_FICTITIOUS) == 0) {
                pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                        pmap = PV_PMAP(pv);
                        if (!PMAP_TRYLOCK(pmap)) {
                                md_gen = m->md.pv_gen;
                                pvh_gen = pvh->pv_gen;
                                rw_runlock(lock);
                                PMAP_LOCK(pmap);
                                rw_rlock(lock);
                                if (md_gen != m->md.pv_gen ||
                                    pvh_gen != pvh->pv_gen) {
                                        PMAP_UNLOCK(pmap);
                                        goto restart;
                                }
                        }
                        pte = pmap_pde(pmap, pv->pv_va);
                        if ((*pte & PG_W) != 0)
                                count++;
                        PMAP_UNLOCK(pmap);
                }
        }
        rw_runlock(lock);
        return (count);
}

/*
 * Returns TRUE if the given page is mapped individually or as part of
 * a 2mpage.  Otherwise, returns FALSE.
 */
boolean_t
pmap_page_is_mapped(vm_page_t m)
{
        struct rwlock *lock;
        boolean_t rv;

        if ((m->oflags & VPO_UNMANAGED) != 0)
                return (FALSE);
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        rw_rlock(lock);
        rv = !TAILQ_EMPTY(&m->md.pv_list) ||
            ((m->flags & PG_FICTITIOUS) == 0 &&
            !TAILQ_EMPTY(&pa_to_pvh(VM_PAGE_TO_PHYS(m))->pv_list));
        rw_runlock(lock);
        return (rv);
}

/*
 * Destroy all managed, non-wired mappings in the given user-space
 * pmap.  This pmap cannot be active on any processor besides the
 * caller.
 *
 * This function cannot be applied to the kernel pmap.  Moreover, it
 * is not intended for general use.  It is only to be used during
 * process termination.  Consequently, it can be implemented in ways
 * that make it faster than pmap_remove().  First, it can more quickly
 * destroy mappings by iterating over the pmap's collection of PV
 * entries, rather than searching the page table.  Second, it doesn't
 * have to test and clear the page table entries atomically, because
 * no processor is currently accessing the user address space.  In
 * particular, a page table entry's dirty bit won't change state once
 * this function starts.
 *
 * Although this function destroys all of the pmap's managed,
 * non-wired mappings, it can delay and batch the invalidation of TLB
 * entries without calling pmap_delayed_invl_started() and
 * pmap_delayed_invl_finished().  Because the pmap is not active on
 * any other processor, none of these TLB entries will ever be used
 * before their eventual invalidation.  Consequently, there is no need
 * for either pmap_remove_all() or pmap_remove_write() to wait for
 * that eventual TLB invalidation.
 */
void
pmap_remove_pages(pmap_t pmap)
{
        pd_entry_t ptepde;
        pt_entry_t *pte, tpte;
        pt_entry_t PG_M, PG_RW, PG_V;
        struct spglist free;
        vm_page_t m, mpte, mt;
        pv_entry_t pv;
        struct md_page *pvh;
        struct pv_chunk *pc, *npc;
        struct rwlock *lock;
        int64_t bit;
        uint64_t inuse, bitmask;
        int allfree, field, freed, idx;
        boolean_t superpage;
        vm_paddr_t pa;

        /*
         * Assert that the given pmap is only active on the current
         * CPU.  Unfortunately, we cannot block another CPU from
         * activating the pmap while this function is executing.
         */
        KASSERT(pmap == PCPU_GET(curpmap), ("non-current pmap %p", pmap));
#ifdef INVARIANTS
        {
                cpuset_t other_cpus;

                other_cpus = all_cpus;
                critical_enter();
                CPU_CLR(PCPU_GET(cpuid), &other_cpus);
                CPU_AND(&other_cpus, &pmap->pm_active);
                critical_exit();
                KASSERT(CPU_EMPTY(&other_cpus), ("pmap active %p", pmap));
        }
#endif

        lock = NULL;
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        SLIST_INIT(&free);
        PMAP_LOCK(pmap);
        TAILQ_FOREACH_SAFE(pc, &pmap->pm_pvchunk, pc_list, npc) {
                allfree = 1;
                freed = 0;
                for (field = 0; field < _NPCM; field++) {
                        inuse = ~pc->pc_map[field] & pc_freemask[field];
                        while (inuse != 0) {
                                bit = bsfq(inuse);
                                bitmask = 1UL << bit;
                                idx = field * 64 + bit;
                                pv = &pc->pc_pventry[idx];
                                inuse &= ~bitmask;

                                pte = pmap_pdpe(pmap, pv->pv_va);
                                ptepde = *pte;
                                pte = pmap_pdpe_to_pde(pte, pv->pv_va);
                                tpte = *pte;
                                if ((tpte & (PG_PS | PG_V)) == PG_V) {
                                        superpage = FALSE;
                                        ptepde = tpte;
                                        pte = (pt_entry_t *)PHYS_TO_DMAP(tpte &
                                            PG_FRAME);
                                        pte = &pte[pmap_pte_index(pv->pv_va)];
                                        tpte = *pte;
                                } else {
                                        /*
                                         * Keep track whether 'tpte' is a
                                         * superpage explicitly instead of
                                         * relying on PG_PS being set.
                                         *
                                         * This is because PG_PS is numerically
                                         * identical to PG_PTE_PAT and thus a
                                         * regular page could be mistaken for
                                         * a superpage.
                                         */
                                        superpage = TRUE;
                                }

                                if ((tpte & PG_V) == 0) {
                                        panic("bad pte va %lx pte %lx",
                                            pv->pv_va, tpte);
                                }

/*
 * We cannot remove wired pages from a process' mapping at this time
 */
                                if (tpte & PG_W) {
                                        allfree = 0;
                                        continue;
                                }

                                if (superpage)
                                        pa = tpte & PG_PS_FRAME;
                                else
                                        pa = tpte & PG_FRAME;

                                m = PHYS_TO_VM_PAGE(pa);
                                KASSERT(m->phys_addr == pa,
                                    ("vm_page_t %p phys_addr mismatch %016jx %016jx",
                                    m, (uintmax_t)m->phys_addr,
                                    (uintmax_t)tpte));

                                KASSERT((m->flags & PG_FICTITIOUS) != 0 ||
                                    m < &vm_page_array[vm_page_array_size],
                                    ("pmap_remove_pages: bad tpte %#jx",
                                    (uintmax_t)tpte));

                                pte_clear(pte);

                                /*
                                 * Update the vm_page_t clean/reference bits.
                                 */
                                if ((tpte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                                        if (superpage) {
                                                for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                                        vm_page_dirty(mt);
                                        } else
                                                vm_page_dirty(m);
                                }

                                CHANGE_PV_LIST_LOCK_TO_VM_PAGE(&lock, m);

                                /* Mark free */
                                pc->pc_map[field] |= bitmask;
                                if (superpage) {
                                        pmap_resident_count_dec(pmap, NBPDR / PAGE_SIZE);
                                        pvh = pa_to_pvh(tpte & PG_PS_FRAME);
                                        TAILQ_REMOVE(&pvh->pv_list, pv, pv_next);
                                        pvh->pv_gen++;
                                        if (TAILQ_EMPTY(&pvh->pv_list)) {
                                                for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                                        if ((mt->aflags & PGA_WRITEABLE) != 0 &&
                                                            TAILQ_EMPTY(&mt->md.pv_list))
                                                                vm_page_aflag_clear(mt, PGA_WRITEABLE);
                                        }
                                        mpte = pmap_remove_pt_page(pmap, pv->pv_va);
                                        if (mpte != NULL) {
                                                pmap_resident_count_dec(pmap, 1);
                                                KASSERT(mpte->wire_count == NPTEPG,
                                                    ("pmap_remove_pages: pte page wire count error"));
                                                mpte->wire_count = 0;
                                                pmap_add_delayed_free_list(mpte, &free, FALSE);
                                        }
                                } else {
                                        pmap_resident_count_dec(pmap, 1);
                                        TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                                        m->md.pv_gen++;
                                        if ((m->aflags & PGA_WRITEABLE) != 0 &&
                                            TAILQ_EMPTY(&m->md.pv_list) &&
                                            (m->flags & PG_FICTITIOUS) == 0) {
                                                pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                                                if (TAILQ_EMPTY(&pvh->pv_list))
                                                        vm_page_aflag_clear(m, PGA_WRITEABLE);
                                        }
                                }
                                pmap_unuse_pt(pmap, pv->pv_va, ptepde, &free);
                                freed++;
                        }
                }
                PV_STAT(atomic_add_long(&pv_entry_frees, freed));
                PV_STAT(atomic_add_int(&pv_entry_spare, freed));
                PV_STAT(atomic_subtract_long(&pv_entry_count, freed));
                if (allfree) {
                        TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                        free_pv_chunk(pc);
                }
        }
        if (lock != NULL)
                rw_wunlock(lock);
        pmap_invalidate_all(pmap);
        PMAP_UNLOCK(pmap);
        vm_page_free_pages_toq(&free, true);
}

static boolean_t
pmap_page_test_mappings(vm_page_t m, boolean_t accessed, boolean_t modified)
{
        struct rwlock *lock;
        pv_entry_t pv;
        struct md_page *pvh;
        pt_entry_t *pte, mask;
        pt_entry_t PG_A, PG_M, PG_RW, PG_V;
        pmap_t pmap;
        int md_gen, pvh_gen;
        boolean_t rv;

        rv = FALSE;
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        rw_rlock(lock);
restart:
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        md_gen = m->md.pv_gen;
                        rw_runlock(lock);
                        PMAP_LOCK(pmap);
                        rw_rlock(lock);
                        if (md_gen != m->md.pv_gen) {
                                PMAP_UNLOCK(pmap);
                                goto restart;
                        }
                }
                pte = pmap_pte(pmap, pv->pv_va);
                mask = 0;
                if (modified) {
                        PG_M = pmap_modified_bit(pmap);
                        PG_RW = pmap_rw_bit(pmap);
                        mask |= PG_RW | PG_M;
                }
                if (accessed) {
                        PG_A = pmap_accessed_bit(pmap);
                        PG_V = pmap_valid_bit(pmap);
                        mask |= PG_V | PG_A;
                }
                rv = (*pte & mask) == mask;
                PMAP_UNLOCK(pmap);
                if (rv)
                        goto out;
        }
        if ((m->flags & PG_FICTITIOUS) == 0) {
                pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                TAILQ_FOREACH(pv, &pvh->pv_list, pv_next) {
                        pmap = PV_PMAP(pv);
                        if (!PMAP_TRYLOCK(pmap)) {
                                md_gen = m->md.pv_gen;
                                pvh_gen = pvh->pv_gen;
                                rw_runlock(lock);
                                PMAP_LOCK(pmap);
                                rw_rlock(lock);
                                if (md_gen != m->md.pv_gen ||
                                    pvh_gen != pvh->pv_gen) {
                                        PMAP_UNLOCK(pmap);
                                        goto restart;
                                }
                        }
                        pte = pmap_pde(pmap, pv->pv_va);
                        mask = 0;
                        if (modified) {
                                PG_M = pmap_modified_bit(pmap);
                                PG_RW = pmap_rw_bit(pmap);
                                mask |= PG_RW | PG_M;
                        }
                        if (accessed) {
                                PG_A = pmap_accessed_bit(pmap);
                                PG_V = pmap_valid_bit(pmap);
                                mask |= PG_V | PG_A;
                        }
                        rv = (*pte & mask) == mask;
                        PMAP_UNLOCK(pmap);
                        if (rv)
                                goto out;
                }
        }
out:
        rw_runlock(lock);
        return (rv);
}

