Assert we are not traversing through superpages in the arm64 pmap.

[FreeBSD/FreeBSD.git] / sys / arm64 / arm64 / pmap.c

/*-
 * 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.
 * Copyright (c) 2014 Andrew Turner
 * All rights reserved.
 * Copyright (c) 2014-2016 The FreeBSD Foundation
 * 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.
 *
 * This software was developed by Andrew Turner 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.
 * 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.
 * 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.
 *
 * 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.
 */

#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_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/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/msgbuf.h>
#include <sys/mutex.h>
#include <sys/physmem.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/sbuf.h>
#include <sys/sx.h>
#include <sys/vmem.h>
#include <sys/vmmeter.h>
#include <sys/sched.h>
#include <sys/sysctl.h>
#include <sys/_unrhdr.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/machdep.h>
#include <machine/md_var.h>
#include <machine/pcb.h>

#define PMAP_ASSERT_STAGE1(pmap)        MPASS((pmap)->pm_stage == PM_STAGE1)
#define PMAP_ASSERT_STAGE2(pmap)        MPASS((pmap)->pm_stage == PM_STAGE2)

#define NL0PG           (PAGE_SIZE/(sizeof (pd_entry_t)))
#define NL1PG           (PAGE_SIZE/(sizeof (pd_entry_t)))
#define NL2PG           (PAGE_SIZE/(sizeof (pd_entry_t)))
#define NL3PG           (PAGE_SIZE/(sizeof (pt_entry_t)))

#define NUL0E           L0_ENTRIES
#define NUL1E           (NUL0E * NL1PG)
#define NUL2E           (NUL1E * NL2PG)

#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 pmap_l2_pindex(v)       ((v) >> L2_SHIFT)
#define pa_to_pvh(pa)           (&pv_table[pmap_l2_pindex(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))

/*
 * The presence of this flag indicates that the mapping is writeable.
 * If the ATTR_S1_AP_RO bit is also set, then the mapping is clean, otherwise
 * it is dirty.  This flag may only be set on managed mappings.
 *
 * The DBM bit is reserved on ARMv8.0 but it seems we can safely treat it
 * as a software managed bit.
 */
#define ATTR_SW_DBM     ATTR_DBM

struct pmap kernel_pmap_store;

/* Used for mapping ACPI memory before VM is initialized */
#define PMAP_PREINIT_MAPPING_COUNT      32
#define PMAP_PREINIT_MAPPING_SIZE       (PMAP_PREINIT_MAPPING_COUNT * L2_SIZE)
static vm_offset_t preinit_map_va;      /* Start VA of pre-init mapping space */
static int vm_initialized = 0;          /* No need to use pre-init maps when set */

/*
 * Reserve a few L2 blocks starting from 'preinit_map_va' pointer.
 * Always map entire L2 block for simplicity.
 * VA of L2 block = preinit_map_va + i * L2_SIZE
 */
static struct pmap_preinit_mapping {
        vm_paddr_t      pa;
        vm_offset_t     va;
        vm_size_t       size;
} pmap_preinit_mapping[PMAP_PREINIT_MAPPING_COUNT];

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) */
vm_offset_t kernel_vm_end = 0;

/*
 * Data for the pv entry allocation mechanism.
 */
static TAILQ_HEAD(pch, pv_chunk) pv_chunks = TAILQ_HEAD_INITIALIZER(pv_chunks);
static struct mtx pv_chunks_mutex;
static struct rwlock pv_list_locks[NPV_LIST_LOCKS];
static struct md_page *pv_table;
static struct md_page pv_dummy;

vm_paddr_t dmap_phys_base;      /* The start of the dmap region */
vm_paddr_t dmap_phys_max;       /* The limit of the dmap region */
vm_offset_t dmap_max_addr;      /* The virtual address limit of the dmap */

/* This code assumes all L1 DMAP entries will be used */
CTASSERT((DMAP_MIN_ADDRESS  & ~L0_OFFSET) == DMAP_MIN_ADDRESS);
CTASSERT((DMAP_MAX_ADDRESS  & ~L0_OFFSET) == DMAP_MAX_ADDRESS);

#define DMAP_TABLES     ((DMAP_MAX_ADDRESS - DMAP_MIN_ADDRESS) >> L0_SHIFT)
extern pt_entry_t pagetable_dmap[];

#define PHYSMAP_SIZE    (2 * (VM_PHYSSEG_MAX - 1))
static vm_paddr_t physmap[PHYSMAP_SIZE];
static u_int physmap_idx;

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

/*
 * This ASID allocator uses a bit vector ("asid_set") to remember which ASIDs
 * that it has currently allocated to a pmap, a cursor ("asid_next") to
 * optimize its search for a free ASID in the bit vector, and an epoch number
 * ("asid_epoch") to indicate when it has reclaimed all previously allocated
 * ASIDs that are not currently active on a processor.
 *
 * The current epoch number is always in the range [0, INT_MAX).  Negative
 * numbers and INT_MAX are reserved for special cases that are described
 * below.
 */
struct asid_set {
        int asid_bits;
        bitstr_t *asid_set;
        int asid_set_size;
        int asid_next;
        int asid_epoch;
        struct mtx asid_set_mutex;
};

static struct asid_set asids;
static struct asid_set vmids;

static SYSCTL_NODE(_vm_pmap, OID_AUTO, asid, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
    "ASID allocator");
SYSCTL_INT(_vm_pmap_asid, OID_AUTO, bits, CTLFLAG_RD, &asids.asid_bits, 0,
    "The number of bits in an ASID");
SYSCTL_INT(_vm_pmap_asid, OID_AUTO, next, CTLFLAG_RD, &asids.asid_next, 0,
    "The last allocated ASID plus one");
SYSCTL_INT(_vm_pmap_asid, OID_AUTO, epoch, CTLFLAG_RD, &asids.asid_epoch, 0,
    "The current epoch number");

static SYSCTL_NODE(_vm_pmap, OID_AUTO, vmid, CTLFLAG_RD, 0, "VMID allocator");
SYSCTL_INT(_vm_pmap_vmid, OID_AUTO, bits, CTLFLAG_RD, &vmids.asid_bits, 0,
    "The number of bits in an VMID");
SYSCTL_INT(_vm_pmap_vmid, OID_AUTO, next, CTLFLAG_RD, &vmids.asid_next, 0,
    "The last allocated VMID plus one");
SYSCTL_INT(_vm_pmap_vmid, OID_AUTO, epoch, CTLFLAG_RD, &vmids.asid_epoch, 0,
    "The current epoch number");

void (*pmap_clean_stage2_tlbi)(void);
void (*pmap_invalidate_vpipt_icache)(void);

/*
 * A pmap's cookie encodes an ASID and epoch number.  Cookies for reserved
 * ASIDs have a negative epoch number, specifically, INT_MIN.  Cookies for
 * dynamically allocated ASIDs have a non-negative epoch number.
 *
 * An invalid ASID is represented by -1.
 *
 * There are two special-case cookie values: (1) COOKIE_FROM(-1, INT_MIN),
 * which indicates that an ASID should never be allocated to the pmap, and
 * (2) COOKIE_FROM(-1, INT_MAX), which indicates that an ASID should be
 * allocated when the pmap is next activated.
 */
#define COOKIE_FROM(asid, epoch)        ((long)((u_int)(asid) | \
                                            ((u_long)(epoch) << 32)))
#define COOKIE_TO_ASID(cookie)          ((int)(cookie))
#define COOKIE_TO_EPOCH(cookie)         ((int)((u_long)(cookie) >> 32))

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

/*
 * 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 vm_page_t reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp);
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 void pmap_abort_ptp(pmap_t pmap, vm_offset_t va, vm_page_t mpte);
static bool pmap_activate_int(pmap_t pmap);
static void pmap_alloc_asid(pmap_t pmap);
static int pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode);
static pt_entry_t *pmap_demote_l1(pmap_t pmap, pt_entry_t *l1, vm_offset_t va);
static pt_entry_t *pmap_demote_l2_locked(pmap_t pmap, pt_entry_t *l2,
    vm_offset_t va, struct rwlock **lockp);
static pt_entry_t *pmap_demote_l2(pmap_t pmap, pt_entry_t *l2, vm_offset_t va);
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 int pmap_enter_l2(pmap_t pmap, vm_offset_t va, pd_entry_t new_l2,
    u_int flags, vm_page_t m, struct rwlock **lockp);
static int pmap_remove_l2(pmap_t pmap, pt_entry_t *l2, vm_offset_t sva,
    pd_entry_t l1e, struct spglist *free, struct rwlock **lockp);
static int pmap_remove_l3(pmap_t pmap, pt_entry_t *l3, vm_offset_t sva,
    pd_entry_t l2e, struct spglist *free, struct rwlock **lockp);
static void pmap_reset_asid_set(pmap_t pmap);
static boolean_t pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va,
    vm_page_t m, struct rwlock **lockp);

static vm_page_t _pmap_alloc_l3(pmap_t pmap, vm_pindex_t ptepindex,
                struct rwlock **lockp);

static void _pmap_unwire_l3(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 *);
static __inline vm_page_t pmap_remove_pt_page(pmap_t pmap, vm_offset_t va);

/*
 * These load the old table data and store the new value.
 * They need to be atomic as the System MMU may write to the table at
 * the same time as the CPU.
 */
#define pmap_clear(table)               atomic_store_64(table, 0)
#define pmap_clear_bits(table, bits)    atomic_clear_64(table, bits)
#define pmap_load(table)                (*table)
#define pmap_load_clear(table)          atomic_swap_64(table, 0)
#define pmap_load_store(table, entry)   atomic_swap_64(table, entry)
#define pmap_set_bits(table, bits)      atomic_set_64(table, bits)
#define pmap_store(table, entry)        atomic_store_64(table, entry)

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

static __inline void
pagecopy(void *s, void *d)
{

        memcpy(d, s, PAGE_SIZE);
}

static __inline pd_entry_t *
pmap_l0(pmap_t pmap, vm_offset_t va)
{

        return (&pmap->pm_l0[pmap_l0_index(va)]);
}

static __inline pd_entry_t *
pmap_l0_to_l1(pd_entry_t *l0, vm_offset_t va)
{
        pd_entry_t *l1;

        l1 = (pd_entry_t *)PHYS_TO_DMAP(pmap_load(l0) & ~ATTR_MASK);
        return (&l1[pmap_l1_index(va)]);
}

static __inline pd_entry_t *
pmap_l1(pmap_t pmap, vm_offset_t va)
{
        pd_entry_t *l0;

        l0 = pmap_l0(pmap, va);
        if ((pmap_load(l0) & ATTR_DESCR_MASK) != L0_TABLE)
                return (NULL);

        return (pmap_l0_to_l1(l0, va));
}

static __inline pd_entry_t *
pmap_l1_to_l2(pd_entry_t *l1p, vm_offset_t va)
{
        pd_entry_t l1, *l2p;

        l1 = pmap_load(l1p);
        KASSERT((l1 & ATTR_DESCR_MASK) == L1_TABLE,
            ("%s: L1 entry %#lx is a leaf", __func__, l1));
        l2p = (pd_entry_t *)PHYS_TO_DMAP(l1 & ~ATTR_MASK);
        return (&l2p[pmap_l2_index(va)]);
}

static __inline pd_entry_t *
pmap_l2(pmap_t pmap, vm_offset_t va)
{
        pd_entry_t *l1;

        l1 = pmap_l1(pmap, va);
        if ((pmap_load(l1) & ATTR_DESCR_MASK) != L1_TABLE)
                return (NULL);

        return (pmap_l1_to_l2(l1, va));
}

static __inline pt_entry_t *
pmap_l2_to_l3(pd_entry_t *l2p, vm_offset_t va)
{
        pd_entry_t l2;
        pt_entry_t *l3p;

        l2 = pmap_load(l2p);
        KASSERT((l2 & ATTR_DESCR_MASK) == L2_TABLE,
            ("%s: L2 entry %#lx is a leaf", __func__, l2));
        l3p = (pt_entry_t *)PHYS_TO_DMAP(l2 & ~ATTR_MASK);
        return (&l3p[pmap_l3_index(va)]);
}

/*
 * Returns the lowest valid pde for a given virtual address.
 * The next level may or may not point to a valid page or block.
 */
static __inline pd_entry_t *
pmap_pde(pmap_t pmap, vm_offset_t va, int *level)
{
        pd_entry_t *l0, *l1, *l2, desc;

        l0 = pmap_l0(pmap, va);
        desc = pmap_load(l0) & ATTR_DESCR_MASK;
        if (desc != L0_TABLE) {
                *level = -1;
                return (NULL);
        }

        l1 = pmap_l0_to_l1(l0, va);
        desc = pmap_load(l1) & ATTR_DESCR_MASK;
        if (desc != L1_TABLE) {
                *level = 0;
                return (l0);
        }

        l2 = pmap_l1_to_l2(l1, va);
        desc = pmap_load(l2) & ATTR_DESCR_MASK;
        if (desc != L2_TABLE) {
                *level = 1;
                return (l1);
        }

        *level = 2;
        return (l2);
}

/*
 * Returns the lowest valid pte block or table entry for a given virtual
 * address. If there are no valid entries return NULL and set the level to
 * the first invalid level.
 */
static __inline pt_entry_t *
pmap_pte(pmap_t pmap, vm_offset_t va, int *level)
{
        pd_entry_t *l1, *l2, desc;
        pt_entry_t *l3;

        l1 = pmap_l1(pmap, va);
        if (l1 == NULL) {
                *level = 0;
                return (NULL);
        }
        desc = pmap_load(l1) & ATTR_DESCR_MASK;
        if (desc == L1_BLOCK) {
                *level = 1;
                return (l1);
        }

        if (desc != L1_TABLE) {
                *level = 1;
                return (NULL);
        }

        l2 = pmap_l1_to_l2(l1, va);
        desc = pmap_load(l2) & ATTR_DESCR_MASK;
        if (desc == L2_BLOCK) {
                *level = 2;
                return (l2);
        }

        if (desc != L2_TABLE) {
                *level = 2;
                return (NULL);
        }

        *level = 3;
        l3 = pmap_l2_to_l3(l2, va);
        if ((pmap_load(l3) & ATTR_DESCR_MASK) != L3_PAGE)
                return (NULL);

        return (l3);
}

bool
pmap_ps_enabled(pmap_t pmap __unused)
{

        return (superpages_enabled != 0);
}

bool
pmap_get_tables(pmap_t pmap, vm_offset_t va, pd_entry_t **l0, pd_entry_t **l1,
    pd_entry_t **l2, pt_entry_t **l3)
{
        pd_entry_t *l0p, *l1p, *l2p;

        if (pmap->pm_l0 == NULL)
                return (false);

        l0p = pmap_l0(pmap, va);
        *l0 = l0p;

        if ((pmap_load(l0p) & ATTR_DESCR_MASK) != L0_TABLE)
                return (false);

        l1p = pmap_l0_to_l1(l0p, va);
        *l1 = l1p;

        if ((pmap_load(l1p) & ATTR_DESCR_MASK) == L1_BLOCK) {
                *l2 = NULL;
                *l3 = NULL;
                return (true);
        }

        if ((pmap_load(l1p) & ATTR_DESCR_MASK) != L1_TABLE)
                return (false);

        l2p = pmap_l1_to_l2(l1p, va);
        *l2 = l2p;

        if ((pmap_load(l2p) & ATTR_DESCR_MASK) == L2_BLOCK) {
                *l3 = NULL;
                return (true);
        }

        if ((pmap_load(l2p) & ATTR_DESCR_MASK) != L2_TABLE)
                return (false);

        *l3 = pmap_l2_to_l3(l2p, va);

        return (true);
}

static __inline int
pmap_l3_valid(pt_entry_t l3)
{

        return ((l3 & ATTR_DESCR_MASK) == L3_PAGE);
}

CTASSERT(L1_BLOCK == L2_BLOCK);

static pt_entry_t
pmap_pte_memattr(pmap_t pmap, vm_memattr_t memattr)
{
        pt_entry_t val;

        if (pmap->pm_stage == PM_STAGE1) {
                val = ATTR_S1_IDX(memattr);
                if (memattr == VM_MEMATTR_DEVICE)
                        val |= ATTR_S1_XN;
                return (val);
        }

        val = 0;

        switch (memattr) {
        case VM_MEMATTR_DEVICE:
                return (ATTR_S2_MEMATTR(ATTR_S2_MEMATTR_DEVICE_nGnRnE) |
                    ATTR_S2_XN(ATTR_S2_XN_ALL));
        case VM_MEMATTR_UNCACHEABLE:
                return (ATTR_S2_MEMATTR(ATTR_S2_MEMATTR_NC));
        case VM_MEMATTR_WRITE_BACK:
                return (ATTR_S2_MEMATTR(ATTR_S2_MEMATTR_WB));
        case VM_MEMATTR_WRITE_THROUGH:
                return (ATTR_S2_MEMATTR(ATTR_S2_MEMATTR_WT));
        default:
                panic("%s: invalid memory attribute %x", __func__, memattr);
        }
}

static pt_entry_t
pmap_pte_prot(pmap_t pmap, vm_prot_t prot)
{
        pt_entry_t val;

        val = 0;
        if (pmap->pm_stage == PM_STAGE1) {
                if ((prot & VM_PROT_EXECUTE) == 0)
                        val |= ATTR_S1_XN;
                if ((prot & VM_PROT_WRITE) == 0)
                        val |= ATTR_S1_AP(ATTR_S1_AP_RO);
        } else {
                if ((prot & VM_PROT_WRITE) != 0)
                        val |= ATTR_S2_S2AP(ATTR_S2_S2AP_WRITE);
                if ((prot & VM_PROT_READ) != 0)
                        val |= ATTR_S2_S2AP(ATTR_S2_S2AP_READ);
                if ((prot & VM_PROT_EXECUTE) == 0)
                        val |= ATTR_S2_XN(ATTR_S2_XN_ALL);
        }

        return (val);
}

/*
 * Checks if the PTE is dirty.
 */
static inline int
pmap_pte_dirty(pmap_t pmap, pt_entry_t pte)
{

        KASSERT((pte & ATTR_SW_MANAGED) != 0, ("pte %#lx is unmanaged", pte));

        if (pmap->pm_stage == PM_STAGE1) {
                KASSERT((pte & (ATTR_S1_AP_RW_BIT | ATTR_SW_DBM)) != 0,
                    ("pte %#lx is writeable and missing ATTR_SW_DBM", pte));

                return ((pte & (ATTR_S1_AP_RW_BIT | ATTR_SW_DBM)) ==
                    (ATTR_S1_AP(ATTR_S1_AP_RW) | ATTR_SW_DBM));
        }

        return ((pte & ATTR_S2_S2AP(ATTR_S2_S2AP_WRITE)) ==
            ATTR_S2_S2AP(ATTR_S2_S2AP_WRITE));
}

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;
}

static pt_entry_t *
pmap_early_page_idx(vm_offset_t l1pt, vm_offset_t va, u_int *l1_slot,
    u_int *l2_slot)
{
        pt_entry_t *l2;
        pd_entry_t *l1;

        l1 = (pd_entry_t *)l1pt;
        *l1_slot = (va >> L1_SHIFT) & Ln_ADDR_MASK;

        /* Check locore has used a table L1 map */
        KASSERT((l1[*l1_slot] & ATTR_DESCR_MASK) == L1_TABLE,
           ("Invalid bootstrap L1 table"));
        /* Find the address of the L2 table */
        l2 = (pt_entry_t *)init_pt_va;
        *l2_slot = pmap_l2_index(va);

        return (l2);
}

static vm_paddr_t
pmap_early_vtophys(vm_offset_t l1pt, vm_offset_t va)
{
        u_int l1_slot, l2_slot;
        pt_entry_t *l2;

        l2 = pmap_early_page_idx(l1pt, va, &l1_slot, &l2_slot);

        return ((l2[l2_slot] & ~ATTR_MASK) + (va & L2_OFFSET));
}

static vm_offset_t
pmap_bootstrap_dmap(vm_offset_t kern_l1, vm_paddr_t min_pa,
    vm_offset_t freemempos)
{
        pt_entry_t *l2;
        vm_offset_t va;
        vm_paddr_t l2_pa, pa;
        u_int l1_slot, l2_slot, prev_l1_slot;
        int i;

        dmap_phys_base = min_pa & ~L1_OFFSET;
        dmap_phys_max = 0;
        dmap_max_addr = 0;
        l2 = NULL;
        prev_l1_slot = -1;

#define DMAP_TABLES     ((DMAP_MAX_ADDRESS - DMAP_MIN_ADDRESS) >> L0_SHIFT)
        memset(pagetable_dmap, 0, PAGE_SIZE * DMAP_TABLES);

        for (i = 0; i < (physmap_idx * 2); i += 2) {
                pa = physmap[i] & ~L2_OFFSET;
                va = pa - dmap_phys_base + DMAP_MIN_ADDRESS;

                /* Create L2 mappings at the start of the region */
                if ((pa & L1_OFFSET) != 0) {
                        l1_slot = ((va - DMAP_MIN_ADDRESS) >> L1_SHIFT);
                        if (l1_slot != prev_l1_slot) {
                                prev_l1_slot = l1_slot;
                                l2 = (pt_entry_t *)freemempos;
                                l2_pa = pmap_early_vtophys(kern_l1,
                                    (vm_offset_t)l2);
                                freemempos += PAGE_SIZE;

                                pmap_store(&pagetable_dmap[l1_slot],
                                    (l2_pa & ~Ln_TABLE_MASK) | L1_TABLE);

