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[FreeBSD/stable/8.git] / sys / i386 / i386 / 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) 2005-2008 Alan L. Cox <alc@cs.rice.edu>
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department and William Jolitz of UUNET Technologies Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from:   @(#)pmap.c      7.7 (Berkeley)  5/12/91
 */
/*-
 * Copyright (c) 2003 Networks Associates Technology, Inc.
 * 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.
 *
 *      In addition to hardware address maps, this
 *      module is called upon to provide software-use-only
 *      maps which may or may not be stored in the same
 *      form as hardware maps.  These pseudo-maps are
 *      used to store intermediate results from copy
 *      operations to and from address spaces.
 *
 *      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_cpu.h"
#include "opt_pmap.h"
#include "opt_msgbuf.h"
#include "opt_smp.h"
#include "opt_xbox.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/msgbuf.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sf_buf.h>
#include <sys/sx.h>
#include <sys/vmmeter.h>
#include <sys/sched.h>
#include <sys/sysctl.h>
#ifdef SMP
#include <sys/smp.h>
#endif

#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_reserv.h>
#include <vm/uma.h>

#include <machine/cpu.h>
#include <machine/cputypes.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/specialreg.h>
#ifdef SMP
#include <machine/smp.h>
#endif

#ifdef XBOX
#include <machine/xbox.h>
#endif

#if !defined(CPU_DISABLE_SSE) && defined(I686_CPU)
#define CPU_ENABLE_SSE
#endif

#ifndef PMAP_SHPGPERPROC
#define PMAP_SHPGPERPROC 200
#endif

#if !defined(DIAGNOSTIC)
#define PMAP_INLINE     __gnu89_inline
#else
#define PMAP_INLINE
#endif

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

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

/*
 * Get PDEs and PTEs for user/kernel address space
 */
#define pmap_pde(m, v)  (&((m)->pm_pdir[(vm_offset_t)(v) >> PDRSHIFT]))
#define pdir_pde(m, v) (m[(vm_offset_t)(v) >> PDRSHIFT])

#define pmap_pde_v(pte)         ((*(int *)pte & PG_V) != 0)
#define pmap_pte_w(pte)         ((*(int *)pte & PG_W) != 0)
#define pmap_pte_m(pte)         ((*(int *)pte & PG_M) != 0)
#define pmap_pte_u(pte)         ((*(int *)pte & PG_A) != 0)
#define pmap_pte_v(pte)         ((*(int *)pte & PG_V) != 0)

#define pmap_pte_set_w(pte, v)  ((v) ? atomic_set_int((u_int *)(pte), PG_W) : \
    atomic_clear_int((u_int *)(pte), PG_W))
#define pmap_pte_set_prot(pte, v) ((*(int *)pte &= ~PG_PROT), (*(int *)pte |= (v)))

struct pmap kernel_pmap_store;
LIST_HEAD(pmaplist, pmap);
static struct pmaplist allpmaps;
static struct mtx allpmaps_lock;

vm_offset_t virtual_avail;      /* VA of first avail page (after kernel bss) */
vm_offset_t virtual_end;        /* VA of last avail page (end of kernel AS) */
int pgeflag = 0;                /* PG_G or-in */
int pseflag = 0;                /* PG_PS or-in */

static int nkpt;
vm_offset_t kernel_vm_end;
extern u_int32_t KERNend;

#ifdef PAE
pt_entry_t pg_nx;
static uma_zone_t pdptzone;
#endif

static int pat_works;                   /* Is page attribute table sane? */

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

static int pg_ps_enabled;
SYSCTL_INT(_vm_pmap, OID_AUTO, pg_ps_enabled, CTLFLAG_RD, &pg_ps_enabled, 0,
    "Are large page mappings enabled?");

/*
 * Data for the pv entry allocation mechanism
 */
static int pv_entry_count = 0, pv_entry_max = 0, pv_entry_high_water = 0;
static struct md_page *pv_table;
static int shpgperproc = PMAP_SHPGPERPROC;

struct pv_chunk *pv_chunkbase;          /* KVA block for pv_chunks */
int pv_maxchunks;                       /* How many chunks we have KVA for */
vm_offset_t pv_vafree;                  /* freelist stored in the PTE */

/*
 * All those kernel PT submaps that BSD is so fond of
 */
struct sysmaps {
        struct  mtx lock;
        pt_entry_t *CMAP1;
        pt_entry_t *CMAP2;
        caddr_t CADDR1;
        caddr_t CADDR2;
};
static struct sysmaps sysmaps_pcpu[MAXCPU];
pt_entry_t *CMAP1 = 0;
static pt_entry_t *CMAP3;
caddr_t CADDR1 = 0, ptvmmap = 0;
static caddr_t CADDR3;
struct msgbuf *msgbufp = 0;

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

static pt_entry_t *PMAP1 = 0, *PMAP2;
static pt_entry_t *PADDR1 = 0, *PADDR2;
#ifdef SMP
static int PMAP1cpu;
static int PMAP1changedcpu;
SYSCTL_INT(_debug, OID_AUTO, PMAP1changedcpu, CTLFLAG_RD, 
           &PMAP1changedcpu, 0,
           "Number of times pmap_pte_quick changed CPU with same PMAP1");
#endif
static int PMAP1changed;
SYSCTL_INT(_debug, OID_AUTO, PMAP1changed, CTLFLAG_RD, 
           &PMAP1changed, 0,
           "Number of times pmap_pte_quick changed PMAP1");
static int PMAP1unchanged;
SYSCTL_INT(_debug, OID_AUTO, PMAP1unchanged, CTLFLAG_RD, 
           &PMAP1unchanged, 0,
           "Number of times pmap_pte_quick didn't change PMAP1");
static struct mtx PMAP2mutex;

static void     free_pv_entry(pmap_t pmap, pv_entry_t pv);
static pv_entry_t get_pv_entry(pmap_t locked_pmap, int try);
static void     pmap_pv_demote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa);
static boolean_t pmap_pv_insert_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa);
static void     pmap_pv_promote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa);
static void     pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va);
static pv_entry_t pmap_pvh_remove(struct md_page *pvh, pmap_t pmap,
                    vm_offset_t va);
static int      pmap_pvh_wired_mappings(struct md_page *pvh, int count);

static boolean_t pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va);
static boolean_t pmap_enter_pde(pmap_t pmap, vm_offset_t va, vm_page_t m,
    vm_prot_t prot);
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);
static void pmap_insert_pt_page(pmap_t pmap, vm_page_t mpte);
static boolean_t pmap_is_modified_pvh(struct md_page *pvh);
static void pmap_kenter_attr(vm_offset_t va, vm_paddr_t pa, int mode);
static vm_page_t pmap_lookup_pt_page(pmap_t pmap, vm_offset_t va);
static void pmap_promote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va);
static boolean_t pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t sva,
    vm_prot_t prot);
static void pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
    vm_page_t *free);
static int pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t sva,
    vm_page_t *free);
static void pmap_remove_pt_page(pmap_t pmap, vm_page_t mpte);
static void pmap_remove_page(struct pmap *pmap, vm_offset_t va,
    vm_page_t *free);
static void pmap_remove_entry(struct pmap *pmap, vm_page_t m,
                                        vm_offset_t va);
static void pmap_insert_entry(pmap_t pmap, vm_offset_t va, vm_page_t m);
static boolean_t pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va,
    vm_page_t m);

static vm_page_t pmap_allocpte(pmap_t pmap, vm_offset_t va, int flags);

static vm_page_t _pmap_allocpte(pmap_t pmap, unsigned ptepindex, int flags);
static int _pmap_unwire_pte_hold(pmap_t pmap, vm_page_t m, vm_page_t *free);
static pt_entry_t *pmap_pte_quick(pmap_t pmap, vm_offset_t va);
static void pmap_pte_release(pt_entry_t *pte);
static int pmap_unuse_pt(pmap_t, vm_offset_t, vm_page_t *);
static vm_offset_t pmap_kmem_choose(vm_offset_t addr);
#ifdef PAE
static void *pmap_pdpt_allocf(uma_zone_t zone, int bytes, u_int8_t *flags, int wait);
#endif

CTASSERT(1 << PDESHIFT == sizeof(pd_entry_t));
CTASSERT(1 << PTESHIFT == sizeof(pt_entry_t));

/*
 * If you get an error here, then you set KVA_PAGES wrong! See the
 * description of KVA_PAGES in sys/i386/include/pmap.h. It must be
 * multiple of 4 for a normal kernel, or a multiple of 8 for a PAE.
 */
CTASSERT(KERNBASE % (1 << 24) == 0);

/*
 * Move the kernel virtual free pointer to the next
 * 4MB.  This is used to help improve performance
 * by using a large (4MB) page for much of the kernel
 * (.text, .data, .bss)
 */
static vm_offset_t
pmap_kmem_choose(vm_offset_t addr)
{
        vm_offset_t newaddr = addr;

#ifndef DISABLE_PSE
        if (cpu_feature & CPUID_PSE)
                newaddr = (addr + PDRMASK) & ~PDRMASK;
#endif
        return newaddr;
}

/*
 *      Bootstrap the system enough to run with virtual memory.
 *
 *      On the i386 this is called after mapping has already been enabled
 *      and just syncs the pmap module with what has already been done.
 *      [We can't call it easily with mapping off since the kernel is not
 *      mapped with PA == VA, hence we would have to relocate every address
 *      from the linked base (virtual) address "KERNBASE" to the actual
 *      (physical) address starting relative to 0]
 */
void
pmap_bootstrap(vm_paddr_t firstaddr)
{
        vm_offset_t va;
        pt_entry_t *pte, *unused;
        struct sysmaps *sysmaps;
        int i;

        /*
         * XXX The calculation of virtual_avail is wrong. It's NKPT*PAGE_SIZE too
         * large. It should instead be correctly calculated in locore.s and
         * not based on 'first' (which is a physical address, not a virtual
         * address, for the start of unused physical memory). The kernel
         * page tables are NOT double mapped and thus should not be included
         * in this calculation.
         */
        virtual_avail = (vm_offset_t) KERNBASE + firstaddr;
        virtual_avail = pmap_kmem_choose(virtual_avail);

        virtual_end = VM_MAX_KERNEL_ADDRESS;

        /*
         * Initialize the kernel pmap (which is statically allocated).
         */
        PMAP_LOCK_INIT(kernel_pmap);
        kernel_pmap->pm_pdir = (pd_entry_t *) (KERNBASE + (u_int)IdlePTD);
#ifdef PAE
        kernel_pmap->pm_pdpt = (pdpt_entry_t *) (KERNBASE + (u_int)IdlePDPT);
#endif
        kernel_pmap->pm_root = NULL;
        kernel_pmap->pm_active = -1;    /* don't allow deactivation */
        TAILQ_INIT(&kernel_pmap->pm_pvchunk);
        LIST_INIT(&allpmaps);
        mtx_init(&allpmaps_lock, "allpmaps", NULL, MTX_SPIN);
        mtx_lock_spin(&allpmaps_lock);
        LIST_INSERT_HEAD(&allpmaps, kernel_pmap, pm_list);
        mtx_unlock_spin(&allpmaps_lock);
        nkpt = NKPT;

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

        va = virtual_avail;
        pte = vtopte(va);

        /*
         * CMAP1/CMAP2 are used for zeroing and copying pages.
         * CMAP3 is used for the idle process page zeroing.
         */
        for (i = 0; i < MAXCPU; i++) {
                sysmaps = &sysmaps_pcpu[i];
                mtx_init(&sysmaps->lock, "SYSMAPS", NULL, MTX_DEF);
                SYSMAP(caddr_t, sysmaps->CMAP1, sysmaps->CADDR1, 1)
                SYSMAP(caddr_t, sysmaps->CMAP2, sysmaps->CADDR2, 1)
        }
        SYSMAP(caddr_t, CMAP1, CADDR1, 1)
        SYSMAP(caddr_t, CMAP3, CADDR3, 1)
        *CMAP3 = 0;

        /*
         * Crashdump maps.
         */
        SYSMAP(caddr_t, unused, crashdumpmap, MAXDUMPPGS)

        /*
         * ptvmmap is used for reading arbitrary physical pages via /dev/mem.
         */
        SYSMAP(caddr_t, unused, ptvmmap, 1)

        /*
         * msgbufp is used to map the system message buffer.
         */
        SYSMAP(struct msgbuf *, unused, msgbufp, atop(round_page(MSGBUF_SIZE)))

        /*
         * ptemap is used for pmap_pte_quick
         */
        SYSMAP(pt_entry_t *, PMAP1, PADDR1, 1);
        SYSMAP(pt_entry_t *, PMAP2, PADDR2, 1);

        mtx_init(&PMAP2mutex, "PMAP2", NULL, MTX_DEF);

        virtual_avail = va;

        *CMAP1 = 0;

        /*
         * Leave in place an identity mapping (virt == phys) for the low 1 MB
         * physical memory region that is used by the ACPI wakeup code.  This
         * mapping must not have PG_G set. 
         */
#ifdef XBOX
        /* FIXME: This is gross, but needed for the XBOX. Since we are in such
         * an early stadium, we cannot yet neatly map video memory ... :-(
         * Better fixes are very welcome! */
        if (!arch_i386_is_xbox)
#endif
        for (i = 1; i < NKPT; i++)
                PTD[i] = 0;

        /* Initialize the PAT MSR if present. */
        pmap_init_pat();

        /* Turn on PG_G on kernel page(s) */
        pmap_set_pg();
}

/*
 * Setup the PAT MSR.
 */
void
pmap_init_pat(void)
{
        uint64_t pat_msr;

        /* Bail if this CPU doesn't implement PAT. */
        if (!(cpu_feature & CPUID_PAT))
                return;

        if (cpu_vendor_id != CPU_VENDOR_INTEL ||
            (I386_CPU_FAMILY(cpu_id) == 6 && I386_CPU_MODEL(cpu_id) >= 0xe)) {
                /*
                 * Leave the indices 0-3 at the default of WB, WT, UC, and UC-.
                 * Program 4 and 5 as WP and WC.
                 * Leave 6 and 7 as UC and UC-.
                 */
                pat_msr = rdmsr(MSR_PAT);
                pat_msr &= ~(PAT_MASK(4) | PAT_MASK(5));
                pat_msr |= PAT_VALUE(4, PAT_WRITE_PROTECTED) |
                    PAT_VALUE(5, PAT_WRITE_COMBINING);
                pat_works = 1;
        } else {
                /*
                 * Due to some Intel errata, we can only safely use the lower 4
                 * PAT entries.  Thus, just replace PAT Index 2 with WC instead
                 * of UC-.
                 *
                 *   Intel Pentium III Processor Specification Update
                 * Errata E.27 (Upper Four PAT Entries Not Usable With Mode B
                 * or Mode C Paging)
                 *
                 *   Intel Pentium IV  Processor Specification Update
                 * Errata N46 (PAT Index MSB May Be Calculated Incorrectly)
                 */
                pat_msr = rdmsr(MSR_PAT);
                pat_msr &= ~PAT_MASK(2);
                pat_msr |= PAT_VALUE(2, PAT_WRITE_COMBINING);
                pat_works = 0;
        }
        wrmsr(MSR_PAT, pat_msr);
}

/*
 * Set PG_G on kernel pages.  Only the BSP calls this when SMP is turned on.
 */
void
pmap_set_pg(void)
{
        pd_entry_t pdir;
        pt_entry_t *pte;
        vm_offset_t va, endva;
        int i; 

        if (pgeflag == 0)
                return;

        i = KERNLOAD/NBPDR;
        endva = KERNBASE + KERNend;

        if (pseflag) {
                va = KERNBASE + KERNLOAD;
                while (va  < endva) {
                        pdir = kernel_pmap->pm_pdir[KPTDI+i];
                        pdir |= pgeflag;
                        kernel_pmap->pm_pdir[KPTDI+i] = PTD[KPTDI+i] = pdir;
                        invltlb();      /* Play it safe, invltlb() every time */
                        i++;
                        va += NBPDR;
                }
        } else {
                va = (vm_offset_t)btext;
                while (va < endva) {
                        pte = vtopte(va);
                        if (*pte)
                                *pte |= pgeflag;
                        invltlb();      /* Play it safe, invltlb() every time */
                        va += PAGE_SIZE;
                }
        }
}