/*
 *      pmap_is_modified:
 *
 *      Return whether or not the specified physical page was modified
 *      in any physical maps.
 */
boolean_t
pmap_is_modified(vm_page_t m)
{

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_is_modified: page %p is not managed", m));

        /*
         * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
         * concurrently set while the object is locked.  Thus, if PGA_WRITEABLE
         * is clear, no PTEs can have PG_M set.
         */
        VM_OBJECT_ASSERT_WLOCKED(m->object);
        if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
                return (FALSE);
        return (pmap_page_test_mappings(m, FALSE, TRUE));
}

/*
 *      pmap_is_prefaultable:
 *
 *      Return whether or not the specified virtual address is eligible
 *      for prefault.
 */
boolean_t
pmap_is_prefaultable(pmap_t pmap, vm_offset_t addr)
{
        pd_entry_t *pde;
        pt_entry_t *pte, PG_V;
        boolean_t rv;

        PG_V = pmap_valid_bit(pmap);
        rv = FALSE;
        PMAP_LOCK(pmap);
        pde = pmap_pde(pmap, addr);
        if (pde != NULL && (*pde & (PG_PS | PG_V)) == PG_V) {
                pte = pmap_pde_to_pte(pde, addr);
                rv = (*pte & PG_V) == 0;
        }
        PMAP_UNLOCK(pmap);
        return (rv);
}

/*
 *      pmap_is_referenced:
 *
 *      Return whether or not the specified physical page was referenced
 *      in any physical maps.
 */
boolean_t
pmap_is_referenced(vm_page_t m)
{

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_is_referenced: page %p is not managed", m));
        return (pmap_page_test_mappings(m, TRUE, FALSE));
}

/*
 * Clear the write and modified bits in each of the given page's mappings.
 */
void
pmap_remove_write(vm_page_t m)
{
        struct md_page *pvh;
        pmap_t pmap;
        struct rwlock *lock;
        pv_entry_t next_pv, pv;
        pd_entry_t *pde;
        pt_entry_t oldpte, *pte, PG_M, PG_RW;
        vm_offset_t va;
        int pvh_gen, md_gen;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_remove_write: page %p is not managed", m));

        /*
         * If the page is not exclusive busied, then PGA_WRITEABLE cannot be
         * set by another thread while the object is locked.  Thus,
         * if PGA_WRITEABLE is clear, no page table entries need updating.
         */
        VM_OBJECT_ASSERT_WLOCKED(m->object);
        if (!vm_page_xbusied(m) && (m->aflags & PGA_WRITEABLE) == 0)
                return;
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy :
            pa_to_pvh(VM_PAGE_TO_PHYS(m));
retry_pv_loop:
        rw_wlock(lock);
        TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_next, next_pv) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        pvh_gen = pvh->pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (pvh_gen != pvh->pv_gen) {
                                PMAP_UNLOCK(pmap);
                                rw_wunlock(lock);
                                goto retry_pv_loop;
                        }
                }
                PG_RW = pmap_rw_bit(pmap);
                va = pv->pv_va;
                pde = pmap_pde(pmap, va);
                if ((*pde & PG_RW) != 0)
                        (void)pmap_demote_pde_locked(pmap, pde, va, &lock);
                KASSERT(lock == VM_PAGE_TO_PV_LIST_LOCK(m),
                    ("inconsistent pv lock %p %p for page %p",
                    lock, VM_PAGE_TO_PV_LIST_LOCK(m), m));
                PMAP_UNLOCK(pmap);
        }
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        pvh_gen = pvh->pv_gen;
                        md_gen = m->md.pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (pvh_gen != pvh->pv_gen ||
                            md_gen != m->md.pv_gen) {
                                PMAP_UNLOCK(pmap);
                                rw_wunlock(lock);
                                goto retry_pv_loop;
                        }
                }
                PG_M = pmap_modified_bit(pmap);
                PG_RW = pmap_rw_bit(pmap);
                pde = pmap_pde(pmap, pv->pv_va);
                KASSERT((*pde & PG_PS) == 0,
                    ("pmap_remove_write: found a 2mpage in page %p's pv list",
                    m));
                pte = pmap_pde_to_pte(pde, pv->pv_va);
retry:
                oldpte = *pte;
                if (oldpte & PG_RW) {
                        if (!atomic_cmpset_long(pte, oldpte, oldpte &
                            ~(PG_RW | PG_M)))
                                goto retry;
                        if ((oldpte & PG_M) != 0)
                                vm_page_dirty(m);
                        pmap_invalidate_page(pmap, pv->pv_va);
                }
                PMAP_UNLOCK(pmap);
        }
        rw_wunlock(lock);
        vm_page_aflag_clear(m, PGA_WRITEABLE);
        pmap_delayed_invl_wait(m);
}

static __inline boolean_t
safe_to_clear_referenced(pmap_t pmap, pt_entry_t pte)
{

        if (!pmap_emulate_ad_bits(pmap))
                return (TRUE);

        KASSERT(pmap->pm_type == PT_EPT, ("invalid pm_type %d", pmap->pm_type));

        /*
         * XWR = 010 or 110 will cause an unconditional EPT misconfiguration
         * so we don't let the referenced (aka EPT_PG_READ) bit to be cleared
         * if the EPT_PG_WRITE bit is set.
         */
        if ((pte & EPT_PG_WRITE) != 0)
                return (FALSE);

        /*
         * XWR = 100 is allowed only if the PMAP_SUPPORTS_EXEC_ONLY is set.
         */
        if ((pte & EPT_PG_EXECUTE) == 0 ||
            ((pmap->pm_flags & PMAP_SUPPORTS_EXEC_ONLY) != 0))
                return (TRUE);
        else
                return (FALSE);
}

/*
 *      pmap_ts_referenced:
 *
 *      Return a count of reference bits for a page, clearing those bits.
 *      It is not necessary for every reference bit to be cleared, but it
 *      is necessary that 0 only be returned when there are truly no
 *      reference bits set.
 *
 *      As an optimization, update the page's dirty field if a modified bit is
 *      found while counting reference bits.  This opportunistic update can be
 *      performed at low cost and can eliminate the need for some future calls
 *      to pmap_is_modified().  However, since this function stops after
 *      finding PMAP_TS_REFERENCED_MAX reference bits, it may not detect some
 *      dirty pages.  Those dirty pages will only be detected by a future call
 *      to pmap_is_modified().
 *
 *      A DI block is not needed within this function, because
 *      invalidations are performed before the PV list lock is
 *      released.
 */
int
pmap_ts_referenced(vm_page_t m)
{
        struct md_page *pvh;
        pv_entry_t pv, pvf;
        pmap_t pmap;
        struct rwlock *lock;
        pd_entry_t oldpde, *pde;
        pt_entry_t *pte, PG_A, PG_M, PG_RW;
        vm_offset_t va;
        vm_paddr_t pa;
        int cleared, md_gen, not_cleared, pvh_gen;
        struct spglist free;
        boolean_t demoted;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_ts_referenced: page %p is not managed", m));
        SLIST_INIT(&free);
        cleared = 0;
        pa = VM_PAGE_TO_PHYS(m);
        lock = PHYS_TO_PV_LIST_LOCK(pa);
        pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy : pa_to_pvh(pa);
        rw_wlock(lock);
retry:
        not_cleared = 0;
        if ((pvf = TAILQ_FIRST(&pvh->pv_list)) == NULL)
                goto small_mappings;
        pv = pvf;
        do {
                if (pvf == NULL)
                        pvf = pv;
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        pvh_gen = pvh->pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (pvh_gen != pvh->pv_gen) {
                                PMAP_UNLOCK(pmap);
                                goto retry;
                        }
                }
                PG_A = pmap_accessed_bit(pmap);
                PG_M = pmap_modified_bit(pmap);
                PG_RW = pmap_rw_bit(pmap);
                va = pv->pv_va;
                pde = pmap_pde(pmap, pv->pv_va);
                oldpde = *pde;
                if ((oldpde & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                        /*
                         * Although "oldpde" is mapping a 2MB page, because
                         * this function is called at a 4KB page granularity,
                         * we only update the 4KB page under test.
                         */
                        vm_page_dirty(m);
                }
                if ((oldpde & PG_A) != 0) {
                        /*
                         * Since this reference bit is shared by 512 4KB
                         * pages, it should not be cleared every time it is
                         * tested.  Apply a simple "hash" function on the
                         * physical page number, the virtual superpage number,
                         * and the pmap address to select one 4KB page out of
                         * the 512 on which testing the reference bit will
                         * result in clearing that reference bit.  This
                         * function is designed to avoid the selection of the
                         * same 4KB page for every 2MB page mapping.
                         *
                         * On demotion, a mapping that hasn't been referenced
                         * is simply destroyed.  To avoid the possibility of a
                         * subsequent page fault on a demoted wired mapping,
                         * always leave its reference bit set.  Moreover,
                         * since the superpage is wired, the current state of
                         * its reference bit won't affect page replacement.
                         */
                        if ((((pa >> PAGE_SHIFT) ^ (pv->pv_va >> PDRSHIFT) ^
                            (uintptr_t)pmap) & (NPTEPG - 1)) == 0 &&
                            (oldpde & PG_W) == 0) {
                                if (safe_to_clear_referenced(pmap, oldpde)) {
                                        atomic_clear_long(pde, PG_A);
                                        pmap_invalidate_page(pmap, pv->pv_va);
                                        demoted = FALSE;
                                } else if (pmap_demote_pde_locked(pmap, pde,
                                    pv->pv_va, &lock)) {
                                        /*
                                         * Remove the mapping to a single page
                                         * so that a subsequent access may
                                         * repromote.  Since the underlying
                                         * page table page is fully populated,
                                         * this removal never frees a page
                                         * table page.
                                         */
                                        demoted = TRUE;
                                        va += VM_PAGE_TO_PHYS(m) - (oldpde &
                                            PG_PS_FRAME);
                                        pte = pmap_pde_to_pte(pde, va);
                                        pmap_remove_pte(pmap, pte, va, *pde,
                                            NULL, &lock);
                                        pmap_invalidate_page(pmap, va);
                                } else
                                        demoted = TRUE;