                                memset(l2, 0, PAGE_SIZE);
                        }
                        KASSERT(l2 != NULL,
                            ("pmap_bootstrap_dmap: NULL l2 map"));
                        for (; va < DMAP_MAX_ADDRESS && pa < physmap[i + 1];
                            pa += L2_SIZE, va += L2_SIZE) {
                                /*
                                 * We are on a boundary, stop to
                                 * create a level 1 block
                                 */
                                if ((pa & L1_OFFSET) == 0)
                                        break;

                                l2_slot = pmap_l2_index(va);
                                KASSERT(l2_slot != 0, ("..."));
                                pmap_store(&l2[l2_slot],
                                    (pa & ~L2_OFFSET) | ATTR_DEFAULT |
                                    ATTR_S1_XN |
                                    ATTR_S1_IDX(VM_MEMATTR_WRITE_BACK) |
                                    L2_BLOCK);
                        }
                        KASSERT(va == (pa - dmap_phys_base + DMAP_MIN_ADDRESS),
                            ("..."));
                }

                for (; va < DMAP_MAX_ADDRESS && pa < physmap[i + 1] &&
                    (physmap[i + 1] - pa) >= L1_SIZE;
                    pa += L1_SIZE, va += L1_SIZE) {
                        l1_slot = ((va - DMAP_MIN_ADDRESS) >> L1_SHIFT);
                        pmap_store(&pagetable_dmap[l1_slot],
                            (pa & ~L1_OFFSET) | ATTR_DEFAULT | ATTR_S1_XN |
                            ATTR_S1_IDX(VM_MEMATTR_WRITE_BACK) | L1_BLOCK);
                }

                /* Create L2 mappings at the end of the region */
                if (pa < physmap[i + 1]) {
                        l1_slot = ((va - DMAP_MIN_ADDRESS) >> L1_SHIFT);
                        if (l1_slot != prev_l1_slot) {
                                prev_l1_slot = l1_slot;
                                l2 = (pt_entry_t *)freemempos;
                                l2_pa = pmap_early_vtophys(kern_l1,
                                    (vm_offset_t)l2);
                                freemempos += PAGE_SIZE;

                                pmap_store(&pagetable_dmap[l1_slot],
                                    (l2_pa & ~Ln_TABLE_MASK) | L1_TABLE);

                                memset(l2, 0, PAGE_SIZE);
                        }
                        KASSERT(l2 != NULL,
                            ("pmap_bootstrap_dmap: NULL l2 map"));
                        for (; va < DMAP_MAX_ADDRESS && pa < physmap[i + 1];
                            pa += L2_SIZE, va += L2_SIZE) {
                                l2_slot = pmap_l2_index(va);
                                pmap_store(&l2[l2_slot],
                                    (pa & ~L2_OFFSET) | ATTR_DEFAULT |
                                    ATTR_S1_XN |
                                    ATTR_S1_IDX(VM_MEMATTR_WRITE_BACK) |
                                    L2_BLOCK);
                        }
                }

                if (pa > dmap_phys_max) {
                        dmap_phys_max = pa;
                        dmap_max_addr = va;
                }
        }

        cpu_tlb_flushID();

        return (freemempos);
}

static vm_offset_t
pmap_bootstrap_l2(vm_offset_t l1pt, vm_offset_t va, vm_offset_t l2_start)
{
        vm_offset_t l2pt;
        vm_paddr_t pa;
        pd_entry_t *l1;
        u_int l1_slot;

        KASSERT((va & L1_OFFSET) == 0, ("Invalid virtual address"));

        l1 = (pd_entry_t *)l1pt;
        l1_slot = pmap_l1_index(va);
        l2pt = l2_start;

        for (; va < VM_MAX_KERNEL_ADDRESS; l1_slot++, va += L1_SIZE) {
                KASSERT(l1_slot < Ln_ENTRIES, ("Invalid L1 index"));

                pa = pmap_early_vtophys(l1pt, l2pt);
                pmap_store(&l1[l1_slot],
                    (pa & ~Ln_TABLE_MASK) | L1_TABLE);
                l2pt += PAGE_SIZE;
        }

        /* Clean the L2 page table */
        memset((void *)l2_start, 0, l2pt - l2_start);

        return l2pt;
}

static vm_offset_t
pmap_bootstrap_l3(vm_offset_t l1pt, vm_offset_t va, vm_offset_t l3_start)
{
        vm_offset_t l3pt;
        vm_paddr_t pa;
        pd_entry_t *l2;
        u_int l2_slot;

        KASSERT((va & L2_OFFSET) == 0, ("Invalid virtual address"));

        l2 = pmap_l2(kernel_pmap, va);
        l2 = (pd_entry_t *)rounddown2((uintptr_t)l2, PAGE_SIZE);
        l2_slot = pmap_l2_index(va);
        l3pt = l3_start;

        for (; va < VM_MAX_KERNEL_ADDRESS; l2_slot++, va += L2_SIZE) {
                KASSERT(l2_slot < Ln_ENTRIES, ("Invalid L2 index"));

                pa = pmap_early_vtophys(l1pt, l3pt);
                pmap_store(&l2[l2_slot],
                    (pa & ~Ln_TABLE_MASK) | ATTR_S1_UXN | L2_TABLE);
                l3pt += PAGE_SIZE;
        }

        /* Clean the L2 page table */
        memset((void *)l3_start, 0, l3pt - l3_start);

        return l3pt;
}

/*
 *      Bootstrap the system enough to run with virtual memory.
 */
void
pmap_bootstrap(vm_offset_t l0pt, vm_offset_t l1pt, vm_paddr_t kernstart,
    vm_size_t kernlen)
{
        vm_offset_t freemempos;
        vm_offset_t dpcpu, msgbufpv;
        vm_paddr_t start_pa, pa, min_pa;
        uint64_t kern_delta;
        int i;

        /* Verify that the ASID is set through TTBR0. */
        KASSERT((READ_SPECIALREG(tcr_el1) & TCR_A1) == 0,
            ("pmap_bootstrap: TCR_EL1.A1 != 0"));

        kern_delta = KERNBASE - kernstart;

        printf("pmap_bootstrap %lx %lx %lx\n", l1pt, kernstart, kernlen);
        printf("%lx\n", l1pt);
        printf("%lx\n", (KERNBASE >> L1_SHIFT) & Ln_ADDR_MASK);

        /* Set this early so we can use the pagetable walking functions */
        kernel_pmap_store.pm_l0 = (pd_entry_t *)l0pt;
        PMAP_LOCK_INIT(kernel_pmap);
        kernel_pmap->pm_l0_paddr = l0pt - kern_delta;
        kernel_pmap->pm_cookie = COOKIE_FROM(-1, INT_MIN);
        kernel_pmap->pm_stage = PM_STAGE1;
        kernel_pmap->pm_asid_set = &asids;

        /* Assume the address we were loaded to is a valid physical address */
        min_pa = KERNBASE - kern_delta;

        physmap_idx = physmem_avail(physmap, nitems(physmap));
        physmap_idx /= 2;

        /*
         * Find the minimum physical address. physmap is sorted,
         * but may contain empty ranges.
         */
        for (i = 0; i < physmap_idx * 2; i += 2) {
                if (physmap[i] == physmap[i + 1])
                        continue;
                if (physmap[i] <= min_pa)
                        min_pa = physmap[i];
        }

        freemempos = KERNBASE + kernlen;
        freemempos = roundup2(freemempos, PAGE_SIZE);

        /* Create a direct map region early so we can use it for pa -> va */
        freemempos = pmap_bootstrap_dmap(l1pt, min_pa, freemempos);

        start_pa = pa = KERNBASE - kern_delta;

        /*
         * Create the l2 tables up to VM_MAX_KERNEL_ADDRESS.  We assume that the
         * loader allocated the first and only l2 page table page used to map
         * the kernel, preloaded files and module metadata.
         */
        freemempos = pmap_bootstrap_l2(l1pt, KERNBASE + L1_SIZE, freemempos);
        /* And the l3 tables for the early devmap */
        freemempos = pmap_bootstrap_l3(l1pt,
            VM_MAX_KERNEL_ADDRESS - (PMAP_MAPDEV_EARLY_SIZE), freemempos);

        cpu_tlb_flushID();

#define alloc_pages(var, np)                                            \
        (var) = freemempos;                                             \
        freemempos += (np * PAGE_SIZE);                                 \
        memset((char *)(var), 0, ((np) * PAGE_SIZE));

        /* Allocate dynamic per-cpu area. */
        alloc_pages(dpcpu, DPCPU_SIZE / PAGE_SIZE);
        dpcpu_init((void *)dpcpu, 0);

        /* Allocate memory for the msgbuf, e.g. for /sbin/dmesg */
        alloc_pages(msgbufpv, round_page(msgbufsize) / PAGE_SIZE);
        msgbufp = (void *)msgbufpv;

        /* Reserve some VA space for early BIOS/ACPI mapping */
        preinit_map_va = roundup2(freemempos, L2_SIZE);

        virtual_avail = preinit_map_va + PMAP_PREINIT_MAPPING_SIZE;
        virtual_avail = roundup2(virtual_avail, L1_SIZE);
        virtual_end = VM_MAX_KERNEL_ADDRESS - (PMAP_MAPDEV_EARLY_SIZE);
        kernel_vm_end = virtual_avail;

        pa = pmap_early_vtophys(l1pt, freemempos);

        physmem_exclude_region(start_pa, pa - start_pa, EXFLAG_NOALLOC);

        cpu_tlb_flushID();
}

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

        TAILQ_INIT(&m->md.pv_list);
        m->md.pv_memattr = VM_MEMATTR_WRITE_BACK;
}

static void
pmap_init_asids(struct asid_set *set, int bits)
{
        int i;

        set->asid_bits = bits;

        /*
         * We may be too early in the overall initialization process to use
         * bit_alloc().
         */
        set->asid_set_size = 1 << set->asid_bits;
        set->asid_set = (bitstr_t *)kmem_malloc(bitstr_size(set->asid_set_size),
            M_WAITOK | M_ZERO);
        for (i = 0; i < ASID_FIRST_AVAILABLE; i++)
                bit_set(set->asid_set, i);
        set->asid_next = ASID_FIRST_AVAILABLE;
        mtx_init(&set->asid_set_mutex, "asid set", NULL, MTX_SPIN);
}

/*
 *      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)
{
        vm_size_t s;
        uint64_t mmfr1;
        int i, pv_npg, vmid_bits;

        /*
         * Are large page mappings enabled?
         */
        TUNABLE_INT_FETCH("vm.pmap.superpages_enabled", &superpages_enabled);
        if (superpages_enabled) {
                KASSERT(MAXPAGESIZES > 1 && pagesizes[1] == 0,
                    ("pmap_init: can't assign to pagesizes[1]"));
                pagesizes[1] = L2_SIZE;
        }

        /*
         * Initialize the ASID allocator.
         */
        pmap_init_asids(&asids,
            (READ_SPECIALREG(tcr_el1) & TCR_ASID_16) != 0 ? 16 : 8);

        if (has_hyp()) {
                mmfr1 = READ_SPECIALREG(id_aa64mmfr1_el1);
                vmid_bits = 8;

                if (ID_AA64MMFR1_VMIDBits_VAL(mmfr1) ==
                    ID_AA64MMFR1_VMIDBits_16)
                        vmid_bits = 16;
                pmap_init_asids(&vmids, vmid_bits);
        }

        /*
         * 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, L2_SIZE);

        /*
         * 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);

        vm_initialized = 1;
}

static SYSCTL_NODE(_vm_pmap, OID_AUTO, l2, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
    "2MB page mapping counters");

static u_long pmap_l2_demotions;
SYSCTL_ULONG(_vm_pmap_l2, OID_AUTO, demotions, CTLFLAG_RD,
    &pmap_l2_demotions, 0, "2MB page demotions");

static u_long pmap_l2_mappings;
SYSCTL_ULONG(_vm_pmap_l2, OID_AUTO, mappings, CTLFLAG_RD,
    &pmap_l2_mappings, 0, "2MB page mappings");

static u_long pmap_l2_p_failures;
SYSCTL_ULONG(_vm_pmap_l2, OID_AUTO, p_failures, CTLFLAG_RD,
    &pmap_l2_p_failures, 0, "2MB page promotion failures");

static u_long pmap_l2_promotions;
SYSCTL_ULONG(_vm_pmap_l2, OID_AUTO, promotions, CTLFLAG_RD,
    &pmap_l2_promotions, 0, "2MB page promotions");

/*
 * Invalidate a single TLB entry.
 */
static __inline void
pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
{
        uint64_t r;

        PMAP_ASSERT_STAGE1(pmap);

        dsb(ishst);
        if (pmap == kernel_pmap) {
                r = atop(va);
                __asm __volatile("tlbi vaae1is, %0" : : "r" (r));
        } else {
                r = ASID_TO_OPERAND(COOKIE_TO_ASID(pmap->pm_cookie)) | atop(va);
                __asm __volatile("tlbi vae1is, %0" : : "r" (r));
        }
        dsb(ish);
        isb();
}

static __inline void
pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        uint64_t end, r, start;

        PMAP_ASSERT_STAGE1(pmap);

        dsb(ishst);
        if (pmap == kernel_pmap) {
                start = atop(sva);
                end = atop(eva);
                for (r = start; r < end; r++)
                        __asm __volatile("tlbi vaae1is, %0" : : "r" (r));
        } else {
                start = end = ASID_TO_OPERAND(COOKIE_TO_ASID(pmap->pm_cookie));
                start |= atop(sva);
                end |= atop(eva);
                for (r = start; r < end; r++)
                        __asm __volatile("tlbi vae1is, %0" : : "r" (r));
        }
        dsb(ish);
        isb();
}

static __inline void
pmap_invalidate_all(pmap_t pmap)
{
        uint64_t r;

        PMAP_ASSERT_STAGE1(pmap);

        dsb(ishst);
        if (pmap == kernel_pmap) {
                __asm __volatile("tlbi vmalle1is");
        } else {
                r = ASID_TO_OPERAND(COOKIE_TO_ASID(pmap->pm_cookie));
                __asm __volatile("tlbi aside1is, %0" : : "r" (r));
        }
        dsb(ish);
        isb();
}

/*
 *      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)
{
        pt_entry_t *pte, tpte;
        vm_paddr_t pa;
        int lvl;

        pa = 0;
        PMAP_LOCK(pmap);
        /*
         * Find the block or page map for this virtual address. pmap_pte
         * will return either a valid block/page entry, or NULL.
         */
        pte = pmap_pte(pmap, va, &lvl);
        if (pte != NULL) {
                tpte = pmap_load(pte);
                pa = tpte & ~ATTR_MASK;
                switch(lvl) {
                case 1:
                        KASSERT((tpte & ATTR_DESCR_MASK) == L1_BLOCK,
                            ("pmap_extract: Invalid L1 pte found: %lx",
                            tpte & ATTR_DESCR_MASK));
                        pa |= (va & L1_OFFSET);
                        break;
                case 2:
                        KASSERT((tpte & ATTR_DESCR_MASK) == L2_BLOCK,
                            ("pmap_extract: Invalid L2 pte found: %lx",
                            tpte & ATTR_DESCR_MASK));
                        pa |= (va & L2_OFFSET);
                        break;
                case 3:
                        KASSERT((tpte & ATTR_DESCR_MASK) == L3_PAGE,
                            ("pmap_extract: Invalid L3 pte found: %lx",
                            tpte & ATTR_DESCR_MASK));
                        pa |= (va & L3_OFFSET);
                        break;
                }
        }
        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)
{
        pt_entry_t *pte, tpte;
        vm_offset_t off;
        vm_page_t m;
        int lvl;
        bool use;

        m = NULL;
        PMAP_LOCK(pmap);
        pte = pmap_pte(pmap, va, &lvl);
        if (pte != NULL) {
                tpte = pmap_load(pte);

                KASSERT(lvl > 0 && lvl <= 3,
                    ("pmap_extract_and_hold: Invalid level %d", lvl));
                CTASSERT(L1_BLOCK == L2_BLOCK);
                KASSERT((lvl == 3 && (tpte & ATTR_DESCR_MASK) == L3_PAGE) ||
                    (lvl < 3 && (tpte & ATTR_DESCR_MASK) == L1_BLOCK),
                    ("pmap_extract_and_hold: Invalid pte at L%d: %lx", lvl,
                     tpte & ATTR_DESCR_MASK));

                use = false;
                if ((prot & VM_PROT_WRITE) == 0)
                        use = true;
                else if (pmap->pm_stage == PM_STAGE1 &&
                    (tpte & ATTR_S1_AP_RW_BIT) == ATTR_S1_AP(ATTR_S1_AP_RW))
                        use = true;
                else if (pmap->pm_stage == PM_STAGE2 &&
                    ((tpte & ATTR_S2_S2AP(ATTR_S2_S2AP_WRITE)) ==
                     ATTR_S2_S2AP(ATTR_S2_S2AP_WRITE)))
                        use = true;

                if (use) {
                        switch(lvl) {
                        case 1:
                                off = va & L1_OFFSET;
                                break;
                        case 2:
                                off = va & L2_OFFSET;
                                break;
                        case 3:
                        default:
                                off = 0;
                        }
                        m = PHYS_TO_VM_PAGE((tpte & ~ATTR_MASK) | off);
                        if (!vm_page_wire_mapped(m))
                                m = NULL;
                }
        }
        PMAP_UNLOCK(pmap);
        return (m);
}

vm_paddr_t
pmap_kextract(vm_offset_t va)
{
        pt_entry_t *pte, tpte;

        if (va >= DMAP_MIN_ADDRESS && va < DMAP_MAX_ADDRESS)
                return (DMAP_TO_PHYS(va));
        pte = pmap_l1(kernel_pmap, va);
        if (pte == NULL)
                return (0);

        /*
         * A concurrent pmap_update_entry() will clear the entry's valid bit
         * but leave the rest of the entry unchanged.  Therefore, we treat a
         * non-zero entry as being valid, and we ignore the valid bit when
         * determining whether the entry maps a block, page, or table.
         */
        tpte = pmap_load(pte);
        if (tpte == 0)
                return (0);
        if ((tpte & ATTR_DESCR_TYPE_MASK) == ATTR_DESCR_TYPE_BLOCK)
                return ((tpte & ~ATTR_MASK) | (va & L1_OFFSET));
        pte = pmap_l1_to_l2(&tpte, va);
        tpte = pmap_load(pte);
        if (tpte == 0)
                return (0);
        if ((tpte & ATTR_DESCR_TYPE_MASK) == ATTR_DESCR_TYPE_BLOCK)
                return ((tpte & ~ATTR_MASK) | (va & L2_OFFSET));
        pte = pmap_l2_to_l3(&tpte, va);
        tpte = pmap_load(pte);
        if (tpte == 0)
                return (0);
        return ((tpte & ~ATTR_MASK) | (va & L3_OFFSET));
}

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

void
pmap_kenter(vm_offset_t sva, vm_size_t size, vm_paddr_t pa, int mode)
{
        pd_entry_t *pde;
        pt_entry_t *pte, attr;
        vm_offset_t va;
        int lvl;

        KASSERT((pa & L3_OFFSET) == 0,
           ("pmap_kenter: Invalid physical address"));
        KASSERT((sva & L3_OFFSET) == 0,
           ("pmap_kenter: Invalid virtual address"));
        KASSERT((size & PAGE_MASK) == 0,
            ("pmap_kenter: Mapping is not page-sized"));

        attr = ATTR_DEFAULT | ATTR_S1_AP(ATTR_S1_AP_RW) | ATTR_S1_XN |
            ATTR_S1_IDX(mode) | L3_PAGE;
        va = sva;
        while (size != 0) {
                pde = pmap_pde(kernel_pmap, va, &lvl);
                KASSERT(pde != NULL,
                    ("pmap_kenter: Invalid page entry, va: 0x%lx", va));
                KASSERT(lvl == 2, ("pmap_kenter: Invalid level %d", lvl));

                pte = pmap_l2_to_l3(pde, va);
                pmap_load_store(pte, (pa & ~L3_OFFSET) | attr);

                va += PAGE_SIZE;
                pa += PAGE_SIZE;
                size -= PAGE_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
}

void
pmap_kenter_device(vm_offset_t sva, vm_size_t size, vm_paddr_t pa)
{

        pmap_kenter(sva, size, pa, VM_MEMATTR_DEVICE);
}

/*
 * Remove a page from the kernel pagetables.
 */
PMAP_INLINE void
pmap_kremove(vm_offset_t va)
{
        pt_entry_t *pte;
        int lvl;

        pte = pmap_pte(kernel_pmap, va, &lvl);
        KASSERT(pte != NULL, ("pmap_kremove: Invalid address"));
        KASSERT(lvl == 3, ("pmap_kremove: Invalid pte level %d", lvl));

        pmap_clear(pte);
        pmap_invalidate_page(kernel_pmap, va);
}

void
pmap_kremove_device(vm_offset_t sva, vm_size_t size)
{
        pt_entry_t *pte;
        vm_offset_t va;
        int lvl;

        KASSERT((sva & L3_OFFSET) == 0,
           ("pmap_kremove_device: Invalid virtual address"));
        KASSERT((size & PAGE_MASK) == 0,
            ("pmap_kremove_device: Mapping is not page-sized"));

        va = sva;
        while (size != 0) {
                pte = pmap_pte(kernel_pmap, va, &lvl);
                KASSERT(pte != NULL, ("Invalid page table, va: 0x%lx", va));
                KASSERT(lvl == 3,
                    ("Invalid device pagetable level: %d != 3", lvl));
                pmap_clear(pte);

                va += PAGE_SIZE;
                size -= PAGE_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
}