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

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

#ifdef PAE
static void *
pmap_pdpt_allocf(uma_zone_t zone, int bytes, u_int8_t *flags, int wait)
{

        /* Inform UMA that this allocator uses kernel_map/object. */
        *flags = UMA_SLAB_KERNEL;
        return ((void *)kmem_alloc_contig(kernel_map, bytes, wait, 0x0ULL,
            0xffffffffULL, 1, 0, VM_MEMATTR_DEFAULT));
}
#endif

/*
 * ABuse the pte nodes for unmapped kva to thread a kva freelist through.
 * Requirements:
 *  - Must deal with pages in order to ensure that none of the PG_* bits
 *    are ever set, PG_V in particular.
 *  - Assumes we can write to ptes without pte_store() atomic ops, even
 *    on PAE systems.  This should be ok.
 *  - Assumes nothing will ever test these addresses for 0 to indicate
 *    no mapping instead of correctly checking PG_V.
 *  - Assumes a vm_offset_t will fit in a pte (true for i386).
 * Because PG_V is never set, there can be no mappings to invalidate.
 */
static vm_offset_t
pmap_ptelist_alloc(vm_offset_t *head)
{
        pt_entry_t *pte;
        vm_offset_t va;

        va = *head;
        if (va == 0)
                return (va);    /* Out of memory */
        pte = vtopte(va);
        *head = *pte;
        if (*head & PG_V)
                panic("pmap_ptelist_alloc: va with PG_V set!");
        *pte = 0;
        return (va);
}

static void
pmap_ptelist_free(vm_offset_t *head, vm_offset_t va)
{
        pt_entry_t *pte;

        if (va & PG_V)
                panic("pmap_ptelist_free: freeing va with PG_V set!");
        pte = vtopte(va);
        *pte = *head;           /* virtual! PG_V is 0 though */
        *head = va;
}

static void
pmap_ptelist_init(vm_offset_t *head, void *base, int npages)
{
        int i;
        vm_offset_t va;

        *head = 0;
        for (i = npages - 1; i >= 0; i--) {
                va = (vm_offset_t)base + i * PAGE_SIZE;
                pmap_ptelist_free(head, va);
        }
}


/*
 *      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_page_t mpte;
        vm_size_t s;
        int i, pv_npg;

        /*
         * Initialize the vm page array entries for the kernel pmap's
         * page table pages.
         */ 
        for (i = 0; i < nkpt; i++) {
                mpte = PHYS_TO_VM_PAGE(PTD[i + KPTDI] & PG_FRAME);
                KASSERT(mpte >= vm_page_array &&
                    mpte < &vm_page_array[vm_page_array_size],
                    ("pmap_init: page table page is out of range"));
                mpte->pindex = i + KPTDI;
                mpte->phys_addr = PTD[i + KPTDI] & PG_FRAME;
        }

        /*
         * Initialize the address space (zone) for the pv entries.  Set a
         * high water mark so that the system can recover from excessive
         * numbers of pv entries.
         */
        TUNABLE_INT_FETCH("vm.pmap.shpgperproc", &shpgperproc);
        pv_entry_max = shpgperproc * maxproc + cnt.v_page_count;
        TUNABLE_INT_FETCH("vm.pmap.pv_entries", &pv_entry_max);
        pv_entry_max = roundup(pv_entry_max, _NPCPV);
        pv_entry_high_water = 9 * (pv_entry_max / 10);

        /*
         * Are large page mappings enabled?
         */
        TUNABLE_INT_FETCH("vm.pmap.pg_ps_enabled", &pg_ps_enabled);

        /*
         * Calculate the size of the pv head table for superpages.
         */
        for (i = 0; phys_avail[i + 1]; i += 2);
        pv_npg = round_4mpage(phys_avail[(i - 2) + 1]) / NBPDR;

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

        pv_maxchunks = MAX(pv_entry_max / _NPCPV, maxproc);
        pv_chunkbase = (struct pv_chunk *)kmem_alloc_nofault(kernel_map,
            PAGE_SIZE * pv_maxchunks);
        if (pv_chunkbase == NULL)
                panic("pmap_init: not enough kvm for pv chunks");
        pmap_ptelist_init(&pv_vafree, pv_chunkbase, pv_maxchunks);
#ifdef PAE
        pdptzone = uma_zcreate("PDPT", NPGPTD * sizeof(pdpt_entry_t), NULL,
            NULL, NULL, NULL, (NPGPTD * sizeof(pdpt_entry_t)) - 1,
            UMA_ZONE_VM | UMA_ZONE_NOFREE);
        uma_zone_set_allocf(pdptzone, pmap_pdpt_allocf);
#endif
}


SYSCTL_INT(_vm_pmap, OID_AUTO, pv_entry_max, CTLFLAG_RD, &pv_entry_max, 0,
        "Max number of PV entries");
SYSCTL_INT(_vm_pmap, OID_AUTO, shpgperproc, CTLFLAG_RD, &shpgperproc, 0,
        "Page share factor per proc");

SYSCTL_NODE(_vm_pmap, OID_AUTO, pde, CTLFLAG_RD, 0,
    "2/4MB page mapping counters");

static u_long pmap_pde_demotions;
SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, demotions, CTLFLAG_RD,
    &pmap_pde_demotions, 0, "2/4MB page demotions");

static u_long pmap_pde_mappings;
SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, mappings, CTLFLAG_RD,
    &pmap_pde_mappings, 0, "2/4MB page mappings");

static u_long pmap_pde_p_failures;
SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, p_failures, CTLFLAG_RD,
    &pmap_pde_p_failures, 0, "2/4MB page promotion failures");

static u_long pmap_pde_promotions;
SYSCTL_ULONG(_vm_pmap_pde, OID_AUTO, promotions, CTLFLAG_RD,
    &pmap_pde_promotions, 0, "2/4MB page promotions");

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

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

        /* The PAT bit is different for PTE's and PDE's. */
        pat_flag = is_pde ? PG_PDE_PAT : PG_PTE_PAT;

        /* If we don't support PAT, map extended modes to older ones. */
        if (!(cpu_feature & CPUID_PAT)) {
                switch (mode) {
                case PAT_UNCACHEABLE:
                case PAT_WRITE_THROUGH:
                case PAT_WRITE_BACK:
                        break;
                case PAT_UNCACHED:
                case PAT_WRITE_COMBINING:
                case PAT_WRITE_PROTECTED:
                        mode = PAT_UNCACHEABLE;
                        break;
                }
        }
        
        /* Map the caching mode to a PAT index. */
        if (pat_works) {
                switch (mode) {
                case PAT_UNCACHEABLE:
                        pat_index = 3;
                        break;
                case PAT_WRITE_THROUGH:
                        pat_index = 1;
                        break;
                case PAT_WRITE_BACK:
                        pat_index = 0;
                        break;
                case PAT_UNCACHED:
                        pat_index = 2;
                        break;
                case PAT_WRITE_COMBINING:
                        pat_index = 5;
                        break;
                case PAT_WRITE_PROTECTED:
                        pat_index = 4;
                        break;
                default:
                        panic("Unknown caching mode %d\n", mode);
                }
        } else {
                switch (mode) {
                case PAT_UNCACHED:
                case PAT_UNCACHEABLE:
                case PAT_WRITE_PROTECTED:
                        pat_index = 3;
                        break;
                case PAT_WRITE_THROUGH:
                        pat_index = 1;
                        break;
                case PAT_WRITE_BACK:
                        pat_index = 0;
                        break;
                case PAT_WRITE_COMBINING:
                        pat_index = 2;
                        break;
                default:
                        panic("Unknown caching mode %d\n", mode);
                }
        }

        /* Map the 3-bit index value into the PAT, PCD, and PWT bits. */
        cache_bits = 0;
        if (pat_index & 0x4)
                cache_bits |= pat_flag;
        if (pat_index & 0x2)
                cache_bits |= PG_NC_PCD;
        if (pat_index & 0x1)
                cache_bits |= PG_NC_PWT;
        return (cache_bits);
}
#ifdef SMP
/*
 * For SMP, these functions have to use the IPI mechanism for coherence.
 *
 * N.B.: Before calling any of the following TLB invalidation functions,
 * the calling processor must ensure that all stores updating a non-
 * kernel page table are globally performed.  Otherwise, another
 * processor could cache an old, pre-update entry without being
 * invalidated.  This can happen one of two ways: (1) The pmap becomes
 * active on another processor after its pm_active field is checked by
 * one of the following functions but before a store updating the page
 * table is globally performed. (2) The pmap becomes active on another
 * processor before its pm_active field is checked but due to
 * speculative loads one of the following functions stills reads the
 * pmap as inactive on the other processor.
 * 
 * The kernel page table is exempt because its pm_active field is
 * immutable.  The kernel page table is always active on every
 * processor.
 */
void
pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
{
        u_int cpumask;
        u_int other_cpus;

        sched_pin();
        if (pmap == kernel_pmap || pmap->pm_active == all_cpus) {
                invlpg(va);
                smp_invlpg(va);
        } else {
                cpumask = PCPU_GET(cpumask);
                other_cpus = PCPU_GET(other_cpus);
                if (pmap->pm_active & cpumask)
                        invlpg(va);
                if (pmap->pm_active & other_cpus)
                        smp_masked_invlpg(pmap->pm_active & other_cpus, va);
        }
        sched_unpin();
}

void
pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        u_int cpumask;
        u_int other_cpus;
        vm_offset_t addr;

        sched_pin();
        if (pmap == kernel_pmap || pmap->pm_active == all_cpus) {
                for (addr = sva; addr < eva; addr += PAGE_SIZE)
                        invlpg(addr);
                smp_invlpg_range(sva, eva);
        } else {
                cpumask = PCPU_GET(cpumask);
                other_cpus = PCPU_GET(other_cpus);
                if (pmap->pm_active & cpumask)
                        for (addr = sva; addr < eva; addr += PAGE_SIZE)
                                invlpg(addr);
                if (pmap->pm_active & other_cpus)
                        smp_masked_invlpg_range(pmap->pm_active & other_cpus,
                            sva, eva);
        }
        sched_unpin();
}

void
pmap_invalidate_all(pmap_t pmap)
{
        u_int cpumask;
        u_int other_cpus;

        sched_pin();
        if (pmap == kernel_pmap || pmap->pm_active == all_cpus) {
                invltlb();
                smp_invltlb();
        } else {
                cpumask = PCPU_GET(cpumask);
                other_cpus = PCPU_GET(other_cpus);
                if (pmap->pm_active & cpumask)
                        invltlb();
                if (pmap->pm_active & other_cpus)
                        smp_masked_invltlb(pmap->pm_active & other_cpus);
        }
        sched_unpin();
}

void
pmap_invalidate_cache(void)
{

        sched_pin();
        wbinvd();
        smp_cache_flush();
        sched_unpin();
}
#else /* !SMP */
/*
 * Normal, non-SMP, 486+ invalidation functions.
 * We inline these within pmap.c for speed.
 */
PMAP_INLINE void
pmap_invalidate_page(pmap_t pmap, vm_offset_t va)
{

        if (pmap == kernel_pmap || pmap->pm_active)
                invlpg(va);
}

PMAP_INLINE void
pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        vm_offset_t addr;

        if (pmap == kernel_pmap || pmap->pm_active)
                for (addr = sva; addr < eva; addr += PAGE_SIZE)
                        invlpg(addr);
}

PMAP_INLINE void
pmap_invalidate_all(pmap_t pmap)
{

        if (pmap == kernel_pmap || pmap->pm_active)
                invltlb();
}

PMAP_INLINE void
pmap_invalidate_cache(void)
{

        wbinvd();
}
#endif /* !SMP */

void
pmap_invalidate_cache_range(vm_offset_t sva, vm_offset_t eva)
{

        KASSERT((sva & PAGE_MASK) == 0,
            ("pmap_invalidate_cache_range: sva not page-aligned"));
        KASSERT((eva & PAGE_MASK) == 0,
            ("pmap_invalidate_cache_range: eva not page-aligned"));

        if (cpu_feature & CPUID_SS)
                ; /* If "Self Snoop" is supported, do nothing. */
        else if (cpu_feature & CPUID_CLFSH) {

                /*
                 * Otherwise, do per-cache line flush.  Use the mfence
                 * instruction to insure that previous stores are
                 * included in the write-back.  The processor
                 * propagates flush to other processors in the cache
                 * coherence domain.
                 */
                mfence();
                for (; eva < sva; eva += cpu_clflush_line_size)
                        clflush(eva);
                mfence();
        } else {

                /*
                 * No targeted cache flush methods are supported by CPU,
                 * globally invalidate cache as a last resort.
                 */
                pmap_invalidate_cache();
        }
}

/*
 * Are we current address space or kernel?  N.B. We return FALSE when
 * a pmap's page table is in use because a kernel thread is borrowing
 * it.  The borrowed page table can change spontaneously, making any
 * dependence on its continued use subject to a race condition.
 */
static __inline int
pmap_is_current(pmap_t pmap)
{

        return (pmap == kernel_pmap ||
                (pmap == vmspace_pmap(curthread->td_proc->p_vmspace) &&
            (pmap->pm_pdir[PTDPTDI] & PG_FRAME) == (PTDpde[0] & PG_FRAME)));
}

/*
 * If the given pmap is not the current or kernel pmap, the returned pte must
 * be released by passing it to pmap_pte_release().
 */
pt_entry_t *
pmap_pte(pmap_t pmap, vm_offset_t va)
{
        pd_entry_t newpf;
        pd_entry_t *pde;

        pde = pmap_pde(pmap, va);
        if (*pde & PG_PS)
                return (pde);
        if (*pde != 0) {
                /* are we current address space or kernel? */
                if (pmap_is_current(pmap))
                        return (vtopte(va));
                mtx_lock(&PMAP2mutex);
                newpf = *pde & PG_FRAME;
                if ((*PMAP2 & PG_FRAME) != newpf) {
                        *PMAP2 = newpf | PG_RW | PG_V | PG_A | PG_M;
                        pmap_invalidate_page(kernel_pmap, (vm_offset_t)PADDR2);
                }
                return (PADDR2 + (i386_btop(va) & (NPTEPG - 1)));
        }
        return (0);
}

/*
 * Releases a pte that was obtained from pmap_pte().  Be prepared for the pte
 * being NULL.
 */
static __inline void
pmap_pte_release(pt_entry_t *pte)
{

        if ((pt_entry_t *)((vm_offset_t)pte & ~PAGE_MASK) == PADDR2)
                mtx_unlock(&PMAP2mutex);
}

static __inline void
invlcaddr(void *caddr)
{

        invlpg((u_int)caddr);
}

/*
 * Super fast pmap_pte routine best used when scanning
 * the pv lists.  This eliminates many coarse-grained
 * invltlb calls.  Note that many of the pv list
 * scans are across different pmaps.  It is very wasteful
 * to do an entire invltlb for checking a single mapping.
 *
 * If the given pmap is not the current pmap, vm_page_queue_mtx
 * must be held and curthread pinned to a CPU.
 */
static pt_entry_t *
pmap_pte_quick(pmap_t pmap, vm_offset_t va)
{
        pd_entry_t newpf;
        pd_entry_t *pde;

        pde = pmap_pde(pmap, va);
        if (*pde & PG_PS)
                return (pde);
        if (*pde != 0) {
                /* are we current address space or kernel? */
                if (pmap_is_current(pmap))
                        return (vtopte(va));
                mtx_assert(&vm_page_queue_mtx, MA_OWNED);
                KASSERT(curthread->td_pinned > 0, ("curthread not pinned"));
                newpf = *pde & PG_FRAME;
                if ((*PMAP1 & PG_FRAME) != newpf) {
                        *PMAP1 = newpf | PG_RW | PG_V | PG_A | PG_M;
#ifdef SMP
                        PMAP1cpu = PCPU_GET(cpuid);
#endif
                        invlcaddr(PADDR1);
                        PMAP1changed++;
                } else
#ifdef SMP
                if (PMAP1cpu != PCPU_GET(cpuid)) {
                        PMAP1cpu = PCPU_GET(cpuid);
                        invlcaddr(PADDR1);
                        PMAP1changedcpu++;
                } else
#endif
                        PMAP1unchanged++;
                return (PADDR1 + (i386_btop(va) & (NPTEPG - 1)));
        }
        return (0);
}