                                if (demoted) {
                                        /*
                                         * The superpage mapping was removed
                                         * entirely and therefore 'pv' is no
                                         * longer valid.
                                         */
                                        if (pvf == pv)
                                                pvf = NULL;
                                        pv = NULL;
                                }
                                cleared++;
                                KASSERT(lock == VM_PAGE_TO_PV_LIST_LOCK(m),
                                    ("inconsistent pv lock %p %p for page %p",
                                    lock, VM_PAGE_TO_PV_LIST_LOCK(m), m));
                        } else
                                not_cleared++;
                }
                PMAP_UNLOCK(pmap);
                /* Rotate the PV list if it has more than one entry. */
                if (pv != NULL && TAILQ_NEXT(pv, pv_next) != NULL) {
                        TAILQ_REMOVE(&pvh->pv_list, pv, pv_next);
                        TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_next);
                        pvh->pv_gen++;
                }
                if (cleared + not_cleared >= PMAP_TS_REFERENCED_MAX)
                        goto out;
        } while ((pv = TAILQ_FIRST(&pvh->pv_list)) != pvf);
small_mappings:
        if ((pvf = TAILQ_FIRST(&m->md.pv_list)) == NULL)
                goto out;
        pv = pvf;
        do {
                if (pvf == NULL)
                        pvf = pv;
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        pvh_gen = pvh->pv_gen;
                        md_gen = m->md.pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (pvh_gen != pvh->pv_gen || md_gen != m->md.pv_gen) {
                                PMAP_UNLOCK(pmap);
                                goto retry;
                        }
                }
                PG_A = pmap_accessed_bit(pmap);
                PG_M = pmap_modified_bit(pmap);
                PG_RW = pmap_rw_bit(pmap);
                pde = pmap_pde(pmap, pv->pv_va);
                KASSERT((*pde & PG_PS) == 0,
                    ("pmap_ts_referenced: found a 2mpage in page %p's pv list",
                    m));
                pte = pmap_pde_to_pte(pde, pv->pv_va);
                if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                        vm_page_dirty(m);
                if ((*pte & PG_A) != 0) {
                        if (safe_to_clear_referenced(pmap, *pte)) {
                                atomic_clear_long(pte, PG_A);
                                pmap_invalidate_page(pmap, pv->pv_va);
                                cleared++;
                        } else if ((*pte & PG_W) == 0) {
                                /*
                                 * Wired pages cannot be paged out so
                                 * doing accessed bit emulation for
                                 * them is wasted effort. We do the
                                 * hard work for unwired pages only.
                                 */
                                pmap_remove_pte(pmap, pte, pv->pv_va,
                                    *pde, &free, &lock);
                                pmap_invalidate_page(pmap, pv->pv_va);
                                cleared++;
                                if (pvf == pv)
                                        pvf = NULL;
                                pv = NULL;
                                KASSERT(lock == VM_PAGE_TO_PV_LIST_LOCK(m),
                                    ("inconsistent pv lock %p %p for page %p",
                                    lock, VM_PAGE_TO_PV_LIST_LOCK(m), m));
                        } else
                                not_cleared++;
                }
                PMAP_UNLOCK(pmap);
                /* Rotate the PV list if it has more than one entry. */
                if (pv != NULL && TAILQ_NEXT(pv, pv_next) != NULL) {
                        TAILQ_REMOVE(&m->md.pv_list, pv, pv_next);
                        TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
                        m->md.pv_gen++;
                }
        } while ((pv = TAILQ_FIRST(&m->md.pv_list)) != pvf && cleared +
            not_cleared < PMAP_TS_REFERENCED_MAX);
out:
        rw_wunlock(lock);
        vm_page_free_pages_toq(&free, true);
        return (cleared + not_cleared);
}

/*
 *      Apply the given advice to the specified range of addresses within the
 *      given pmap.  Depending on the advice, clear the referenced and/or
 *      modified flags in each mapping and set the mapped page's dirty field.
 */
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
        struct rwlock *lock;
        pml4_entry_t *pml4e;
        pdp_entry_t *pdpe;
        pd_entry_t oldpde, *pde;
        pt_entry_t *pte, PG_A, PG_G, PG_M, PG_RW, PG_V;
        vm_offset_t va, va_next;
        vm_page_t m;
        boolean_t anychanged;

        if (advice != MADV_DONTNEED && advice != MADV_FREE)
                return;

        /*
         * A/D bit emulation requires an alternate code path when clearing
         * the modified and accessed bits below. Since this function is
         * advisory in nature we skip it entirely for pmaps that require
         * A/D bit emulation.
         */
        if (pmap_emulate_ad_bits(pmap))
                return;

        PG_A = pmap_accessed_bit(pmap);
        PG_G = pmap_global_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);
        anychanged = FALSE;
        pmap_delayed_invl_started();
        PMAP_LOCK(pmap);
        for (; sva < eva; sva = va_next) {
                pml4e = pmap_pml4e(pmap, sva);
                if ((*pml4e & PG_V) == 0) {
                        va_next = (sva + NBPML4) & ~PML4MASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }
                pdpe = pmap_pml4e_to_pdpe(pml4e, sva);
                if ((*pdpe & PG_V) == 0) {
                        va_next = (sva + NBPDP) & ~PDPMASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }
                va_next = (sva + NBPDR) & ~PDRMASK;
                if (va_next < sva)
                        va_next = eva;
                pde = pmap_pdpe_to_pde(pdpe, sva);
                oldpde = *pde;
                if ((oldpde & PG_V) == 0)
                        continue;
                else if ((oldpde & PG_PS) != 0) {
                        if ((oldpde & PG_MANAGED) == 0)
                                continue;
                        lock = NULL;
                        if (!pmap_demote_pde_locked(pmap, pde, sva, &lock)) {
                                if (lock != NULL)
                                        rw_wunlock(lock);

                                /*
                                 * The large page mapping was destroyed.
                                 */
                                continue;
                        }

                        /*
                         * Unless the page mappings are wired, remove the
                         * mapping to a single page so that a subsequent
                         * access may repromote.  Since the underlying page
                         * table page is fully populated, this removal never
                         * frees a page table page.
                         */
                        if ((oldpde & PG_W) == 0) {
                                pte = pmap_pde_to_pte(pde, sva);
                                KASSERT((*pte & PG_V) != 0,
                                    ("pmap_advise: invalid PTE"));
                                pmap_remove_pte(pmap, pte, sva, *pde, NULL,
                                    &lock);
                                anychanged = TRUE;
                        }
                        if (lock != NULL)
                                rw_wunlock(lock);
                }
                if (va_next > eva)
                        va_next = eva;
                va = va_next;
                for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
                    sva += PAGE_SIZE) {
                        if ((*pte & (PG_MANAGED | PG_V)) != (PG_MANAGED | PG_V))
                                goto maybe_invlrng;
                        else if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                                if (advice == MADV_DONTNEED) {
                                        /*
                                         * Future calls to pmap_is_modified()
                                         * can be avoided by making the page
                                         * dirty now.
                                         */
                                        m = PHYS_TO_VM_PAGE(*pte & PG_FRAME);
                                        vm_page_dirty(m);
                                }
                                atomic_clear_long(pte, PG_M | PG_A);
                        } else if ((*pte & PG_A) != 0)
                                atomic_clear_long(pte, PG_A);
                        else
                                goto maybe_invlrng;

                        if ((*pte & PG_G) != 0) {
                                if (va == va_next)
                                        va = sva;
                        } else
                                anychanged = TRUE;
                        continue;
maybe_invlrng:
                        if (va != va_next) {
                                pmap_invalidate_range(pmap, va, sva);
                                va = va_next;
                        }
                }
                if (va != va_next)
                        pmap_invalidate_range(pmap, va, sva);
        }
        if (anychanged)
                pmap_invalidate_all(pmap);
        PMAP_UNLOCK(pmap);
        pmap_delayed_invl_finished();
}

/*
 *      Clear the modify bits on the specified physical page.
 */
void
pmap_clear_modify(vm_page_t m)
{
        struct md_page *pvh;
        pmap_t pmap;
        pv_entry_t next_pv, pv;
        pd_entry_t oldpde, *pde;
        pt_entry_t oldpte, *pte, PG_M, PG_RW, PG_V;
        struct rwlock *lock;
        vm_offset_t va;
        int md_gen, pvh_gen;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("pmap_clear_modify: page %p is not managed", m));
        VM_OBJECT_ASSERT_WLOCKED(m->object);
        KASSERT(!vm_page_xbusied(m),
            ("pmap_clear_modify: page %p is exclusive busied", m));

        /*
         * If the page is not PGA_WRITEABLE, then no PTEs can have PG_M set.
         * If the object containing the page is locked and the page is not
         * exclusive busied, then PGA_WRITEABLE cannot be concurrently set.
         */
        if ((m->aflags & PGA_WRITEABLE) == 0)
                return;
        pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy :
            pa_to_pvh(VM_PAGE_TO_PHYS(m));
        lock = VM_PAGE_TO_PV_LIST_LOCK(m);
        rw_wlock(lock);
restart:
        TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_next, next_pv) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        pvh_gen = pvh->pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (pvh_gen != pvh->pv_gen) {
                                PMAP_UNLOCK(pmap);
                                goto restart;
                        }
                }
                PG_M = pmap_modified_bit(pmap);
                PG_V = pmap_valid_bit(pmap);
                PG_RW = pmap_rw_bit(pmap);
                va = pv->pv_va;
                pde = pmap_pde(pmap, va);
                oldpde = *pde;
                if ((oldpde & PG_RW) != 0) {
                        if (pmap_demote_pde_locked(pmap, pde, va, &lock)) {
                                if ((oldpde & PG_W) == 0) {
                                        /*
                                         * Write protect the mapping to a
                                         * single page so that a subsequent
                                         * write access may repromote.
                                         */
                                        va += VM_PAGE_TO_PHYS(m) - (oldpde &
                                            PG_PS_FRAME);
                                        pte = pmap_pde_to_pte(pde, va);
                                        oldpte = *pte;
                                        if ((oldpte & PG_V) != 0) {
                                                while (!atomic_cmpset_long(pte,
                                                    oldpte,
                                                    oldpte & ~(PG_M | PG_RW)))
                                                        oldpte = *pte;
                                                vm_page_dirty(m);
                                                pmap_invalidate_page(pmap, va);
                                        }
                                }
                        }
                }
                PMAP_UNLOCK(pmap);
        }
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_next) {
                pmap = PV_PMAP(pv);
                if (!PMAP_TRYLOCK(pmap)) {
                        md_gen = m->md.pv_gen;
                        pvh_gen = pvh->pv_gen;
                        rw_wunlock(lock);
                        PMAP_LOCK(pmap);
                        rw_wlock(lock);
                        if (pvh_gen != pvh->pv_gen || md_gen != m->md.pv_gen) {
                                PMAP_UNLOCK(pmap);
                                goto restart;
                        }
                }
                PG_M = pmap_modified_bit(pmap);
                PG_RW = pmap_rw_bit(pmap);
                pde = pmap_pde(pmap, pv->pv_va);
                KASSERT((*pde & PG_PS) == 0, ("pmap_clear_modify: found"
                    " a 2mpage in page %p's pv list", m));
                pte = pmap_pde_to_pte(pde, pv->pv_va);
                if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                        atomic_clear_long(pte, PG_M);
                        pmap_invalidate_page(pmap, pv->pv_va);
                }
                PMAP_UNLOCK(pmap);
        }
        rw_wunlock(lock);
}