/*
 *      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)
{
        pd_entry_t *pde;
        pt_entry_t *pte, pa;
        vm_offset_t va;
        vm_page_t m;
        int i, lvl;

        va = sva;
        for (i = 0; i < count; i++) {
                pde = pmap_pde(kernel_pmap, va, &lvl);
                KASSERT(pde != NULL,
                    ("pmap_qenter: Invalid page entry, va: 0x%lx", va));
                KASSERT(lvl == 2,
                    ("pmap_qenter: Invalid level %d", lvl));

                m = ma[i];
                pa = VM_PAGE_TO_PHYS(m) | ATTR_DEFAULT |
                    ATTR_S1_AP(ATTR_S1_AP_RW) | ATTR_S1_XN |
                    ATTR_S1_IDX(m->md.pv_memattr) | L3_PAGE;
                pte = pmap_l2_to_l3(pde, va);
                pmap_load_store(pte, pa);

                va += L3_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
}

/*
 * This routine tears out page mappings from the
 * kernel -- it is meant only for temporary mappings.
 */
void
pmap_qremove(vm_offset_t sva, int count)
{
        pt_entry_t *pte;
        vm_offset_t va;
        int lvl;

        KASSERT(sva >= VM_MIN_KERNEL_ADDRESS, ("usermode va %lx", sva));

        va = sva;
        while (count-- > 0) {
                pte = pmap_pte(kernel_pmap, va, &lvl);
                KASSERT(lvl == 3,
                    ("Invalid device pagetable level: %d != 3", lvl));
                if (pte != NULL) {
                        pmap_clear(pte);
                }

                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);
}

/*
 * Decrements a page table page's reference count, which is used to record the
 * number of valid page table entries within the page.  If the reference 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_l3(pmap_t pmap, vm_offset_t va, vm_page_t m, struct spglist *free)
{

        --m->ref_count;
        if (m->ref_count == 0) {
                _pmap_unwire_l3(pmap, va, m, free);
                return (TRUE);
        } else
                return (FALSE);
}

static void
_pmap_unwire_l3(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 >= (NUL2E + NUL1E)) {
                /* l1 page */
                pd_entry_t *l0;

                l0 = pmap_l0(pmap, va);
                pmap_clear(l0);
        } else if (m->pindex >= NUL2E) {
                /* l2 page */
                pd_entry_t *l1;

                l1 = pmap_l1(pmap, va);
                pmap_clear(l1);
        } else {
                /* l3 page */
                pd_entry_t *l2;

                l2 = pmap_l2(pmap, va);
                pmap_clear(l2);
        }
        pmap_resident_count_dec(pmap, 1);
        if (m->pindex < NUL2E) {
                /* We just released an l3, unhold the matching l2 */
                pd_entry_t *l1, tl1;
                vm_page_t l2pg;

                l1 = pmap_l1(pmap, va);
                tl1 = pmap_load(l1);
                l2pg = PHYS_TO_VM_PAGE(tl1 & ~ATTR_MASK);
                pmap_unwire_l3(pmap, va, l2pg, free);
        } else if (m->pindex < (NUL2E + NUL1E)) {
                /* We just released an l2, unhold the matching l1 */
                pd_entry_t *l0, tl0;
                vm_page_t l1pg;

                l0 = pmap_l0(pmap, va);
                tl0 = pmap_load(l0);
                l1pg = PHYS_TO_VM_PAGE(tl0 & ~ATTR_MASK);
                pmap_unwire_l3(pmap, va, l1pg, free);
        }
        pmap_invalidate_page(pmap, va);

        /*
         * 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 reference count.
 */
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 & ~ATTR_MASK);
        return (pmap_unwire_l3(pmap, va, mpte, free));
}

/*
 * Release a page table page reference after a failed attempt to create a
 * mapping.
 */
static void
pmap_abort_ptp(pmap_t pmap, vm_offset_t va, vm_page_t mpte)
{
        struct spglist free;

        SLIST_INIT(&free);
        if (pmap_unwire_l3(pmap, va, mpte, &free)) {
                /*
                 * Although "va" was never mapped, the TLB could nonetheless
                 * have intermediate entries that refer to the freed page
                 * table pages.  Invalidate those entries.
                 *
                 * XXX redundant invalidation (See _pmap_unwire_l3().)
                 */
                pmap_invalidate_page(pmap, va);
                vm_page_free_pages_toq(&free, true);
        }
}

void
pmap_pinit0(pmap_t pmap)
{

        PMAP_LOCK_INIT(pmap);
        bzero(&pmap->pm_stats, sizeof(pmap->pm_stats));
        pmap->pm_l0_paddr = READ_SPECIALREG(ttbr0_el1);
        pmap->pm_l0 = (pd_entry_t *)PHYS_TO_DMAP(pmap->pm_l0_paddr);
        pmap->pm_root.rt_root = 0;
        pmap->pm_cookie = COOKIE_FROM(ASID_RESERVED_FOR_PID_0, INT_MIN);
        pmap->pm_stage = PM_STAGE1;
        pmap->pm_asid_set = &asids;

        PCPU_SET(curpmap, pmap);
}

int
pmap_pinit_stage(pmap_t pmap, enum pmap_stage stage)
{
        vm_page_t l0pt;

        /*
         * allocate the l0 page
         */
        while ((l0pt = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
            VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL)
                vm_wait(NULL);

        pmap->pm_l0_paddr = VM_PAGE_TO_PHYS(l0pt);
        pmap->pm_l0 = (pd_entry_t *)PHYS_TO_DMAP(pmap->pm_l0_paddr);

        if ((l0pt->flags & PG_ZERO) == 0)
                pagezero(pmap->pm_l0);

        pmap->pm_root.rt_root = 0;
        bzero(&pmap->pm_stats, sizeof(pmap->pm_stats));
        pmap->pm_cookie = COOKIE_FROM(-1, INT_MAX);

        pmap->pm_stage = stage;
        switch (stage) {
        case PM_STAGE1:
                pmap->pm_asid_set = &asids;
                break;
        case PM_STAGE2:
                pmap->pm_asid_set = &vmids;
                break;
        default:
                panic("%s: Invalid pmap type %d", __func__, stage);
                break;
        }

        /* XXX Temporarily disable deferred ASID allocation. */
        pmap_alloc_asid(pmap);

        return (1);
}

int
pmap_pinit(pmap_t pmap)
{

        return (pmap_pinit_stage(pmap, PM_STAGE1));
}

/*
 * 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_alloc_l3(pmap_t pmap, vm_pindex_t ptepindex, struct rwlock **lockp)
{
        vm_page_t m, l1pg, l2pg;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        /*
         * 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);
                        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);

        /*
         * Because of AArch64's weak memory consistency model, we must have a
         * barrier here to ensure that the stores for zeroing "m", whether by
         * pmap_zero_page() or an earlier function, are visible before adding
         * "m" to the page table.  Otherwise, a page table walk by another
         * processor's MMU could see the mapping to "m" and a stale, non-zero
         * PTE within "m".
         */
        dmb(ishst);

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

        if (ptepindex >= (NUL2E + NUL1E)) {
                pd_entry_t *l0;
                vm_pindex_t l0index;

                l0index = ptepindex - (NUL2E + NUL1E);
                l0 = &pmap->pm_l0[l0index];
                pmap_store(l0, VM_PAGE_TO_PHYS(m) | L0_TABLE);
        } else if (ptepindex >= NUL2E) {
                vm_pindex_t l0index, l1index;
                pd_entry_t *l0, *l1;
                pd_entry_t tl0;

                l1index = ptepindex - NUL2E;
                l0index = l1index >> L0_ENTRIES_SHIFT;

                l0 = &pmap->pm_l0[l0index];
                tl0 = pmap_load(l0);
                if (tl0 == 0) {
                        /* recurse for allocating page dir */
                        if (_pmap_alloc_l3(pmap, NUL2E + NUL1E + l0index,
                            lockp) == NULL) {
                                vm_page_unwire_noq(m);
                                vm_page_free_zero(m);
                                return (NULL);
                        }
                } else {
                        l1pg = PHYS_TO_VM_PAGE(tl0 & ~ATTR_MASK);
                        l1pg->ref_count++;
                }

                l1 = (pd_entry_t *)PHYS_TO_DMAP(pmap_load(l0) & ~ATTR_MASK);
                l1 = &l1[ptepindex & Ln_ADDR_MASK];
                pmap_store(l1, VM_PAGE_TO_PHYS(m) | L1_TABLE);
        } else {
                vm_pindex_t l0index, l1index;
                pd_entry_t *l0, *l1, *l2;
                pd_entry_t tl0, tl1;

                l1index = ptepindex >> Ln_ENTRIES_SHIFT;
                l0index = l1index >> L0_ENTRIES_SHIFT;

                l0 = &pmap->pm_l0[l0index];
                tl0 = pmap_load(l0);
                if (tl0 == 0) {
                        /* recurse for allocating page dir */
                        if (_pmap_alloc_l3(pmap, NUL2E + l1index,
                            lockp) == NULL) {
                                vm_page_unwire_noq(m);
                                vm_page_free_zero(m);
                                return (NULL);
                        }
                        tl0 = pmap_load(l0);
                        l1 = (pd_entry_t *)PHYS_TO_DMAP(tl0 & ~ATTR_MASK);
                        l1 = &l1[l1index & Ln_ADDR_MASK];
                } else {
                        l1 = (pd_entry_t *)PHYS_TO_DMAP(tl0 & ~ATTR_MASK);
                        l1 = &l1[l1index & Ln_ADDR_MASK];
                        tl1 = pmap_load(l1);
                        if (tl1 == 0) {
                                /* recurse for allocating page dir */
                                if (_pmap_alloc_l3(pmap, NUL2E + l1index,
                                    lockp) == NULL) {
                                        vm_page_unwire_noq(m);
                                        vm_page_free_zero(m);
                                        return (NULL);
                                }
                        } else {
                                l2pg = PHYS_TO_VM_PAGE(tl1 & ~ATTR_MASK);
                                l2pg->ref_count++;
                        }
                }

                l2 = (pd_entry_t *)PHYS_TO_DMAP(pmap_load(l1) & ~ATTR_MASK);
                l2 = &l2[ptepindex & Ln_ADDR_MASK];
                pmap_store(l2, VM_PAGE_TO_PHYS(m) | L2_TABLE);
        }

        pmap_resident_count_inc(pmap, 1);

        return (m);
}

static pd_entry_t *
pmap_alloc_l2(pmap_t pmap, vm_offset_t va, vm_page_t *l2pgp,
    struct rwlock **lockp)
{
        pd_entry_t *l1, *l2;
        vm_page_t l2pg;
        vm_pindex_t l2pindex;

retry:
        l1 = pmap_l1(pmap, va);
        if (l1 != NULL && (pmap_load(l1) & ATTR_DESCR_MASK) == L1_TABLE) {
                l2 = pmap_l1_to_l2(l1, va);
                if (va < VM_MAXUSER_ADDRESS) {
                        /* Add a reference to the L2 page. */
                        l2pg = PHYS_TO_VM_PAGE(pmap_load(l1) & ~ATTR_MASK);
                        l2pg->ref_count++;
                } else
                        l2pg = NULL;
        } else if (va < VM_MAXUSER_ADDRESS) {
                /* Allocate a L2 page. */
                l2pindex = pmap_l2_pindex(va) >> Ln_ENTRIES_SHIFT;
                l2pg = _pmap_alloc_l3(pmap, NUL2E + l2pindex, lockp);
                if (l2pg == NULL) {
                        if (lockp != NULL)
                                goto retry;
                        else
                                return (NULL);
                }
                l2 = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(l2pg));
                l2 = &l2[pmap_l2_index(va)];
        } else
                panic("pmap_alloc_l2: missing page table page for va %#lx",
                    va);
        *l2pgp = l2pg;
        return (l2);
}

static vm_page_t
pmap_alloc_l3(pmap_t pmap, vm_offset_t va, struct rwlock **lockp)
{
        vm_pindex_t ptepindex;
        pd_entry_t *pde, tpde;
#ifdef INVARIANTS
        pt_entry_t *pte;
#endif
        vm_page_t m;
        int lvl;

        /*
         * Calculate pagetable page index
         */
        ptepindex = pmap_l2_pindex(va);
retry:
        /*
         * Get the page directory entry
         */
        pde = pmap_pde(pmap, va, &lvl);

        /*
         * If the page table page is mapped, we just increment the hold count,
         * and activate it. If we get a level 2 pde it will point to a level 3
         * table.
         */
        switch (lvl) {
        case -1:
                break;
        case 0:
#ifdef INVARIANTS
                pte = pmap_l0_to_l1(pde, va);
                KASSERT(pmap_load(pte) == 0,
                    ("pmap_alloc_l3: TODO: l0 superpages"));
#endif
                break;
        case 1:
#ifdef INVARIANTS
                pte = pmap_l1_to_l2(pde, va);
                KASSERT(pmap_load(pte) == 0,
                    ("pmap_alloc_l3: TODO: l1 superpages"));
#endif
                break;
        case 2:
                tpde = pmap_load(pde);
                if (tpde != 0) {
                        m = PHYS_TO_VM_PAGE(tpde & ~ATTR_MASK);
                        m->ref_count++;
                        return (m);
                }
                break;
        default:
                panic("pmap_alloc_l3: Invalid level %d", lvl);
        }

        /*
         * Here if the pte page isn't mapped, or if it has been deallocated.
         */
        m = _pmap_alloc_l3(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)
{
        struct asid_set *set;
        vm_page_t m;
        int asid;

        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)"));

        set = pmap->pm_asid_set;
        KASSERT(set != NULL, ("%s: NULL asid set", __func__));

        /*
         * Allow the ASID to be reused. In stage 2 VMIDs we don't invalidate
         * the entries when removing them so rely on a later tlb invalidation.
         * this will happen when updating the VMID generation. Because of this
         * we don't reuse VMIDs within a generation.
         */
        if (pmap->pm_stage == PM_STAGE1) {
                mtx_lock_spin(&set->asid_set_mutex);
                if (COOKIE_TO_EPOCH(pmap->pm_cookie) == set->asid_epoch) {
                        asid = COOKIE_TO_ASID(pmap->pm_cookie);
                        KASSERT(asid >= ASID_FIRST_AVAILABLE &&
                            asid < set->asid_set_size,
                            ("pmap_release: pmap cookie has out-of-range asid"));
                        bit_clear(set->asid_set, asid);
                }
                mtx_unlock_spin(&set->asid_set_mutex);
        }

        m = PHYS_TO_VM_PAGE(pmap->pm_l0_paddr);
        vm_page_unwire_noq(m);
        vm_page_free_zero(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 | CTLFLAG_MPSAFE,
    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 | CTLFLAG_MPSAFE,
    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 *l0, *l1, *l2;

        mtx_assert(&kernel_map->system_mtx, MA_OWNED);

        addr = roundup2(addr, L2_SIZE);
        if (addr - 1 >= vm_map_max(kernel_map))
                addr = vm_map_max(kernel_map);
        while (kernel_vm_end < addr) {
                l0 = pmap_l0(kernel_pmap, kernel_vm_end);
                KASSERT(pmap_load(l0) != 0,
                    ("pmap_growkernel: No level 0 kernel entry"));

                l1 = pmap_l0_to_l1(l0, kernel_vm_end);
                if (pmap_load(l1) == 0) {
                        /* We need a new PDP entry */
                        nkpg = vm_page_alloc(NULL, kernel_vm_end >> L1_SHIFT,
                            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);
                        /* See the dmb() in _pmap_alloc_l3(). */
                        dmb(ishst);
                        paddr = VM_PAGE_TO_PHYS(nkpg);
                        pmap_store(l1, paddr | L1_TABLE);
                        continue; /* try again */
                }
                l2 = pmap_l1_to_l2(l1, kernel_vm_end);
                if (pmap_load(l2) != 0) {
                        kernel_vm_end = (kernel_vm_end + L2_SIZE) & ~L2_OFFSET;
                        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, kernel_vm_end >> L2_SHIFT,
                    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);
                /* See the dmb() in _pmap_alloc_l3(). */
                dmb(ishst);
                paddr = VM_PAGE_TO_PHYS(nkpg);
                pmap_store(l2, paddr | L2_TABLE);

                kernel_vm_end = (kernel_vm_end + L2_SIZE) & ~L2_OFFSET;
                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 };

#if 0
#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
#endif /* 0 */

/*
 * 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;
        pv_entry_t pv;
        vm_offset_t va;
        vm_page_t m, m_pc;
        struct spglist free;
        uint64_t inuse;
        int bit, field, freed, lvl;
        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;
        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;

        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 pv_chunks_mutex is owned and the
                 * corresponding pmap is locked.
                 */
                if (pmap != next_pmap) {
                        if (pmap != NULL && pmap != locked_pmap)
                                PMAP_UNLOCK(pmap);
                        pmap = next_pmap;
                        /* Avoid deadlock and lock recursion. */
                        if (pmap > locked_pmap) {
                                RELEASE_PV_LIST_LOCK(lockp);
                                PMAP_LOCK(pmap);
                                mtx_lock(&pv_chunks_mutex);
                                continue;
                        } else if (pmap != locked_pmap) {
                                if (PMAP_TRYLOCK(pmap)) {
                                        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;
                                }
                        }
                }

                /*
                 * 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 = ffsl(inuse) - 1;
                                pv = &pc->pc_pventry[field * 64 + bit];
                                va = pv->pv_va;
                                pde = pmap_pde(pmap, va, &lvl);
                                if (lvl != 2)
                                        continue;
                                pte = pmap_l2_to_l3(pde, va);
                                tpte = pmap_load(pte);
                                if ((tpte & ATTR_SW_WIRED) != 0)
                                        continue;
                                tpte = pmap_load_clear(pte);
                                m = PHYS_TO_VM_PAGE(tpte & ~ATTR_MASK);
                                if (pmap_pte_dirty(pmap, tpte))
                                        vm_page_dirty(m);
                                if ((tpte & ATTR_AF) != 0) {
                                        pmap_invalidate_page(pmap, va);
                                        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);
                                        }
                                }
                                pc->pc_map[field] |= 1UL << bit;
                                pmap_unuse_pt(pmap, va, pmap_load(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);
        if (pmap != NULL && pmap != locked_pmap)
                PMAP_UNLOCK(pmap);
        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->ref_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_noq(m);
        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 = ffsl(pc->pc_map[field]) - 1;
                                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);
}

/*
 * 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) {
                bit_count((bitstr_t *)pc->pc_map, 0,
                    sizeof(pc->pc_map) * NBBY, &free);
                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_l2(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((va & L2_OFFSET) == 0,
            ("pmap_pv_demote_l2: va is not 2mpage aligned"));
        KASSERT((pa & L2_OFFSET) == 0,
            ("pmap_pv_demote_l2: 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);
        pv = pmap_pvh_remove(pvh, pmap, va);
        KASSERT(pv != NULL, ("pmap_pv_demote_l2: 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 Ln_ENTRIES - 1 pv entries. */
        PV_STAT(atomic_add_long(&pv_entry_allocs, Ln_ENTRIES - 1));
        va_last = va + L2_SIZE - 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_l2: missing spare"));
                for (field = 0; field < _NPCM; field++) {
                        while (pc->pc_map[field]) {
                                bit = ffsl(pc->pc_map[field]) - 1;
                                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_l2: 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, Ln_ENTRIES - 1));
        PV_STAT(atomic_subtract_int(&pv_entry_spare, Ln_ENTRIES - 1));
}

/*
 * 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_l2(pmap_t pmap, vm_offset_t va, pd_entry_t l2e, 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 = l2e & ~ATTR_MASK;
        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);
}

static void
pmap_remove_kernel_l2(pmap_t pmap, pt_entry_t *l2, vm_offset_t va)
{
        pt_entry_t newl2, oldl2;
        vm_page_t ml3;
        vm_paddr_t ml3pa;

        KASSERT(!VIRT_IN_DMAP(va), ("removing direct mapping of %#lx", va));
        KASSERT(pmap == kernel_pmap, ("pmap %p is not kernel_pmap", pmap));
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        ml3 = pmap_remove_pt_page(pmap, va);
        if (ml3 == NULL)
                panic("pmap_remove_kernel_l2: Missing pt page");

        ml3pa = VM_PAGE_TO_PHYS(ml3);
        newl2 = ml3pa | L2_TABLE;

        /*
         * If this page table page was unmapped by a promotion, then it
         * contains valid mappings.  Zero it to invalidate those mappings.
         */
        if (ml3->valid != 0)
                pagezero((void *)PHYS_TO_DMAP(ml3pa));

        /*
         * Demote the mapping.  The caller must have already invalidated the
         * mapping (i.e., the "break" in break-before-make).
         */
        oldl2 = pmap_load_store(l2, newl2);
        KASSERT(oldl2 == 0, ("%s: found existing mapping at %p: %#lx",
            __func__, l2, oldl2));
}

/*
 * pmap_remove_l2: Do the things to unmap a level 2 superpage.
 */
static int
pmap_remove_l2(pmap_t pmap, pt_entry_t *l2, vm_offset_t sva,
    pd_entry_t l1e, struct spglist *free, struct rwlock **lockp)
{
        struct md_page *pvh;
        pt_entry_t old_l2;
        vm_offset_t eva, va;
        vm_page_t m, ml3;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT((sva & L2_OFFSET) == 0, ("pmap_remove_l2: sva is not aligned"));
        old_l2 = pmap_load_clear(l2);
        KASSERT((old_l2 & ATTR_DESCR_MASK) == L2_BLOCK,
            ("pmap_remove_l2: L2e %lx is not a block mapping", old_l2));