/*
 *      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)
{
        vm_paddr_t rtval;
        pt_entry_t *pte;
        pd_entry_t pde;

        rtval = 0;
        PMAP_LOCK(pmap);
        pde = pmap->pm_pdir[va >> PDRSHIFT];
        if (pde != 0) {
                if ((pde & PG_PS) != 0)
                        rtval = (pde & PG_PS_FRAME) | (va & PDRMASK);
                else {
                        pte = pmap_pte(pmap, va);
                        rtval = (*pte & PG_FRAME) | (va & PAGE_MASK);
                        pmap_pte_release(pte);
                }
        }
        PMAP_UNLOCK(pmap);
        return (rtval);
}

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

        m = NULL;
        vm_page_lock_queues();
        PMAP_LOCK(pmap);
        pde = *pmap_pde(pmap, va);
        if (pde != 0) {
                if (pde & PG_PS) {
                        if ((pde & PG_RW) || (prot & VM_PROT_WRITE) == 0) {
                                m = PHYS_TO_VM_PAGE((pde & PG_PS_FRAME) |
                                    (va & PDRMASK));
                                vm_page_hold(m);
                        }
                } else {
                        sched_pin();
                        pte = *pmap_pte_quick(pmap, va);
                        if (pte != 0 &&
                            ((pte & PG_RW) || (prot & VM_PROT_WRITE) == 0)) {
                                m = PHYS_TO_VM_PAGE(pte & PG_FRAME);
                                vm_page_hold(m);
                        }
                        sched_unpin();
                }
        }
        vm_page_unlock_queues();
        PMAP_UNLOCK(pmap);
        return (m);
}

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

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

        pte = vtopte(va);
        pte_store(pte, pa | PG_RW | PG_V | pgeflag);
}

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

        pte = vtopte(va);
        pte_store(pte, pa | PG_RW | PG_V | pgeflag | pmap_cache_bits(mode, 0));
}

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

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

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

        va = sva = *virt;
        while (start < end) {
                pmap_kenter(va, start);
                va += PAGE_SIZE;
                start += PAGE_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
        *virt = va;
        return (sva);
}


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

        oldpte = 0;
        pte = vtopte(sva);
        endpte = pte + count;
        while (pte < endpte) {
                oldpte |= *pte;
                pte_store(pte, VM_PAGE_TO_PHYS(*ma) | pgeflag |
                    pmap_cache_bits((*ma)->md.pat_mode, 0) | PG_RW | PG_V);
                pte++;
                ma++;
        }
        if ((oldpte & PG_V) != 0)
                pmap_invalidate_range(kernel_pmap, sva, sva + count *
                    PAGE_SIZE);
}

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

        va = sva;
        while (count-- > 0) {
                pmap_kremove(va);
                va += PAGE_SIZE;
        }
        pmap_invalidate_range(kernel_pmap, sva, va);
}

/***************************************************
 * Page table page management routines.....
 ***************************************************/
static __inline void
pmap_free_zero_pages(vm_page_t free)
{
        vm_page_t m;

        while (free != NULL) {
                m = free;
                free = m->right;
                /* Preserve the page's PG_ZERO setting. */
                vm_page_free_toq(m);
        }
}

/*
 * 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, vm_page_t *free, boolean_t set_PG_ZERO)
{

        if (set_PG_ZERO)
                m->flags |= PG_ZERO;
        else
                m->flags &= ~PG_ZERO;
        m->right = *free;
        *free = m;
}

/*
 * Inserts the specified page table page into the specified pmap's collection
 * of idle page table pages.  Each of a pmap's page table pages is responsible
 * for mapping a distinct range of virtual addresses.  The pmap's collection is
 * ordered by this virtual address range.
 */
static void
pmap_insert_pt_page(pmap_t pmap, vm_page_t mpte)
{
        vm_page_t root;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        root = pmap->pm_root;
        if (root == NULL) {
                mpte->left = NULL;
                mpte->right = NULL;
        } else {
                root = vm_page_splay(mpte->pindex, root);
                if (mpte->pindex < root->pindex) {
                        mpte->left = root->left;
                        mpte->right = root;
                        root->left = NULL;
                } else if (mpte->pindex == root->pindex)
                        panic("pmap_insert_pt_page: pindex already inserted");
                else {
                        mpte->right = root->right;
                        mpte->left = root;
                        root->right = NULL;
                }
        }
        pmap->pm_root = mpte;
}

/*
 * Looks for a page table page mapping the specified virtual address in the
 * specified pmap's collection of idle page table pages.  Returns NULL if there
 * is no page table page corresponding to the specified virtual address.
 */
static vm_page_t
pmap_lookup_pt_page(pmap_t pmap, vm_offset_t va)
{
        vm_page_t mpte;
        vm_pindex_t pindex = va >> PDRSHIFT;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        if ((mpte = pmap->pm_root) != NULL && mpte->pindex != pindex) {
                mpte = vm_page_splay(pindex, mpte);
                if ((pmap->pm_root = mpte)->pindex != pindex)
                        mpte = NULL;
        }
        return (mpte);
}

/*
 * Removes the specified page table page from the specified pmap's collection
 * of idle page table pages.  The specified page table page must be a member of
 * the pmap's collection.
 */
static void
pmap_remove_pt_page(pmap_t pmap, vm_page_t mpte)
{
        vm_page_t root;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        if (mpte != pmap->pm_root)
                vm_page_splay(mpte->pindex, pmap->pm_root);
        if (mpte->left == NULL)
                root = mpte->right;
        else {
                root = vm_page_splay(mpte->pindex, mpte->left);
                root->right = mpte->right;
        }
        pmap->pm_root = root;
}

/*
 * This routine unholds page table pages, and if the hold count
 * drops to zero, then it decrements the wire count.
 */
static __inline int
pmap_unwire_pte_hold(pmap_t pmap, vm_page_t m, vm_page_t *free)
{

        --m->wire_count;
        if (m->wire_count == 0)
                return _pmap_unwire_pte_hold(pmap, m, free);
        else
                return 0;
}

static int 
_pmap_unwire_pte_hold(pmap_t pmap, vm_page_t m, vm_page_t *free)
{
        vm_offset_t pteva;

        /*
         * unmap the page table page
         */
        pmap->pm_pdir[m->pindex] = 0;
        --pmap->pm_stats.resident_count;

        /*
         * This is a release store so that the ordinary store unmapping
         * the page table page is globally performed before TLB shoot-
         * down is begun.
         */
        atomic_subtract_rel_int(&cnt.v_wire_count, 1);

        /*
         * Do an invltlb to make the invalidated mapping
         * take effect immediately.
         */
        pteva = VM_MAXUSER_ADDRESS + i386_ptob(m->pindex);
        pmap_invalidate_page(pmap, pteva);

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

        return 1;
}

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

        if (va >= VM_MAXUSER_ADDRESS)
                return 0;
        ptepde = *pmap_pde(pmap, va);
        mpte = PHYS_TO_VM_PAGE(ptepde & PG_FRAME);
        return pmap_unwire_pte_hold(pmap, mpte, free);
}

void
pmap_pinit0(pmap_t pmap)
{

        PMAP_LOCK_INIT(pmap);
        pmap->pm_pdir = (pd_entry_t *)(KERNBASE + (vm_offset_t)IdlePTD);
#ifdef PAE
        pmap->pm_pdpt = (pdpt_entry_t *)(KERNBASE + (vm_offset_t)IdlePDPT);
#endif
        pmap->pm_root = NULL;
        pmap->pm_active = 0;
        PCPU_SET(curpmap, pmap);
        TAILQ_INIT(&pmap->pm_pvchunk);
        bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
        mtx_lock_spin(&allpmaps_lock);
        LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
        mtx_unlock_spin(&allpmaps_lock);
}

/*
 * Initialize a preallocated and zeroed pmap structure,
 * such as one in a vmspace structure.
 */
int
pmap_pinit(pmap_t pmap)
{
        vm_page_t m, ptdpg[NPGPTD];
        vm_paddr_t pa;
        static int color;
        int i;

        PMAP_LOCK_INIT(pmap);

        /*
         * No need to allocate page table space yet but we do need a valid
         * page directory table.
         */
        if (pmap->pm_pdir == NULL) {
                pmap->pm_pdir = (pd_entry_t *)kmem_alloc_nofault(kernel_map,
                    NBPTD);

                if (pmap->pm_pdir == NULL) {
                        PMAP_LOCK_DESTROY(pmap);
                        return (0);
                }
#ifdef PAE
                pmap->pm_pdpt = uma_zalloc(pdptzone, M_WAITOK | M_ZERO);
                KASSERT(((vm_offset_t)pmap->pm_pdpt &
                    ((NPGPTD * sizeof(pdpt_entry_t)) - 1)) == 0,
                    ("pmap_pinit: pdpt misaligned"));
                KASSERT(pmap_kextract((vm_offset_t)pmap->pm_pdpt) < (4ULL<<30),
                    ("pmap_pinit: pdpt above 4g"));
#endif
                pmap->pm_root = NULL;
        }
        KASSERT(pmap->pm_root == NULL,
            ("pmap_pinit: pmap has reserved page table page(s)"));

        /*
         * allocate the page directory page(s)
         */
        for (i = 0; i < NPGPTD;) {
                m = vm_page_alloc(NULL, color++,
                    VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ | VM_ALLOC_WIRED |
                    VM_ALLOC_ZERO);
                if (m == NULL)
                        VM_WAIT;
                else {
                        ptdpg[i++] = m;
                }
        }

        pmap_qenter((vm_offset_t)pmap->pm_pdir, ptdpg, NPGPTD);

        for (i = 0; i < NPGPTD; i++) {
                if ((ptdpg[i]->flags & PG_ZERO) == 0)
                        bzero(pmap->pm_pdir + (i * NPDEPG), PAGE_SIZE);
        }

        mtx_lock_spin(&allpmaps_lock);
        LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
        mtx_unlock_spin(&allpmaps_lock);
        /* Wire in kernel global address entries. */
        bcopy(PTD + KPTDI, pmap->pm_pdir + KPTDI, nkpt * sizeof(pd_entry_t));

        /* install self-referential address mapping entry(s) */
        for (i = 0; i < NPGPTD; i++) {
                pa = VM_PAGE_TO_PHYS(ptdpg[i]);
                pmap->pm_pdir[PTDPTDI + i] = pa | PG_V | PG_RW | PG_A | PG_M;
#ifdef PAE
                pmap->pm_pdpt[i] = pa | PG_V;
#endif
        }

        pmap->pm_active = 0;
        TAILQ_INIT(&pmap->pm_pvchunk);
        bzero(&pmap->pm_stats, sizeof pmap->pm_stats);

        return (1);
}

/*
 * this routine is called if the page table page is not
 * mapped correctly.
 */
static vm_page_t
_pmap_allocpte(pmap_t pmap, unsigned ptepindex, int flags)
{
        vm_paddr_t ptepa;
        vm_page_t m;

        KASSERT((flags & (M_NOWAIT | M_WAITOK)) == M_NOWAIT ||
            (flags & (M_NOWAIT | M_WAITOK)) == M_WAITOK,
            ("_pmap_allocpte: flags is neither M_NOWAIT nor M_WAITOK"));

        /*
         * Allocate a page table page.
         */
        if ((m = vm_page_alloc(NULL, ptepindex, VM_ALLOC_NOOBJ |
            VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL) {
                if (flags & M_WAITOK) {
                        PMAP_UNLOCK(pmap);
                        vm_page_unlock_queues();
                        VM_WAIT;
                        vm_page_lock_queues();
                        PMAP_LOCK(pmap);
                }

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

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

        pmap->pm_stats.resident_count++;

        ptepa = VM_PAGE_TO_PHYS(m);
        pmap->pm_pdir[ptepindex] =
                (pd_entry_t) (ptepa | PG_U | PG_RW | PG_V | PG_A | PG_M);

        return m;
}

static vm_page_t
pmap_allocpte(pmap_t pmap, vm_offset_t va, int flags)
{
        unsigned ptepindex;
        pd_entry_t ptepa;
        vm_page_t m;

        KASSERT((flags & (M_NOWAIT | M_WAITOK)) == M_NOWAIT ||
            (flags & (M_NOWAIT | M_WAITOK)) == M_WAITOK,
            ("pmap_allocpte: flags is neither M_NOWAIT nor M_WAITOK"));

        /*
         * Calculate pagetable page index
         */
        ptepindex = va >> PDRSHIFT;
retry:
        /*
         * Get the page directory entry
         */
        ptepa = pmap->pm_pdir[ptepindex];

        /*
         * This supports switching from a 4MB page to a
         * normal 4K page.
         */
        if (ptepa & PG_PS) {
                (void)pmap_demote_pde(pmap, &pmap->pm_pdir[ptepindex], va);
                ptepa = pmap->pm_pdir[ptepindex];
        }

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


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

#ifdef SMP
/*
 * Deal with a SMP shootdown of other users of the pmap that we are
 * trying to dispose of.  This can be a bit hairy.
 */
static cpumask_t *lazymask;
static u_int lazyptd;
static volatile u_int lazywait;

void pmap_lazyfix_action(void);

void
pmap_lazyfix_action(void)
{
        cpumask_t mymask = PCPU_GET(cpumask);

#ifdef COUNT_IPIS
        (*ipi_lazypmap_counts[PCPU_GET(cpuid)])++;
#endif
        if (rcr3() == lazyptd)
                load_cr3(PCPU_GET(curpcb)->pcb_cr3);
        atomic_clear_int(lazymask, mymask);
        atomic_store_rel_int(&lazywait, 1);
}

static void
pmap_lazyfix_self(cpumask_t mymask)
{

        if (rcr3() == lazyptd)
                load_cr3(PCPU_GET(curpcb)->pcb_cr3);
        atomic_clear_int(lazymask, mymask);
}


static void
pmap_lazyfix(pmap_t pmap)
{
        cpumask_t mymask, mask;
        u_int spins;

        while ((mask = pmap->pm_active) != 0) {
                spins = 50000000;
                mask = mask & -mask;    /* Find least significant set bit */
                mtx_lock_spin(&smp_ipi_mtx);
#ifdef PAE
                lazyptd = vtophys(pmap->pm_pdpt);
#else
                lazyptd = vtophys(pmap->pm_pdir);
#endif
                mymask = PCPU_GET(cpumask);
                if (mask == mymask) {
                        lazymask = &pmap->pm_active;
                        pmap_lazyfix_self(mymask);
                } else {
                        atomic_store_rel_int((u_int *)&lazymask,
                            (u_int)&pmap->pm_active);
                        atomic_store_rel_int(&lazywait, 0);
                        ipi_selected(mask, IPI_LAZYPMAP);
                        while (lazywait == 0) {
                                ia32_pause();
                                if (--spins == 0)
                                        break;
                        }
                }
                mtx_unlock_spin(&smp_ipi_mtx);
                if (spins == 0)
                        printf("pmap_lazyfix: spun for 50000000\n");
        }
}

#else   /* SMP */

/*
 * Cleaning up on uniprocessor is easy.  For various reasons, we're
 * unlikely to have to even execute this code, including the fact
 * that the cleanup is deferred until the parent does a wait(2), which
 * means that another userland process has run.
 */
static void
pmap_lazyfix(pmap_t pmap)
{
        u_int cr3;

        cr3 = vtophys(pmap->pm_pdir);
        if (cr3 == rcr3()) {
                load_cr3(PCPU_GET(curpcb)->pcb_cr3);
                pmap->pm_active &= ~(PCPU_GET(cpumask));
        }
}
#endif  /* SMP */