/*
 * Miscellaneous support routines follow
 */

/* Adjust the cache mode for a 4KB page mapped via a PTE. */
static __inline void
pmap_pte_attr(pt_entry_t *pte, int cache_bits, int mask)
{
        u_int opte, npte;

        /*
         * The cache mode bits are all in the low 32-bits of the
         * PTE, so we can just spin on updating the low 32-bits.
         */
        do {
                opte = *(u_int *)pte;
                npte = opte & ~mask;
                npte |= cache_bits;
        } while (npte != opte && !atomic_cmpset_int((u_int *)pte, opte, npte));
}

/* Adjust the cache mode for a 2MB page mapped via a PDE. */
static __inline void
pmap_pde_attr(pd_entry_t *pde, int cache_bits, int mask)
{
        u_int opde, npde;

        /*
         * The cache mode bits are all in the low 32-bits of the
         * PDE, so we can just spin on updating the low 32-bits.
         */
        do {
                opde = *(u_int *)pde;
                npde = opde & ~mask;
                npde |= cache_bits;
        } while (npde != opde && !atomic_cmpset_int((u_int *)pde, opde, npde));
}

/*
 * Map a set of physical memory pages into the kernel virtual
 * address space. Return a pointer to where it is mapped. This
 * routine is intended to be used for mapping device memory,
 * NOT real memory.
 */
void *
pmap_mapdev_attr(vm_paddr_t pa, vm_size_t size, int mode)
{
        struct pmap_preinit_mapping *ppim;
        vm_offset_t va, offset;
        vm_size_t tmpsize;
        int i;

        offset = pa & PAGE_MASK;
        size = round_page(offset + size);
        pa = trunc_page(pa);

        if (!pmap_initialized) {
                va = 0;
                for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                        ppim = pmap_preinit_mapping + i;
                        if (ppim->va == 0) {
                                ppim->pa = pa;
                                ppim->sz = size;
                                ppim->mode = mode;
                                ppim->va = virtual_avail;
                                virtual_avail += size;
                                va = ppim->va;
                                break;
                        }
                }
                if (va == 0)
                        panic("%s: too many preinit mappings", __func__);
        } else {
                /*
                 * If we have a preinit mapping, re-use it.
                 */
                for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                        ppim = pmap_preinit_mapping + i;
                        if (ppim->pa == pa && ppim->sz == size &&
                            ppim->mode == mode)
                                return ((void *)(ppim->va + offset));
                }
                /*
                 * If the specified range of physical addresses fits within
                 * the direct map window, use the direct map.
                 */
                if (pa < dmaplimit && pa + size < dmaplimit) {
                        va = PHYS_TO_DMAP(pa);
                        if (!pmap_change_attr(va, size, mode))
                                return ((void *)(va + offset));
                }
                va = kva_alloc(size);
                if (va == 0)
                        panic("%s: Couldn't allocate KVA", __func__);
        }
        for (tmpsize = 0; tmpsize < size; tmpsize += PAGE_SIZE)
                pmap_kenter_attr(va + tmpsize, pa + tmpsize, mode);
        pmap_invalidate_range(kernel_pmap, va, va + tmpsize);
        pmap_invalidate_cache_range(va, va + tmpsize, FALSE);
        return ((void *)(va + offset));
}

void *
pmap_mapdev(vm_paddr_t pa, vm_size_t size)
{

        return (pmap_mapdev_attr(pa, size, PAT_UNCACHEABLE));
}

void *
pmap_mapbios(vm_paddr_t pa, vm_size_t size)
{

        return (pmap_mapdev_attr(pa, size, PAT_WRITE_BACK));
}

void
pmap_unmapdev(vm_offset_t va, vm_size_t size)
{
        struct pmap_preinit_mapping *ppim;
        vm_offset_t offset;
        int i;

        /* If we gave a direct map region in pmap_mapdev, do nothing */
        if (va >= DMAP_MIN_ADDRESS && va < DMAP_MAX_ADDRESS)
                return;
        offset = va & PAGE_MASK;
        size = round_page(offset + size);
        va = trunc_page(va);
        for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                ppim = pmap_preinit_mapping + i;
                if (ppim->va == va && ppim->sz == size) {
                        if (pmap_initialized)
                                return;
                        ppim->pa = 0;
                        ppim->va = 0;
                        ppim->sz = 0;
                        ppim->mode = 0;
                        if (va + size == virtual_avail)
                                virtual_avail = va;
                        return;
                }
        }
        if (pmap_initialized)
                kva_free(va, size);
}

/*
 * Tries to demote a 1GB page mapping.
 */
static boolean_t
pmap_demote_pdpe(pmap_t pmap, pdp_entry_t *pdpe, vm_offset_t va)
{
        pdp_entry_t newpdpe, oldpdpe;
        pd_entry_t *firstpde, newpde, *pde;
        pt_entry_t PG_A, PG_M, PG_RW, PG_V;
        vm_paddr_t pdpgpa;
        vm_page_t pdpg;

        PG_A = pmap_accessed_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        oldpdpe = *pdpe;
        KASSERT((oldpdpe & (PG_PS | PG_V)) == (PG_PS | PG_V),
            ("pmap_demote_pdpe: oldpdpe is missing PG_PS and/or PG_V"));
        if ((pdpg = vm_page_alloc(NULL, va >> PDPSHIFT, VM_ALLOC_INTERRUPT |
            VM_ALLOC_NOOBJ | VM_ALLOC_WIRED)) == NULL) {
                CTR2(KTR_PMAP, "pmap_demote_pdpe: failure for va %#lx"
                    " in pmap %p", va, pmap);
                return (FALSE);
        }
        pdpgpa = VM_PAGE_TO_PHYS(pdpg);
        firstpde = (pd_entry_t *)PHYS_TO_DMAP(pdpgpa);
        newpdpe = pdpgpa | PG_M | PG_A | (oldpdpe & PG_U) | PG_RW | PG_V;
        KASSERT((oldpdpe & PG_A) != 0,
            ("pmap_demote_pdpe: oldpdpe is missing PG_A"));
        KASSERT((oldpdpe & (PG_M | PG_RW)) != PG_RW,
            ("pmap_demote_pdpe: oldpdpe is missing PG_M"));
        newpde = oldpdpe;

        /*
         * Initialize the page directory page.
         */
        for (pde = firstpde; pde < firstpde + NPDEPG; pde++) {
                *pde = newpde;
                newpde += NBPDR;
        }

        /*
         * Demote the mapping.
         */
        *pdpe = newpdpe;

        /*
         * Invalidate a stale recursive mapping of the page directory page.
         */
        pmap_invalidate_page(pmap, (vm_offset_t)vtopde(va));

        pmap_pdpe_demotions++;
        CTR2(KTR_PMAP, "pmap_demote_pdpe: success for va %#lx"
            " in pmap %p", va, pmap);
        return (TRUE);
}

/*
 * Sets the memory attribute for the specified page.
 */
void
pmap_page_set_memattr(vm_page_t m, vm_memattr_t ma)
{

        m->md.pat_mode = ma;

        /*
         * If "m" is a normal page, update its direct mapping.  This update
         * can be relied upon to perform any cache operations that are
         * required for data coherence.
         */
        if ((m->flags & PG_FICTITIOUS) == 0 &&
            pmap_change_attr(PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m)), PAGE_SIZE,
            m->md.pat_mode))
                panic("memory attribute change on the direct map failed");
}

/*
 * Changes the specified virtual address range's memory type to that given by
 * the parameter "mode".  The specified virtual address range must be
 * completely contained within either the direct map or the kernel map.  If
 * the virtual address range is contained within the kernel map, then the
 * memory type for each of the corresponding ranges of the direct map is also
 * changed.  (The corresponding ranges of the direct map are those ranges that
 * map the same physical pages as the specified virtual address range.)  These
 * changes to the direct map are necessary because Intel describes the
 * behavior of their processors as "undefined" if two or more mappings to the
 * same physical page have different memory types.
 *
 * Returns zero if the change completed successfully, and either EINVAL or
 * ENOMEM if the change failed.  Specifically, EINVAL is returned if some part
 * of the virtual address range was not mapped, and ENOMEM is returned if
 * there was insufficient memory available to complete the change.  In the
 * latter case, the memory type may have been changed on some part of the
 * virtual address range or the direct map.
 */
int
pmap_change_attr(vm_offset_t va, vm_size_t size, int mode)
{
        int error;

        PMAP_LOCK(kernel_pmap);
        error = pmap_change_attr_locked(va, size, mode);
        PMAP_UNLOCK(kernel_pmap);
        return (error);
}

static int
pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode)
{
        vm_offset_t base, offset, tmpva;
        vm_paddr_t pa_start, pa_end, pa_end1;
        pdp_entry_t *pdpe;
        pd_entry_t *pde;
        pt_entry_t *pte;
        int cache_bits_pte, cache_bits_pde, error;
        boolean_t changed;

        PMAP_LOCK_ASSERT(kernel_pmap, MA_OWNED);
        base = trunc_page(va);
        offset = va & PAGE_MASK;
        size = round_page(offset + size);

        /*
         * Only supported on kernel virtual addresses, including the direct
         * map but excluding the recursive map.
         */
        if (base < DMAP_MIN_ADDRESS)
                return (EINVAL);

        cache_bits_pde = pmap_cache_bits(kernel_pmap, mode, 1);
        cache_bits_pte = pmap_cache_bits(kernel_pmap, mode, 0);
        changed = FALSE;

        /*
         * Pages that aren't mapped aren't supported.  Also break down 2MB pages
         * into 4KB pages if required.
         */
        for (tmpva = base; tmpva < base + size; ) {
                pdpe = pmap_pdpe(kernel_pmap, tmpva);
                if (pdpe == NULL || *pdpe == 0)
                        return (EINVAL);
                if (*pdpe & PG_PS) {
                        /*
                         * If the current 1GB page already has the required
                         * memory type, then we need not demote this page. Just
                         * increment tmpva to the next 1GB page frame.
                         */
                        if ((*pdpe & X86_PG_PDE_CACHE) == cache_bits_pde) {
                                tmpva = trunc_1gpage(tmpva) + NBPDP;
                                continue;
                        }