        /*
         * Since a promotion must break the 4KB page mappings before making
         * the 2MB page mapping, a pmap_invalidate_page() suffices.
         */
        pmap_invalidate_page(pmap, sva);

        if (old_l2 & ATTR_SW_WIRED)
                pmap->pm_stats.wired_count -= L2_SIZE / PAGE_SIZE;
        pmap_resident_count_dec(pmap, L2_SIZE / PAGE_SIZE);
        if (old_l2 & ATTR_SW_MANAGED) {
                CHANGE_PV_LIST_LOCK_TO_PHYS(lockp, old_l2 & ~ATTR_MASK);
                pvh = pa_to_pvh(old_l2 & ~ATTR_MASK);
                pmap_pvh_free(pvh, pmap, sva);
                eva = sva + L2_SIZE;
                for (va = sva, m = PHYS_TO_VM_PAGE(old_l2 & ~ATTR_MASK);
                    va < eva; va += PAGE_SIZE, m++) {
                        if (pmap_pte_dirty(pmap, old_l2))
                                vm_page_dirty(m);
                        if (old_l2 & ATTR_AF)
                                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);
                }
        }
        if (pmap == kernel_pmap) {
                pmap_remove_kernel_l2(pmap, l2, sva);
        } else {
                ml3 = pmap_remove_pt_page(pmap, sva);
                if (ml3 != NULL) {
                        KASSERT(ml3->valid == VM_PAGE_BITS_ALL,
                            ("pmap_remove_l2: l3 page not promoted"));
                        pmap_resident_count_dec(pmap, 1);
                        KASSERT(ml3->ref_count == NL3PG,
                            ("pmap_remove_l2: l3 page ref count error"));
                        ml3->ref_count = 0;
                        pmap_add_delayed_free_list(ml3, free, FALSE);
                }
        }
        return (pmap_unuse_pt(pmap, sva, l1e, free));
}

/*
 * pmap_remove_l3: do the things to unmap a page in a process
 */
static int
pmap_remove_l3(pmap_t pmap, pt_entry_t *l3, vm_offset_t va,
    pd_entry_t l2e, struct spglist *free, struct rwlock **lockp)
{
        struct md_page *pvh;
        pt_entry_t old_l3;
        vm_page_t m;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        old_l3 = pmap_load_clear(l3);
        pmap_invalidate_page(pmap, va);
        if (old_l3 & ATTR_SW_WIRED)
                pmap->pm_stats.wired_count -= 1;
        pmap_resident_count_dec(pmap, 1);
        if (old_l3 & ATTR_SW_MANAGED) {
                m = PHYS_TO_VM_PAGE(old_l3 & ~ATTR_MASK);
                if (pmap_pte_dirty(pmap, old_l3))
                        vm_page_dirty(m);
                if (old_l3 & ATTR_AF)
                        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);
                }
        }
        return (pmap_unuse_pt(pmap, va, l2e, free));
}

/*
 * Remove the specified range of addresses from the L3 page table that is
 * identified by the given L2 entry.
 */
static void
pmap_remove_l3_range(pmap_t pmap, pd_entry_t l2e, vm_offset_t sva,
    vm_offset_t eva, struct spglist *free, struct rwlock **lockp)
{
        struct md_page *pvh;
        struct rwlock *new_lock;
        pt_entry_t *l3, old_l3;
        vm_offset_t va;
        vm_page_t l3pg, m;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT(rounddown2(sva, L2_SIZE) + L2_SIZE == roundup2(eva, L2_SIZE),
            ("pmap_remove_l3_range: range crosses an L3 page table boundary"));
        l3pg = sva < VM_MAXUSER_ADDRESS ? PHYS_TO_VM_PAGE(l2e & ~ATTR_MASK) :
            NULL;
        va = eva;
        for (l3 = pmap_l2_to_l3(&l2e, sva); sva != eva; l3++, sva += L3_SIZE) {
                if (!pmap_l3_valid(pmap_load(l3))) {
                        if (va != eva) {
                                pmap_invalidate_range(pmap, va, sva);
                                va = eva;
                        }
                        continue;
                }
                old_l3 = pmap_load_clear(l3);
                if ((old_l3 & ATTR_SW_WIRED) != 0)
                        pmap->pm_stats.wired_count--;
                pmap_resident_count_dec(pmap, 1);
                if ((old_l3 & ATTR_SW_MANAGED) != 0) {
                        m = PHYS_TO_VM_PAGE(old_l3 & ~ATTR_MASK);
                        if (pmap_pte_dirty(pmap, old_l3))
                                vm_page_dirty(m);
                        if ((old_l3 & ATTR_AF) != 0)
                                vm_page_aflag_set(m, PGA_REFERENCED);
                        new_lock = PHYS_TO_PV_LIST_LOCK(VM_PAGE_TO_PHYS(m));
                        if (new_lock != *lockp) {
                                if (*lockp != NULL) {
                                        /*
                                         * Pending TLB invalidations must be
                                         * performed before the PV list lock is
                                         * released.  Otherwise, a concurrent
                                         * pmap_remove_all() on a physical page
                                         * could return while a stale TLB entry
                                         * still provides access to that page. 
                                         */
                                        if (va != eva) {
                                                pmap_invalidate_range(pmap, va,
                                                    sva);
                                                va = eva;
                                        }
                                        rw_wunlock(*lockp);
                                }
                                *lockp = new_lock;
                                rw_wlock(*lockp);
                        }
                        pmap_pvh_free(&m->md, pmap, sva);
                        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);
                        }
                }
                if (va == eva)
                        va = sva;
                if (l3pg != NULL && pmap_unwire_l3(pmap, sva, l3pg, free)) {
                        sva += L3_SIZE;
                        break;
                }
        }
        if (va != eva)
                pmap_invalidate_range(pmap, va, sva);
}

/*
 *      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;
        pd_entry_t *l0, *l1, *l2;
        pt_entry_t l3_paddr;
        struct spglist free;

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

        SLIST_INIT(&free);

        PMAP_LOCK(pmap);

        lock = NULL;
        for (; sva < eva; sva = va_next) {
                if (pmap->pm_stats.resident_count == 0)
                        break;

                l0 = pmap_l0(pmap, sva);
                if (pmap_load(l0) == 0) {
                        va_next = (sva + L0_SIZE) & ~L0_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                l1 = pmap_l0_to_l1(l0, sva);
                if (pmap_load(l1) == 0) {
                        va_next = (sva + L1_SIZE) & ~L1_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                /*
                 * Calculate index for next page table.
                 */
                va_next = (sva + L2_SIZE) & ~L2_OFFSET;
                if (va_next < sva)
                        va_next = eva;

                l2 = pmap_l1_to_l2(l1, sva);
                if (l2 == NULL)
                        continue;

                l3_paddr = pmap_load(l2);

                if ((l3_paddr & ATTR_DESCR_MASK) == L2_BLOCK) {
                        if (sva + L2_SIZE == va_next && eva >= va_next) {
                                pmap_remove_l2(pmap, l2, sva, pmap_load(l1),
                                    &free, &lock);
                                continue;
                        } else if (pmap_demote_l2_locked(pmap, l2, sva,
                            &lock) == NULL)
                                continue;
                        l3_paddr = pmap_load(l2);
                }

                /*
                 * Weed out invalid mappings.
                 */
                if ((l3_paddr & ATTR_DESCR_MASK) != L2_TABLE)
                        continue;

                /*
                 * 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;

                pmap_remove_l3_range(pmap, l3_paddr, sva, va_next, &free,
                    &lock);
        }
        if (lock != NULL)
                rw_wunlock(lock);
        PMAP_UNLOCK(pmap);
        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;
        pd_entry_t *pde, tpde;
        pt_entry_t *pte, tpte;
        vm_offset_t va;
        struct spglist free;
        int lvl, 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;
                pte = pmap_pte(pmap, va, &lvl);
                KASSERT(pte != NULL,
                    ("pmap_remove_all: no page table entry found"));
                KASSERT(lvl == 2,
                    ("pmap_remove_all: invalid pte level %d", lvl));

                pmap_demote_l2_locked(pmap, pte, va, &lock);
                PMAP_UNLOCK(pmap);
        }
        while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                pmap = PV_PMAP(pv);
                PMAP_ASSERT_STAGE1(pmap);
                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;
                        }
                }
                pmap_resident_count_dec(pmap, 1);

                pde = pmap_pde(pmap, pv->pv_va, &lvl);
                KASSERT(pde != NULL,
                    ("pmap_remove_all: no page directory entry found"));
                KASSERT(lvl == 2,
                    ("pmap_remove_all: invalid pde level %d", lvl));
                tpde = pmap_load(pde);

                pte = pmap_l2_to_l3(pde, pv->pv_va);
                tpte = pmap_load_clear(pte);
                if (tpte & ATTR_SW_WIRED)
                        pmap->pm_stats.wired_count--;
                if ((tpte & ATTR_AF) != 0) {
                        pmap_invalidate_page(pmap, pv->pv_va);
                        vm_page_aflag_set(m, PGA_REFERENCED);
                }

                /*
                 * Update the vm_page_t clean and reference bits.
                 */
                if (pmap_pte_dirty(pmap, tpte))
                        vm_page_dirty(m);
                pmap_unuse_pt(pmap, pv->pv_va, tpde, &free);
                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);
        vm_page_free_pages_toq(&free, true);
}

/*
 * pmap_protect_l2: do the things to protect a 2MB page in a pmap
 */
static void
pmap_protect_l2(pmap_t pmap, pt_entry_t *l2, vm_offset_t sva, pt_entry_t mask,
    pt_entry_t nbits)
{
        pd_entry_t old_l2;
        vm_page_t m, mt;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PMAP_ASSERT_STAGE1(pmap);
        KASSERT((sva & L2_OFFSET) == 0,
            ("pmap_protect_l2: sva is not 2mpage aligned"));
        old_l2 = pmap_load(l2);
        KASSERT((old_l2 & ATTR_DESCR_MASK) == L2_BLOCK,
            ("pmap_protect_l2: L2e %lx is not a block mapping", old_l2));

        /*
         * Return if the L2 entry already has the desired access restrictions
         * in place.
         */
retry:
        if ((old_l2 & mask) == nbits)
                return;

        /*
         * When a dirty read/write superpage mapping is write protected,
         * update the dirty field of each of the superpage's constituent 4KB
         * pages.
         */
        if ((old_l2 & ATTR_SW_MANAGED) != 0 &&
            (nbits & ATTR_S1_AP(ATTR_S1_AP_RO)) != 0 &&
            pmap_pte_dirty(pmap, old_l2)) {
                m = PHYS_TO_VM_PAGE(old_l2 & ~ATTR_MASK);
                for (mt = m; mt < &m[L2_SIZE / PAGE_SIZE]; mt++)
                        vm_page_dirty(mt);
        }

        if (!atomic_fcmpset_64(l2, &old_l2, (old_l2 & ~mask) | nbits))
                goto retry;

        /*
         * Since a promotion must break the 4KB page mappings before making
         * the 2MB page mapping, a pmap_invalidate_page() suffices.
         */
        pmap_invalidate_page(pmap, sva);
}

/*
 *      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, va_next;
        pd_entry_t *l0, *l1, *l2;
        pt_entry_t *l3p, l3, mask, nbits;

        PMAP_ASSERT_STAGE1(pmap);
        KASSERT((prot & ~VM_PROT_ALL) == 0, ("invalid prot %x", prot));
        if (prot == VM_PROT_NONE) {
                pmap_remove(pmap, sva, eva);
                return;
        }

        mask = nbits = 0;
        if ((prot & VM_PROT_WRITE) == 0) {
                mask |= ATTR_S1_AP_RW_BIT | ATTR_SW_DBM;
                nbits |= ATTR_S1_AP(ATTR_S1_AP_RO);
        }
        if ((prot & VM_PROT_EXECUTE) == 0) {
                mask |= ATTR_S1_XN;
                nbits |= ATTR_S1_XN;
        }
        if (mask == 0)
                return;

        PMAP_LOCK(pmap);
        for (; sva < eva; sva = va_next) {
                l0 = pmap_l0(pmap, sva);
                if (pmap_load(l0) == 0) {
                        va_next = (sva + L0_SIZE) & ~L0_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                l1 = pmap_l0_to_l1(l0, sva);
                if (pmap_load(l1) == 0) {
                        va_next = (sva + L1_SIZE) & ~L1_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                va_next = (sva + L2_SIZE) & ~L2_OFFSET;
                if (va_next < sva)
                        va_next = eva;

                l2 = pmap_l1_to_l2(l1, sva);
                if (pmap_load(l2) == 0)
                        continue;

                if ((pmap_load(l2) & ATTR_DESCR_MASK) == L2_BLOCK) {
                        if (sva + L2_SIZE == va_next && eva >= va_next) {
                                pmap_protect_l2(pmap, l2, sva, mask, nbits);
                                continue;
                        } else if (pmap_demote_l2(pmap, l2, sva) == NULL)
                                continue;
                }
                KASSERT((pmap_load(l2) & ATTR_DESCR_MASK) == L2_TABLE,
                    ("pmap_protect: Invalid L2 entry after demotion"));

                if (va_next > eva)
                        va_next = eva;

                va = va_next;
                for (l3p = pmap_l2_to_l3(l2, sva); sva != va_next; l3p++,
                    sva += L3_SIZE) {
                        l3 = pmap_load(l3p);
retry:
                        /*
                         * Go to the next L3 entry if the current one is
                         * invalid or already has the desired access
                         * restrictions in place.  (The latter case occurs
                         * frequently.  For example, in a "buildworld"
                         * workload, almost 1 out of 4 L3 entries already
                         * have the desired restrictions.)
                         */
                        if (!pmap_l3_valid(l3) || (l3 & mask) == nbits) {
                                if (va != va_next) {
                                        pmap_invalidate_range(pmap, va, sva);
                                        va = va_next;
                                }
                                continue;
                        }

                        /*
                         * When a dirty read/write mapping is write protected,
                         * update the page's dirty field.
                         */
                        if ((l3 & ATTR_SW_MANAGED) != 0 &&
                            (nbits & ATTR_S1_AP(ATTR_S1_AP_RO)) != 0 &&
                            pmap_pte_dirty(pmap, l3))
                                vm_page_dirty(PHYS_TO_VM_PAGE(l3 & ~ATTR_MASK));

                        if (!atomic_fcmpset_64(l3p, &l3, (l3 & ~mask) | nbits))
                                goto retry;
                        if (va == va_next)
                                va = sva;
                }
                if (va != va_next)
                        pmap_invalidate_range(pmap, va, sva);
        }
        PMAP_UNLOCK(pmap);
}

/*
 * 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.
 *
 * If "promoted" is false, then the page table page "mpte" must be zero filled.
 */
static __inline int
pmap_insert_pt_page(pmap_t pmap, vm_page_t mpte, bool promoted)
{

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        mpte->valid = promoted ? VM_PAGE_BITS_ALL : 0;
        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_l2_pindex(va)));
}

/*
 * Performs a break-before-make update of a pmap entry. This is needed when
 * either promoting or demoting pages to ensure the TLB doesn't get into an
 * inconsistent state.
 */
static void
pmap_update_entry(pmap_t pmap, pd_entry_t *pte, pd_entry_t newpte,
    vm_offset_t va, vm_size_t size)
{
        register_t intr;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        /*
         * Ensure we don't get switched out with the page table in an
         * inconsistent state. We also need to ensure no interrupts fire
         * as they may make use of an address we are about to invalidate.
         */
        intr = intr_disable();

        /*
         * Clear the old mapping's valid bit, but leave the rest of the entry
         * unchanged, so that a lockless, concurrent pmap_kextract() can still
         * lookup the physical address.
         */
        pmap_clear_bits(pte, ATTR_DESCR_VALID);
        pmap_invalidate_range(pmap, va, va + size);

        /* Create the new mapping */
        pmap_store(pte, newpte);
        dsb(ishst);

        intr_restore(intr);
}

#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_l2(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 & L2_OFFSET) == 0,
            ("pmap_pv_promote_l2: 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 = va & ~L2_OFFSET;
        pv = pmap_pvh_remove(&m->md, pmap, va);
        KASSERT(pv != NULL, ("pmap_pv_promote_l2: 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 + L2_SIZE - PAGE_SIZE;
        do {
                m++;
                va += PAGE_SIZE;
                pmap_pvh_free(&m->md, pmap, va);
        } while (va < va_last);
}

/*
 * Tries to promote the 512, contiguous 4KB page mappings that are within a
 * single level 2 table entry 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_l2(pmap_t pmap, pd_entry_t *l2, vm_offset_t va,
    struct rwlock **lockp)
{
        pt_entry_t *firstl3, *l3, newl2, oldl3, pa;
        vm_page_t mpte;
        vm_offset_t sva;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PMAP_ASSERT_STAGE1(pmap);

        sva = va & ~L2_OFFSET;
        firstl3 = pmap_l2_to_l3(l2, sva);
        newl2 = pmap_load(firstl3);

setl2:
        if (((newl2 & (~ATTR_MASK | ATTR_AF)) & L2_OFFSET) != ATTR_AF) {
                atomic_add_long(&pmap_l2_p_failures, 1);
                CTR2(KTR_PMAP, "pmap_promote_l2: failure for va %#lx"
                    " in pmap %p", va, pmap);
                return;
        }

        if ((newl2 & (ATTR_S1_AP_RW_BIT | ATTR_SW_DBM)) ==
            (ATTR_S1_AP(ATTR_S1_AP_RO) | ATTR_SW_DBM)) {
                if (!atomic_fcmpset_64(l2, &newl2, newl2 & ~ATTR_SW_DBM))
                        goto setl2;
                newl2 &= ~ATTR_SW_DBM;
        }

        pa = newl2 + L2_SIZE - PAGE_SIZE;
        for (l3 = firstl3 + NL3PG - 1; l3 > firstl3; l3--) {
                oldl3 = pmap_load(l3);
setl3:
                if ((oldl3 & (ATTR_S1_AP_RW_BIT | ATTR_SW_DBM)) ==
                    (ATTR_S1_AP(ATTR_S1_AP_RO) | ATTR_SW_DBM)) {
                        if (!atomic_fcmpset_64(l3, &oldl3, oldl3 &
                            ~ATTR_SW_DBM))
                                goto setl3;
                        oldl3 &= ~ATTR_SW_DBM;
                }
                if (oldl3 != pa) {
                        atomic_add_long(&pmap_l2_p_failures, 1);
                        CTR2(KTR_PMAP, "pmap_promote_l2: failure for va %#lx"
                            " in pmap %p", va, pmap);
                        return;
                }
                pa -= PAGE_SIZE;
        }

        /*
         * Save the page table page in its current state until the L2
         * mapping the superpage is demoted by pmap_demote_l2() or
         * destroyed by pmap_remove_l3().
         */
        mpte = PHYS_TO_VM_PAGE(pmap_load(l2) & ~ATTR_MASK);
        KASSERT(mpte >= vm_page_array &&
            mpte < &vm_page_array[vm_page_array_size],
            ("pmap_promote_l2: page table page is out of range"));
        KASSERT(mpte->pindex == pmap_l2_pindex(va),
            ("pmap_promote_l2: page table page's pindex is wrong"));
        if (pmap_insert_pt_page(pmap, mpte, true)) {
                atomic_add_long(&pmap_l2_p_failures, 1);
                CTR2(KTR_PMAP,
                    "pmap_promote_l2: failure for va %#lx in pmap %p", va,
                    pmap);
                return;
        }

        if ((newl2 & ATTR_SW_MANAGED) != 0)
                pmap_pv_promote_l2(pmap, va, newl2 & ~ATTR_MASK, lockp);

        newl2 &= ~ATTR_DESCR_MASK;
        newl2 |= L2_BLOCK;

        pmap_update_entry(pmap, l2, newl2, sva, L2_SIZE);

        atomic_add_long(&pmap_l2_promotions, 1);
        CTR2(KTR_PMAP, "pmap_promote_l2: 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.
 */
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 new_l3, orig_l3;
        pt_entry_t *l2, *l3;
        pv_entry_t pv;
        vm_paddr_t opa, pa;
        vm_page_t mpte, om;
        boolean_t nosleep;
        int lvl, rv;

        va = trunc_page(va);
        if ((m->oflags & VPO_UNMANAGED) == 0)
                VM_PAGE_OBJECT_BUSY_ASSERT(m);
        pa = VM_PAGE_TO_PHYS(m);
        new_l3 = (pt_entry_t)(pa | ATTR_DEFAULT | L3_PAGE);
        new_l3 |= pmap_pte_memattr(pmap, m->md.pv_memattr);
        new_l3 |= pmap_pte_prot(pmap, prot);

        if ((flags & PMAP_ENTER_WIRED) != 0)
                new_l3 |= ATTR_SW_WIRED;
        if (pmap->pm_stage == PM_STAGE1) {
                if (va < VM_MAXUSER_ADDRESS)
                        new_l3 |= ATTR_S1_AP(ATTR_S1_AP_USER) | ATTR_S1_PXN;
                else
                        new_l3 |= ATTR_S1_UXN;
                if (pmap != kernel_pmap)
                        new_l3 |= ATTR_S1_nG;
        } else {
                /*
                 * Clear the access flag on executable mappings, this will be
                 * set later when the page is accessed. The fault handler is
                 * required to invalidate the I-cache.
                 *
                 * TODO: Switch to the valid flag to allow hardware management
                 * of the access flag. Much of the pmap code assumes the
                 * valid flag is set and fails to destroy the old page tables
                 * correctly if it is clear.
                 */
                if (prot & VM_PROT_EXECUTE)
                        new_l3 &= ~ATTR_AF;
        }
        if ((m->oflags & VPO_UNMANAGED) == 0) {
                new_l3 |= ATTR_SW_MANAGED;
                if ((prot & VM_PROT_WRITE) != 0) {
                        new_l3 |= ATTR_SW_DBM;
                        if ((flags & VM_PROT_WRITE) == 0) {
                                if (pmap->pm_stage == PM_STAGE1)
                                        new_l3 |= ATTR_S1_AP(ATTR_S1_AP_RO);
                                else
                                        new_l3 &=
                                            ~ATTR_S2_S2AP(ATTR_S2_S2AP_WRITE);
                        }
                }
        }