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

        KASSERT(pmap->pm_stats.resident_count == 0,
            ("pmap_release: pmap resident count %ld != 0",
            pmap->pm_stats.resident_count));
        KASSERT(pmap->pm_root == NULL,
            ("pmap_release: pmap has reserved page table page(s)"));

        pmap_lazyfix(pmap);
        mtx_lock_spin(&allpmaps_lock);
        LIST_REMOVE(pmap, pm_list);
        mtx_unlock_spin(&allpmaps_lock);

        for (i = 0; i < NPGPTD; i++)
                ptdpg[i] = PHYS_TO_VM_PAGE(pmap->pm_pdir[PTDPTDI + i] &
                    PG_FRAME);

        bzero(pmap->pm_pdir + PTDPTDI, (nkpt + NPGPTD) *
            sizeof(*pmap->pm_pdir));

        pmap_qremove((vm_offset_t)pmap->pm_pdir, NPGPTD);

        for (i = 0; i < NPGPTD; i++) {
                m = ptdpg[i];
#ifdef PAE
                KASSERT(VM_PAGE_TO_PHYS(m) == (pmap->pm_pdpt[i] & PG_FRAME),
                    ("pmap_release: got wrong ptd page"));
#endif
                m->wire_count--;
                atomic_subtract_int(&cnt.v_wire_count, 1);
                vm_page_free_zero(m);
        }
        PMAP_LOCK_DESTROY(pmap);
}
\f
static int
kvm_size(SYSCTL_HANDLER_ARGS)
{
        unsigned long ksize = VM_MAX_KERNEL_ADDRESS - KERNBASE;

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

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

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

/*
 * grow the number of kernel page table entries, if needed
 */
void
pmap_growkernel(vm_offset_t addr)
{
        struct pmap *pmap;
        vm_paddr_t ptppaddr;
        vm_page_t nkpg;
        pd_entry_t newpdir;
        pt_entry_t *pde;

        mtx_assert(&kernel_map->system_mtx, MA_OWNED);
        if (kernel_vm_end == 0) {
                kernel_vm_end = KERNBASE;
                nkpt = 0;
                while (pdir_pde(PTD, kernel_vm_end)) {
                        kernel_vm_end = (kernel_vm_end + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
                        nkpt++;
                        if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                                kernel_vm_end = kernel_map->max_offset;
                                break;
                        }
                }
        }
        addr = roundup2(addr, PAGE_SIZE * NPTEPG);
        if (addr - 1 >= kernel_map->max_offset)
                addr = kernel_map->max_offset;
        while (kernel_vm_end < addr) {
                if (pdir_pde(PTD, kernel_vm_end)) {
                        kernel_vm_end = (kernel_vm_end + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
                        if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                                kernel_vm_end = kernel_map->max_offset;
                                break;
                        }
                        continue;
                }

                nkpg = vm_page_alloc(NULL, kernel_vm_end >> PDRSHIFT,
                    VM_ALLOC_INTERRUPT | VM_ALLOC_NOOBJ | VM_ALLOC_WIRED |
                    VM_ALLOC_ZERO);
                if (nkpg == NULL)
                        panic("pmap_growkernel: no memory to grow kernel");

                nkpt++;

                if ((nkpg->flags & PG_ZERO) == 0)
                        pmap_zero_page(nkpg);
                ptppaddr = VM_PAGE_TO_PHYS(nkpg);
                newpdir = (pd_entry_t) (ptppaddr | PG_V | PG_RW | PG_A | PG_M);
                pdir_pde(PTD, kernel_vm_end) = newpdir;

                mtx_lock_spin(&allpmaps_lock);
                LIST_FOREACH(pmap, &allpmaps, pm_list) {
                        pde = pmap_pde(pmap, kernel_vm_end);
                        pde_store(pde, newpdir);
                }
                mtx_unlock_spin(&allpmaps_lock);
                kernel_vm_end = (kernel_vm_end + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
                if (kernel_vm_end - 1 >= kernel_map->max_offset) {
                        kernel_vm_end = kernel_map->max_offset;
                        break;
                }
        }
}


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

CTASSERT(sizeof(struct pv_chunk) == PAGE_SIZE);
CTASSERT(_NPCM == 11);

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_9      0xfffffffful    /* Free values for index 0 through 9 */
#define PC_FREE10       0x0000fffful    /* Free values for index 10 */

static uint32_t pc_freemask[11] = {
        PC_FREE0_9, PC_FREE0_9, PC_FREE0_9,
        PC_FREE0_9, PC_FREE0_9, PC_FREE0_9,
        PC_FREE0_9, PC_FREE0_9, PC_FREE0_9,
        PC_FREE0_9, PC_FREE10
};

SYSCTL_INT(_vm_pmap, OID_AUTO, pv_entry_count, CTLFLAG_RD, &pv_entry_count, 0,
        "Current number of pv entries");

#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;
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_INT(_vm_pmap, OID_AUTO, pv_entry_spare, CTLFLAG_RD, &pv_entry_spare, 0,
        "Current number of spare pv entries");

static int pmap_collect_inactive, pmap_collect_active;

SYSCTL_INT(_vm_pmap, OID_AUTO, pmap_collect_inactive, CTLFLAG_RD, &pmap_collect_inactive, 0,
        "Current number times pmap_collect called on inactive queue");
SYSCTL_INT(_vm_pmap, OID_AUTO, pmap_collect_active, CTLFLAG_RD, &pmap_collect_active, 0,
        "Current number times pmap_collect called on active queue");
#endif

/*
 * We are in a serious low memory condition.  Resort to
 * drastic measures to free some pages so we can allocate
 * another pv entry chunk.  This is normally called to
 * unmap inactive pages, and if necessary, active pages.
 */
static void
pmap_collect(pmap_t locked_pmap, struct vpgqueues *vpq)
{
        struct md_page *pvh;
        pd_entry_t *pde;
        pmap_t pmap;
        pt_entry_t *pte, tpte;
        pv_entry_t next_pv, pv;
        vm_offset_t va;
        vm_page_t m, free;

        sched_pin();
        TAILQ_FOREACH(m, &vpq->pl, pageq) {
                if (m->hold_count || m->busy)
                        continue;
                TAILQ_FOREACH_SAFE(pv, &m->md.pv_list, pv_list, next_pv) {
                        va = pv->pv_va;
                        pmap = PV_PMAP(pv);
                        /* Avoid deadlock and lock recursion. */
                        if (pmap > locked_pmap)
                                PMAP_LOCK(pmap);
                        else if (pmap != locked_pmap && !PMAP_TRYLOCK(pmap))
                                continue;
                        pmap->pm_stats.resident_count--;
                        pde = pmap_pde(pmap, va);
                        KASSERT((*pde & PG_PS) == 0, ("pmap_collect: found"
                            " a 4mpage in page %p's pv list", m));
                        pte = pmap_pte_quick(pmap, va);
                        tpte = pte_load_clear(pte);
                        KASSERT((tpte & PG_W) == 0,
                            ("pmap_collect: wired pte %#jx", (uintmax_t)tpte));
                        if (tpte & PG_A)
                                vm_page_flag_set(m, PG_REFERENCED);
                        if ((tpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                                vm_page_dirty(m);
                        free = NULL;
                        pmap_unuse_pt(pmap, va, &free);
                        pmap_invalidate_page(pmap, va);
                        pmap_free_zero_pages(free);
                        TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                        if (TAILQ_EMPTY(&m->md.pv_list)) {
                                pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                                if (TAILQ_EMPTY(&pvh->pv_list))
                                        vm_page_flag_clear(m, PG_WRITEABLE);
                        }
                        free_pv_entry(pmap, pv);
                        if (pmap != locked_pmap)
                                PMAP_UNLOCK(pmap);
                }
        }
        sched_unpin();
}


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

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        PV_STAT(pv_entry_frees++);
        PV_STAT(pv_entry_spare++);
        pv_entry_count--;
        pc = pv_to_chunk(pv);
        idx = pv - &pc->pc_pventry[0];
        field = idx / 32;
        bit = idx % 32;
        pc->pc_map[field] |= 1ul << bit;
        /* move to head of list */
        TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
        for (idx = 0; idx < _NPCM; idx++)
                if (pc->pc_map[idx] != pc_freemask[idx]) {
                        TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
                        return;
                }
        PV_STAT(pv_entry_spare -= _NPCPV);
        PV_STAT(pc_chunk_count--);
        PV_STAT(pc_chunk_frees++);
        /* entire chunk is free, return it */
        m = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)pc));
        pmap_qremove((vm_offset_t)pc, 1);
        vm_page_unwire(m, 0);
        vm_page_free(m);
        pmap_ptelist_free(&pv_vafree, (vm_offset_t)pc);
}

/*
 * get a new pv_entry, allocating a block from the system
 * when needed.
 */
static pv_entry_t
get_pv_entry(pmap_t pmap, int try)
{
        static const struct timeval printinterval = { 60, 0 };
        static struct timeval lastprint;
        static vm_pindex_t colour;
        struct vpgqueues *pq;
        int bit, field;
        pv_entry_t pv;
        struct pv_chunk *pc;
        vm_page_t m;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        PV_STAT(pv_entry_allocs++);
        pv_entry_count++;
        if (pv_entry_count > pv_entry_high_water)
                if (ratecheck(&lastprint, &printinterval))
                        printf("Approaching the limit on PV entries, consider "
                            "increasing either the vm.pmap.shpgperproc or the "
                            "vm.pmap.pv_entry_max tunable.\n");
        pq = NULL;
retry:
        pc = TAILQ_FIRST(&pmap->pm_pvchunk);
        if (pc != NULL) {
                for (field = 0; field < _NPCM; field++) {
                        if (pc->pc_map[field]) {
                                bit = bsfl(pc->pc_map[field]);
                                break;
                        }
                }
                if (field < _NPCM) {
                        pv = &pc->pc_pventry[field * 32 + bit];
                        pc->pc_map[field] &= ~(1ul << bit);
                        /* If this was the last item, move it to tail */
                        for (field = 0; field < _NPCM; field++)
                                if (pc->pc_map[field] != 0) {
                                        PV_STAT(pv_entry_spare--);
                                        return (pv);    /* not full, return */
                                }
                        TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                        TAILQ_INSERT_TAIL(&pmap->pm_pvchunk, pc, pc_list);
                        PV_STAT(pv_entry_spare--);
                        return (pv);
                }
        }
        /*
         * Access to the ptelist "pv_vafree" is synchronized by the page
         * queues lock.  If "pv_vafree" is currently non-empty, it will
         * remain non-empty until pmap_ptelist_alloc() completes.
         */
        if (pv_vafree == 0 || (m = vm_page_alloc(NULL, colour, (pq ==
            &vm_page_queues[PQ_ACTIVE] ? VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL) |
            VM_ALLOC_NOOBJ | VM_ALLOC_WIRED)) == NULL) {
                if (try) {
                        pv_entry_count--;
                        PV_STAT(pc_chunk_tryfail++);
                        return (NULL);
                }
                /*
                 * Reclaim pv entries: At first, destroy mappings to
                 * inactive pages.  After that, if a pv chunk entry
                 * is still needed, destroy mappings to active pages.
                 */
                if (pq == NULL) {
                        PV_STAT(pmap_collect_inactive++);
                        pq = &vm_page_queues[PQ_INACTIVE];
                } else if (pq == &vm_page_queues[PQ_INACTIVE]) {
                        PV_STAT(pmap_collect_active++);
                        pq = &vm_page_queues[PQ_ACTIVE];
                } else
                        panic("get_pv_entry: increase vm.pmap.shpgperproc");
                pmap_collect(pmap, pq);
                goto retry;
        }
        PV_STAT(pc_chunk_count++);
        PV_STAT(pc_chunk_allocs++);
        colour++;
        pc = (struct pv_chunk *)pmap_ptelist_alloc(&pv_vafree);
        pmap_qenter((vm_offset_t)pc, &m, 1);
        pc->pc_pmap = pmap;
        pc->pc_map[0] = pc_freemask[0] & ~1ul;  /* preallocated bit 0 */
        for (field = 1; field < _NPCM; field++)
                pc->pc_map[field] = pc_freemask[field];
        pv = &pc->pc_pventry[0];
        TAILQ_INSERT_HEAD(&pmap->pm_pvchunk, pc, pc_list);
        PV_STAT(pv_entry_spare += _NPCPV - 1);
        return (pv);
}

static __inline pv_entry_t
pmap_pvh_remove(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
{
        pv_entry_t pv;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        TAILQ_FOREACH(pv, &pvh->pv_list, pv_list) {
                if (pmap == PV_PMAP(pv) && va == pv->pv_va) {
                        TAILQ_REMOVE(&pvh->pv_list, pv, pv_list);
                        break;
                }
        }
        return (pv);
}

static void
pmap_pv_demote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa)
{
        struct md_page *pvh;
        pv_entry_t pv;
        vm_offset_t va_last;
        vm_page_t m;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        KASSERT((pa & PDRMASK) == 0,
            ("pmap_pv_demote_pde: pa is not 4mpage aligned"));

        /*
         * Transfer the 4mpage's pv entry for this mapping to the first
         * page's pv list.
         */
        pvh = pa_to_pvh(pa);
        va = trunc_4mpage(va);
        pv = pmap_pvh_remove(pvh, pmap, va);
        KASSERT(pv != NULL, ("pmap_pv_demote_pde: pv not found"));
        m = PHYS_TO_VM_PAGE(pa);
        TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
        /* Instantiate the remaining NPTEPG - 1 pv entries. */
        va_last = va + NBPDR - PAGE_SIZE;
        do {
                m++;
                KASSERT((m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) == 0,
                    ("pmap_pv_demote_pde: page %p is not managed", m));
                va += PAGE_SIZE;
                pmap_insert_entry(pmap, va, m);
        } while (va < va_last);
}

static void
pmap_pv_promote_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa)
{
        struct md_page *pvh;
        pv_entry_t pv;
        vm_offset_t va_last;
        vm_page_t m;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        KASSERT((pa & PDRMASK) == 0,
            ("pmap_pv_promote_pde: pa is not 4mpage aligned"));

        /*
         * Transfer the first page's pv entry for this mapping to the
         * 4mpage'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 pmap_collect() and that pmap_collect()
         * removes one of the mappings that is being promoted.
         */
        m = PHYS_TO_VM_PAGE(pa);
        va = trunc_4mpage(va);
        pv = pmap_pvh_remove(&m->md, pmap, va);
        KASSERT(pv != NULL, ("pmap_pv_promote_pde: pv not found"));
        pvh = pa_to_pvh(pa);
        TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_list);
        /* Free the remaining NPTEPG - 1 pv entries. */
        va_last = va + NBPDR - PAGE_SIZE;
        do {
                m++;
                va += PAGE_SIZE;
                pmap_pvh_free(&m->md, pmap, va);
        } while (va < va_last);
}

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);
}

static void
pmap_remove_entry(pmap_t pmap, vm_page_t m, vm_offset_t va)
{
        struct md_page *pvh;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        pmap_pvh_free(&m->md, pmap, va);
        if (TAILQ_EMPTY(&m->md.pv_list)) {
                pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                if (TAILQ_EMPTY(&pvh->pv_list))
                        vm_page_flag_clear(m, PG_WRITEABLE);
        }
}

/*
 * Create a pv entry for page at pa for
 * (pmap, va).
 */
static void
pmap_insert_entry(pmap_t pmap, vm_offset_t va, vm_page_t m)
{
        pv_entry_t pv;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        pv = get_pv_entry(pmap, FALSE);
        pv->pv_va = va;
        TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
}

/*
 * Conditionally create a pv entry.
 */
static boolean_t
pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va, vm_page_t m)
{
        pv_entry_t pv;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        if (pv_entry_count < pv_entry_high_water && 
            (pv = get_pv_entry(pmap, TRUE)) != NULL) {
                pv->pv_va = va;
                TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
                return (TRUE);
        } else
                return (FALSE);
}