                        /*
                         * If the current offset aligns with a 1GB page frame
                         * and there is at least 1GB left within the range, then
                         * we need not break down this page into 2MB pages.
                         */
                        if ((tmpva & PDPMASK) == 0 &&
                            tmpva + PDPMASK < base + size) {
                                tmpva += NBPDP;
                                continue;
                        }
                        if (!pmap_demote_pdpe(kernel_pmap, pdpe, tmpva))
                                return (ENOMEM);
                }
                pde = pmap_pdpe_to_pde(pdpe, tmpva);
                if (*pde == 0)
                        return (EINVAL);
                if (*pde & PG_PS) {
                        /*
                         * If the current 2MB page already has the required
                         * memory type, then we need not demote this page. Just
                         * increment tmpva to the next 2MB page frame.
                         */
                        if ((*pde & X86_PG_PDE_CACHE) == cache_bits_pde) {
                                tmpva = trunc_2mpage(tmpva) + NBPDR;
                                continue;
                        }

                        /*
                         * If the current offset aligns with a 2MB page frame
                         * and there is at least 2MB left within the range, then
                         * we need not break down this page into 4KB pages.
                         */
                        if ((tmpva & PDRMASK) == 0 &&
                            tmpva + PDRMASK < base + size) {
                                tmpva += NBPDR;
                                continue;
                        }
                        if (!pmap_demote_pde(kernel_pmap, pde, tmpva))
                                return (ENOMEM);
                }
                pte = pmap_pde_to_pte(pde, tmpva);
                if (*pte == 0)
                        return (EINVAL);
                tmpva += PAGE_SIZE;
        }
        error = 0;

        /*
         * Ok, all the pages exist, so run through them updating their
         * cache mode if required.
         */
        pa_start = pa_end = 0;
        for (tmpva = base; tmpva < base + size; ) {
                pdpe = pmap_pdpe(kernel_pmap, tmpva);
                if (*pdpe & PG_PS) {
                        if ((*pdpe & X86_PG_PDE_CACHE) != cache_bits_pde) {
                                pmap_pde_attr(pdpe, cache_bits_pde,
                                    X86_PG_PDE_CACHE);
                                changed = TRUE;
                        }
                        if (tmpva >= VM_MIN_KERNEL_ADDRESS &&
                            (*pdpe & PG_PS_FRAME) < dmaplimit) {
                                if (pa_start == pa_end) {
                                        /* Start physical address run. */
                                        pa_start = *pdpe & PG_PS_FRAME;
                                        pa_end = pa_start + NBPDP;
                                } else if (pa_end == (*pdpe & PG_PS_FRAME))
                                        pa_end += NBPDP;
                                else {
                                        /* Run ended, update direct map. */
                                        error = pmap_change_attr_locked(
                                            PHYS_TO_DMAP(pa_start),
                                            pa_end - pa_start, mode);
                                        if (error != 0)
                                                break;
                                        /* Start physical address run. */
                                        pa_start = *pdpe & PG_PS_FRAME;
                                        pa_end = pa_start + NBPDP;
                                }
                        }
                        tmpva = trunc_1gpage(tmpva) + NBPDP;
                        continue;
                }
                pde = pmap_pdpe_to_pde(pdpe, tmpva);
                if (*pde & PG_PS) {
                        if ((*pde & X86_PG_PDE_CACHE) != cache_bits_pde) {
                                pmap_pde_attr(pde, cache_bits_pde,
                                    X86_PG_PDE_CACHE);
                                changed = TRUE;
                        }
                        if (tmpva >= VM_MIN_KERNEL_ADDRESS &&
                            (*pde & PG_PS_FRAME) < dmaplimit) {
                                if (pa_start == pa_end) {
                                        /* Start physical address run. */
                                        pa_start = *pde & PG_PS_FRAME;
                                        pa_end = pa_start + NBPDR;
                                } else if (pa_end == (*pde & PG_PS_FRAME))
                                        pa_end += NBPDR;
                                else {
                                        /* Run ended, update direct map. */
                                        error = pmap_change_attr_locked(
                                            PHYS_TO_DMAP(pa_start),
                                            pa_end - pa_start, mode);
                                        if (error != 0)
                                                break;
                                        /* Start physical address run. */
                                        pa_start = *pde & PG_PS_FRAME;
                                        pa_end = pa_start + NBPDR;
                                }
                        }
                        tmpva = trunc_2mpage(tmpva) + NBPDR;
                } else {
                        pte = pmap_pde_to_pte(pde, tmpva);
                        if ((*pte & X86_PG_PTE_CACHE) != cache_bits_pte) {
                                pmap_pte_attr(pte, cache_bits_pte,
                                    X86_PG_PTE_CACHE);
                                changed = TRUE;
                        }
                        if (tmpva >= VM_MIN_KERNEL_ADDRESS &&
                            (*pte & PG_FRAME) < dmaplimit) {
                                if (pa_start == pa_end) {
                                        /* Start physical address run. */
                                        pa_start = *pte & PG_FRAME;
                                        pa_end = pa_start + PAGE_SIZE;
                                } else if (pa_end == (*pte & PG_FRAME))
                                        pa_end += PAGE_SIZE;
                                else {
                                        /* Run ended, update direct map. */
                                        error = pmap_change_attr_locked(
                                            PHYS_TO_DMAP(pa_start),
                                            pa_end - pa_start, mode);
                                        if (error != 0)
                                                break;
                                        /* Start physical address run. */
                                        pa_start = *pte & PG_FRAME;
                                        pa_end = pa_start + PAGE_SIZE;
                                }
                        }
                        tmpva += PAGE_SIZE;
                }
        }
        if (error == 0 && pa_start != pa_end && pa_start < dmaplimit) {
                pa_end1 = MIN(pa_end, dmaplimit);
                if (pa_start != pa_end1)
                        error = pmap_change_attr_locked(PHYS_TO_DMAP(pa_start),
                            pa_end1 - pa_start, mode);
        }

        /*
         * Flush CPU caches if required to make sure any data isn't cached that
         * shouldn't be, etc.
         */
        if (changed) {
                pmap_invalidate_range(kernel_pmap, base, tmpva);
                pmap_invalidate_cache_range(base, tmpva, FALSE);
        }
        return (error);
}

/*
 * Demotes any mapping within the direct map region that covers more than the
 * specified range of physical addresses.  This range's size must be a power
 * of two and its starting address must be a multiple of its size.  Since the
 * demotion does not change any attributes of the mapping, a TLB invalidation
 * is not mandatory.  The caller may, however, request a TLB invalidation.
 */
void
pmap_demote_DMAP(vm_paddr_t base, vm_size_t len, boolean_t invalidate)
{
        pdp_entry_t *pdpe;
        pd_entry_t *pde;
        vm_offset_t va;
        boolean_t changed;

        if (len == 0)
                return;
        KASSERT(powerof2(len), ("pmap_demote_DMAP: len is not a power of 2"));
        KASSERT((base & (len - 1)) == 0,
            ("pmap_demote_DMAP: base is not a multiple of len"));
        if (len < NBPDP && base < dmaplimit) {
                va = PHYS_TO_DMAP(base);
                changed = FALSE;
                PMAP_LOCK(kernel_pmap);
                pdpe = pmap_pdpe(kernel_pmap, va);
                if ((*pdpe & X86_PG_V) == 0)
                        panic("pmap_demote_DMAP: invalid PDPE");
                if ((*pdpe & PG_PS) != 0) {
                        if (!pmap_demote_pdpe(kernel_pmap, pdpe, va))
                                panic("pmap_demote_DMAP: PDPE failed");
                        changed = TRUE;
                }
                if (len < NBPDR) {
                        pde = pmap_pdpe_to_pde(pdpe, va);
                        if ((*pde & X86_PG_V) == 0)
                                panic("pmap_demote_DMAP: invalid PDE");
                        if ((*pde & PG_PS) != 0) {
                                if (!pmap_demote_pde(kernel_pmap, pde, va))
                                        panic("pmap_demote_DMAP: PDE failed");
                                changed = TRUE;
                        }
                }
                if (changed && invalidate)
                        pmap_invalidate_page(kernel_pmap, va);
                PMAP_UNLOCK(kernel_pmap);
        }
}

/*
 * perform the pmap work for mincore
 */
int
pmap_mincore(pmap_t pmap, vm_offset_t addr, vm_paddr_t *locked_pa)
{
        pd_entry_t *pdep;
        pt_entry_t pte, PG_A, PG_M, PG_RW, PG_V;
        vm_paddr_t pa;
        int val;

        PG_A = pmap_accessed_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        PMAP_LOCK(pmap);
retry:
        pdep = pmap_pde(pmap, addr);
        if (pdep != NULL && (*pdep & PG_V)) {
                if (*pdep & PG_PS) {
                        pte = *pdep;
                        /* Compute the physical address of the 4KB page. */
                        pa = ((*pdep & PG_PS_FRAME) | (addr & PDRMASK)) &
                            PG_FRAME;
                        val = MINCORE_SUPER;
                } else {
                        pte = *pmap_pde_to_pte(pdep, addr);
                        pa = pte & PG_FRAME;
                        val = 0;
                }
        } else {
                pte = 0;
                pa = 0;
                val = 0;
        }
        if ((pte & PG_V) != 0) {
                val |= MINCORE_INCORE;
                if ((pte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                        val |= MINCORE_MODIFIED | MINCORE_MODIFIED_OTHER;
                if ((pte & PG_A) != 0)
                        val |= MINCORE_REFERENCED | MINCORE_REFERENCED_OTHER;
        }
        if ((val & (MINCORE_MODIFIED_OTHER | MINCORE_REFERENCED_OTHER)) !=
            (MINCORE_MODIFIED_OTHER | MINCORE_REFERENCED_OTHER) &&
            (pte & (PG_MANAGED | PG_V)) == (PG_MANAGED | PG_V)) {
                /* Ensure that "PHYS_TO_VM_PAGE(pa)->object" doesn't change. */
                if (vm_page_pa_tryrelock(pmap, pa, locked_pa))
                        goto retry;
        } else
                PA_UNLOCK_COND(*locked_pa);
        PMAP_UNLOCK(pmap);
        return (val);
}

static uint64_t
pmap_pcid_alloc(pmap_t pmap, u_int cpuid)
{
        uint32_t gen, new_gen, pcid_next;