        CTR2(KTR_PMAP, "pmap_enter: %.16lx -> %.16lx", va, pa);

        lock = NULL;
        PMAP_LOCK(pmap);
        if (psind == 1) {
                /* Assert the required virtual and physical alignment. */
                KASSERT((va & L2_OFFSET) == 0, ("pmap_enter: va unaligned"));
                KASSERT(m->psind > 0, ("pmap_enter: m->psind < psind"));
                rv = pmap_enter_l2(pmap, va, (new_l3 & ~L3_PAGE) | L2_BLOCK,
                    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, &lvl);
        if (pde != NULL && lvl == 2) {
                l3 = pmap_l2_to_l3(pde, va);
                if (va < VM_MAXUSER_ADDRESS && mpte == NULL) {
                        mpte = PHYS_TO_VM_PAGE(pmap_load(pde) & ~ATTR_MASK);
                        mpte->ref_count++;
                }
                goto havel3;
        } else if (pde != NULL && lvl == 1) {
                l2 = pmap_l1_to_l2(pde, va);
                if ((pmap_load(l2) & ATTR_DESCR_MASK) == L2_BLOCK &&
                    (l3 = pmap_demote_l2_locked(pmap, l2, va, &lock)) != NULL) {
                        l3 = &l3[pmap_l3_index(va)];
                        if (va < VM_MAXUSER_ADDRESS) {
                                mpte = PHYS_TO_VM_PAGE(
                                    pmap_load(l2) & ~ATTR_MASK);
                                mpte->ref_count++;
                        }
                        goto havel3;
                }
                /* We need to allocate an L3 table. */
        }
        if (va < VM_MAXUSER_ADDRESS) {
                nosleep = (flags & PMAP_ENTER_NOSLEEP) != 0;

                /*
                 * We use _pmap_alloc_l3() instead of pmap_alloc_l3() in order
                 * to handle the possibility that a superpage mapping for "va"
                 * was created while we slept.
                 */
                mpte = _pmap_alloc_l3(pmap, pmap_l2_pindex(va),
                    nosleep ? NULL : &lock);
                if (mpte == NULL && nosleep) {
                        CTR0(KTR_PMAP, "pmap_enter: mpte == NULL");
                        rv = KERN_RESOURCE_SHORTAGE;
                        goto out;
                }
                goto retry;
        } else
                panic("pmap_enter: missing L3 table for kernel va %#lx", va);

havel3:
        orig_l3 = pmap_load(l3);
        opa = orig_l3 & ~ATTR_MASK;
        pv = NULL;

        /*
         * Is the specified virtual address already mapped?
         */
        if (pmap_l3_valid(orig_l3)) {
                /*
                 * Only allow adding new entries on stage 2 tables for now.
                 * This simplifies cache invalidation as we may need to call
                 * into EL2 to perform such actions.
                 */
                PMAP_ASSERT_STAGE1(pmap);
                /*
                 * 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 ((flags & PMAP_ENTER_WIRED) != 0 &&
                    (orig_l3 & ATTR_SW_WIRED) == 0)
                        pmap->pm_stats.wired_count++;
                else if ((flags & PMAP_ENTER_WIRED) == 0 &&
                    (orig_l3 & ATTR_SW_WIRED) != 0)
                        pmap->pm_stats.wired_count--;

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

                /*
                 * Has the physical page changed?
                 */
                if (opa == pa) {
                        /*
                         * No, might be a protection or wiring change.
                         */
                        if ((orig_l3 & ATTR_SW_MANAGED) != 0 &&
                            (new_l3 & ATTR_SW_DBM) != 0)
                                vm_page_aflag_set(m, PGA_WRITEABLE);
                        goto validate;
                }

                /*
                 * The physical page has changed.  Temporarily invalidate
                 * the mapping.
                 */
                orig_l3 = pmap_load_clear(l3);
                KASSERT((orig_l3 & ~ATTR_MASK) == opa,
                    ("pmap_enter: unexpected pa update for %#lx", va));
                if ((orig_l3 & ATTR_SW_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 (pmap_pte_dirty(pmap, orig_l3))
                                vm_page_dirty(om);
                        if ((orig_l3 & ATTR_AF) != 0) {
                                pmap_invalidate_page(pmap, va);
                                vm_page_aflag_set(om, PGA_REFERENCED);
                        }
                        CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, opa);
                        pv = pmap_pvh_remove(&om->md, pmap, va);
                        if ((m->oflags & VPO_UNMANAGED) != 0)
                                free_pv_entry(pmap, pv);
                        if ((om->a.flags & 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);
                } else {
                        KASSERT((orig_l3 & ATTR_AF) != 0,
                            ("pmap_enter: unmanaged mapping lacks ATTR_AF"));
                        pmap_invalidate_page(pmap, va);
                }
                orig_l3 = 0;
        } else {
                /*
                 * Increment the counters.
                 */
                if ((new_l3 & ATTR_SW_WIRED) != 0)
                        pmap->pm_stats.wired_count++;
                pmap_resident_count_inc(pmap, 1);
        }
        /*
         * Enter on the PV list if part of our managed memory.
         */
        if ((m->oflags & VPO_UNMANAGED) == 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 ((new_l3 & ATTR_SW_DBM) != 0)
                        vm_page_aflag_set(m, PGA_WRITEABLE);
        }

validate:
        if (pmap->pm_stage == PM_STAGE1) {
                /*
                 * Sync icache if exec permission and attribute
                 * VM_MEMATTR_WRITE_BACK is set. Do it now, before the mapping
                 * is stored and made valid for hardware table walk. If done
                 * later, then other can access this page before caches are
                 * properly synced. Don't do it for kernel memory which is
                 * mapped with exec permission even if the memory isn't going
                 * to hold executable code. The only time when icache sync is
                 * needed is after kernel module is loaded and the relocation
                 * info is processed. And it's done in elf_cpu_load_file().
                */
                if ((prot & VM_PROT_EXECUTE) &&  pmap != kernel_pmap &&
                    m->md.pv_memattr == VM_MEMATTR_WRITE_BACK &&
                    (opa != pa || (orig_l3 & ATTR_S1_XN))) {
                        PMAP_ASSERT_STAGE1(pmap);
                        cpu_icache_sync_range(PHYS_TO_DMAP(pa), PAGE_SIZE);
                }
        } else {
                cpu_dcache_wb_range(PHYS_TO_DMAP(pa), PAGE_SIZE);
        }

        /*
         * Update the L3 entry
         */
        if (pmap_l3_valid(orig_l3)) {
                PMAP_ASSERT_STAGE1(pmap);
                KASSERT(opa == pa, ("pmap_enter: invalid update"));
                if ((orig_l3 & ~ATTR_AF) != (new_l3 & ~ATTR_AF)) {
                        /* same PA, different attributes */
                        orig_l3 = pmap_load_store(l3, new_l3);
                        pmap_invalidate_page(pmap, va);
                        if ((orig_l3 & ATTR_SW_MANAGED) != 0 &&
                            pmap_pte_dirty(pmap, orig_l3))
                                vm_page_dirty(m);
                } else {
                        /*
                         * orig_l3 == new_l3
                         * This can happens if multiple threads simultaneously
                         * access not yet mapped page. This bad for performance
                         * since this can cause full demotion-NOP-promotion
                         * cycle.
                         * Another possible reasons are:
                         * - VM and pmap memory layout are diverged
                         * - tlb flush is missing somewhere and CPU doesn't see
                         *   actual mapping.
                         */
                        CTR4(KTR_PMAP, "%s: already mapped page - "
                            "pmap %p va 0x%#lx pte 0x%lx",
                            __func__, pmap, va, new_l3);
                }
        } else {
                /* New mapping */
                pmap_store(l3, new_l3);
                dsb(ishst);
        }

#if VM_NRESERVLEVEL > 0
        /*
         * Try to promote from level 3 pages to a level 2 superpage. This
         * currently only works on stage 1 pmaps as pmap_promote_l2 looks at
         * stage 1 specific fields and performs a break-before-make sequence
         * that is incorrect a stage 2 pmap.
         */
        if ((mpte == NULL || mpte->ref_count == NL3PG) &&
            pmap_ps_enabled(pmap) && pmap->pm_stage == PM_STAGE1 &&
            (m->flags & PG_FICTITIOUS) == 0 &&
            vm_reserv_level_iffullpop(m) == 0) {
                pmap_promote_l2(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 new_l2;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PMAP_ASSERT_STAGE1(pmap);

        new_l2 = (pd_entry_t)(VM_PAGE_TO_PHYS(m) | ATTR_DEFAULT |
            ATTR_S1_IDX(m->md.pv_memattr) | ATTR_S1_AP(ATTR_S1_AP_RO) |
            L2_BLOCK);
        if ((m->oflags & VPO_UNMANAGED) == 0) {
                new_l2 |= ATTR_SW_MANAGED;
                new_l2 &= ~ATTR_AF;
        }
        if ((prot & VM_PROT_EXECUTE) == 0 ||
            m->md.pv_memattr == VM_MEMATTR_DEVICE)
                new_l2 |= ATTR_S1_XN;
        if (va < VM_MAXUSER_ADDRESS)
                new_l2 |= ATTR_S1_AP(ATTR_S1_AP_USER) | ATTR_S1_PXN;
        else
                new_l2 |= ATTR_S1_UXN;
        if (pmap != kernel_pmap)
                new_l2 |= ATTR_S1_nG;
        return (pmap_enter_l2(pmap, va, new_l2, PMAP_ENTER_NOSLEEP |
            PMAP_ENTER_NOREPLACE | PMAP_ENTER_NORECLAIM, NULL, lockp) ==
            KERN_SUCCESS);
}

/*
 * Returns true if every page table entry in the specified page table is
 * zero.
 */
static bool
pmap_every_pte_zero(vm_paddr_t pa)
{
        pt_entry_t *pt_end, *pte;

        KASSERT((pa & PAGE_MASK) == 0, ("pa is misaligned"));
        pte = (pt_entry_t *)PHYS_TO_DMAP(pa);
        for (pt_end = pte + Ln_ENTRIES; pte < pt_end; pte++) {
                if (*pte != 0)
                        return (false);
        }
        return (true);
}

/*
 * 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_l2(pmap_t pmap, vm_offset_t va, pd_entry_t new_l2, u_int flags,
    vm_page_t m, struct rwlock **lockp)
{
        struct spglist free;
        pd_entry_t *l2, old_l2;
        vm_page_t l2pg, mt;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        if ((l2 = pmap_alloc_l2(pmap, va, &l2pg, (flags &
            PMAP_ENTER_NOSLEEP) != 0 ? NULL : lockp)) == NULL) {
                CTR2(KTR_PMAP, "pmap_enter_l2: failure for va %#lx in pmap %p",
                    va, pmap);
                return (KERN_RESOURCE_SHORTAGE);
        }

        /*
         * If there are existing mappings, either abort or remove them.
         */
        if ((old_l2 = pmap_load(l2)) != 0) {
                KASSERT(l2pg == NULL || l2pg->ref_count > 1,
                    ("pmap_enter_l2: l2pg's ref count is too low"));
                if ((flags & PMAP_ENTER_NOREPLACE) != 0 && (va <
                    VM_MAXUSER_ADDRESS || (old_l2 & ATTR_DESCR_MASK) ==
                    L2_BLOCK || !pmap_every_pte_zero(old_l2 & ~ATTR_MASK))) {
                        if (l2pg != NULL)
                                l2pg->ref_count--;
                        CTR2(KTR_PMAP, "pmap_enter_l2: failure for va %#lx"
                            " in pmap %p", va, pmap);
                        return (KERN_FAILURE);
                }
                SLIST_INIT(&free);
                if ((old_l2 & ATTR_DESCR_MASK) == L2_BLOCK)
                        (void)pmap_remove_l2(pmap, l2, va,
                            pmap_load(pmap_l1(pmap, va)), &free, lockp);
                else
                        pmap_remove_l3_range(pmap, old_l2, va, va + L2_SIZE,
                            &free, lockp);
                if (va < VM_MAXUSER_ADDRESS) {
                        vm_page_free_pages_toq(&free, true);
                        KASSERT(pmap_load(l2) == 0,
                            ("pmap_enter_l2: non-zero L2 entry %p", l2));
                } else {
                        KASSERT(SLIST_EMPTY(&free),
                            ("pmap_enter_l2: freed kernel page table page"));

                        /*
                         * Both pmap_remove_l2() and pmap_remove_l3_range()
                         * will leave the kernel page table page zero filled.
                         * Nonetheless, the TLB could have an intermediate
                         * entry for the kernel page table page.
                         */
                        mt = PHYS_TO_VM_PAGE(pmap_load(l2) & ~ATTR_MASK);
                        if (pmap_insert_pt_page(pmap, mt, false))
                                panic("pmap_enter_l2: trie insert failed");
                        pmap_clear(l2);
                        pmap_invalidate_page(pmap, va);
                }
        }

        if ((new_l2 & ATTR_SW_MANAGED) != 0) {
                /*
                 * Abort this mapping if its PV entry could not be created.
                 */
                if (!pmap_pv_insert_l2(pmap, va, new_l2, flags, lockp)) {
                        if (l2pg != NULL)
                                pmap_abort_ptp(pmap, va, l2pg);
                        CTR2(KTR_PMAP,
                            "pmap_enter_l2: failure for va %#lx in pmap %p",
                            va, pmap);
                        return (KERN_RESOURCE_SHORTAGE);
                }
                if ((new_l2 & ATTR_SW_DBM) != 0)
                        for (mt = m; mt < &m[L2_SIZE / PAGE_SIZE]; mt++)
                                vm_page_aflag_set(mt, PGA_WRITEABLE);
        }

        /*
         * Increment counters.
         */
        if ((new_l2 & ATTR_SW_WIRED) != 0)
                pmap->pm_stats.wired_count += L2_SIZE / PAGE_SIZE;
        pmap->pm_stats.resident_count += L2_SIZE / PAGE_SIZE;

        /*
         * Map the superpage.
         */
        pmap_store(l2, new_l2);
        dsb(ishst);

        atomic_add_long(&pmap_l2_mappings, 1);
        CTR2(KTR_PMAP, "pmap_enter_l2: 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 & L2_OFFSET) == 0 && va + L2_SIZE <= end &&
                    m->psind == 1 && pmap_ps_enabled(pmap) &&
                    pmap_enter_2mpage(pmap, va, m, prot, &lock))
                        m = &m[L2_SIZE / 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)
{
        pd_entry_t *pde;
        pt_entry_t *l2, *l3, l3_val;
        vm_paddr_t pa;
        int lvl;

        KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva ||
            (m->oflags & VPO_UNMANAGED) != 0,
            ("pmap_enter_quick_locked: managed mapping within the clean submap"));
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PMAP_ASSERT_STAGE1(pmap);

        CTR2(KTR_PMAP, "pmap_enter_quick_locked: %p %lx", pmap, va);
        /*
         * In the case that a page table page is not
         * resident, we are creating it here.
         */
        if (va < VM_MAXUSER_ADDRESS) {
                vm_pindex_t l2pindex;

                /*
                 * Calculate pagetable page index
                 */
                l2pindex = pmap_l2_pindex(va);
                if (mpte && (mpte->pindex == l2pindex)) {
                        mpte->ref_count++;
                } else {
                        /*
                         * Get the l2 entry
                         */
                        pde = pmap_pde(pmap, va, &lvl);

                        /*
                         * 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 (lvl == 1) {
                                l2 = pmap_l1_to_l2(pde, va);
                                if ((pmap_load(l2) & ATTR_DESCR_MASK) ==
                                    L2_BLOCK)
                                        return (NULL);
                        }
                        if (lvl == 2 && pmap_load(pde) != 0) {
                                mpte =
                                    PHYS_TO_VM_PAGE(pmap_load(pde) & ~ATTR_MASK);
                                mpte->ref_count++;
                        } else {
                                /*
                                 * Pass NULL instead of the PV list lock
                                 * pointer, because we don't intend to sleep.
                                 */
                                mpte = _pmap_alloc_l3(pmap, l2pindex, NULL);
                                if (mpte == NULL)
                                        return (mpte);
                        }
                }
                l3 = (pt_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(mpte));
                l3 = &l3[pmap_l3_index(va)];
        } else {
                mpte = NULL;
                pde = pmap_pde(kernel_pmap, va, &lvl);
                KASSERT(pde != NULL,
                    ("pmap_enter_quick_locked: Invalid page entry, va: 0x%lx",
                     va));
                KASSERT(lvl == 2,
                    ("pmap_enter_quick_locked: Invalid level %d", lvl));
                l3 = pmap_l2_to_l3(pde, va);
        }

        /*
         * Abort if a mapping already exists.
         */
        if (pmap_load(l3) != 0) {
                if (mpte != NULL)
                        mpte->ref_count--;
                return (NULL);
        }

        /*
         * 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)
                        pmap_abort_ptp(pmap, va, mpte);
                return (NULL);
        }

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

        pa = VM_PAGE_TO_PHYS(m);
        l3_val = pa | ATTR_DEFAULT | ATTR_S1_IDX(m->md.pv_memattr) |
            ATTR_S1_AP(ATTR_S1_AP_RO) | L3_PAGE;
        if ((prot & VM_PROT_EXECUTE) == 0 ||
            m->md.pv_memattr == VM_MEMATTR_DEVICE)
                l3_val |= ATTR_S1_XN;
        if (va < VM_MAXUSER_ADDRESS)
                l3_val |= ATTR_S1_AP(ATTR_S1_AP_USER) | ATTR_S1_PXN;
        else
                l3_val |= ATTR_S1_UXN;
        if (pmap != kernel_pmap)
                l3_val |= ATTR_S1_nG;

        /*
         * Now validate mapping with RO protection
         */
        if ((m->oflags & VPO_UNMANAGED) == 0) {
                l3_val |= ATTR_SW_MANAGED;
                l3_val &= ~ATTR_AF;
        }

        /* Sync icache before the mapping is stored to PTE */
        if ((prot & VM_PROT_EXECUTE) && pmap != kernel_pmap &&
            m->md.pv_memattr == VM_MEMATTR_WRITE_BACK)
                cpu_icache_sync_range(PHYS_TO_DMAP(pa), PAGE_SIZE);

        pmap_store(l3, l3_val);
        dsb(ishst);

        return (mpte);
}

/*
 * 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)
{

        VM_OBJECT_ASSERT_WLOCKED(object);
        KASSERT(object->type == OBJT_DEVICE || object->type == OBJT_SG,
            ("pmap_object_init_pt: non-device object"));
}

/*
 *      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.
 */
void
pmap_unwire(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        vm_offset_t va_next;
        pd_entry_t *l0, *l1, *l2;
        pt_entry_t *l3;

        PMAP_LOCK(pmap);
        for (; sva < eva; sva = va_next) {
                l0 = pmap_l0(pmap, sva);
                if (pmap_load(l0) == 0) {
                        va_next = (sva + L0_SIZE) & ~L0_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                l1 = pmap_l0_to_l1(l0, sva);
                if (pmap_load(l1) == 0) {
                        va_next = (sva + L1_SIZE) & ~L1_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                va_next = (sva + L2_SIZE) & ~L2_OFFSET;
                if (va_next < sva)
                        va_next = eva;

                l2 = pmap_l1_to_l2(l1, sva);
                if (pmap_load(l2) == 0)
                        continue;

                if ((pmap_load(l2) & ATTR_DESCR_MASK) == L2_BLOCK) {
                        if ((pmap_load(l2) & ATTR_SW_WIRED) == 0)
                                panic("pmap_unwire: l2 %#jx is missing "
                                    "ATTR_SW_WIRED", (uintmax_t)pmap_load(l2));

                        /*
                         * Are we unwiring the entire large page?  If not,
                         * demote the mapping and fall through.
                         */
                        if (sva + L2_SIZE == va_next && eva >= va_next) {
                                pmap_clear_bits(l2, ATTR_SW_WIRED);
                                pmap->pm_stats.wired_count -= L2_SIZE /
                                    PAGE_SIZE;
                                continue;
                        } else if (pmap_demote_l2(pmap, l2, sva) == NULL)
                                panic("pmap_unwire: demotion failed");
                }
                KASSERT((pmap_load(l2) & ATTR_DESCR_MASK) == L2_TABLE,
                    ("pmap_unwire: Invalid l2 entry after demotion"));

                if (va_next > eva)
                        va_next = eva;
                for (l3 = pmap_l2_to_l3(l2, sva); sva != va_next; l3++,
                    sva += L3_SIZE) {
                        if (pmap_load(l3) == 0)
                                continue;
                        if ((pmap_load(l3) & ATTR_SW_WIRED) == 0)
                                panic("pmap_unwire: l3 %#jx is missing "
                                    "ATTR_SW_WIRED", (uintmax_t)pmap_load(l3));

                        /*
                         * ATTR_SW_WIRED must be cleared atomically.  Although
                         * the pmap lock synchronizes access to ATTR_SW_WIRED,
                         * the System MMU may write to the entry concurrently.
                         */
                        pmap_clear_bits(l3, ATTR_SW_WIRED);
                        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.
 *
 *      Because the executable mappings created by this routine are copied,
 *      it should not have to flush the instruction cache.
 */
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;
        pd_entry_t *l0, *l1, *l2, srcptepaddr;
        pt_entry_t *dst_pte, mask, nbits, ptetemp, *src_pte;
        vm_offset_t addr, end_addr, va_next;
        vm_page_t dst_l2pg, dstmpte, srcmpte;