/*
 * Create the pv entries for each of the pages within a superpage.
 */
static boolean_t
pmap_pv_insert_pde(pmap_t pmap, vm_offset_t va, vm_paddr_t pa)
{
        struct md_page *pvh;
        pv_entry_t pv;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        if (pv_entry_count < pv_entry_high_water && 
            (pv = get_pv_entry(pmap, TRUE)) != NULL) {
                pv->pv_va = va;
                pvh = pa_to_pvh(pa);
                TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_list);
                return (TRUE);
        } else
                return (FALSE);
}

/*
 * Tries to demote a 2- or 4MB page mapping.
 */
static boolean_t
pmap_demote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
{
        pd_entry_t newpde, oldpde;
        pmap_t allpmaps_entry;
        pt_entry_t *firstpte, newpte, *pte;
        vm_paddr_t mptepa;
        vm_page_t free, mpte;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        mpte = pmap_lookup_pt_page(pmap, va);
        if (mpte != NULL)
                pmap_remove_pt_page(pmap, mpte);
        else {
                KASSERT((*pde & PG_W) == 0,
                    ("pmap_demote_pde: page table page for a wired mapping"
                    " is missing"));
                free = NULL;
                pmap_remove_pde(pmap, pde, trunc_4mpage(va), &free);
                pmap_invalidate_page(pmap, trunc_4mpage(va));
                pmap_free_zero_pages(free);
                CTR2(KTR_PMAP, "pmap_demote_pde: failure for va %#x"
                    " in pmap %p", va, pmap);
                return (FALSE);
        }
        mptepa = VM_PAGE_TO_PHYS(mpte);

        /*
         * Temporarily map the page table page (mpte) into the kernel's
         * address space at either PADDR1 or PADDR2.
         */
        if (curthread->td_pinned > 0 && mtx_owned(&vm_page_queue_mtx)) {
                if ((*PMAP1 & PG_FRAME) != mptepa) {
                        *PMAP1 = mptepa | PG_RW | PG_V | PG_A | PG_M;
#ifdef SMP
                        PMAP1cpu = PCPU_GET(cpuid);
#endif
                        invlcaddr(PADDR1);
                        PMAP1changed++;
                } else
#ifdef SMP
                if (PMAP1cpu != PCPU_GET(cpuid)) {
                        PMAP1cpu = PCPU_GET(cpuid);
                        invlcaddr(PADDR1);
                        PMAP1changedcpu++;
                } else
#endif
                        PMAP1unchanged++;
                firstpte = PADDR1;
        } else {
                mtx_lock(&PMAP2mutex);
                if ((*PMAP2 & PG_FRAME) != mptepa) {
                        *PMAP2 = mptepa | PG_RW | PG_V | PG_A | PG_M;
                        pmap_invalidate_page(kernel_pmap, (vm_offset_t)PADDR2);
                }
                firstpte = PADDR2;
        }
        oldpde = *pde;
        newpde = mptepa | PG_M | PG_A | (oldpde & PG_U) | PG_RW | PG_V;
        KASSERT((oldpde & (PG_A | PG_V)) == (PG_A | PG_V),
            ("pmap_demote_pde: oldpde is missing PG_A and/or PG_V"));
        KASSERT((oldpde & (PG_M | PG_RW)) != PG_RW,
            ("pmap_demote_pde: oldpde is missing PG_M"));
        KASSERT((oldpde & PG_PS) != 0,
            ("pmap_demote_pde: oldpde is missing PG_PS"));
        newpte = oldpde & ~PG_PS;
        if ((newpte & PG_PDE_PAT) != 0)
                newpte ^= PG_PDE_PAT | PG_PTE_PAT;

        /*
         * If the mapping has changed attributes, update the page table
         * entries.
         */ 
        KASSERT((*firstpte & PG_FRAME) == (newpte & PG_FRAME),
            ("pmap_demote_pde: firstpte and newpte map different physical"
            " addresses"));
        if ((*firstpte & PG_PTE_PROMOTE) != (newpte & PG_PTE_PROMOTE))
                for (pte = firstpte; pte < firstpte + NPTEPG; pte++) {
                        *pte = newpte;  
                        newpte += PAGE_SIZE;
                }
        
        /*
         * Demote the mapping.  This pmap is locked.  The old PDE has
         * PG_A set.  If the old PDE has PG_RW set, it also has PG_M
         * set.  Thus, there is no danger of a race with another
         * processor changing the setting of PG_A and/or PG_M between
         * the read above and the store below. 
         */
        if (pmap == kernel_pmap) {
                /*
                 * A harmless race exists between this loop and the bcopy()
                 * in pmap_pinit() that initializes the kernel segment of
                 * the new page table.  Specifically, that bcopy() may copy
                 * the new PDE from the PTD, which is first in allpmaps, to
                 * the new page table before this loop updates that new
                 * page table.
                 */
                mtx_lock_spin(&allpmaps_lock);
                LIST_FOREACH(allpmaps_entry, &allpmaps, pm_list) {
                        pde = pmap_pde(allpmaps_entry, va);
                        KASSERT(*pde == newpde || (*pde & PG_PTE_PROMOTE) ==
                            (oldpde & PG_PTE_PROMOTE),
                            ("pmap_demote_pde: pde was %#jx, expected %#jx",
                            (uintmax_t)*pde, (uintmax_t)oldpde));
                        pde_store(pde, newpde);
                }
                mtx_unlock_spin(&allpmaps_lock);
        } else
                pde_store(pde, newpde); 
        if (firstpte == PADDR2)
                mtx_unlock(&PMAP2mutex);

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

        /*
         * Demote the pv entry.  This depends on the earlier demotion
         * of the mapping.  Specifically, the (re)creation of a per-
         * page pv entry might trigger the execution of pmap_collect(),
         * which might reclaim a newly (re)created per-page pv entry
         * and destroy the associated mapping.  In order to destroy
         * the mapping, the PDE must have already changed from mapping
         * the 2mpage to referencing the page table page.
         */
        if ((oldpde & PG_MANAGED) != 0)
                pmap_pv_demote_pde(pmap, va, oldpde & PG_PS_FRAME);

        pmap_pde_demotions++;
        CTR2(KTR_PMAP, "pmap_demote_pde: success for va %#x"
            " in pmap %p", va, pmap);
        return (TRUE);
}

/*
 * pmap_remove_pde: do the things to unmap a superpage in a process
 */
static void
pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
    vm_page_t *free)
{
        struct md_page *pvh;
        pd_entry_t oldpde;
        vm_offset_t eva, va;
        vm_page_t m, mpte;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT((sva & PDRMASK) == 0,
            ("pmap_remove_pde: sva is not 4mpage aligned"));
        oldpde = pte_load_clear(pdq);
        if (oldpde & PG_W)
                pmap->pm_stats.wired_count -= NBPDR / PAGE_SIZE;

        /*
         * Machines that don't support invlpg, also don't support
         * PG_G.
         */
        if (oldpde & PG_G)
                pmap_invalidate_page(kernel_pmap, sva);
        pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
        if (oldpde & PG_MANAGED) {
                pvh = pa_to_pvh(oldpde & PG_PS_FRAME);
                pmap_pvh_free(pvh, pmap, sva);
                eva = sva + NBPDR;
                for (va = sva, m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
                    va < eva; va += PAGE_SIZE, m++) {
                        if ((oldpde & (PG_M | PG_RW)) == (PG_M | PG_RW))
                                vm_page_dirty(m);
                        if (oldpde & PG_A)
                                vm_page_flag_set(m, PG_REFERENCED);
                        if (TAILQ_EMPTY(&m->md.pv_list) &&
                            TAILQ_EMPTY(&pvh->pv_list))
                                vm_page_flag_clear(m, PG_WRITEABLE);
                }
        }
        if (pmap == kernel_pmap) {
                if (!pmap_demote_pde(pmap, pdq, sva))
                        panic("pmap_remove_pde: failed demotion");
        } else {
                mpte = pmap_lookup_pt_page(pmap, sva);
                if (mpte != NULL) {
                        pmap_remove_pt_page(pmap, mpte);
                        pmap->pm_stats.resident_count--;
                        KASSERT(mpte->wire_count == NPTEPG,
                            ("pmap_remove_pde: pte page wire count error"));
                        mpte->wire_count = 0;
                        pmap_add_delayed_free_list(mpte, free, FALSE);
                        atomic_subtract_int(&cnt.v_wire_count, 1);
                }
        }
}

/*
 * pmap_remove_pte: do the things to unmap a page in a process
 */
static int
pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t va, vm_page_t *free)
{
        pt_entry_t oldpte;
        vm_page_t m;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        oldpte = pte_load_clear(ptq);
        if (oldpte & PG_W)
                pmap->pm_stats.wired_count -= 1;
        /*
         * Machines that don't support invlpg, also don't support
         * PG_G.
         */
        if (oldpte & PG_G)
                pmap_invalidate_page(kernel_pmap, va);
        pmap->pm_stats.resident_count -= 1;
        if (oldpte & PG_MANAGED) {
                m = PHYS_TO_VM_PAGE(oldpte & PG_FRAME);
                if ((oldpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                        vm_page_dirty(m);
                if (oldpte & PG_A)
                        vm_page_flag_set(m, PG_REFERENCED);
                pmap_remove_entry(pmap, m, va);
        }
        return (pmap_unuse_pt(pmap, va, free));
}

/*
 * Remove a single page from a process address space
 */
static void
pmap_remove_page(pmap_t pmap, vm_offset_t va, vm_page_t *free)
{
        pt_entry_t *pte;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        KASSERT(curthread->td_pinned > 0, ("curthread not pinned"));
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        if ((pte = pmap_pte_quick(pmap, va)) == NULL || *pte == 0)
                return;
        pmap_remove_pte(pmap, pte, va, free);
        pmap_invalidate_page(pmap, va);
}

/*
 *      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)
{
        vm_offset_t pdnxt;
        pd_entry_t ptpaddr;
        pt_entry_t *pte;
        vm_page_t free = NULL;
        int anyvalid;

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

        anyvalid = 0;

        vm_page_lock_queues();
        sched_pin();
        PMAP_LOCK(pmap);

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

        for (; sva < eva; sva = pdnxt) {
                unsigned pdirindex;

                /*
                 * Calculate index for next page table.
                 */
                pdnxt = (sva + NBPDR) & ~PDRMASK;
                if (pdnxt < sva)
                        pdnxt = eva;
                if (pmap->pm_stats.resident_count == 0)
                        break;

                pdirindex = sva >> PDRSHIFT;
                ptpaddr = pmap->pm_pdir[pdirindex];

                /*
                 * Weed out invalid mappings. Note: we assume that the page
                 * directory table is always allocated, and in kernel virtual.
                 */
                if (ptpaddr == 0)
                        continue;

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

                for (pte = pmap_pte_quick(pmap, sva); sva != pdnxt; pte++,
                    sva += PAGE_SIZE) {
                        if (*pte == 0)
                                continue;

                        /*
                         * The TLB entry for a PG_G mapping is invalidated
                         * by pmap_remove_pte().
                         */
                        if ((*pte & PG_G) == 0)
                                anyvalid = 1;
                        if (pmap_remove_pte(pmap, pte, sva, &free))
                                break;
                }
        }
out:
        sched_unpin();
        if (anyvalid)
                pmap_invalidate_all(pmap);
        vm_page_unlock_queues();
        PMAP_UNLOCK(pmap);
        pmap_free_zero_pages(free);
}

/*
 *      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;
        pt_entry_t *pte, tpte;
        pd_entry_t *pde;
        vm_offset_t va;
        vm_page_t free;

        KASSERT((m->flags & PG_FICTITIOUS) == 0,
            ("pmap_remove_all: page %p is fictitious", m));
        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        sched_pin();
        pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
        while ((pv = TAILQ_FIRST(&pvh->pv_list)) != NULL) {
                va = pv->pv_va;
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pde = pmap_pde(pmap, va);
                (void)pmap_demote_pde(pmap, pde, va);
                PMAP_UNLOCK(pmap);
        }
        while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pmap->pm_stats.resident_count--;
                pde = pmap_pde(pmap, pv->pv_va);
                KASSERT((*pde & PG_PS) == 0, ("pmap_remove_all: found"
                    " a 4mpage in page %p's pv list", m));
                pte = pmap_pte_quick(pmap, pv->pv_va);
                tpte = pte_load_clear(pte);
                if (tpte & PG_W)
                        pmap->pm_stats.wired_count--;
                if (tpte & PG_A)
                        vm_page_flag_set(m, PG_REFERENCED);

                /*
                 * Update the vm_page_t clean and reference bits.
                 */
                if ((tpte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                        vm_page_dirty(m);
                free = NULL;
                pmap_unuse_pt(pmap, pv->pv_va, &free);
                pmap_invalidate_page(pmap, pv->pv_va);
                pmap_free_zero_pages(free);
                TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                free_pv_entry(pmap, pv);
                PMAP_UNLOCK(pmap);
        }
        vm_page_flag_clear(m, PG_WRITEABLE);
        sched_unpin();
}

/*
 * pmap_protect_pde: do the things to protect a 4mpage in a process
 */
static boolean_t
pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t sva, vm_prot_t prot)
{
        pd_entry_t newpde, oldpde;
        vm_offset_t eva, va;
        vm_page_t m;
        boolean_t anychanged;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        KASSERT((sva & PDRMASK) == 0,
            ("pmap_protect_pde: sva is not 4mpage aligned"));
        anychanged = FALSE;
retry:
        oldpde = newpde = *pde;
        if (oldpde & PG_MANAGED) {
                eva = sva + NBPDR;
                for (va = sva, m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
                    va < eva; va += PAGE_SIZE, m++) {
                        /*
                         * In contrast to the analogous operation on a 4KB page
                         * mapping, the mapping's PG_A flag is not cleared and
                         * the page's PG_REFERENCED flag is not set.  The
                         * reason is that pmap_demote_pde() expects that a 2/4MB
                         * page mapping with a stored page table page has PG_A
                         * set.
                         */
                        if ((oldpde & (PG_M | PG_RW)) == (PG_M | PG_RW))
                                vm_page_dirty(m);
                }
        }
        if ((prot & VM_PROT_WRITE) == 0)
                newpde &= ~(PG_RW | PG_M);
#ifdef PAE
        if ((prot & VM_PROT_EXECUTE) == 0)
                newpde |= pg_nx;
#endif
        if (newpde != oldpde) {
                if (!pde_cmpset(pde, oldpde, newpde))
                        goto retry;
                if (oldpde & PG_G)
                        pmap_invalidate_page(pmap, sva);
                else
                        anychanged = TRUE;
        }
        return (anychanged);
}

/*
 *      Set the physical protection on the
 *      specified range of this map as requested.
 */
void
pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
{
        vm_offset_t pdnxt;
        pd_entry_t ptpaddr;
        pt_entry_t *pte;
        int anychanged;

        if ((prot & VM_PROT_READ) == VM_PROT_NONE) {
                pmap_remove(pmap, sva, eva);
                return;
        }

#ifdef PAE
        if ((prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) ==
            (VM_PROT_WRITE|VM_PROT_EXECUTE))
                return;
#else
        if (prot & VM_PROT_WRITE)
                return;
#endif

        anychanged = 0;

        vm_page_lock_queues();
        sched_pin();
        PMAP_LOCK(pmap);
        for (; sva < eva; sva = pdnxt) {
                pt_entry_t obits, pbits;
                unsigned pdirindex;

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

                pdirindex = sva >> PDRSHIFT;
                ptpaddr = pmap->pm_pdir[pdirindex];

                /*
                 * Weed out invalid mappings. Note: we assume that the page
                 * directory table is always allocated, and in kernel virtual.
                 */
                if (ptpaddr == 0)
                        continue;