        CRITICAL_ASSERT(curthread);
        gen = PCPU_GET(pcid_gen);
        if (pmap->pm_pcids[cpuid].pm_pcid == PMAP_PCID_KERN)
                return (pti ? 0 : CR3_PCID_SAVE);
        if (pmap->pm_pcids[cpuid].pm_gen == gen)
                return (CR3_PCID_SAVE);
        pcid_next = PCPU_GET(pcid_next);
        KASSERT((!pti && pcid_next <= PMAP_PCID_OVERMAX) ||
            (pti && pcid_next <= PMAP_PCID_OVERMAX_KERN),
            ("cpu %d pcid_next %#x", cpuid, pcid_next));
        if ((!pti && pcid_next == PMAP_PCID_OVERMAX) ||
            (pti && pcid_next == PMAP_PCID_OVERMAX_KERN)) {
                new_gen = gen + 1;
                if (new_gen == 0)
                        new_gen = 1;
                PCPU_SET(pcid_gen, new_gen);
                pcid_next = PMAP_PCID_KERN + 1;
        } else {
                new_gen = gen;
        }
        pmap->pm_pcids[cpuid].pm_pcid = pcid_next;
        pmap->pm_pcids[cpuid].pm_gen = new_gen;
        PCPU_SET(pcid_next, pcid_next + 1);
        return (0);
}

static uint64_t
pmap_pcid_alloc_checked(pmap_t pmap, u_int cpuid)
{
        uint64_t cached;

        cached = pmap_pcid_alloc(pmap, cpuid);
        KASSERT(pmap->pm_pcids[cpuid].pm_pcid >= 0 &&
            pmap->pm_pcids[cpuid].pm_pcid < PMAP_PCID_OVERMAX,
            ("pmap %p cpu %d pcid %#x", pmap, cpuid,
            pmap->pm_pcids[cpuid].pm_pcid));
        KASSERT(pmap->pm_pcids[cpuid].pm_pcid != PMAP_PCID_KERN ||
            pmap == kernel_pmap,
            ("non-kernel pmap pmap %p cpu %d pcid %#x",
            pmap, cpuid, pmap->pm_pcids[cpuid].pm_pcid));
        return (cached);
}

static void
pmap_activate_sw_pti_post(pmap_t pmap)
{

        if (pmap->pm_ucr3 != PMAP_NO_CR3)
                PCPU_GET(tssp)->tss_rsp0 = ((vm_offset_t)PCPU_PTR(pti_stack) +
                    PC_PTI_STACK_SZ * sizeof(uint64_t)) & ~0xful;
}

static void inline
pmap_activate_sw_pcid_pti(pmap_t pmap, u_int cpuid, const bool invpcid_works1)
{
        struct invpcid_descr d;
        uint64_t cached, cr3, kcr3, ucr3;

        cached = pmap_pcid_alloc_checked(pmap, cpuid);
        cr3 = rcr3();
        if ((cr3 & ~CR3_PCID_MASK) != pmap->pm_cr3)
                load_cr3(pmap->pm_cr3 | pmap->pm_pcids[cpuid].pm_pcid);
        PCPU_SET(curpmap, pmap);
        kcr3 = pmap->pm_cr3 | pmap->pm_pcids[cpuid].pm_pcid;
        ucr3 = pmap->pm_ucr3 | pmap->pm_pcids[cpuid].pm_pcid |
            PMAP_PCID_USER_PT;

        if (!cached && pmap->pm_ucr3 != PMAP_NO_CR3) {
                /*
                 * Explicitly invalidate translations cached from the
                 * user page table.  They are not automatically
                 * flushed by reload of cr3 with the kernel page table
                 * pointer above.
                 *
                 * Note that the if() condition is resolved statically
                 * by using the function argument instead of
                 * runtime-evaluated invpcid_works value.
                 */
                if (invpcid_works1) {
                        d.pcid = PMAP_PCID_USER_PT |
                            pmap->pm_pcids[cpuid].pm_pcid;
                        d.pad = 0;
                        d.addr = 0;
                        invpcid(&d, INVPCID_CTX);
                } else {
                        pmap_pti_pcid_invalidate(ucr3, kcr3);
                }
        }

        PCPU_SET(kcr3, kcr3 | CR3_PCID_SAVE);
        PCPU_SET(ucr3, ucr3 | CR3_PCID_SAVE);
        if (cached)
                PCPU_INC(pm_save_cnt);
}

static void
pmap_activate_sw_pcid_invpcid_pti(pmap_t pmap, u_int cpuid)
{

        pmap_activate_sw_pcid_pti(pmap, cpuid, true);
        pmap_activate_sw_pti_post(pmap);
}

static void
pmap_activate_sw_pcid_noinvpcid_pti(pmap_t pmap, u_int cpuid)
{
        register_t rflags;

        /*
         * If the INVPCID instruction is not available,
         * invltlb_pcid_handler() is used to handle an invalidate_all
         * IPI, which checks for curpmap == smp_tlb_pmap.  The below
         * sequence of operations has a window where %CR3 is loaded
         * with the new pmap's PML4 address, but the curpmap value has
         * not yet been updated.  This causes the invltlb IPI handler,
         * which is called between the updates, to execute as a NOP,
         * which leaves stale TLB entries.
         *
         * Note that the most typical use of pmap_activate_sw(), from
         * the context switch, is immune to this race, because
         * interrupts are disabled (while the thread lock is owned),
         * and the IPI happens after curpmap is updated.  Protect
         * other callers in a similar way, by disabling interrupts
         * around the %cr3 register reload and curpmap assignment.
         */
        rflags = intr_disable();
        pmap_activate_sw_pcid_pti(pmap, cpuid, false);
        intr_restore(rflags);
        pmap_activate_sw_pti_post(pmap);
}

static void
pmap_activate_sw_pcid_nopti(pmap_t pmap, u_int cpuid)
{
        uint64_t cached, cr3;

        cached = pmap_pcid_alloc_checked(pmap, cpuid);
        cr3 = rcr3();
        if (!cached || (cr3 & ~CR3_PCID_MASK) != pmap->pm_cr3)
                load_cr3(pmap->pm_cr3 | pmap->pm_pcids[cpuid].pm_pcid |
                    cached);
        PCPU_SET(curpmap, pmap);
        if (cached)
                PCPU_INC(pm_save_cnt);
}

static void
pmap_activate_sw_pcid_noinvpcid_nopti(pmap_t pmap, u_int cpuid)
{
        register_t rflags;

        rflags = intr_disable();
        pmap_activate_sw_pcid_nopti(pmap, cpuid);
        intr_restore(rflags);
}

static void
pmap_activate_sw_nopcid_nopti(pmap_t pmap, u_int cpuid __unused)
{

        load_cr3(pmap->pm_cr3);
        PCPU_SET(curpmap, pmap);
}

static void
pmap_activate_sw_nopcid_pti(pmap_t pmap, u_int cpuid __unused)
{

        pmap_activate_sw_nopcid_nopti(pmap, cpuid);
        PCPU_SET(kcr3, pmap->pm_cr3);
        PCPU_SET(ucr3, pmap->pm_ucr3);
        pmap_activate_sw_pti_post(pmap);
}

DEFINE_IFUNC(static, void, pmap_activate_sw_mode, (pmap_t, u_int), static)
{

        if (pmap_pcid_enabled && pti && invpcid_works)
                return (pmap_activate_sw_pcid_invpcid_pti);
        else if (pmap_pcid_enabled && pti && !invpcid_works)
                return (pmap_activate_sw_pcid_noinvpcid_pti);
        else if (pmap_pcid_enabled && !pti && invpcid_works)
                return (pmap_activate_sw_pcid_nopti);
        else if (pmap_pcid_enabled && !pti && !invpcid_works)
                return (pmap_activate_sw_pcid_noinvpcid_nopti);
        else if (!pmap_pcid_enabled && pti)
                return (pmap_activate_sw_nopcid_pti);
        else /* if (!pmap_pcid_enabled && !pti) */
                return (pmap_activate_sw_nopcid_nopti);
}

void
pmap_activate_sw(struct thread *td)
{
        pmap_t oldpmap, pmap;
        u_int cpuid;

        oldpmap = PCPU_GET(curpmap);
        pmap = vmspace_pmap(td->td_proc->p_vmspace);
        if (oldpmap == pmap)
                return;
        cpuid = PCPU_GET(cpuid);
#ifdef SMP
        CPU_SET_ATOMIC(cpuid, &pmap->pm_active);
#else
        CPU_SET(cpuid, &pmap->pm_active);
#endif
        pmap_activate_sw_mode(pmap, cpuid);
#ifdef SMP
        CPU_CLR_ATOMIC(cpuid, &oldpmap->pm_active);
#else
        CPU_CLR(cpuid, &oldpmap->pm_active);
#endif
}

void
pmap_activate(struct thread *td)
{

        critical_enter();
        pmap_activate_sw(td);
        critical_exit();
}

void
pmap_activate_boot(pmap_t pmap)
{
        uint64_t kcr3;
        u_int cpuid;

        /*
         * kernel_pmap must be never deactivated, and we ensure that
         * by never activating it at all.
         */
        MPASS(pmap != kernel_pmap);

        cpuid = PCPU_GET(cpuid);
#ifdef SMP
        CPU_SET_ATOMIC(cpuid, &pmap->pm_active);
#else
        CPU_SET(cpuid, &pmap->pm_active);
#endif
        PCPU_SET(curpmap, pmap);
        if (pti) {
                kcr3 = pmap->pm_cr3;
                if (pmap_pcid_enabled)
                        kcr3 |= pmap->pm_pcids[cpuid].pm_pcid | CR3_PCID_SAVE;
        } else {
                kcr3 = PMAP_NO_CR3;
        }
        PCPU_SET(kcr3, kcr3);
        PCPU_SET(ucr3, PMAP_NO_CR3);
}

void
pmap_sync_icache(pmap_t pm, vm_offset_t va, vm_size_t sz)
{
}

/*
 *      Increase the starting virtual address of the given mapping if a
 *      different alignment might result in more superpage mappings.
 */
void
pmap_align_superpage(vm_object_t object, vm_ooffset_t offset,
    vm_offset_t *addr, vm_size_t size)
{
        vm_offset_t superpage_offset;

        if (size < NBPDR)
                return;
        if (object != NULL && (object->flags & OBJ_COLORED) != 0)
                offset += ptoa(object->pg_color);
        superpage_offset = offset & PDRMASK;
        if (size - ((NBPDR - superpage_offset) & PDRMASK) < NBPDR ||
            (*addr & PDRMASK) == superpage_offset)
                return;
        if ((*addr & PDRMASK) < superpage_offset)
                *addr = (*addr & ~PDRMASK) + superpage_offset;
        else
                *addr = ((*addr + PDRMASK) & ~PDRMASK) + superpage_offset;
}