        PMAP_ASSERT_STAGE1(dst_pmap);
        PMAP_ASSERT_STAGE1(src_pmap);

        if (dst_addr != src_addr)
                return;
        end_addr = src_addr + len;
        lock = NULL;
        if (dst_pmap < src_pmap) {
                PMAP_LOCK(dst_pmap);
                PMAP_LOCK(src_pmap);
        } else {
                PMAP_LOCK(src_pmap);
                PMAP_LOCK(dst_pmap);
        }
        for (addr = src_addr; addr < end_addr; addr = va_next) {
                l0 = pmap_l0(src_pmap, addr);
                if (pmap_load(l0) == 0) {
                        va_next = (addr + L0_SIZE) & ~L0_OFFSET;
                        if (va_next < addr)
                                va_next = end_addr;
                        continue;
                }
                l1 = pmap_l0_to_l1(l0, addr);
                if (pmap_load(l1) == 0) {
                        va_next = (addr + L1_SIZE) & ~L1_OFFSET;
                        if (va_next < addr)
                                va_next = end_addr;
                        continue;
                }
                va_next = (addr + L2_SIZE) & ~L2_OFFSET;
                if (va_next < addr)
                        va_next = end_addr;
                l2 = pmap_l1_to_l2(l1, addr);
                srcptepaddr = pmap_load(l2);
                if (srcptepaddr == 0)
                        continue;
                if ((srcptepaddr & ATTR_DESCR_MASK) == L2_BLOCK) {
                        if ((addr & L2_OFFSET) != 0 ||
                            addr + L2_SIZE > end_addr)
                                continue;
                        l2 = pmap_alloc_l2(dst_pmap, addr, &dst_l2pg, NULL);
                        if (l2 == NULL)
                                break;
                        if (pmap_load(l2) == 0 &&
                            ((srcptepaddr & ATTR_SW_MANAGED) == 0 ||
                            pmap_pv_insert_l2(dst_pmap, addr, srcptepaddr,
                            PMAP_ENTER_NORECLAIM, &lock))) {
                                mask = ATTR_AF | ATTR_SW_WIRED;
                                nbits = 0;
                                if ((srcptepaddr & ATTR_SW_DBM) != 0)
                                        nbits |= ATTR_S1_AP_RW_BIT;
                                pmap_store(l2, (srcptepaddr & ~mask) | nbits);
                                pmap_resident_count_inc(dst_pmap, L2_SIZE /
                                    PAGE_SIZE);
                                atomic_add_long(&pmap_l2_mappings, 1);
                        } else
                                pmap_abort_ptp(dst_pmap, addr, dst_l2pg);
                        continue;
                }
                KASSERT((srcptepaddr & ATTR_DESCR_MASK) == L2_TABLE,
                    ("pmap_copy: invalid L2 entry"));
                srcptepaddr &= ~ATTR_MASK;
                srcmpte = PHYS_TO_VM_PAGE(srcptepaddr);
                KASSERT(srcmpte->ref_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_l3_index(addr)];
                dstmpte = NULL;
                for (; addr < va_next; addr += PAGE_SIZE, src_pte++) {
                        ptetemp = pmap_load(src_pte);

                        /*
                         * We only virtual copy managed pages.
                         */
                        if ((ptetemp & ATTR_SW_MANAGED) == 0)
                                continue;

                        if (dstmpte != NULL) {
                                KASSERT(dstmpte->pindex == pmap_l2_pindex(addr),
                                    ("dstmpte pindex/addr mismatch"));
                                dstmpte->ref_count++;
                        } else if ((dstmpte = pmap_alloc_l3(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_l3_index(addr)];
                        if (pmap_load(dst_pte) == 0 &&
                            pmap_try_insert_pv_entry(dst_pmap, addr,
                            PHYS_TO_VM_PAGE(ptetemp & ~ATTR_MASK), &lock)) {
                                /*
                                 * Clear the wired, modified, and accessed
                                 * (referenced) bits during the copy.
                                 */
                                mask = ATTR_AF | ATTR_SW_WIRED;
                                nbits = 0;
                                if ((ptetemp & ATTR_SW_DBM) != 0)
                                        nbits |= ATTR_S1_AP_RW_BIT;
                                pmap_store(dst_pte, (ptetemp & ~mask) | nbits);
                                pmap_resident_count_inc(dst_pmap, 1);
                        } else {
                                pmap_abort_ptp(dst_pmap, addr, dstmpte);
                                goto out;
                        }
                        /* Have we copied all of the valid mappings? */ 
                        if (dstmpte->ref_count >= srcmpte->ref_count)
                                break;
                }
        }
out:
        /*
         * XXX This barrier may not be needed because the destination pmap is
         * not active.
         */
        dsb(ishst);

        if (lock != NULL)
                rw_wunlock(lock);
        PMAP_UNLOCK(src_pmap);
        PMAP_UNLOCK(dst_pmap);
}

/*
 *      pmap_zero_page zeros the specified hardware page by mapping
 *      the page into KVM and using bzero to clear its contents.
 */
void
pmap_zero_page(vm_page_t m)
{
        vm_offset_t va = PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));

        pagezero((void *)va);
}

/*
 *      pmap_zero_page_area zeros the specified hardware page by mapping
 *      the page into KVM and using bzero to clear its contents.
 *
 *      off and size may 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);
}

/*
 *      pmap_copy_page copies the specified (machine independent)
 *      page by mapping the page into virtual memory and using
 *      bcopy to copy the page, one machine dependent page at a
 *      time.
 */
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 m_a, m_b;
        vm_paddr_t p_a, p_b;
        vm_offset_t a_pg_offset, b_pg_offset;
        int cnt;

        while (xfersize > 0) {
                a_pg_offset = a_offset & PAGE_MASK;
                m_a = ma[a_offset >> PAGE_SHIFT];
                p_a = m_a->phys_addr;
                b_pg_offset = b_offset & PAGE_MASK;
                m_b = mb[b_offset >> PAGE_SHIFT];
                p_b = m_b->phys_addr;
                cnt = min(xfersize, PAGE_SIZE - a_pg_offset);
                cnt = min(cnt, PAGE_SIZE - b_pg_offset);
                if (__predict_false(!PHYS_IN_DMAP(p_a))) {
                        panic("!DMAP a %lx", p_a);
                } else {
                        a_cp = (char *)PHYS_TO_DMAP(p_a) + a_pg_offset;
                }
                if (__predict_false(!PHYS_IN_DMAP(p_b))) {
                        panic("!DMAP b %lx", p_b);
                } else {
                        b_cp = (char *)PHYS_TO_DMAP(p_b) + b_pg_offset;
                }
                bcopy(a_cp, b_cp, cnt);
                a_offset += cnt;
                b_offset += cnt;
                xfersize -= cnt;
        }
}

vm_offset_t
pmap_quick_enter_page(vm_page_t m)
{

        return (PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m)));
}

void
pmap_quick_remove_page(vm_offset_t addr)
{
}

/*
 * 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, lvl, 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, &lvl);
                if (pte != NULL && (pmap_load(pte) & ATTR_SW_WIRED) != 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_pte(pmap, pv->pv_va, &lvl);
                        if (pte != NULL &&
                            (pmap_load(pte) & ATTR_SW_WIRED) != 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.
 */
bool
pmap_page_is_mapped(vm_page_t m)
{
        struct rwlock *lock;
        bool 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.
 */
void
pmap_remove_pages(pmap_t pmap)
{
        pd_entry_t *pde;
        pt_entry_t *pte, tpte;
        struct spglist free;
        vm_page_t m, ml3, 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, lvl;
        vm_paddr_t pa;

        KASSERT(pmap == PCPU_GET(curpmap), ("non-current pmap %p", pmap));

        lock = NULL;

        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 = ffsl(inuse) - 1;
                                bitmask = 1UL << bit;
                                idx = field * 64 + bit;
                                pv = &pc->pc_pventry[idx];
                                inuse &= ~bitmask;

                                pde = pmap_pde(pmap, pv->pv_va, &lvl);
                                KASSERT(pde != NULL,
                                    ("Attempting to remove an unmapped page"));

                                switch(lvl) {
                                case 1:
                                        pte = pmap_l1_to_l2(pde, pv->pv_va);
                                        tpte = pmap_load(pte); 
                                        KASSERT((tpte & ATTR_DESCR_MASK) ==
                                            L2_BLOCK,
                                            ("Attempting to remove an invalid "
                                            "block: %lx", tpte));
                                        break;
                                case 2:
                                        pte = pmap_l2_to_l3(pde, pv->pv_va);
                                        tpte = pmap_load(pte);
                                        KASSERT((tpte & ATTR_DESCR_MASK) ==
                                            L3_PAGE,
                                            ("Attempting to remove an invalid "
                                             "page: %lx", tpte));
                                        break;
                                default:
                                        panic(
                                            "Invalid page directory level: %d",
                                            lvl);
                                }

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

                                pa = tpte & ~ATTR_MASK;

                                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 pte %#jx",
                                    (uintmax_t)tpte));

                                /*
                                 * Because this pmap is not active on other
                                 * processors, the dirty bit cannot have
                                 * changed state since we last loaded pte.
                                 */
                                pmap_clear(pte);

                                /*
                                 * Update the vm_page_t clean/reference bits.
                                 */
                                if (pmap_pte_dirty(pmap, tpte)) {
                                        switch (lvl) {
                                        case 1:
                                                for (mt = m; mt < &m[L2_SIZE / PAGE_SIZE]; mt++)
                                                        vm_page_dirty(mt);
                                                break;
                                        case 2:
                                                vm_page_dirty(m);
                                                break;
                                        }
                                }

                                CHANGE_PV_LIST_LOCK_TO_VM_PAGE(&lock, m);

                                /* Mark free */
                                pc->pc_map[field] |= bitmask;
                                switch (lvl) {
                                case 1:
                                        pmap_resident_count_dec(pmap,
                                            L2_SIZE / PAGE_SIZE);
                                        pvh = pa_to_pvh(tpte & ~ATTR_MASK);
                                        TAILQ_REMOVE(&pvh->pv_list, pv,pv_next);
                                        pvh->pv_gen++;
                                        if (TAILQ_EMPTY(&pvh->pv_list)) {
                                                for (mt = m; mt < &m[L2_SIZE / PAGE_SIZE]; mt++)
                                                        if ((mt->a.flags & PGA_WRITEABLE) != 0 &&
                                                            TAILQ_EMPTY(&mt->md.pv_list))
                                                                vm_page_aflag_clear(mt, PGA_WRITEABLE);
                                        }
                                        ml3 = pmap_remove_pt_page(pmap,
                                            pv->pv_va);
                                        if (ml3 != NULL) {
                                                KASSERT(ml3->valid == VM_PAGE_BITS_ALL,
                                                    ("pmap_remove_pages: l3 page not promoted"));
                                                pmap_resident_count_dec(pmap,1);
                                                KASSERT(ml3->ref_count == NL3PG,
                                                    ("pmap_remove_pages: l3 page ref count error"));
                                                ml3->ref_count = 0;
                                                pmap_add_delayed_free_list(ml3,
                                                    &free, FALSE);
                                        }
                                        break;
                                case 2:
                                        pmap_resident_count_dec(pmap, 1);
                                        TAILQ_REMOVE(&m->md.pv_list, pv,
                                            pv_next);
                                        m->md.pv_gen++;
                                        if ((m->a.flags & 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);
                                        }
                                        break;
                                }
                                pmap_unuse_pt(pmap, pv->pv_va, pmap_load(pde),
                                    &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);
}

/*
 * This is used to check if a page has been accessed or modified.
 */
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, value;
        pmap_t pmap;
        int lvl, 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);
                PMAP_ASSERT_STAGE1(pmap);
                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, &lvl);
                KASSERT(lvl == 3,
                    ("pmap_page_test_mappings: Invalid level %d", lvl));
                mask = 0;
                value = 0;
                if (modified) {
                        mask |= ATTR_S1_AP_RW_BIT;
                        value |= ATTR_S1_AP(ATTR_S1_AP_RW);
                }
                if (accessed) {
                        mask |= ATTR_AF | ATTR_DESCR_MASK;
                        value |= ATTR_AF | L3_PAGE;
                }
                rv = (pmap_load(pte) & mask) == value;
                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);
                        PMAP_ASSERT_STAGE1(pmap);
                        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_pte(pmap, pv->pv_va, &lvl);
                        KASSERT(lvl == 2,
                            ("pmap_page_test_mappings: Invalid level %d", lvl));
                        mask = 0;
                        value = 0;
                        if (modified) {
                                mask |= ATTR_S1_AP_RW_BIT;
                                value |= ATTR_S1_AP(ATTR_S1_AP_RW);
                        }
                        if (accessed) {
                                mask |= ATTR_AF | ATTR_DESCR_MASK;
                                value |= ATTR_AF | L2_BLOCK;
                        }
                        rv = (pmap_load(pte) & mask) == value;
                        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 busied then this check is racy.
         */
        if (!pmap_page_is_write_mapped(m))
                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)
{
        pt_entry_t *pte;
        boolean_t rv;
        int lvl;

        rv = FALSE;
        PMAP_LOCK(pmap);
        pte = pmap_pte(pmap, addr, &lvl);
        if (pte != NULL && pmap_load(pte) != 0) {
                rv = TRUE;
        }
        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;
        pt_entry_t oldpte, *pte;
        vm_offset_t va;
        int lvl, md_gen, pvh_gen;

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

        if (!pmap_page_is_write_mapped(m))
                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);
                PMAP_ASSERT_STAGE1(pmap);
                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;
                        }
                }
                va = pv->pv_va;
                pte = pmap_pte(pmap, pv->pv_va, &lvl);
                if ((pmap_load(pte) & ATTR_SW_DBM) != 0)
                        (void)pmap_demote_l2_locked(pmap, pte, 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);
                PMAP_ASSERT_STAGE1(pmap);
                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;
                        }
                }
                pte = pmap_pte(pmap, pv->pv_va, &lvl);
                oldpte = pmap_load(pte);
retry:
                if ((oldpte & ATTR_SW_DBM) != 0) {
                        if (!atomic_fcmpset_long(pte, &oldpte,
                            (oldpte | ATTR_S1_AP_RW_BIT) & ~ATTR_SW_DBM))
                                goto retry;
                        if ((oldpte & ATTR_S1_AP_RW_BIT) ==
                            ATTR_S1_AP(ATTR_S1_AP_RW))
                                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_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().
 */
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 *pde, tpde;
        pt_entry_t *pte, tpte;
        vm_offset_t va;
        vm_paddr_t pa;
        int cleared, lvl, md_gen, not_cleared, pvh_gen;
        struct spglist free;

        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;
                        }
                }
                va = pv->pv_va;
                pde = pmap_pde(pmap, pv->pv_va, &lvl);
                KASSERT(pde != NULL, ("pmap_ts_referenced: no l1 table found"));
                KASSERT(lvl == 1,
                    ("pmap_ts_referenced: invalid pde level %d", lvl));
                tpde = pmap_load(pde);
                KASSERT((tpde & ATTR_DESCR_MASK) == L1_TABLE,
                    ("pmap_ts_referenced: found an invalid l1 table"));
                pte = pmap_l1_to_l2(pde, pv->pv_va);
                tpte = pmap_load(pte);
                if (pmap_pte_dirty(pmap, tpte)) {
                        /*
                         * Although "tpte" 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 ((tpte & ATTR_AF) != 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 >> L2_SHIFT) ^
                            (uintptr_t)pmap) & (Ln_ENTRIES - 1)) == 0 &&
                            (tpte & ATTR_SW_WIRED) == 0) {
                                pmap_clear_bits(pte, ATTR_AF);
                                pmap_invalidate_page(pmap, pv->pv_va);
                                cleared++;
                        } 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;
                        }
                }
                pde = pmap_pde(pmap, pv->pv_va, &lvl);
                KASSERT(pde != NULL, ("pmap_ts_referenced: no l2 table found"));
                KASSERT(lvl == 2,
                    ("pmap_ts_referenced: invalid pde level %d", lvl));
                tpde = pmap_load(pde);
                KASSERT((tpde & ATTR_DESCR_MASK) == L2_TABLE,
                    ("pmap_ts_referenced: found an invalid l2 table"));
                pte = pmap_l2_to_l3(pde, pv->pv_va);
                tpte = pmap_load(pte);
                if (pmap_pte_dirty(pmap, tpte))
                        vm_page_dirty(m);
                if ((tpte & ATTR_AF) != 0) {
                        if ((tpte & ATTR_SW_WIRED) == 0) {
                                pmap_clear_bits(pte, ATTR_AF);
                                pmap_invalidate_page(pmap, pv->pv_va);
                                cleared++;
                        } 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;
        vm_offset_t va, va_next;
        vm_page_t m;
        pd_entry_t *l0, *l1, *l2, oldl2;
        pt_entry_t *l3, oldl3;

        PMAP_ASSERT_STAGE1(pmap);

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

        PMAP_LOCK(pmap);
        for (; sva < eva; sva = va_next) {
                l0 = pmap_l0(pmap, sva);
                if (pmap_load(l0) == 0) {
                        va_next = (sva + L0_SIZE) & ~L0_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }
                l1 = pmap_l0_to_l1(l0, sva);
                if (pmap_load(l1) == 0) {
                        va_next = (sva + L1_SIZE) & ~L1_OFFSET;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }
                va_next = (sva + L2_SIZE) & ~L2_OFFSET;
                if (va_next < sva)
                        va_next = eva;
                l2 = pmap_l1_to_l2(l1, sva);
                oldl2 = pmap_load(l2);
                if (oldl2 == 0)
                        continue;
                if ((oldl2 & ATTR_DESCR_MASK) == L2_BLOCK) {
                        if ((oldl2 & ATTR_SW_MANAGED) == 0)
                                continue;
                        lock = NULL;
                        if (!pmap_demote_l2_locked(pmap, l2, sva, &lock)) {
                                if (lock != NULL)
                                        rw_wunlock(lock);

                                /*
                                 * The 2MB 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.  Choosing the last page
                         * within the address range [sva, min(va_next, eva))
                         * generally results in more repromotions.  Since the
                         * underlying page table page is fully populated, this
                         * removal never frees a page table page.
                         */
                        if ((oldl2 & ATTR_SW_WIRED) == 0) {
                                va = eva;
                                if (va > va_next)
                                        va = va_next;
                                va -= PAGE_SIZE;
                                KASSERT(va >= sva,
                                    ("pmap_advise: no address gap"));
                                l3 = pmap_l2_to_l3(l2, va);
                                KASSERT(pmap_load(l3) != 0,
                                    ("pmap_advise: invalid PTE"));
                                pmap_remove_l3(pmap, l3, va, pmap_load(l2),
                                    NULL, &lock);
                        }
                        if (lock != NULL)
                                rw_wunlock(lock);
                }
                KASSERT((pmap_load(l2) & ATTR_DESCR_MASK) == L2_TABLE,
                    ("pmap_advise: invalid L2 entry after demotion"));
                if (va_next > eva)
                        va_next = eva;
                va = va_next;
                for (l3 = pmap_l2_to_l3(l2, sva); sva != va_next; l3++,
                    sva += L3_SIZE) {
                        oldl3 = pmap_load(l3);
                        if ((oldl3 & (ATTR_SW_MANAGED | ATTR_DESCR_MASK)) !=
                            (ATTR_SW_MANAGED | L3_PAGE))
                                goto maybe_invlrng;
                        else if (pmap_pte_dirty(pmap, oldl3)) {
                                if (advice == MADV_DONTNEED) {
                                        /*
                                         * Future calls to pmap_is_modified()
                                         * can be avoided by making the page
                                         * dirty now.
                                         */
                                        m = PHYS_TO_VM_PAGE(oldl3 & ~ATTR_MASK);
                                        vm_page_dirty(m);
                                }
                                while (!atomic_fcmpset_long(l3, &oldl3,
                                    (oldl3 & ~ATTR_AF) |
                                    ATTR_S1_AP(ATTR_S1_AP_RO)))
                                        cpu_spinwait();
                        } else if ((oldl3 & ATTR_AF) != 0)
                                pmap_clear_bits(l3, ATTR_AF);
                        else
                                goto maybe_invlrng;
                        if (va == va_next)
                                va = sva;
                        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);
        }
        PMAP_UNLOCK(pmap);
}

/*
 *      Clear the modify bits on the specified physical page.
 */
void
pmap_clear_modify(vm_page_t m)
{
        struct md_page *pvh;
        struct rwlock *lock;
        pmap_t pmap;
        pv_entry_t next_pv, pv;
        pd_entry_t *l2, oldl2;
        pt_entry_t *l3, oldl3;
        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_page_assert_busied(m);

        if (!pmap_page_is_write_mapped(m))
                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);
                PMAP_ASSERT_STAGE1(pmap);
                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;
                        }
                }
                va = pv->pv_va;
                l2 = pmap_l2(pmap, va);
                oldl2 = pmap_load(l2);
                /* If oldl2 has ATTR_SW_DBM set, then it is also dirty. */
                if ((oldl2 & ATTR_SW_DBM) != 0 &&
                    pmap_demote_l2_locked(pmap, l2, va, &lock) &&
                    (oldl2 & ATTR_SW_WIRED) == 0) {
                        /*
                         * Write protect the mapping to a single page so that
                         * a subsequent write access may repromote.
                         */
                        va += VM_PAGE_TO_PHYS(m) - (oldl2 & ~ATTR_MASK);
                        l3 = pmap_l2_to_l3(l2, va);
                        oldl3 = pmap_load(l3);
                        while (!atomic_fcmpset_long(l3, &oldl3,
                            (oldl3 & ~ATTR_SW_DBM) | ATTR_S1_AP(ATTR_S1_AP_RO)))
                                cpu_spinwait();
                        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);
                PMAP_ASSERT_STAGE1(pmap);
                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;
                        }
                }
                l2 = pmap_l2(pmap, pv->pv_va);
                l3 = pmap_l2_to_l3(l2, pv->pv_va);
                oldl3 = pmap_load(l3);
                if (pmap_l3_valid(oldl3) &&
                    (oldl3 & (ATTR_S1_AP_RW_BIT | ATTR_SW_DBM)) == ATTR_SW_DBM){
                        pmap_set_bits(l3, ATTR_S1_AP(ATTR_S1_AP_RO));
                        pmap_invalidate_page(pmap, pv->pv_va);
                }
                PMAP_UNLOCK(pmap);
        }
        rw_wunlock(lock);
}

void *
pmap_mapbios(vm_paddr_t pa, vm_size_t size)
{
        struct pmap_preinit_mapping *ppim;
        vm_offset_t va, offset;
        pd_entry_t *pde;
        pt_entry_t *l2;
        int i, lvl, l2_blocks, free_l2_count, start_idx;

        if (!vm_initialized) {
                /*
                 * No L3 ptables so map entire L2 blocks where start VA is:
                 *      preinit_map_va + start_idx * L2_SIZE
                 * There may be duplicate mappings (multiple VA -> same PA) but
                 * ARM64 dcache is always PIPT so that's acceptable.
                 */
                 if (size == 0)
                         return (NULL);