                /*
                 * Check for large page.
                 */
                if ((ptpaddr & PG_PS) != 0) {
                        /*
                         * Are we protecting the entire large page?  If not,
                         * demote the mapping and fall through.
                         */
                        if (sva + NBPDR == pdnxt && eva >= pdnxt) {
                                /*
                                 * The TLB entry for a PG_G mapping is
                                 * invalidated by pmap_protect_pde().
                                 */
                                if (pmap_protect_pde(pmap,
                                    &pmap->pm_pdir[pdirindex], sva, prot))
                                        anychanged = 1;
                                continue;
                        } else if (!pmap_demote_pde(pmap,
                            &pmap->pm_pdir[pdirindex], sva)) {
                                /* The large page mapping was destroyed. */
                                continue;
                        }
                }

                if (pdnxt > eva)
                        pdnxt = eva;

                for (pte = pmap_pte_quick(pmap, sva); sva != pdnxt; pte++,
                    sva += PAGE_SIZE) {
                        vm_page_t m;

retry:
                        /*
                         * Regardless of whether a pte is 32 or 64 bits in
                         * size, PG_RW, PG_A, and PG_M are among the least
                         * significant 32 bits.
                         */
                        obits = pbits = *pte;
                        if ((pbits & PG_V) == 0)
                                continue;
                        if (pbits & PG_MANAGED) {
                                m = NULL;
                                if (pbits & PG_A) {
                                        m = PHYS_TO_VM_PAGE(pbits & PG_FRAME);
                                        vm_page_flag_set(m, PG_REFERENCED);
                                        pbits &= ~PG_A;
                                }
                                if ((pbits & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                                        if (m == NULL)
                                                m = PHYS_TO_VM_PAGE(pbits & PG_FRAME);
                                        vm_page_dirty(m);
                                }
                        }

                        if ((prot & VM_PROT_WRITE) == 0)
                                pbits &= ~(PG_RW | PG_M);
#ifdef PAE
                        if ((prot & VM_PROT_EXECUTE) == 0)
                                pbits |= pg_nx;
#endif

                        if (pbits != obits) {
#ifdef PAE
                                if (!atomic_cmpset_64(pte, obits, pbits))
                                        goto retry;
#else
                                if (!atomic_cmpset_int((u_int *)pte, obits,
                                    pbits))
                                        goto retry;
#endif
                                if (obits & PG_G)
                                        pmap_invalidate_page(pmap, sva);
                                else
                                        anychanged = 1;
                        }
                }
        }
        sched_unpin();
        if (anychanged)
                pmap_invalidate_all(pmap);
        vm_page_unlock_queues();
        PMAP_UNLOCK(pmap);
}

/*
 * Tries to promote the 512 or 1024, contiguous 4KB page mappings that are
 * within a single page table page (PTP) to a single 2- or 4MB 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.
 *
 * Managed (PG_MANAGED) mappings within the kernel address space are not
 * promoted.  The reason is that kernel PDEs are replicated in each pmap but
 * pmap_clear_ptes() and pmap_ts_referenced() only read the PDE from the kernel
 * pmap.
 */
static void
pmap_promote_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
{
        pd_entry_t newpde;
        pmap_t allpmaps_entry;
        pt_entry_t *firstpte, oldpte, pa, *pte;
        vm_offset_t oldpteva;
        vm_page_t mpte;

        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

        /*
         * Examine the first PTE in the specified PTP.  Abort if this PTE is
         * either invalid, unused, or does not map the first 4KB physical page
         * within a 2- or 4MB page.
         */
        firstpte = vtopte(trunc_4mpage(va));
setpde:
        newpde = *firstpte;
        if ((newpde & ((PG_FRAME & PDRMASK) | PG_A | PG_V)) != (PG_A | PG_V)) {
                pmap_pde_p_failures++;
                CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#x"
                    " in pmap %p", va, pmap);
                return;
        }
        if ((*firstpte & PG_MANAGED) != 0 && pmap == kernel_pmap) {
                pmap_pde_p_failures++;
                CTR2(KTR_PMAP, "pmap_promote_pde: failure for va %#x"
                    " in pmap %p", va, pmap);
                return;
        }
        if ((newpde & (PG_M | PG_RW)) == PG_RW) {
                /*
                 * When PG_M is already clear, PG_RW can be cleared without
                 * a TLB invalidation.
                 */
                if (!atomic_cmpset_int((u_int *)firstpte, newpde, newpde &
                    ~PG_RW))  
                        goto setpde;
                newpde &= ~PG_RW;
        }

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

        /*
         * Save the page table page in its current state until the PDE
         * mapping the superpage is demoted by pmap_demote_pde() or
         * destroyed by pmap_remove_pde(). 
         */
        mpte = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
        KASSERT(mpte >= vm_page_array &&
            mpte < &vm_page_array[vm_page_array_size],
            ("pmap_promote_pde: page table page is out of range"));
        KASSERT(mpte->pindex == va >> PDRSHIFT,
            ("pmap_promote_pde: page table page's pindex is wrong"));
        pmap_insert_pt_page(pmap, mpte);

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

        /*
         * Propagate the PAT index to its proper position.
         */
        if ((newpde & PG_PTE_PAT) != 0)
                newpde ^= PG_PDE_PAT | PG_PTE_PAT;

        /*
         * Map the superpage.
         */
        if (pmap == kernel_pmap) {
                mtx_lock_spin(&allpmaps_lock);
                LIST_FOREACH(allpmaps_entry, &allpmaps, pm_list) {
                        pde = pmap_pde(allpmaps_entry, va);
                        pde_store(pde, PG_PS | newpde);
                }
                mtx_unlock_spin(&allpmaps_lock);
        } else
                pde_store(pde, PG_PS | newpde);

        pmap_pde_promotions++;
        CTR2(KTR_PMAP, "pmap_promote_pde: success for va %#x"
            " in pmap %p", va, pmap);
}

/*
 *      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.
 */
void
pmap_enter(pmap_t pmap, vm_offset_t va, vm_prot_t access, vm_page_t m,
    vm_prot_t prot, boolean_t wired)
{
        vm_paddr_t pa;
        pd_entry_t *pde;
        pt_entry_t *pte;
        vm_paddr_t opa;
        pt_entry_t origpte, newpte;
        vm_page_t mpte, om;
        boolean_t invlva;

        va = trunc_page(va);
        KASSERT(va <= VM_MAX_KERNEL_ADDRESS, ("pmap_enter: toobig"));
        KASSERT(va < UPT_MIN_ADDRESS || va >= UPT_MAX_ADDRESS,
            ("pmap_enter: invalid to pmap_enter page table pages (va: 0x%x)", va));

        mpte = NULL;

        vm_page_lock_queues();
        PMAP_LOCK(pmap);
        sched_pin();

        /*
         * In the case that a page table page is not
         * resident, we are creating it here.
         */
        if (va < VM_MAXUSER_ADDRESS) {
                mpte = pmap_allocpte(pmap, va, M_WAITOK);
        }

        pde = pmap_pde(pmap, va);
        if ((*pde & PG_PS) != 0)
                panic("pmap_enter: attempted pmap_enter on 4MB page");
        pte = pmap_pte_quick(pmap, va);

        /*
         * Page Directory table entry not valid, we need a new PT page
         */
        if (pte == NULL) {
                panic("pmap_enter: invalid page directory pdir=%#jx, va=%#x",
                        (uintmax_t)pmap->pm_pdir[PTDPTDI], va);
        }

        pa = VM_PAGE_TO_PHYS(m);
        om = NULL;
        origpte = *pte;
        opa = origpte & PG_FRAME;

        /*
         * Mapping has not changed, must be protection or wiring change.
         */
        if (origpte && (opa == pa)) {
                /*
                 * 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 (wired && ((origpte & PG_W) == 0))
                        pmap->pm_stats.wired_count++;
                else if (!wired && (origpte & PG_W))
                        pmap->pm_stats.wired_count--;

                /*
                 * Remove extra pte reference
                 */
                if (mpte)
                        mpte->wire_count--;

                /*
                 * We might be turning off write access to the page,
                 * so we go ahead and sense modify status.
                 */
                if (origpte & PG_MANAGED) {
                        om = m;
                        pa |= PG_MANAGED;
                }
                goto validate;
        } 
        /*
         * Mapping has changed, invalidate old range and fall through to
         * handle validating new mapping.
         */
        if (opa) {
                if (origpte & PG_W)
                        pmap->pm_stats.wired_count--;
                if (origpte & PG_MANAGED) {
                        om = PHYS_TO_VM_PAGE(opa);
                        pmap_remove_entry(pmap, om, va);
                }
                if (mpte != NULL) {
                        mpte->wire_count--;
                        KASSERT(mpte->wire_count > 0,
                            ("pmap_enter: missing reference to page table page,"
                             " va: 0x%x", va));
                }
        } else
                pmap->pm_stats.resident_count++;

        /*
         * Enter on the PV list if part of our managed memory.
         */
        if ((m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) == 0) {
                KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva,
                    ("pmap_enter: managed mapping within the clean submap"));
                pmap_insert_entry(pmap, va, m);
                pa |= PG_MANAGED;
        }

        /*
         * Increment counters
         */
        if (wired)
                pmap->pm_stats.wired_count++;

validate:
        /*
         * Now validate mapping with desired protection/wiring.
         */
        newpte = (pt_entry_t)(pa | pmap_cache_bits(m->md.pat_mode, 0) | PG_V);
        if ((prot & VM_PROT_WRITE) != 0) {
                newpte |= PG_RW;
                vm_page_flag_set(m, PG_WRITEABLE);
        }
#ifdef PAE
        if ((prot & VM_PROT_EXECUTE) == 0)
                newpte |= pg_nx;
#endif
        if (wired)
                newpte |= PG_W;
        if (va < VM_MAXUSER_ADDRESS)
                newpte |= PG_U;
        if (pmap == kernel_pmap)
                newpte |= pgeflag;

        /*
         * if the mapping or permission bits are different, we need
         * to update the pte.
         */
        if ((origpte & ~(PG_M|PG_A)) != newpte) {
                newpte |= PG_A;
                if ((access & VM_PROT_WRITE) != 0)
                        newpte |= PG_M;
                if (origpte & PG_V) {
                        invlva = FALSE;
                        origpte = pte_load_store(pte, newpte);
                        if (origpte & PG_A) {
                                if (origpte & PG_MANAGED)
                                        vm_page_flag_set(om, PG_REFERENCED);
                                if (opa != VM_PAGE_TO_PHYS(m))
                                        invlva = TRUE;
#ifdef PAE
                                if ((origpte & PG_NX) == 0 &&
                                    (newpte & PG_NX) != 0)
                                        invlva = TRUE;
#endif
                        }
                        if ((origpte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                                if ((origpte & PG_MANAGED) != 0)
                                        vm_page_dirty(om);
                                if ((prot & VM_PROT_WRITE) == 0)
                                        invlva = TRUE;
                        }
                        if (invlva)
                                pmap_invalidate_page(pmap, va);
                } else
                        pte_store(pte, newpte);
        }

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

        sched_unpin();
        vm_page_unlock_queues();
        PMAP_UNLOCK(pmap);
}

/*
 * Tries to create a 2- or 4MB page mapping.  Returns TRUE if successful and
 * FALSE otherwise.  Fails if (1) a page table page cannot be allocated without
 * blocking, (2) a mapping already exists at the specified virtual address, or
 * (3) a pv entry cannot be allocated without reclaiming another pv entry. 
 */
static boolean_t
pmap_enter_pde(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot)
{
        pd_entry_t *pde, newpde;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);
        pde = pmap_pde(pmap, va);
        if (*pde != 0) {
                CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                    " in pmap %p", va, pmap);
                return (FALSE);
        }
        newpde = VM_PAGE_TO_PHYS(m) | pmap_cache_bits(m->md.pat_mode, 1) |
            PG_PS | PG_V;
        if ((m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) == 0) {
                newpde |= PG_MANAGED;

                /*
                 * Abort this mapping if its PV entry could not be created.
                 */
                if (!pmap_pv_insert_pde(pmap, va, VM_PAGE_TO_PHYS(m))) {
                        CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
                            " in pmap %p", va, pmap);
                        return (FALSE);
                }
        }
#ifdef PAE
        if ((prot & VM_PROT_EXECUTE) == 0)
                newpde |= pg_nx;
#endif
        if (va < VM_MAXUSER_ADDRESS)
                newpde |= PG_U;

        /*
         * Increment counters.
         */
        pmap->pm_stats.resident_count += NBPDR / PAGE_SIZE;

        /*
         * Map the superpage.
         */
        pde_store(pde, newpde);

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

/*
 * 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)
{
        vm_offset_t va;
        vm_page_t m, mpte;
        vm_pindex_t diff, psize;

        VM_OBJECT_LOCK_ASSERT(m_start->object, MA_OWNED);
        psize = atop(end - start);
        mpte = NULL;
        m = m_start;
        PMAP_LOCK(pmap);
        while (m != NULL && (diff = m->pindex - m_start->pindex) < psize) {
                va = start + ptoa(diff);
                if ((va & PDRMASK) == 0 && va + NBPDR <= end &&
                    (VM_PAGE_TO_PHYS(m) & PDRMASK) == 0 &&
                    pg_ps_enabled && vm_reserv_level_iffullpop(m) == 0 &&
                    pmap_enter_pde(pmap, va, m, prot))
                        m = &m[NBPDR / PAGE_SIZE - 1];
                else
                        mpte = pmap_enter_quick_locked(pmap, va, m, prot,
                            mpte);
                m = TAILQ_NEXT(m, listq);
        }
        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)
{

        PMAP_LOCK(pmap);
        (void) pmap_enter_quick_locked(pmap, va, m, prot, NULL);
        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)
{
        pt_entry_t *pte;
        vm_paddr_t pa;
        vm_page_t free;

        KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva ||
            (m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) != 0,
            ("pmap_enter_quick_locked: managed mapping within the clean submap"));
        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        PMAP_LOCK_ASSERT(pmap, MA_OWNED);

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

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

                        /*
                         * If the page table page is mapped, we just increment
                         * the hold count, and activate it.
                         */
                        if (ptepa) {
                                if (ptepa & PG_PS)
                                        return (NULL);
                                mpte = PHYS_TO_VM_PAGE(ptepa & PG_FRAME);
                                mpte->wire_count++;
                        } else {
                                mpte = _pmap_allocpte(pmap, ptepindex,
                                    M_NOWAIT);
                                if (mpte == NULL)
                                        return (mpte);
                        }
                }
        } else {
                mpte = NULL;
        }

        /*
         * This call to vtopte makes the assumption that we are
         * entering the page into the current pmap.  In order to support
         * quick entry into any pmap, one would likely use pmap_pte_quick.
         * But that isn't as quick as vtopte.
         */
        pte = vtopte(va);
        if (*pte) {
                if (mpte != NULL) {
                        mpte->wire_count--;
                        mpte = NULL;
                }
                return (mpte);
        }

        /*
         * Enter on the PV list if part of our managed memory.
         */
        if ((m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) == 0 &&
            !pmap_try_insert_pv_entry(pmap, va, m)) {
                if (mpte != NULL) {
                        free = NULL;
                        if (pmap_unwire_pte_hold(pmap, mpte, &free)) {
                                pmap_invalidate_page(pmap, va);
                                pmap_free_zero_pages(free);
                        }
                        
                        mpte = NULL;
                }
                return (mpte);
        }

        /*
         * Increment counters
         */
        pmap->pm_stats.resident_count++;

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

        /*
         * Now validate mapping with RO protection
         */
        if (m->flags & (PG_FICTITIOUS|PG_UNMANAGED))
                pte_store(pte, pa | PG_V | PG_U);
        else
                pte_store(pte, pa | PG_V | PG_U | PG_MANAGED);
        return mpte;
}

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

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

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

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

                /*
                 * Abort the mapping if the first page is not physically
                 * aligned to a 2/4MB page boundary.
                 */
                ptepa = VM_PAGE_TO_PHYS(p);
                if (ptepa & (NBPDR - 1))
                        return;