#ifdef INVARIANTS
static unsigned long num_dirty_emulations;
SYSCTL_ULONG(_vm_pmap, OID_AUTO, num_dirty_emulations, CTLFLAG_RW,
             &num_dirty_emulations, 0, NULL);

static unsigned long num_accessed_emulations;
SYSCTL_ULONG(_vm_pmap, OID_AUTO, num_accessed_emulations, CTLFLAG_RW,
             &num_accessed_emulations, 0, NULL);

static unsigned long num_superpage_accessed_emulations;
SYSCTL_ULONG(_vm_pmap, OID_AUTO, num_superpage_accessed_emulations, CTLFLAG_RW,
             &num_superpage_accessed_emulations, 0, NULL);

static unsigned long ad_emulation_superpage_promotions;
SYSCTL_ULONG(_vm_pmap, OID_AUTO, ad_emulation_superpage_promotions, CTLFLAG_RW,
             &ad_emulation_superpage_promotions, 0, NULL);
#endif  /* INVARIANTS */

int
pmap_emulate_accessed_dirty(pmap_t pmap, vm_offset_t va, int ftype)
{
        int rv;
        struct rwlock *lock;
#if VM_NRESERVLEVEL > 0
        vm_page_t m, mpte;
#endif
        pd_entry_t *pde;
        pt_entry_t *pte, PG_A, PG_M, PG_RW, PG_V;

        KASSERT(ftype == VM_PROT_READ || ftype == VM_PROT_WRITE,
            ("pmap_emulate_accessed_dirty: invalid fault type %d", ftype));

        if (!pmap_emulate_ad_bits(pmap))
                return (-1);

        PG_A = pmap_accessed_bit(pmap);
        PG_M = pmap_modified_bit(pmap);
        PG_V = pmap_valid_bit(pmap);
        PG_RW = pmap_rw_bit(pmap);

        rv = -1;
        lock = NULL;
        PMAP_LOCK(pmap);

        pde = pmap_pde(pmap, va);
        if (pde == NULL || (*pde & PG_V) == 0)
                goto done;

        if ((*pde & PG_PS) != 0) {
                if (ftype == VM_PROT_READ) {
#ifdef INVARIANTS
                        atomic_add_long(&num_superpage_accessed_emulations, 1);
#endif
                        *pde |= PG_A;
                        rv = 0;
                }
                goto done;
        }

        pte = pmap_pde_to_pte(pde, va);
        if ((*pte & PG_V) == 0)
                goto done;

        if (ftype == VM_PROT_WRITE) {
                if ((*pte & PG_RW) == 0)
                        goto done;
                /*
                 * Set the modified and accessed bits simultaneously.
                 *
                 * Intel EPT PTEs that do software emulation of A/D bits map
                 * PG_A and PG_M to EPT_PG_READ and EPT_PG_WRITE respectively.
                 * An EPT misconfiguration is triggered if the PTE is writable
                 * but not readable (WR=10). This is avoided by setting PG_A
                 * and PG_M simultaneously.
                 */
                *pte |= PG_M | PG_A;
        } else {
                *pte |= PG_A;
        }

#if VM_NRESERVLEVEL > 0
        /* try to promote the mapping */
        if (va < VM_MAXUSER_ADDRESS)
                mpte = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
        else
                mpte = NULL;

        m = PHYS_TO_VM_PAGE(*pte & PG_FRAME);

        if ((mpte == NULL || mpte->wire_count == NPTEPG) &&
            pmap_ps_enabled(pmap) &&
            (m->flags & PG_FICTITIOUS) == 0 &&
            vm_reserv_level_iffullpop(m) == 0) {
                pmap_promote_pde(pmap, pde, va, &lock);
#ifdef INVARIANTS
                atomic_add_long(&ad_emulation_superpage_promotions, 1);
#endif
        }
#endif

#ifdef INVARIANTS
        if (ftype == VM_PROT_WRITE)
                atomic_add_long(&num_dirty_emulations, 1);
        else
                atomic_add_long(&num_accessed_emulations, 1);
#endif
        rv = 0;         /* success */
done:
        if (lock != NULL)
                rw_wunlock(lock);
        PMAP_UNLOCK(pmap);
        return (rv);
}

void
pmap_get_mapping(pmap_t pmap, vm_offset_t va, uint64_t *ptr, int *num)
{
        pml4_entry_t *pml4;
        pdp_entry_t *pdp;
        pd_entry_t *pde;
        pt_entry_t *pte, PG_V;
        int idx;

        idx = 0;
        PG_V = pmap_valid_bit(pmap);
        PMAP_LOCK(pmap);

        pml4 = pmap_pml4e(pmap, va);
        ptr[idx++] = *pml4;
        if ((*pml4 & PG_V) == 0)
                goto done;

        pdp = pmap_pml4e_to_pdpe(pml4, va);
        ptr[idx++] = *pdp;
        if ((*pdp & PG_V) == 0 || (*pdp & PG_PS) != 0)
                goto done;

        pde = pmap_pdpe_to_pde(pdp, va);
        ptr[idx++] = *pde;
        if ((*pde & PG_V) == 0 || (*pde & PG_PS) != 0)
                goto done;

        pte = pmap_pde_to_pte(pde, va);
        ptr[idx++] = *pte;

done:
        PMAP_UNLOCK(pmap);
        *num = idx;
}

/**
 * Get the kernel virtual address of a set of physical pages. If there are
 * physical addresses not covered by the DMAP perform a transient mapping
 * that will be removed when calling pmap_unmap_io_transient.
 *
 * \param page        The pages the caller wishes to obtain the virtual
 *                    address on the kernel memory map.
 * \param vaddr       On return contains the kernel virtual memory address
 *                    of the pages passed in the page parameter.
 * \param count       Number of pages passed in.
 * \param can_fault   TRUE if the thread using the mapped pages can take
 *                    page faults, FALSE otherwise.
 *
 * \returns TRUE if the caller must call pmap_unmap_io_transient when
 *          finished or FALSE otherwise.
 *
 */
boolean_t
pmap_map_io_transient(vm_page_t page[], vm_offset_t vaddr[], int count,
    boolean_t can_fault)
{
        vm_paddr_t paddr;
        boolean_t needs_mapping;
        pt_entry_t *pte;
        int cache_bits, error __unused, i;

        /*
         * Allocate any KVA space that we need, this is done in a separate
         * loop to prevent calling vmem_alloc while pinned.
         */
        needs_mapping = FALSE;
        for (i = 0; i < count; i++) {
                paddr = VM_PAGE_TO_PHYS(page[i]);
                if (__predict_false(paddr >= dmaplimit)) {
                        error = vmem_alloc(kernel_arena, PAGE_SIZE,
                            M_BESTFIT | M_WAITOK, &vaddr[i]);
                        KASSERT(error == 0, ("vmem_alloc failed: %d", error));
                        needs_mapping = TRUE;
                } else {
                        vaddr[i] = PHYS_TO_DMAP(paddr);
                }
        }

        /* Exit early if everything is covered by the DMAP */
        if (!needs_mapping)
                return (FALSE);

        /*
         * NB:  The sequence of updating a page table followed by accesses
         * to the corresponding pages used in the !DMAP case is subject to
         * the situation described in the "AMD64 Architecture Programmer's
         * Manual Volume 2: System Programming" rev. 3.23, "7.3.1 Special
         * Coherency Considerations".  Therefore, issuing the INVLPG right
         * after modifying the PTE bits is crucial.
         */
        if (!can_fault)
                sched_pin();
        for (i = 0; i < count; i++) {
                paddr = VM_PAGE_TO_PHYS(page[i]);
                if (paddr >= dmaplimit) {
                        if (can_fault) {
                                /*
                                 * Slow path, since we can get page faults
                                 * while mappings are active don't pin the
                                 * thread to the CPU and instead add a global
                                 * mapping visible to all CPUs.
                                 */
                                pmap_qenter(vaddr[i], &page[i], 1);
                        } else {
                                pte = vtopte(vaddr[i]);
                                cache_bits = pmap_cache_bits(kernel_pmap,
                                    page[i]->md.pat_mode, 0);
                                pte_store(pte, paddr | X86_PG_RW | X86_PG_V |
                                    cache_bits);
                                invlpg(vaddr[i]);
                        }
                }
        }

        return (needs_mapping);
}

void
pmap_unmap_io_transient(vm_page_t page[], vm_offset_t vaddr[], int count,
    boolean_t can_fault)
{
        vm_paddr_t paddr;
        int i;

        if (!can_fault)
                sched_unpin();
        for (i = 0; i < count; i++) {
                paddr = VM_PAGE_TO_PHYS(page[i]);
                if (paddr >= dmaplimit) {
                        if (can_fault)
                                pmap_qremove(vaddr[i], 1);
                        vmem_free(kernel_arena, vaddr[i], PAGE_SIZE);
                }
        }
}

vm_offset_t
pmap_quick_enter_page(vm_page_t m)
{
        vm_paddr_t paddr;

        paddr = VM_PAGE_TO_PHYS(m);
        if (paddr < dmaplimit)
                return (PHYS_TO_DMAP(paddr));
        mtx_lock_spin(&qframe_mtx);
        KASSERT(*vtopte(qframe) == 0, ("qframe busy"));
        pte_store(vtopte(qframe), paddr | X86_PG_RW | X86_PG_V | X86_PG_A |
            X86_PG_M | pmap_cache_bits(kernel_pmap, m->md.pat_mode, 0));
        return (qframe);
}

void
pmap_quick_remove_page(vm_offset_t addr)
{

        if (addr != qframe)
                return;
        pte_store(vtopte(qframe), 0);
        invlpg(qframe);
        mtx_unlock_spin(&qframe_mtx);
}

static vm_page_t
pmap_pti_alloc_page(void)
{
        vm_page_t m;

        VM_OBJECT_ASSERT_WLOCKED(pti_obj);
        m = vm_page_grab(pti_obj, pti_pg_idx++, VM_ALLOC_NOBUSY |
            VM_ALLOC_WIRED | VM_ALLOC_ZERO);
        return (m);
}

static bool
pmap_pti_free_page(vm_page_t m)
{

        KASSERT(m->wire_count > 0, ("page %p not wired", m));
        if (!vm_page_unwire_noq(m))
                return (false);
        vm_page_free_zero(m);
        return (true);
}

static void
pmap_pti_init(void)
{
        vm_page_t pml4_pg;
        pdp_entry_t *pdpe;
        vm_offset_t va;
        int i;