                 /* Calculate how many L2 blocks are needed for the mapping */
                l2_blocks = (roundup2(pa + size, L2_SIZE) -
                    rounddown2(pa, L2_SIZE)) >> L2_SHIFT;

                offset = pa & L2_OFFSET;

                if (preinit_map_va == 0)
                        return (NULL);

                /* Map 2MiB L2 blocks from reserved VA space */

                free_l2_count = 0;
                start_idx = -1;
                /* Find enough free contiguous VA space */
                for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                        ppim = pmap_preinit_mapping + i;
                        if (free_l2_count > 0 && ppim->pa != 0) {
                                /* Not enough space here */
                                free_l2_count = 0;
                                start_idx = -1;
                                continue;
                        }

                        if (ppim->pa == 0) {
                                /* Free L2 block */
                                if (start_idx == -1)
                                        start_idx = i;
                                free_l2_count++;
                                if (free_l2_count == l2_blocks)
                                        break;
                        }
                }
                if (free_l2_count != l2_blocks)
                        panic("%s: too many preinit mappings", __func__);

                va = preinit_map_va + (start_idx * L2_SIZE);
                for (i = start_idx; i < start_idx + l2_blocks; i++) {
                        /* Mark entries as allocated */
                        ppim = pmap_preinit_mapping + i;
                        ppim->pa = pa;
                        ppim->va = va + offset;
                        ppim->size = size;
                }

                /* Map L2 blocks */
                pa = rounddown2(pa, L2_SIZE);
                for (i = 0; i < l2_blocks; i++) {
                        pde = pmap_pde(kernel_pmap, va, &lvl);
                        KASSERT(pde != NULL,
                            ("pmap_mapbios: Invalid page entry, va: 0x%lx",
                            va));
                        KASSERT(lvl == 1,
                            ("pmap_mapbios: Invalid level %d", lvl));

                        /* Insert L2_BLOCK */
                        l2 = pmap_l1_to_l2(pde, va);
                        pmap_load_store(l2,
                            pa | ATTR_DEFAULT | ATTR_S1_XN |
                            ATTR_S1_IDX(VM_MEMATTR_WRITE_BACK) | L2_BLOCK);

                        va += L2_SIZE;
                        pa += L2_SIZE;
                }
                pmap_invalidate_all(kernel_pmap);

                va = preinit_map_va + (start_idx * L2_SIZE);

        } else {
                /* kva_alloc may be used to map the pages */
                offset = pa & PAGE_MASK;
                size = round_page(offset + size);

                va = kva_alloc(size);
                if (va == 0)
                        panic("%s: Couldn't allocate KVA", __func__);

                pde = pmap_pde(kernel_pmap, va, &lvl);
                KASSERT(lvl == 2, ("pmap_mapbios: Invalid level %d", lvl));

                /* L3 table is linked */
                va = trunc_page(va);
                pa = trunc_page(pa);
                pmap_kenter(va, size, pa, memory_mapping_mode(pa));
        }

        return ((void *)(va + offset));
}

void
pmap_unmapbios(vm_offset_t va, vm_size_t size)
{
        struct pmap_preinit_mapping *ppim;
        vm_offset_t offset, tmpsize, va_trunc;
        pd_entry_t *pde;
        pt_entry_t *l2;
        int i, lvl, l2_blocks, block;
        bool preinit_map;

        l2_blocks =
           (roundup2(va + size, L2_SIZE) - rounddown2(va, L2_SIZE)) >> L2_SHIFT;
        KASSERT(l2_blocks > 0, ("pmap_unmapbios: invalid size %lx", size));

        /* Remove preinit mapping */
        preinit_map = false;
        block = 0;
        for (i = 0; i < PMAP_PREINIT_MAPPING_COUNT; i++) {
                ppim = pmap_preinit_mapping + i;
                if (ppim->va == va) {
                        KASSERT(ppim->size == size,
                            ("pmap_unmapbios: size mismatch"));
                        ppim->va = 0;
                        ppim->pa = 0;
                        ppim->size = 0;
                        preinit_map = true;
                        offset = block * L2_SIZE;
                        va_trunc = rounddown2(va, L2_SIZE) + offset;

                        /* Remove L2_BLOCK */
                        pde = pmap_pde(kernel_pmap, va_trunc, &lvl);
                        KASSERT(pde != NULL,
                            ("pmap_unmapbios: Invalid page entry, va: 0x%lx",
                            va_trunc));
                        l2 = pmap_l1_to_l2(pde, va_trunc);
                        pmap_clear(l2);

                        if (block == (l2_blocks - 1))
                                break;
                        block++;
                }
        }
        if (preinit_map) {
                pmap_invalidate_all(kernel_pmap);
                return;
        }

        /* Unmap the pages reserved with kva_alloc. */
        if (vm_initialized) {
                offset = va & PAGE_MASK;
                size = round_page(offset + size);
                va = trunc_page(va);

                pde = pmap_pde(kernel_pmap, va, &lvl);
                KASSERT(pde != NULL,
                    ("pmap_unmapbios: Invalid page entry, va: 0x%lx", va));
                KASSERT(lvl == 2, ("pmap_unmapbios: Invalid level %d", lvl));

                /* Unmap and invalidate the pages */
                for (tmpsize = 0; tmpsize < size; tmpsize += PAGE_SIZE)
                        pmap_kremove(va + tmpsize);

                kva_free(va, size);
        }
}

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

        m->md.pv_memattr = 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.pv_memattr) != 0)
                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;
        pt_entry_t l3, *pte, *newpte;
        int lvl;

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

        if (!VIRT_IN_DMAP(base) &&
            !(base >= VM_MIN_KERNEL_ADDRESS && base < VM_MAX_KERNEL_ADDRESS))
                return (EINVAL);

        for (tmpva = base; tmpva < base + size; ) {
                pte = pmap_pte(kernel_pmap, tmpva, &lvl);
                if (pte == NULL)
                        return (EINVAL);

                if ((pmap_load(pte) & ATTR_S1_IDX_MASK) == ATTR_S1_IDX(mode)) {
                        /*
                         * We already have the correct attribute,
                         * ignore this entry.
                         */
                        switch (lvl) {
                        default:
                                panic("Invalid DMAP table level: %d\n", lvl);
                        case 1:
                                tmpva = (tmpva & ~L1_OFFSET) + L1_SIZE;
                                break;
                        case 2:
                                tmpva = (tmpva & ~L2_OFFSET) + L2_SIZE;
                                break;
                        case 3:
                                tmpva += PAGE_SIZE;
                                break;
                        }
                } else {
                        /*
                         * Split the entry to an level 3 table, then
                         * set the new attribute.
                         */
                        switch (lvl) {
                        default:
                                panic("Invalid DMAP table level: %d\n", lvl);
                        case 1:
                                newpte = pmap_demote_l1(kernel_pmap, pte,
                                    tmpva & ~L1_OFFSET);
                                if (newpte == NULL)
                                        return (EINVAL);
                                pte = pmap_l1_to_l2(pte, tmpva);
                        case 2:
                                newpte = pmap_demote_l2(kernel_pmap, pte,
                                    tmpva);
                                if (newpte == NULL)
                                        return (EINVAL);
                                pte = pmap_l2_to_l3(pte, tmpva);
                        case 3:
                                /* Update the entry */
                                l3 = pmap_load(pte);
                                l3 &= ~ATTR_S1_IDX_MASK;
                                l3 |= ATTR_S1_IDX(mode);
                                if (mode == VM_MEMATTR_DEVICE)
                                        l3 |= ATTR_S1_XN;

                                pmap_update_entry(kernel_pmap, pte, l3, tmpva,
                                    PAGE_SIZE);

                                /*
                                 * If moving to a non-cacheable entry flush
                                 * the cache.
                                 */
                                if (mode == VM_MEMATTR_UNCACHEABLE)
                                        cpu_dcache_wbinv_range(tmpva, L3_SIZE);

                                break;
                        }
                        tmpva += PAGE_SIZE;
                }
        }

        return (0);
}

/*
 * Create an L2 table to map all addresses within an L1 mapping.
 */
static pt_entry_t *
pmap_demote_l1(pmap_t pmap, pt_entry_t *l1, vm_offset_t va)
{
        pt_entry_t *l2, newl2, oldl1;
        vm_offset_t tmpl1;
        vm_paddr_t l2phys, phys;
        vm_page_t ml2;
        int i;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        oldl1 = pmap_load(l1);
        KASSERT((oldl1 & ATTR_DESCR_MASK) == L1_BLOCK,
            ("pmap_demote_l1: Demoting a non-block entry"));
        KASSERT((va & L1_OFFSET) == 0,
            ("pmap_demote_l1: Invalid virtual address %#lx", va));
        KASSERT((oldl1 & ATTR_SW_MANAGED) == 0,
            ("pmap_demote_l1: Level 1 table shouldn't be managed"));

        tmpl1 = 0;
        if (va <= (vm_offset_t)l1 && va + L1_SIZE > (vm_offset_t)l1) {
                tmpl1 = kva_alloc(PAGE_SIZE);
                if (tmpl1 == 0)
                        return (NULL);
        }

        if ((ml2 = vm_page_alloc(NULL, 0, VM_ALLOC_INTERRUPT |
            VM_ALLOC_NOOBJ | VM_ALLOC_WIRED)) == NULL) {
                CTR2(KTR_PMAP, "pmap_demote_l1: failure for va %#lx"
                    " in pmap %p", va, pmap);
                return (NULL);
        }

        l2phys = VM_PAGE_TO_PHYS(ml2);
        l2 = (pt_entry_t *)PHYS_TO_DMAP(l2phys);

        /* Address the range points at */
        phys = oldl1 & ~ATTR_MASK;
        /* The attributed from the old l1 table to be copied */
        newl2 = oldl1 & ATTR_MASK;

        /* Create the new entries */
        for (i = 0; i < Ln_ENTRIES; i++) {
                l2[i] = newl2 | phys;
                phys += L2_SIZE;
        }
        KASSERT(l2[0] == ((oldl1 & ~ATTR_DESCR_MASK) | L2_BLOCK),
            ("Invalid l2 page (%lx != %lx)", l2[0],
            (oldl1 & ~ATTR_DESCR_MASK) | L2_BLOCK));

        if (tmpl1 != 0) {
                pmap_kenter(tmpl1, PAGE_SIZE,
                    DMAP_TO_PHYS((vm_offset_t)l1) & ~L3_OFFSET,
                    VM_MEMATTR_WRITE_BACK);
                l1 = (pt_entry_t *)(tmpl1 + ((vm_offset_t)l1 & PAGE_MASK));
        }

        pmap_update_entry(pmap, l1, l2phys | L1_TABLE, va, PAGE_SIZE);

        if (tmpl1 != 0) {
                pmap_kremove(tmpl1);
                kva_free(tmpl1, PAGE_SIZE);
        }

        return (l2);
}

static void
pmap_fill_l3(pt_entry_t *firstl3, pt_entry_t newl3)
{
        pt_entry_t *l3;

        for (l3 = firstl3; l3 - firstl3 < Ln_ENTRIES; l3++) {
                *l3 = newl3;
                newl3 += L3_SIZE;
        }
}

static void
pmap_demote_l2_abort(pmap_t pmap, vm_offset_t va, pt_entry_t *l2,
    struct rwlock **lockp)
{
        struct spglist free;

        SLIST_INIT(&free);
        (void)pmap_remove_l2(pmap, l2, va, pmap_load(pmap_l1(pmap, va)), &free,
            lockp);
        vm_page_free_pages_toq(&free, true);
}

/*
 * Create an L3 table to map all addresses within an L2 mapping.
 */
static pt_entry_t *
pmap_demote_l2_locked(pmap_t pmap, pt_entry_t *l2, vm_offset_t va,
    struct rwlock **lockp)
{
        pt_entry_t *l3, newl3, oldl2;
        vm_offset_t tmpl2;
        vm_paddr_t l3phys;
        vm_page_t ml3;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PMAP_ASSERT_STAGE1(pmap);
        l3 = NULL;
        oldl2 = pmap_load(l2);
        KASSERT((oldl2 & ATTR_DESCR_MASK) == L2_BLOCK,
            ("pmap_demote_l2: Demoting a non-block entry"));
        va &= ~L2_OFFSET;

        tmpl2 = 0;
        if (va <= (vm_offset_t)l2 && va + L2_SIZE > (vm_offset_t)l2) {
                tmpl2 = kva_alloc(PAGE_SIZE);
                if (tmpl2 == 0)
                        return (NULL);
        }

        /*
         * Invalidate the 2MB page mapping and return "failure" if the
         * mapping was never accessed.
         */
        if ((oldl2 & ATTR_AF) == 0) {
                KASSERT((oldl2 & ATTR_SW_WIRED) == 0,
                    ("pmap_demote_l2: a wired mapping is missing ATTR_AF"));
                pmap_demote_l2_abort(pmap, va, l2, lockp);
                CTR2(KTR_PMAP, "pmap_demote_l2: failure for va %#lx in pmap %p",
                    va, pmap);
                goto fail;
        }

        if ((ml3 = pmap_remove_pt_page(pmap, va)) == NULL) {
                KASSERT((oldl2 & ATTR_SW_WIRED) == 0,
                    ("pmap_demote_l2: page table page for a wired mapping"
                    " is missing"));

                /*
                 * If the page table page is missing and the mapping
                 * is for a kernel address, the mapping must belong to
                 * the direct map.  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.
                 */
                KASSERT(va < VM_MAXUSER_ADDRESS || VIRT_IN_DMAP(va),
                    ("pmap_demote_l2: No saved mpte for va %#lx", va));

                /*
                 * 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.
                 */
                ml3 = vm_page_alloc(NULL, pmap_l2_pindex(va),
                    (VIRT_IN_DMAP(va) ? VM_ALLOC_INTERRUPT : VM_ALLOC_NORMAL) |
                    VM_ALLOC_NOOBJ | VM_ALLOC_WIRED);

                /*
                 * If the allocation of the new page table page fails,
                 * invalidate the 2MB page mapping and return "failure".
                 */
                if (ml3 == NULL) {
                        pmap_demote_l2_abort(pmap, va, l2, lockp);
                        CTR2(KTR_PMAP, "pmap_demote_l2: failure for va %#lx"
                            " in pmap %p", va, pmap);
                        goto fail;
                }

                if (va < VM_MAXUSER_ADDRESS) {
                        ml3->ref_count = NL3PG;
                        pmap_resident_count_inc(pmap, 1);
                }
        }
        l3phys = VM_PAGE_TO_PHYS(ml3);
        l3 = (pt_entry_t *)PHYS_TO_DMAP(l3phys);
        newl3 = (oldl2 & ~ATTR_DESCR_MASK) | L3_PAGE;
        KASSERT((oldl2 & (ATTR_S1_AP_RW_BIT | ATTR_SW_DBM)) !=
            (ATTR_S1_AP(ATTR_S1_AP_RO) | ATTR_SW_DBM),
            ("pmap_demote_l2: L2 entry is writeable but not dirty"));

        /*
         * If the page table page is not leftover from an earlier promotion,
         * or the mapping attributes have changed, (re)initialize the L3 table.
         *
         * When pmap_update_entry() clears the old L2 mapping, it (indirectly)
         * performs a dsb().  That dsb() ensures that the stores for filling
         * "l3" are visible before "l3" is added to the page table.
         */
        if (ml3->valid == 0 || (l3[0] & ATTR_MASK) != (newl3 & ATTR_MASK))
                pmap_fill_l3(l3, newl3);

        /*
         * Map the temporary page so we don't lose access to the l2 table.
         */
        if (tmpl2 != 0) {
                pmap_kenter(tmpl2, PAGE_SIZE,
                    DMAP_TO_PHYS((vm_offset_t)l2) & ~L3_OFFSET,
                    VM_MEMATTR_WRITE_BACK);
                l2 = (pt_entry_t *)(tmpl2 + ((vm_offset_t)l2 & PAGE_MASK));
        }

        /*
         * The spare PV entries must be reserved prior to demoting the
         * mapping, that is, prior to changing the PDE.  Otherwise, the state
         * of the L2 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_l2() failing to find the expected
         * PV entry for the 2MB page mapping that is being demoted.
         */
        if ((oldl2 & ATTR_SW_MANAGED) != 0)
                reserve_pv_entries(pmap, Ln_ENTRIES - 1, lockp);

        /*
         * Pass PAGE_SIZE so that a single TLB invalidation is performed on
         * the 2MB page mapping.
         */
        pmap_update_entry(pmap, l2, l3phys | L2_TABLE, va, PAGE_SIZE);

        /*
         * Demote the PV entry.
         */
        if ((oldl2 & ATTR_SW_MANAGED) != 0)
                pmap_pv_demote_l2(pmap, va, oldl2 & ~ATTR_MASK, lockp);

        atomic_add_long(&pmap_l2_demotions, 1);
        CTR3(KTR_PMAP, "pmap_demote_l2: success for va %#lx"
            " in pmap %p %lx", va, pmap, l3[0]);

fail:
        if (tmpl2 != 0) {
                pmap_kremove(tmpl2);
                kva_free(tmpl2, PAGE_SIZE);
        }

        return (l3);

}

static pt_entry_t *
pmap_demote_l2(pmap_t pmap, pt_entry_t *l2, vm_offset_t va)
{
        struct rwlock *lock;
        pt_entry_t *l3;

        lock = NULL;
        l3 = pmap_demote_l2_locked(pmap, l2, va, &lock);
        if (lock != NULL)
                rw_wunlock(lock);
        return (l3);
}

/*
 * Perform the pmap work for mincore(2).  If the page is not both referenced and
 * modified by this pmap, returns its physical address so that the caller can
 * find other mappings.
 */
int
pmap_mincore(pmap_t pmap, vm_offset_t addr, vm_paddr_t *pap)
{
        pt_entry_t *pte, tpte;
        vm_paddr_t mask, pa;
        int lvl, val;
        bool managed;

        PMAP_ASSERT_STAGE1(pmap);
        PMAP_LOCK(pmap);
        pte = pmap_pte(pmap, addr, &lvl);
        if (pte != NULL) {
                tpte = pmap_load(pte);

                switch (lvl) {
                case 3:
                        mask = L3_OFFSET;
                        break;
                case 2:
                        mask = L2_OFFSET;
                        break;
                case 1:
                        mask = L1_OFFSET;
                        break;
                default:
                        panic("pmap_mincore: invalid level %d", lvl);
                }

                managed = (tpte & ATTR_SW_MANAGED) != 0;
                val = MINCORE_INCORE;
                if (lvl != 3)
                        val |= MINCORE_PSIND(3 - lvl);
                if ((managed && pmap_pte_dirty(pmap, tpte)) || (!managed &&
                    (tpte & ATTR_S1_AP_RW_BIT) == ATTR_S1_AP(ATTR_S1_AP_RW)))
                        val |= MINCORE_MODIFIED | MINCORE_MODIFIED_OTHER;
                if ((tpte & ATTR_AF) == ATTR_AF)
                        val |= MINCORE_REFERENCED | MINCORE_REFERENCED_OTHER;

                pa = (tpte & ~ATTR_MASK) | (addr & mask);
        } else {
                managed = false;
                val = 0;
        }

        if ((val & (MINCORE_MODIFIED_OTHER | MINCORE_REFERENCED_OTHER)) !=
            (MINCORE_MODIFIED_OTHER | MINCORE_REFERENCED_OTHER) && managed) {
                *pap = pa;
        }
        PMAP_UNLOCK(pmap);
        return (val);
}

/*
 * Garbage collect every ASID that is neither active on a processor nor
 * reserved.
 */
static void
pmap_reset_asid_set(pmap_t pmap)
{
        pmap_t curpmap;
        int asid, cpuid, epoch;
        struct asid_set *set;
        enum pmap_stage stage;

        set = pmap->pm_asid_set;
        stage = pmap->pm_stage;

        set = pmap->pm_asid_set;
        KASSERT(set != NULL, ("%s: NULL asid set", __func__));
        mtx_assert(&set->asid_set_mutex, MA_OWNED);