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

                /*
                 * Map using 2/4MB pages.  Since "ptepa" is 2/4M aligned and
                 * "size" is a multiple of 2/4M, adding the PAT setting to
                 * "pa" will not affect the termination of this loop.
                 */
                PMAP_LOCK(pmap);
                for (pa = ptepa | pmap_cache_bits(pat_mode, 1); pa < ptepa +
                    size; pa += NBPDR) {
                        pde = pmap_pde(pmap, addr);
                        if (*pde == 0) {
                                pde_store(pde, pa | PG_PS | PG_M | PG_A |
                                    PG_U | PG_RW | PG_V);
                                pmap->pm_stats.resident_count += NBPDR /
                                    PAGE_SIZE;
                                pmap_pde_mappings++;
                        }
                        /* Else continue on if the PDE is already valid. */
                        addr += NBPDR;
                }
                PMAP_UNLOCK(pmap);
        }
}

/*
 *      Routine:        pmap_change_wiring
 *      Function:       Change the wiring attribute for a map/virtual-address
 *                      pair.
 *      In/out conditions:
 *                      The mapping must already exist in the pmap.
 */
void
pmap_change_wiring(pmap_t pmap, vm_offset_t va, boolean_t wired)
{
        pd_entry_t *pde;
        pt_entry_t *pte;
        boolean_t are_queues_locked;

        are_queues_locked = FALSE;
retry:
        PMAP_LOCK(pmap);
        pde = pmap_pde(pmap, va);
        if ((*pde & PG_PS) != 0) {
                if (!wired != ((*pde & PG_W) == 0)) {
                        if (!are_queues_locked) {
                                are_queues_locked = TRUE;
                                if (!mtx_trylock(&vm_page_queue_mtx)) {
                                        PMAP_UNLOCK(pmap);
                                        vm_page_lock_queues();
                                        goto retry;
                                }
                        }
                        if (!pmap_demote_pde(pmap, pde, va))
                                panic("pmap_change_wiring: demotion failed");
                } else
                        goto out;
        }
        pte = pmap_pte(pmap, va);

        if (wired && !pmap_pte_w(pte))
                pmap->pm_stats.wired_count++;
        else if (!wired && pmap_pte_w(pte))
                pmap->pm_stats.wired_count--;

        /*
         * Wiring is not a hardware characteristic so there is no need to
         * invalidate TLB.
         */
        pmap_pte_set_w(pte, wired);
        pmap_pte_release(pte);
out:
        if (are_queues_locked)
                vm_page_unlock_queues();
        PMAP_UNLOCK(pmap);
}



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

void
pmap_copy(pmap_t dst_pmap, pmap_t src_pmap, vm_offset_t dst_addr, vm_size_t len,
    vm_offset_t src_addr)
{
        vm_page_t   free;
        vm_offset_t addr;
        vm_offset_t end_addr = src_addr + len;
        vm_offset_t pdnxt;

        if (dst_addr != src_addr)
                return;

        if (!pmap_is_current(src_pmap))
                return;

        vm_page_lock_queues();
        if (dst_pmap < src_pmap) {
                PMAP_LOCK(dst_pmap);
                PMAP_LOCK(src_pmap);
        } else {
                PMAP_LOCK(src_pmap);
                PMAP_LOCK(dst_pmap);
        }
        sched_pin();
        for (addr = src_addr; addr < end_addr; addr = pdnxt) {
                pt_entry_t *src_pte, *dst_pte;
                vm_page_t dstmpte, srcmpte;
                pd_entry_t srcptepaddr;
                unsigned ptepindex;

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

                pdnxt = (addr + NBPDR) & ~PDRMASK;
                if (pdnxt < addr)
                        pdnxt = end_addr;
                ptepindex = addr >> PDRSHIFT;

                srcptepaddr = src_pmap->pm_pdir[ptepindex];
                if (srcptepaddr == 0)
                        continue;
                        
                if (srcptepaddr & PG_PS) {
                        if (dst_pmap->pm_pdir[ptepindex] == 0 &&
                            ((srcptepaddr & PG_MANAGED) == 0 ||
                            pmap_pv_insert_pde(dst_pmap, addr, srcptepaddr &
                            PG_PS_FRAME))) {
                                dst_pmap->pm_pdir[ptepindex] = srcptepaddr &
                                    ~PG_W;
                                dst_pmap->pm_stats.resident_count +=
                                    NBPDR / PAGE_SIZE;
                        }
                        continue;
                }

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

                if (pdnxt > end_addr)
                        pdnxt = end_addr;

                src_pte = vtopte(addr);
                while (addr < pdnxt) {
                        pt_entry_t ptetemp;
                        ptetemp = *src_pte;
                        /*
                         * we only virtual copy managed pages
                         */
                        if ((ptetemp & PG_MANAGED) != 0) {
                                dstmpte = pmap_allocpte(dst_pmap, addr,
                                    M_NOWAIT);
                                if (dstmpte == NULL)
                                        goto out;
                                dst_pte = pmap_pte_quick(dst_pmap, addr);
                                if (*dst_pte == 0 &&
                                    pmap_try_insert_pv_entry(dst_pmap, addr,
                                    PHYS_TO_VM_PAGE(ptetemp & PG_FRAME))) {
                                        /*
                                         * Clear the wired, modified, and
                                         * accessed (referenced) bits
                                         * during the copy.
                                         */
                                        *dst_pte = ptetemp & ~(PG_W | PG_M |
                                            PG_A);
                                        dst_pmap->pm_stats.resident_count++;
                                } else {
                                        free = NULL;
                                        if (pmap_unwire_pte_hold(dst_pmap,
                                            dstmpte, &free)) {
                                                pmap_invalidate_page(dst_pmap,
                                                    addr);
                                                pmap_free_zero_pages(free);
                                        }
                                        goto out;
                                }
                                if (dstmpte->wire_count >= srcmpte->wire_count)
                                        break;
                        }
                        addr += PAGE_SIZE;
                        src_pte++;
                }
        }
out:
        sched_unpin();
        vm_page_unlock_queues();
        PMAP_UNLOCK(src_pmap);
        PMAP_UNLOCK(dst_pmap);
}       

static __inline void
pagezero(void *page)
{
#if defined(I686_CPU)
        if (cpu_class == CPUCLASS_686) {
#if defined(CPU_ENABLE_SSE)
                if (cpu_feature & CPUID_SSE2)
                        sse2_pagezero(page);
                else
#endif
                        i686_pagezero(page);
        } else
#endif
                bzero(page, PAGE_SIZE);
}

/*
 *      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)
{
        struct sysmaps *sysmaps;

        sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
        mtx_lock(&sysmaps->lock);
        if (*sysmaps->CMAP2)
                panic("pmap_zero_page: CMAP2 busy");
        sched_pin();
        *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M |
            pmap_cache_bits(m->md.pat_mode, 0);
        invlcaddr(sysmaps->CADDR2);
        pagezero(sysmaps->CADDR2);
        *sysmaps->CMAP2 = 0;
        sched_unpin();
        mtx_unlock(&sysmaps->lock);
}

/*
 *      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)
{
        struct sysmaps *sysmaps;

        sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
        mtx_lock(&sysmaps->lock);
        if (*sysmaps->CMAP2)
                panic("pmap_zero_page_area: CMAP2 busy");
        sched_pin();
        *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M |
            pmap_cache_bits(m->md.pat_mode, 0);
        invlcaddr(sysmaps->CADDR2);
        if (off == 0 && size == PAGE_SIZE) 
                pagezero(sysmaps->CADDR2);
        else
                bzero((char *)sysmaps->CADDR2 + off, size);
        *sysmaps->CMAP2 = 0;
        sched_unpin();
        mtx_unlock(&sysmaps->lock);
}

/*
 *      pmap_zero_page_idle zeros the specified hardware page by mapping 
 *      the page into KVM and using bzero to clear its contents.  This
 *      is intended to be called from the vm_pagezero process only and
 *      outside of Giant.
 */
void
pmap_zero_page_idle(vm_page_t m)
{

        if (*CMAP3)
                panic("pmap_zero_page_idle: CMAP3 busy");
        sched_pin();
        *CMAP3 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M |
            pmap_cache_bits(m->md.pat_mode, 0);
        invlcaddr(CADDR3);
        pagezero(CADDR3);
        *CMAP3 = 0;
        sched_unpin();
}

/*
 *      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 src, vm_page_t dst)
{
        struct sysmaps *sysmaps;

        sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
        mtx_lock(&sysmaps->lock);
        if (*sysmaps->CMAP1)
                panic("pmap_copy_page: CMAP1 busy");
        if (*sysmaps->CMAP2)
                panic("pmap_copy_page: CMAP2 busy");
        sched_pin();
        invlpg((u_int)sysmaps->CADDR1);
        invlpg((u_int)sysmaps->CADDR2);
        *sysmaps->CMAP1 = PG_V | VM_PAGE_TO_PHYS(src) | PG_A |
            pmap_cache_bits(src->md.pat_mode, 0);
        *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(dst) | PG_A | PG_M |
            pmap_cache_bits(dst->md.pat_mode, 0);
        bcopy(sysmaps->CADDR1, sysmaps->CADDR2, PAGE_SIZE);
        *sysmaps->CMAP1 = 0;
        *sysmaps->CMAP2 = 0;
        sched_unpin();
        mtx_unlock(&sysmaps->lock);
}

/*
 * 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;
        pv_entry_t pv;
        int loops = 0;

        if (m->flags & PG_FICTITIOUS)
                return FALSE;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                if (PV_PMAP(pv) == pmap) {
                        return TRUE;
                }
                loops++;
                if (loops >= 16)
                        break;
        }
        if (loops < 16) {
                pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                TAILQ_FOREACH(pv, &pvh->pv_list, pv_list) {
                        if (PV_PMAP(pv) == pmap)
                                return (TRUE);
                        loops++;
                        if (loops >= 16)
                                break;
                }
        }
        return (FALSE);
}

/*
 *      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)
{
        int count;

        count = 0;
        if ((m->flags & PG_FICTITIOUS) != 0)
                return (count);
        count = pmap_pvh_wired_mappings(&m->md, count);
        return (pmap_pvh_wired_mappings(pa_to_pvh(VM_PAGE_TO_PHYS(m)), count));
}

/*
 *      pmap_pvh_wired_mappings:
 *
 *      Return the updated number "count" of managed mappings that are wired.
 */
static int
pmap_pvh_wired_mappings(struct md_page *pvh, int count)
{
        pmap_t pmap;
        pt_entry_t *pte;
        pv_entry_t pv;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        sched_pin();
        TAILQ_FOREACH(pv, &pvh->pv_list, pv_list) {
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pte = pmap_pte_quick(pmap, pv->pv_va);
                if ((*pte & PG_W) != 0)
                        count++;
                PMAP_UNLOCK(pmap);
        }
        sched_unpin();
        return (count);
}

/*
 * Returns TRUE if the given page is mapped individually or as part of
 * a 4mpage.  Otherwise, returns FALSE.
 */
boolean_t
pmap_page_is_mapped(vm_page_t m)
{
        struct md_page *pvh;

        if ((m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) != 0)
                return (FALSE);
        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        if (TAILQ_EMPTY(&m->md.pv_list)) {
                pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                return (!TAILQ_EMPTY(&pvh->pv_list));
        } else
                return (TRUE);
}

/*
 * Remove all pages from specified address space
 * this aids process exit speeds.  Also, this code
 * is special cased for current process only, but
 * can have the more generic (and slightly slower)
 * mode enabled.  This is much faster than pmap_remove
 * in the case of running down an entire address space.
 */
void
pmap_remove_pages(pmap_t pmap)
{
        pt_entry_t *pte, tpte;
        vm_page_t free = NULL;
        vm_page_t m, mpte, mt;
        pv_entry_t pv;
        struct md_page *pvh;
        struct pv_chunk *pc, *npc;
        int field, idx;
        int32_t bit;
        uint32_t inuse, bitmask;
        int allfree;

        if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) {
                printf("warning: pmap_remove_pages called with non-current pmap\n");
                return;
        }
        vm_page_lock_queues();
        PMAP_LOCK(pmap);
        sched_pin();
        TAILQ_FOREACH_SAFE(pc, &pmap->pm_pvchunk, pc_list, npc) {
                allfree = 1;
                for (field = 0; field < _NPCM; field++) {
                        inuse = (~(pc->pc_map[field])) & pc_freemask[field];
                        while (inuse != 0) {
                                bit = bsfl(inuse);
                                bitmask = 1UL << bit;
                                idx = field * 32 + bit;
                                pv = &pc->pc_pventry[idx];
                                inuse &= ~bitmask;

                                pte = pmap_pde(pmap, pv->pv_va);
                                tpte = *pte;
                                if ((tpte & PG_PS) == 0) {
                                        pte = vtopte(pv->pv_va);
                                        tpte = *pte & ~PG_PTE_PAT;
                                }

                                if (tpte == 0) {
                                        printf(
                                            "TPTE at %p  IS ZERO @ VA %08x\n",
                                            pte, pv->pv_va);
                                        panic("bad pte");
                                }

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

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

                                KASSERT(m < &vm_page_array[vm_page_array_size],
                                        ("pmap_remove_pages: bad tpte %#jx",
                                        (uintmax_t)tpte));

                                pte_clear(pte);

                                /*
                                 * Update the vm_page_t clean/reference bits.
                                 */
                                if ((tpte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                                        if ((tpte & PG_PS) != 0) {
                                                for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                                        vm_page_dirty(mt);
                                        } else
                                                vm_page_dirty(m);
                                }

                                /* Mark free */
                                PV_STAT(pv_entry_frees++);
                                PV_STAT(pv_entry_spare++);
                                pv_entry_count--;
                                pc->pc_map[field] |= bitmask;
                                if ((tpte & PG_PS) != 0) {
                                        pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                                        pvh = pa_to_pvh(tpte & PG_PS_FRAME);
                                        TAILQ_REMOVE(&pvh->pv_list, pv, pv_list);
                                        if (TAILQ_EMPTY(&pvh->pv_list)) {
                                                for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
                                                        if (TAILQ_EMPTY(&mt->md.pv_list))
                                                                vm_page_flag_clear(mt, PG_WRITEABLE);
                                        }
                                        mpte = pmap_lookup_pt_page(pmap, pv->pv_va);
                                        if (mpte != NULL) {
                                                pmap_remove_pt_page(pmap, mpte);
                                                pmap->pm_stats.resident_count--;
                                                KASSERT(mpte->wire_count == NPTEPG,
                                                    ("pmap_remove_pages: pte page wire count error"));
                                                mpte->wire_count = 0;
                                                pmap_add_delayed_free_list(mpte, &free, FALSE);
                                                atomic_subtract_int(&cnt.v_wire_count, 1);
                                        }
                                } else {
                                        pmap->pm_stats.resident_count--;
                                        TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                                        if (TAILQ_EMPTY(&m->md.pv_list)) {
                                                pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
                                                if (TAILQ_EMPTY(&pvh->pv_list))
                                                        vm_page_flag_clear(m, PG_WRITEABLE);
                                        }
                                        pmap_unuse_pt(pmap, pv->pv_va, &free);
                                }
                        }
                }
                if (allfree) {
                        PV_STAT(pv_entry_spare -= _NPCPV);
                        PV_STAT(pc_chunk_count--);
                        PV_STAT(pc_chunk_frees++);
                        TAILQ_REMOVE(&pmap->pm_pvchunk, pc, pc_list);
                        m = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)pc));
                        pmap_qremove((vm_offset_t)pc, 1);
                        vm_page_unwire(m, 0);
                        vm_page_free(m);
                        pmap_ptelist_free(&pv_vafree, (vm_offset_t)pc);
                }
        }
        sched_unpin();
        pmap_invalidate_all(pmap);
        vm_page_unlock_queues();
        PMAP_UNLOCK(pmap);
        pmap_free_zero_pages(free);
}

/*
 *      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)
{

        if (m->flags & PG_FICTITIOUS)
                return (FALSE);
        if (pmap_is_modified_pvh(&m->md))
                return (TRUE);
        return (pmap_is_modified_pvh(pa_to_pvh(VM_PAGE_TO_PHYS(m))));
}