        if (!pti)
                return;
        pti_obj = vm_pager_allocate(OBJT_PHYS, NULL, 0, VM_PROT_ALL, 0, NULL);
        VM_OBJECT_WLOCK(pti_obj);
        pml4_pg = pmap_pti_alloc_page();
        pti_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pml4_pg));
        for (va = VM_MIN_KERNEL_ADDRESS; va <= VM_MAX_KERNEL_ADDRESS &&
            va >= VM_MIN_KERNEL_ADDRESS && va > NBPML4; va += NBPML4) {
                pdpe = pmap_pti_pdpe(va);
                pmap_pti_wire_pte(pdpe);
        }
        pmap_pti_add_kva_locked((vm_offset_t)&__pcpu[0],
            (vm_offset_t)&__pcpu[0] + sizeof(__pcpu[0]) * MAXCPU, false);
        pmap_pti_add_kva_locked((vm_offset_t)gdt, (vm_offset_t)gdt +
            sizeof(struct user_segment_descriptor) * NGDT * MAXCPU, false);
        pmap_pti_add_kva_locked((vm_offset_t)idt, (vm_offset_t)idt +
            sizeof(struct gate_descriptor) * NIDT, false);
        pmap_pti_add_kva_locked((vm_offset_t)common_tss,
            (vm_offset_t)common_tss + sizeof(struct amd64tss) * MAXCPU, false);
        CPU_FOREACH(i) {
                /* Doublefault stack IST 1 */
                va = common_tss[i].tss_ist1;
                pmap_pti_add_kva_locked(va - PAGE_SIZE, va, false);
                /* NMI stack IST 2 */
                va = common_tss[i].tss_ist2 + sizeof(struct nmi_pcpu);
                pmap_pti_add_kva_locked(va - PAGE_SIZE, va, false);
                /* MC# stack IST 3 */
                va = common_tss[i].tss_ist3 + sizeof(struct nmi_pcpu);
                pmap_pti_add_kva_locked(va - PAGE_SIZE, va, false);
                /* DB# stack IST 4 */
                va = common_tss[i].tss_ist4 + sizeof(struct nmi_pcpu);
                pmap_pti_add_kva_locked(va - PAGE_SIZE, va, false);
        }
        pmap_pti_add_kva_locked((vm_offset_t)kernphys + KERNBASE,
            (vm_offset_t)etext, true);
        pti_finalized = true;
        VM_OBJECT_WUNLOCK(pti_obj);
}
SYSINIT(pmap_pti, SI_SUB_CPU + 1, SI_ORDER_ANY, pmap_pti_init, NULL);

static pdp_entry_t *
pmap_pti_pdpe(vm_offset_t va)
{
        pml4_entry_t *pml4e;
        pdp_entry_t *pdpe;
        vm_page_t m;
        vm_pindex_t pml4_idx;
        vm_paddr_t mphys;

        VM_OBJECT_ASSERT_WLOCKED(pti_obj);

        pml4_idx = pmap_pml4e_index(va);
        pml4e = &pti_pml4[pml4_idx];
        m = NULL;
        if (*pml4e == 0) {
                if (pti_finalized)
                        panic("pml4 alloc after finalization\n");
                m = pmap_pti_alloc_page();
                if (*pml4e != 0) {
                        pmap_pti_free_page(m);
                        mphys = *pml4e & ~PAGE_MASK;
                } else {
                        mphys = VM_PAGE_TO_PHYS(m);
                        *pml4e = mphys | X86_PG_RW | X86_PG_V;
                }
        } else {
                mphys = *pml4e & ~PAGE_MASK;
        }
        pdpe = (pdp_entry_t *)PHYS_TO_DMAP(mphys) + pmap_pdpe_index(va);
        return (pdpe);
}

static void
pmap_pti_wire_pte(void *pte)
{
        vm_page_t m;

        VM_OBJECT_ASSERT_WLOCKED(pti_obj);
        m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((uintptr_t)pte));
        m->wire_count++;
}

static void
pmap_pti_unwire_pde(void *pde, bool only_ref)
{
        vm_page_t m;

        VM_OBJECT_ASSERT_WLOCKED(pti_obj);
        m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((uintptr_t)pde));
        MPASS(m->wire_count > 0);
        MPASS(only_ref || m->wire_count > 1);
        pmap_pti_free_page(m);
}

static void
pmap_pti_unwire_pte(void *pte, vm_offset_t va)
{
        vm_page_t m;
        pd_entry_t *pde;

        VM_OBJECT_ASSERT_WLOCKED(pti_obj);
        m = PHYS_TO_VM_PAGE(DMAP_TO_PHYS((uintptr_t)pte));
        MPASS(m->wire_count > 0);
        if (pmap_pti_free_page(m)) {
                pde = pmap_pti_pde(va);
                MPASS((*pde & (X86_PG_PS | X86_PG_V)) == X86_PG_V);
                *pde = 0;
                pmap_pti_unwire_pde(pde, false);
        }
}

static pd_entry_t *
pmap_pti_pde(vm_offset_t va)
{
        pdp_entry_t *pdpe;
        pd_entry_t *pde;
        vm_page_t m;
        vm_pindex_t pd_idx;
        vm_paddr_t mphys;

        VM_OBJECT_ASSERT_WLOCKED(pti_obj);

        pdpe = pmap_pti_pdpe(va);
        if (*pdpe == 0) {
                m = pmap_pti_alloc_page();
                if (*pdpe != 0) {
                        pmap_pti_free_page(m);
                        MPASS((*pdpe & X86_PG_PS) == 0);
                        mphys = *pdpe & ~PAGE_MASK;
                } else {
                        mphys =  VM_PAGE_TO_PHYS(m);
                        *pdpe = mphys | X86_PG_RW | X86_PG_V;
                }
        } else {
                MPASS((*pdpe & X86_PG_PS) == 0);
                mphys = *pdpe & ~PAGE_MASK;
        }

        pde = (pd_entry_t *)PHYS_TO_DMAP(mphys);
        pd_idx = pmap_pde_index(va);
        pde += pd_idx;
        return (pde);
}

static pt_entry_t *
pmap_pti_pte(vm_offset_t va, bool *unwire_pde)
{
        pd_entry_t *pde;
        pt_entry_t *pte;
        vm_page_t m;
        vm_paddr_t mphys;

        VM_OBJECT_ASSERT_WLOCKED(pti_obj);

        pde = pmap_pti_pde(va);
        if (unwire_pde != NULL) {
                *unwire_pde = true;
                pmap_pti_wire_pte(pde);
        }
        if (*pde == 0) {
                m = pmap_pti_alloc_page();
                if (*pde != 0) {
                        pmap_pti_free_page(m);
                        MPASS((*pde & X86_PG_PS) == 0);
                        mphys = *pde & ~(PAGE_MASK | pg_nx);
                } else {
                        mphys = VM_PAGE_TO_PHYS(m);
                        *pde = mphys | X86_PG_RW | X86_PG_V;
                        if (unwire_pde != NULL)
                                *unwire_pde = false;
                }
        } else {
                MPASS((*pde & X86_PG_PS) == 0);
                mphys = *pde & ~(PAGE_MASK | pg_nx);
        }

        pte = (pt_entry_t *)PHYS_TO_DMAP(mphys);
        pte += pmap_pte_index(va);

        return (pte);
}

static void
pmap_pti_add_kva_locked(vm_offset_t sva, vm_offset_t eva, bool exec)
{
        vm_paddr_t pa;
        pd_entry_t *pde;
        pt_entry_t *pte, ptev;
        bool unwire_pde;

        VM_OBJECT_ASSERT_WLOCKED(pti_obj);

        sva = trunc_page(sva);
        MPASS(sva > VM_MAXUSER_ADDRESS);
        eva = round_page(eva);
        MPASS(sva < eva);
        for (; sva < eva; sva += PAGE_SIZE) {
                pte = pmap_pti_pte(sva, &unwire_pde);
                pa = pmap_kextract(sva);
                ptev = pa | X86_PG_RW | X86_PG_V | X86_PG_A | X86_PG_G |
                    (exec ? 0 : pg_nx) | pmap_cache_bits(kernel_pmap,
                    VM_MEMATTR_DEFAULT, FALSE);
                if (*pte == 0) {
                        pte_store(pte, ptev);
                        pmap_pti_wire_pte(pte);
                } else {
                        KASSERT(!pti_finalized,
                            ("pti overlap after fin %#lx %#lx %#lx",
                            sva, *pte, ptev));
                        KASSERT(*pte == ptev,
                            ("pti non-identical pte after fin %#lx %#lx %#lx",
                            sva, *pte, ptev));
                }
                if (unwire_pde) {
                        pde = pmap_pti_pde(sva);
                        pmap_pti_unwire_pde(pde, true);
                }
        }
}

void
pmap_pti_add_kva(vm_offset_t sva, vm_offset_t eva, bool exec)
{

        if (!pti)
                return;
        VM_OBJECT_WLOCK(pti_obj);
        pmap_pti_add_kva_locked(sva, eva, exec);
        VM_OBJECT_WUNLOCK(pti_obj);
}

void
pmap_pti_remove_kva(vm_offset_t sva, vm_offset_t eva)
{
        pt_entry_t *pte;
        vm_offset_t va;

        if (!pti)
                return;
        sva = rounddown2(sva, PAGE_SIZE);
        MPASS(sva > VM_MAXUSER_ADDRESS);
        eva = roundup2(eva, PAGE_SIZE);
        MPASS(sva < eva);
        VM_OBJECT_WLOCK(pti_obj);
        for (va = sva; va < eva; va += PAGE_SIZE) {
                pte = pmap_pti_pte(va, NULL);
                KASSERT((*pte & X86_PG_V) != 0,
                    ("invalid pte va %#lx pte %#lx pt %#lx", va,
                    (u_long)pte, *pte));
                pte_clear(pte);
                pmap_pti_unwire_pte(pte, va);
        }
        pmap_invalidate_range(kernel_pmap, sva, eva);
        VM_OBJECT_WUNLOCK(pti_obj);
}

#include "opt_ddb.h"
#ifdef DDB
#include <sys/kdb.h>
#include <ddb/ddb.h>

DB_SHOW_COMMAND(pte, pmap_print_pte)
{
        pmap_t pmap;
        pml4_entry_t *pml4;
        pdp_entry_t *pdp;
        pd_entry_t *pde;
        pt_entry_t *pte, PG_V;
        vm_offset_t va;

        if (!have_addr) {
                db_printf("show pte addr\n");
                return;
        }
        va = (vm_offset_t)addr;

        if (kdb_thread != NULL)
                pmap = vmspace_pmap(kdb_thread->td_proc->p_vmspace);
        else
                pmap = PCPU_GET(curpmap);

        PG_V = pmap_valid_bit(pmap);
        pml4 = pmap_pml4e(pmap, va);
        db_printf("VA %#016lx pml4e %#016lx", va, *pml4);
        if ((*pml4 & PG_V) == 0) {
                db_printf("\n");
                return;
        }
        pdp = pmap_pml4e_to_pdpe(pml4, va);
        db_printf(" pdpe %#016lx", *pdp);
        if ((*pdp & PG_V) == 0 || (*pdp & PG_PS) != 0) {
                db_printf("\n");
                return;
        }
        pde = pmap_pdpe_to_pde(pdp, va);
        db_printf(" pde %#016lx", *pde);
        if ((*pde & PG_V) == 0 || (*pde & PG_PS) != 0) {
                db_printf("\n");
                return;
        }
        pte = pmap_pde_to_pte(pde, va);
        db_printf(" pte %#016lx\n", *pte);
}

DB_SHOW_COMMAND(phys2dmap, pmap_phys2dmap)
{
        vm_paddr_t a;

        if (have_addr) {
                a = (vm_paddr_t)addr;
                db_printf("0x%jx\n", (uintmax_t)PHYS_TO_DMAP(a));
        } else {
                db_printf("show phys2dmap addr\n");
        }
}
#endif