        /*
         * Ensure that the store to asid_epoch is globally visible before the
         * loads from pc_curpmap are performed.
         */
        epoch = set->asid_epoch + 1;
        if (epoch == INT_MAX)
                epoch = 0;
        set->asid_epoch = epoch;
        dsb(ishst);
        if (stage == PM_STAGE1) {
                __asm __volatile("tlbi vmalle1is");
        } else {
                KASSERT(pmap_clean_stage2_tlbi != NULL,
                    ("%s: Unset stage 2 tlb invalidation callback\n",
                    __func__));
                pmap_clean_stage2_tlbi();
        }
        dsb(ish);
        bit_nclear(set->asid_set, ASID_FIRST_AVAILABLE,
            set->asid_set_size - 1);
        CPU_FOREACH(cpuid) {
                if (cpuid == curcpu)
                        continue;
                if (stage == PM_STAGE1) {
                        curpmap = pcpu_find(cpuid)->pc_curpmap;
                        PMAP_ASSERT_STAGE1(pmap);
                } else {
                        curpmap = pcpu_find(cpuid)->pc_curvmpmap;
                        if (curpmap == NULL)
                                continue;
                        PMAP_ASSERT_STAGE2(pmap);
                }
                KASSERT(curpmap->pm_asid_set == set, ("Incorrect set"));
                asid = COOKIE_TO_ASID(curpmap->pm_cookie);
                if (asid == -1)
                        continue;
                bit_set(set->asid_set, asid);
                curpmap->pm_cookie = COOKIE_FROM(asid, epoch);
        }
}

/*
 * Allocate a new ASID for the specified pmap.
 */
static void
pmap_alloc_asid(pmap_t pmap)
{
        struct asid_set *set;
        int new_asid;

        set = pmap->pm_asid_set;
        KASSERT(set != NULL, ("%s: NULL asid set", __func__));

        mtx_lock_spin(&set->asid_set_mutex);

        /*
         * While this processor was waiting to acquire the asid set mutex,
         * pmap_reset_asid_set() running on another processor might have
         * updated this pmap's cookie to the current epoch.  In which case, we
         * don't need to allocate a new ASID.
         */
        if (COOKIE_TO_EPOCH(pmap->pm_cookie) == set->asid_epoch)
                goto out;

        bit_ffc_at(set->asid_set, set->asid_next, set->asid_set_size,
            &new_asid);
        if (new_asid == -1) {
                bit_ffc_at(set->asid_set, ASID_FIRST_AVAILABLE,
                    set->asid_next, &new_asid);
                if (new_asid == -1) {
                        pmap_reset_asid_set(pmap);
                        bit_ffc_at(set->asid_set, ASID_FIRST_AVAILABLE,
                            set->asid_set_size, &new_asid);
                        KASSERT(new_asid != -1, ("ASID allocation failure"));
                }
        }
        bit_set(set->asid_set, new_asid);
        set->asid_next = new_asid + 1;
        pmap->pm_cookie = COOKIE_FROM(new_asid, set->asid_epoch);
out:
        mtx_unlock_spin(&set->asid_set_mutex);
}

/*
 * Compute the value that should be stored in ttbr0 to activate the specified
 * pmap.  This value may change from time to time.
 */
uint64_t
pmap_to_ttbr0(pmap_t pmap)
{

        return (ASID_TO_OPERAND(COOKIE_TO_ASID(pmap->pm_cookie)) |
            pmap->pm_l0_paddr);
}

static bool
pmap_activate_int(pmap_t pmap)
{
        struct asid_set *set;
        int epoch;

        KASSERT(PCPU_GET(curpmap) != NULL, ("no active pmap"));
        KASSERT(pmap != kernel_pmap, ("kernel pmap activation"));

        if ((pmap->pm_stage == PM_STAGE1 && pmap == PCPU_GET(curpmap)) ||
            (pmap->pm_stage == PM_STAGE2 && pmap == PCPU_GET(curvmpmap))) {
                /*
                 * Handle the possibility that the old thread was preempted
                 * after an "ic" or "tlbi" instruction but before it performed
                 * a "dsb" instruction.  If the old thread migrates to a new
                 * processor, its completion of a "dsb" instruction on that
                 * new processor does not guarantee that the "ic" or "tlbi"
                 * instructions performed on the old processor have completed.
                 */
                dsb(ish);
                return (false);
        }

        set = pmap->pm_asid_set;
        KASSERT(set != NULL, ("%s: NULL asid set", __func__));

        /*
         * Ensure that the store to curpmap is globally visible before the
         * load from asid_epoch is performed.
         */
        if (pmap->pm_stage == PM_STAGE1)
                PCPU_SET(curpmap, pmap);
        else
                PCPU_SET(curvmpmap, pmap);
        dsb(ish);
        epoch = COOKIE_TO_EPOCH(pmap->pm_cookie);
        if (epoch >= 0 && epoch != set->asid_epoch)
                pmap_alloc_asid(pmap);

        if (pmap->pm_stage == PM_STAGE1) {
                set_ttbr0(pmap_to_ttbr0(pmap));
                if (PCPU_GET(bcast_tlbi_workaround) != 0)
                        invalidate_local_icache();
        }
        return (true);
}

void
pmap_activate_vm(pmap_t pmap)
{

        PMAP_ASSERT_STAGE2(pmap);

        (void)pmap_activate_int(pmap);
}

void
pmap_activate(struct thread *td)
{
        pmap_t  pmap;

        pmap = vmspace_pmap(td->td_proc->p_vmspace);
        PMAP_ASSERT_STAGE1(pmap);
        critical_enter();
        (void)pmap_activate_int(pmap);
        critical_exit();
}

/*
 * To eliminate the unused parameter "old", we would have to add an instruction
 * to cpu_switch().
 */
struct pcb *
pmap_switch(struct thread *old __unused, struct thread *new)
{
        pcpu_bp_harden bp_harden;
        struct pcb *pcb;

        /* Store the new curthread */
        PCPU_SET(curthread, new);

        /* And the new pcb */
        pcb = new->td_pcb;
        PCPU_SET(curpcb, pcb);

        /*
         * TODO: We may need to flush the cache here if switching
         * to a user process.
         */

        if (pmap_activate_int(vmspace_pmap(new->td_proc->p_vmspace))) {
                /*
                 * Stop userspace from training the branch predictor against
                 * other processes. This will call into a CPU specific
                 * function that clears the branch predictor state.
                 */
                bp_harden = PCPU_GET(bp_harden);
                if (bp_harden != NULL)
                        bp_harden();
        }

        return (pcb);
}

void
pmap_sync_icache(pmap_t pmap, vm_offset_t va, vm_size_t sz)
{

        PMAP_ASSERT_STAGE1(pmap);
        if (va >= VM_MIN_KERNEL_ADDRESS) {
                cpu_icache_sync_range(va, sz);
        } else {
                u_int len, offset;
                vm_paddr_t pa;

                /* Find the length of data in this page to flush */
                offset = va & PAGE_MASK;
                len = imin(PAGE_SIZE - offset, sz);

                while (sz != 0) {
                        /* Extract the physical address & find it in the DMAP */
                        pa = pmap_extract(pmap, va);
                        if (pa != 0)
                                cpu_icache_sync_range(PHYS_TO_DMAP(pa), len);

                        /* Move to the next page */
                        sz -= len;
                        va += len;
                        /* Set the length for the next iteration */
                        len = imin(PAGE_SIZE, sz);
                }
        }
}

static int
pmap_stage2_fault(pmap_t pmap, uint64_t esr, uint64_t far)
{
        pd_entry_t *pdep;
        pt_entry_t *ptep, pte;
        int rv, lvl, dfsc;

        PMAP_ASSERT_STAGE2(pmap);
        rv = KERN_FAILURE;

        /* Data and insn aborts use same encoding for FSC field. */
        dfsc = esr & ISS_DATA_DFSC_MASK;
        switch (dfsc) {
        case ISS_DATA_DFSC_TF_L0:
        case ISS_DATA_DFSC_TF_L1:
        case ISS_DATA_DFSC_TF_L2:
        case ISS_DATA_DFSC_TF_L3:
                PMAP_LOCK(pmap);
                pdep = pmap_pde(pmap, far, &lvl);
                if (pdep == NULL || lvl != (dfsc - ISS_DATA_DFSC_TF_L1)) {
                        PMAP_LOCK(pmap);
                        break;
                }

                switch (lvl) {
                case 0:
                        ptep = pmap_l0_to_l1(pdep, far);
                        break;
                case 1:
                        ptep = pmap_l1_to_l2(pdep, far);
                        break;
                case 2:
                        ptep = pmap_l2_to_l3(pdep, far);
                        break;
                default:
                        panic("%s: Invalid pde level %d", __func__,lvl);
                }
                goto fault_exec;

        case ISS_DATA_DFSC_AFF_L1:
        case ISS_DATA_DFSC_AFF_L2:
        case ISS_DATA_DFSC_AFF_L3:
                PMAP_LOCK(pmap);
                ptep = pmap_pte(pmap, far, &lvl);
fault_exec:
                if (ptep != NULL && (pte = pmap_load(ptep)) != 0) {
                        if (icache_vmid) {
                                pmap_invalidate_vpipt_icache();
                        } else {
                                /*
                                 * If accessing an executable page invalidate
                                 * the I-cache so it will be valid when we
                                 * continue execution in the guest. The D-cache
                                 * is assumed to already be clean to the Point
                                 * of Coherency.
                                 */
                                if ((pte & ATTR_S2_XN_MASK) !=
                                    ATTR_S2_XN(ATTR_S2_XN_NONE)) {
                                        invalidate_icache();
                                }
                        }
                        pmap_set_bits(ptep, ATTR_AF | ATTR_DESCR_VALID);
                        rv = KERN_SUCCESS;
                }
                PMAP_UNLOCK(pmap);
                break;
        }

        return (rv);
}

int
pmap_fault(pmap_t pmap, uint64_t esr, uint64_t far)
{
        pt_entry_t pte, *ptep;
        register_t intr;
        uint64_t ec, par;
        int lvl, rv;

        rv = KERN_FAILURE;

        ec = ESR_ELx_EXCEPTION(esr);
        switch (ec) {
        case EXCP_INSN_ABORT_L:
        case EXCP_INSN_ABORT:
        case EXCP_DATA_ABORT_L:
        case EXCP_DATA_ABORT:
                break;
        default:
                return (rv);
        }

        if (pmap->pm_stage == PM_STAGE2)
                return (pmap_stage2_fault(pmap, esr, far));

        /* Data and insn aborts use same encoding for FSC field. */
        switch (esr & ISS_DATA_DFSC_MASK) {
        case ISS_DATA_DFSC_AFF_L1:
        case ISS_DATA_DFSC_AFF_L2:
        case ISS_DATA_DFSC_AFF_L3:
                PMAP_LOCK(pmap);
                ptep = pmap_pte(pmap, far, &lvl);
                if (ptep != NULL) {
                        pmap_set_bits(ptep, ATTR_AF);
                        rv = KERN_SUCCESS;
                        /*
                         * XXXMJ as an optimization we could mark the entry
                         * dirty if this is a write fault.
                         */
                }
                PMAP_UNLOCK(pmap);
                break;
        case ISS_DATA_DFSC_PF_L1:
        case ISS_DATA_DFSC_PF_L2:
        case ISS_DATA_DFSC_PF_L3:
                if ((ec != EXCP_DATA_ABORT_L && ec != EXCP_DATA_ABORT) ||
                    (esr & ISS_DATA_WnR) == 0)
                        return (rv);
                PMAP_LOCK(pmap);
                ptep = pmap_pte(pmap, far, &lvl);
                if (ptep != NULL &&
                    ((pte = pmap_load(ptep)) & ATTR_SW_DBM) != 0) {
                        if ((pte & ATTR_S1_AP_RW_BIT) ==
                            ATTR_S1_AP(ATTR_S1_AP_RO)) {
                                pmap_clear_bits(ptep, ATTR_S1_AP_RW_BIT);
                                pmap_invalidate_page(pmap, far);
                        }
                        rv = KERN_SUCCESS;
                }
                PMAP_UNLOCK(pmap);
                break;
        case ISS_DATA_DFSC_TF_L0:
        case ISS_DATA_DFSC_TF_L1:
        case ISS_DATA_DFSC_TF_L2:
        case ISS_DATA_DFSC_TF_L3:
                /*
                 * Retry the translation.  A break-before-make sequence can
                 * produce a transient fault.
                 */
                if (pmap == kernel_pmap) {
                        /*
                         * The translation fault may have occurred within a
                         * critical section.  Therefore, we must check the
                         * address without acquiring the kernel pmap's lock.
                         */
                        if (pmap_kextract(far) != 0)
                                rv = KERN_SUCCESS;
                } else {
                        PMAP_LOCK(pmap);
                        /* Ask the MMU to check the address. */
                        intr = intr_disable();
                        par = arm64_address_translate_s1e0r(far);
                        intr_restore(intr);
                        PMAP_UNLOCK(pmap);

                        /*
                         * If the translation was successful, then we can
                         * return success to the trap handler.
                         */
                        if (PAR_SUCCESS(par))
                                rv = KERN_SUCCESS;
                }
                break;
        }

        return (rv);
}

/*
 *      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 < L2_SIZE)
                return;
        if (object != NULL && (object->flags & OBJ_COLORED) != 0)
                offset += ptoa(object->pg_color);
        superpage_offset = offset & L2_OFFSET;
        if (size - ((L2_SIZE - superpage_offset) & L2_OFFSET) < L2_SIZE ||
            (*addr & L2_OFFSET) == superpage_offset)
                return;
        if ((*addr & L2_OFFSET) < superpage_offset)
                *addr = (*addr & ~L2_OFFSET) + superpage_offset;
        else
                *addr = ((*addr + L2_OFFSET) & ~L2_OFFSET) + superpage_offset;
}

/**
 * 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;
        int error, 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(!PHYS_IN_DMAP(paddr))) {
                        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);

        if (!can_fault)
                sched_pin();
        for (i = 0; i < count; i++) {
                paddr = VM_PAGE_TO_PHYS(page[i]);
                if (!PHYS_IN_DMAP(paddr)) {
                        panic(
                           "pmap_map_io_transient: TODO: Map out of DMAP data");
                }
        }

        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 (!PHYS_IN_DMAP(paddr)) {
                        panic("ARM64TODO: pmap_unmap_io_transient: Unmap data");
                }
        }
}

boolean_t
pmap_is_valid_memattr(pmap_t pmap __unused, vm_memattr_t mode)
{

        return (mode >= VM_MEMATTR_DEVICE && mode <= VM_MEMATTR_WRITE_THROUGH);
}

/*
 * Track a range of the kernel's virtual address space that is contiguous
 * in various mapping attributes.
 */
struct pmap_kernel_map_range {
        vm_offset_t sva;
        pt_entry_t attrs;
        int l3pages;
        int l3contig;
        int l2blocks;
        int l1blocks;
};

static void
sysctl_kmaps_dump(struct sbuf *sb, struct pmap_kernel_map_range *range,
    vm_offset_t eva)
{
        const char *mode;
        int index;

        if (eva <= range->sva)
                return;

        index = range->attrs & ATTR_S1_IDX_MASK;
        switch (index) {
        case ATTR_S1_IDX(VM_MEMATTR_DEVICE):
                mode = "DEV";
                break;
        case ATTR_S1_IDX(VM_MEMATTR_UNCACHEABLE):
                mode = "UC";
                break;
        case ATTR_S1_IDX(VM_MEMATTR_WRITE_BACK):
                mode = "WB";
                break;
        case ATTR_S1_IDX(VM_MEMATTR_WRITE_THROUGH):
                mode = "WT";
                break;
        default:
                printf(
                    "%s: unknown memory type %x for range 0x%016lx-0x%016lx\n",
                    __func__, index, range->sva, eva);
                mode = "??";
                break;
        }

        sbuf_printf(sb, "0x%016lx-0x%016lx r%c%c%c %3s %d %d %d %d\n",
            range->sva, eva,
            (range->attrs & ATTR_S1_AP_RW_BIT) == ATTR_S1_AP_RW ? 'w' : '-',
            (range->attrs & ATTR_S1_PXN) != 0 ? '-' : 'x',
            (range->attrs & ATTR_S1_AP_USER) != 0 ? 'u' : 's',
            mode, range->l1blocks, range->l2blocks, range->l3contig,
            range->l3pages);

        /* Reset to sentinel value. */
        range->sva = 0xfffffffffffffffful;
}

/*
 * Determine whether the attributes specified by a page table entry match those
 * being tracked by the current range.
 */
static bool
sysctl_kmaps_match(struct pmap_kernel_map_range *range, pt_entry_t attrs)
{

        return (range->attrs == attrs);
}

static void
sysctl_kmaps_reinit(struct pmap_kernel_map_range *range, vm_offset_t va,
    pt_entry_t attrs)
{

        memset(range, 0, sizeof(*range));
        range->sva = va;
        range->attrs = attrs;
}

/*
 * Given a leaf PTE, derive the mapping's attributes.  If they do not match
 * those of the current run, dump the address range and its attributes, and
 * begin a new run.
 */
static void
sysctl_kmaps_check(struct sbuf *sb, struct pmap_kernel_map_range *range,
    vm_offset_t va, pd_entry_t l0e, pd_entry_t l1e, pd_entry_t l2e,
    pt_entry_t l3e)
{
        pt_entry_t attrs;

        attrs = l0e & (ATTR_S1_AP_MASK | ATTR_S1_XN);
        attrs |= l1e & (ATTR_S1_AP_MASK | ATTR_S1_XN);
        if ((l1e & ATTR_DESCR_MASK) == L1_BLOCK)
                attrs |= l1e & ATTR_S1_IDX_MASK;
        attrs |= l2e & (ATTR_S1_AP_MASK | ATTR_S1_XN);
        if ((l2e & ATTR_DESCR_MASK) == L2_BLOCK)
                attrs |= l2e & ATTR_S1_IDX_MASK;
        attrs |= l3e & (ATTR_S1_AP_MASK | ATTR_S1_XN | ATTR_S1_IDX_MASK);

        if (range->sva > va || !sysctl_kmaps_match(range, attrs)) {
                sysctl_kmaps_dump(sb, range, va);
                sysctl_kmaps_reinit(range, va, attrs);
        }
}

static int
sysctl_kmaps(SYSCTL_HANDLER_ARGS)
{
        struct pmap_kernel_map_range range;
        struct sbuf sbuf, *sb;
        pd_entry_t l0e, *l1, l1e, *l2, l2e;
        pt_entry_t *l3, l3e;
        vm_offset_t sva;
        vm_paddr_t pa;
        int error, i, j, k, l;

        error = sysctl_wire_old_buffer(req, 0);
        if (error != 0)
                return (error);
        sb = &sbuf;
        sbuf_new_for_sysctl(sb, NULL, PAGE_SIZE, req);

        /* Sentinel value. */
        range.sva = 0xfffffffffffffffful;

        /*
         * Iterate over the kernel page tables without holding the kernel pmap
         * lock.  Kernel page table pages are never freed, so at worst we will
         * observe inconsistencies in the output.
         */
        for (sva = 0xffff000000000000ul, i = pmap_l0_index(sva); i < Ln_ENTRIES;
            i++) {
                if (i == pmap_l0_index(DMAP_MIN_ADDRESS))
                        sbuf_printf(sb, "\nDirect map:\n");
                else if (i == pmap_l0_index(VM_MIN_KERNEL_ADDRESS))
                        sbuf_printf(sb, "\nKernel map:\n");

                l0e = kernel_pmap->pm_l0[i];
                if ((l0e & ATTR_DESCR_VALID) == 0) {
                        sysctl_kmaps_dump(sb, &range, sva);
                        sva += L0_SIZE;
                        continue;
                }
                pa = l0e & ~ATTR_MASK;
                l1 = (pd_entry_t *)PHYS_TO_DMAP(pa);

                for (j = pmap_l1_index(sva); j < Ln_ENTRIES; j++) {
                        l1e = l1[j];
                        if ((l1e & ATTR_DESCR_VALID) == 0) {
                                sysctl_kmaps_dump(sb, &range, sva);
                                sva += L1_SIZE;
                                continue;
                        }
                        if ((l1e & ATTR_DESCR_MASK) == L1_BLOCK) {
                                sysctl_kmaps_check(sb, &range, sva, l0e, l1e,
                                    0, 0);
                                range.l1blocks++;
                                sva += L1_SIZE;
                                continue;
                        }
                        pa = l1e & ~ATTR_MASK;
                        l2 = (pd_entry_t *)PHYS_TO_DMAP(pa);

                        for (k = pmap_l2_index(sva); k < Ln_ENTRIES; k++) {
                                l2e = l2[k];
                                if ((l2e & ATTR_DESCR_VALID) == 0) {
                                        sysctl_kmaps_dump(sb, &range, sva);
                                        sva += L2_SIZE;
                                        continue;
                                }
                                if ((l2e & ATTR_DESCR_MASK) == L2_BLOCK) {
                                        sysctl_kmaps_check(sb, &range, sva,
                                            l0e, l1e, l2e, 0);
                                        range.l2blocks++;
                                        sva += L2_SIZE;
                                        continue;
                                }
                                pa = l2e & ~ATTR_MASK;
                                l3 = (pt_entry_t *)PHYS_TO_DMAP(pa);

                                for (l = pmap_l3_index(sva); l < Ln_ENTRIES;
                                    l++, sva += L3_SIZE) {
                                        l3e = l3[l];
                                        if ((l3e & ATTR_DESCR_VALID) == 0) {
                                                sysctl_kmaps_dump(sb, &range,
                                                    sva);
                                                continue;
                                        }
                                        sysctl_kmaps_check(sb, &range, sva,
                                            l0e, l1e, l2e, l3e);
                                        if ((l3e & ATTR_CONTIGUOUS) != 0)
                                                range.l3contig += l % 16 == 0 ?
                                                    1 : 0;
                                        else
                                                range.l3pages++;
                                }
                        }
                }
        }

        error = sbuf_finish(sb);
        sbuf_delete(sb);
        return (error);
}
SYSCTL_OID(_vm_pmap, OID_AUTO, kernel_maps,
    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
    NULL, 0, sysctl_kmaps, "A",
    "Dump kernel address layout");