/*
 * Returns TRUE if any of the given mappings were used to modify
 * physical memory.  Otherwise, returns FALSE.  Both page and 2mpage
 * mappings are supported.
 */
static boolean_t
pmap_is_modified_pvh(struct md_page *pvh)
{
        pv_entry_t pv;
        pt_entry_t *pte;
        pmap_t pmap;
        boolean_t rv;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        rv = FALSE;
        sched_pin();
        TAILQ_FOREACH(pv, &pvh->pv_list, pv_list) {
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pte = pmap_pte_quick(pmap, pv->pv_va);
                rv = (*pte & (PG_M | PG_RW)) == (PG_M | PG_RW);
                PMAP_UNLOCK(pmap);
                if (rv)
                        break;
        }
        sched_unpin();
        return (rv);
}

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

        rv = FALSE;
        PMAP_LOCK(pmap);
        pde = pmap_pde(pmap, addr);
        if (*pde != 0 && (*pde & PG_PS) == 0) {
                pte = vtopte(addr);
                rv = *pte == 0;
        }
        PMAP_UNLOCK(pmap);
        return (rv);
}

/*
 * 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;
        pv_entry_t next_pv, pv;
        pmap_t pmap;
        pd_entry_t *pde;
        pt_entry_t oldpte, *pte;
        vm_offset_t va;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        if ((m->flags & PG_FICTITIOUS) != 0 ||
            (m->flags & PG_WRITEABLE) == 0)
                return;
        sched_pin();
        pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
        TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_list, next_pv) {
                va = pv->pv_va;
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pde = pmap_pde(pmap, va);
                if ((*pde & PG_RW) != 0)
                        (void)pmap_demote_pde(pmap, pde, va);
                PMAP_UNLOCK(pmap);
        }
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pde = pmap_pde(pmap, pv->pv_va);
                KASSERT((*pde & PG_PS) == 0, ("pmap_clear_write: found"
                    " a 4mpage in page %p's pv list", m));
                pte = pmap_pte_quick(pmap, pv->pv_va);
retry:
                oldpte = *pte;
                if ((oldpte & PG_RW) != 0) {
                        /*
                         * Regardless of whether a pte is 32 or 64 bits
                         * in size, PG_RW and PG_M are among the least
                         * significant 32 bits.
                         */
                        if (!atomic_cmpset_int((u_int *)pte, oldpte,
                            oldpte & ~(PG_RW | PG_M)))
                                goto retry;
                        if ((oldpte & PG_M) != 0)
                                vm_page_dirty(m);
                        pmap_invalidate_page(pmap, pv->pv_va);
                }
                PMAP_UNLOCK(pmap);
        }
        vm_page_flag_clear(m, PG_WRITEABLE);
        sched_unpin();
}

/*
 *      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.
 *
 *      XXX: The exact number of bits to check and clear is a matter that
 *      should be tested and standardized at some point in the future for
 *      optimal aging of shared pages.
 */
int
pmap_ts_referenced(vm_page_t m)
{
        struct md_page *pvh;
        pv_entry_t pv, pvf, pvn;
        pmap_t pmap;
        pd_entry_t oldpde, *pde;
        pt_entry_t *pte;
        vm_offset_t va;
        int rtval = 0;

        if (m->flags & PG_FICTITIOUS)
                return (rtval);
        sched_pin();
        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
        TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_list, pvn) {
                va = pv->pv_va;
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pde = pmap_pde(pmap, va);
                oldpde = *pde;
                if ((oldpde & PG_A) != 0) {
                        if (pmap_demote_pde(pmap, pde, va)) {
                                if ((oldpde & PG_W) == 0) {
                                        /*
                                         * Remove the mapping to a single page
                                         * so that a subsequent access may
                                         * repromote.  Since the underlying
                                         * page table page is fully populated,
                                         * this removal never frees a page
                                         * table page.
                                         */
                                        va += VM_PAGE_TO_PHYS(m) - (oldpde &
                                            PG_PS_FRAME);
                                        pmap_remove_page(pmap, va, NULL);
                                        rtval++;
                                        if (rtval > 4) {
                                                PMAP_UNLOCK(pmap);
                                                return (rtval);
                                        }
                                }
                        }
                }
                PMAP_UNLOCK(pmap);
        }
        if ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                pvf = pv;
                do {
                        pvn = TAILQ_NEXT(pv, pv_list);
                        TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                        TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
                        pmap = PV_PMAP(pv);
                        PMAP_LOCK(pmap);
                        pde = pmap_pde(pmap, pv->pv_va);
                        KASSERT((*pde & PG_PS) == 0, ("pmap_ts_referenced:"
                            " found a 4mpage in page %p's pv list", m));
                        pte = pmap_pte_quick(pmap, pv->pv_va);
                        if ((*pte & PG_A) != 0) {
                                atomic_clear_int((u_int *)pte, PG_A);
                                pmap_invalidate_page(pmap, pv->pv_va);
                                rtval++;
                                if (rtval > 4)
                                        pvn = NULL;
                        }
                        PMAP_UNLOCK(pmap);
                } while ((pv = pvn) != NULL && pv != pvf);
        }
        sched_unpin();
        return (rtval);
}

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

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        if ((m->flags & PG_FICTITIOUS) != 0)
                return;
        sched_pin();
        pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
        TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_list, next_pv) {
                va = pv->pv_va;
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pde = pmap_pde(pmap, va);
                oldpde = *pde;
                if ((oldpde & PG_RW) != 0) {
                        if (pmap_demote_pde(pmap, pde, va)) {
                                if ((oldpde & PG_W) == 0) {
                                        /*
                                         * Write protect the mapping to a
                                         * single page so that a subsequent
                                         * write access may repromote.
                                         */
                                        va += VM_PAGE_TO_PHYS(m) - (oldpde &
                                            PG_PS_FRAME);
                                        pte = pmap_pte_quick(pmap, va);
                                        oldpte = *pte;
                                        if ((oldpte & PG_V) != 0) {
                                                /*
                                                 * Regardless of whether a pte is 32 or 64 bits
                                                 * in size, PG_RW and PG_M are among the least
                                                 * significant 32 bits.
                                                 */
                                                while (!atomic_cmpset_int((u_int *)pte,
                                                    oldpte,
                                                    oldpte & ~(PG_M | PG_RW)))
                                                        oldpte = *pte;
                                                vm_page_dirty(m);
                                                pmap_invalidate_page(pmap, va);
                                        }
                                }
                        }
                }
                PMAP_UNLOCK(pmap);
        }
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pde = pmap_pde(pmap, pv->pv_va);
                KASSERT((*pde & PG_PS) == 0, ("pmap_clear_modify: found"
                    " a 4mpage in page %p's pv list", m));
                pte = pmap_pte_quick(pmap, pv->pv_va);
                if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
                        /*
                         * Regardless of whether a pte is 32 or 64 bits
                         * in size, PG_M is among the least significant
                         * 32 bits. 
                         */
                        atomic_clear_int((u_int *)pte, PG_M);
                        pmap_invalidate_page(pmap, pv->pv_va);
                }
                PMAP_UNLOCK(pmap);
        }
        sched_unpin();
}

/*
 *      pmap_clear_reference:
 *
 *      Clear the reference bit on the specified physical page.
 */
void
pmap_clear_reference(vm_page_t m)
{
        struct md_page *pvh;
        pv_entry_t next_pv, pv;
        pmap_t pmap;
        pd_entry_t oldpde, *pde;
        pt_entry_t *pte;
        vm_offset_t va;

        mtx_assert(&vm_page_queue_mtx, MA_OWNED);
        if ((m->flags & PG_FICTITIOUS) != 0)
                return;
        sched_pin();
        pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
        TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_list, next_pv) {
                va = pv->pv_va;
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pde = pmap_pde(pmap, va);
                oldpde = *pde;
                if ((oldpde & PG_A) != 0) {
                        if (pmap_demote_pde(pmap, pde, va)) {
                                /*
                                 * Remove the mapping to a single page so
                                 * that a subsequent access may repromote.
                                 * Since the underlying page table page is
                                 * fully populated, this removal never frees
                                 * a page table page.
                                 */
                                va += VM_PAGE_TO_PHYS(m) - (oldpde &
                                    PG_PS_FRAME);
                                pmap_remove_page(pmap, va, NULL);
                        }
                }
                PMAP_UNLOCK(pmap);
        }
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                pmap = PV_PMAP(pv);
                PMAP_LOCK(pmap);
                pde = pmap_pde(pmap, pv->pv_va);
                KASSERT((*pde & PG_PS) == 0, ("pmap_clear_reference: found"
                    " a 4mpage in page %p's pv list", m));
                pte = pmap_pte_quick(pmap, pv->pv_va);
                if ((*pte & PG_A) != 0) {
                        /*
                         * Regardless of whether a pte is 32 or 64 bits
                         * in size, PG_A is among the least significant
                         * 32 bits. 
                         */
                        atomic_clear_int((u_int *)pte, PG_A);
                        pmap_invalidate_page(pmap, pv->pv_va);
                }
                PMAP_UNLOCK(pmap);
        }
        sched_unpin();
}

/*
 * Miscellaneous support routines follow
 */

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

        offset = pa & PAGE_MASK;
        size = roundup(offset + size, PAGE_SIZE);
        pa = pa & PG_FRAME;

        if (pa < KERNLOAD && pa + size <= KERNLOAD)
                va = KERNBASE + pa;
        else
                va = kmem_alloc_nofault(kernel_map, size);
        if (!va)
                panic("pmap_mapdev: Couldn't alloc kernel virtual memory");

        for (tmpsize = 0; tmpsize < size; tmpsize += PAGE_SIZE)
                pmap_kenter_attr(va + tmpsize, pa + tmpsize, mode);
        pmap_invalidate_range(kernel_pmap, va, va + tmpsize);
        pmap_invalidate_cache_range(va, va + size);
        return ((void *)(va + offset));
}

void *
pmap_mapdev(vm_paddr_t pa, vm_size_t size)
{

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

void *
pmap_mapbios(vm_paddr_t pa, vm_size_t size)
{

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

void
pmap_unmapdev(vm_offset_t va, vm_size_t size)
{
        vm_offset_t base, offset, tmpva;

        if (va >= KERNBASE && va + size <= KERNBASE + KERNLOAD)
                return;
        base = trunc_page(va);
        offset = va & PAGE_MASK;
        size = roundup(offset + size, PAGE_SIZE);
        for (tmpva = base; tmpva < (base + size); tmpva += PAGE_SIZE)
                pmap_kremove(tmpva);
        pmap_invalidate_range(kernel_pmap, va, tmpva);
        kmem_free(kernel_map, base, size);
}

/*
 * Sets the memory attribute for the specified page.
 */
void
pmap_page_set_memattr(vm_page_t m, vm_memattr_t ma)
{
        struct sysmaps *sysmaps;
        vm_offset_t sva, eva;

        m->md.pat_mode = ma;
        if ((m->flags & PG_FICTITIOUS) != 0)
                return;

        /*
         * If "m" is a normal page, flush it from the cache.
         * See pmap_invalidate_cache_range().
         *
         * First, try to find an existing mapping of the page by sf
         * buffer. sf_buf_invalidate_cache() modifies mapping and
         * flushes the cache.
         */    
        if (sf_buf_invalidate_cache(m))
                return;

        /*
         * If page is not mapped by sf buffer, but CPU does not
         * support self snoop, map the page transient and do
         * invalidation. In the worst case, whole cache is flushed by
         * pmap_invalidate_cache_range().
         */
        if ((cpu_feature & (CPUID_SS|CPUID_CLFSH)) == CPUID_CLFSH) {
                sysmaps = &sysmaps_pcpu[PCPU_GET(cpuid)];
                mtx_lock(&sysmaps->lock);
                if (*sysmaps->CMAP2)
                        panic("pmap_page_set_memattr: CMAP2 busy");
                sched_pin();
                *sysmaps->CMAP2 = PG_V | PG_RW | VM_PAGE_TO_PHYS(m) |
                    PG_A | PG_M | pmap_cache_bits(m->md.pat_mode, 0);
                invlcaddr(sysmaps->CADDR2);
                sva = (vm_offset_t)sysmaps->CADDR2;
                eva = sva + PAGE_SIZE;
        } else
                sva = eva = 0; /* gcc */
        pmap_invalidate_cache_range(sva, eva);
        if (sva != 0) {
                *sysmaps->CMAP2 = 0;
                sched_unpin();
                mtx_unlock(&sysmaps->lock);
        }
}

int
pmap_change_attr(vm_offset_t va, vm_size_t size, int mode)
{
        vm_offset_t base, offset, tmpva;
        pt_entry_t *pte;
        u_int opte, npte;
        pd_entry_t *pde;
        boolean_t changed;

        base = trunc_page(va);
        offset = va & PAGE_MASK;
        size = roundup(offset + size, PAGE_SIZE);

        /*
         * Only supported on kernel virtual addresses above the recursive map.
         */
        if (base < VM_MIN_KERNEL_ADDRESS)
                return (EINVAL);

        /* 4MB pages and pages that aren't mapped aren't supported. */
        for (tmpva = base; tmpva < (base + size); tmpva += PAGE_SIZE) {
                pde = pmap_pde(kernel_pmap, tmpva);
                if (*pde & PG_PS)
                        return (EINVAL);
                if (*pde == 0)
                        return (EINVAL);
                pte = vtopte(tmpva);
                if (*pte == 0)
                        return (EINVAL);
        }

        changed = FALSE;

        /*
         * Ok, all the pages exist and are 4k, so run through them updating
         * their cache mode.
         */
        for (tmpva = base; size > 0; ) {
                pte = vtopte(tmpva);

                /*
                 * The cache mode bits are all in the low 32-bits of the
                 * PTE, so we can just spin on updating the low 32-bits.
                 */
                do {
                        opte = *(u_int *)pte;
                        npte = opte & ~(PG_PTE_PAT | PG_NC_PCD | PG_NC_PWT);
                        npte |= pmap_cache_bits(mode, 0);
                } while (npte != opte &&
                    !atomic_cmpset_int((u_int *)pte, opte, npte));
                if (npte != opte)
                        changed = TRUE;
                tmpva += PAGE_SIZE;
                size -= PAGE_SIZE;
        }

        /*
         * Flush CPU caches to make sure any data isn't cached that shouldn't
         * be, etc.
         */    
        if (changed) {
                pmap_invalidate_range(kernel_pmap, base, tmpva);
                pmap_invalidate_cache_range(base, tmpva);
        }
        return (0);
}

/*
 * perform the pmap work for mincore
 */
int
pmap_mincore(pmap_t pmap, vm_offset_t addr)
{
        pd_entry_t *pdep;
        pt_entry_t *ptep, pte;
        vm_paddr_t pa;
        vm_page_t m;
        int val = 0;
        
        PMAP_LOCK(pmap);
        pdep = pmap_pde(pmap, addr);
        if (*pdep != 0) {
                if (*pdep & PG_PS) {
                        pte = *pdep;
                        val = MINCORE_SUPER;
                        /* Compute the physical address of the 4KB page. */
                        pa = ((*pdep & PG_PS_FRAME) | (addr & PDRMASK)) &
                            PG_FRAME;
                } else {
                        ptep = pmap_pte(pmap, addr);
                        pte = *ptep;
                        pmap_pte_release(ptep);
                        pa = pte & PG_FRAME;
                }
        } else {
                pte = 0;
                pa = 0;
        }
        PMAP_UNLOCK(pmap);

        if (pte != 0) {
                val |= MINCORE_INCORE;
                if ((pte & PG_MANAGED) == 0)
                        return val;

                m = PHYS_TO_VM_PAGE(pa);

                /*
                 * Modified by us
                 */
                if ((pte & (PG_M | PG_RW)) == (PG_M | PG_RW))
                        val |= MINCORE_MODIFIED|MINCORE_MODIFIED_OTHER;
                else {
                        /*
                         * Modified by someone else
                         */
                        vm_page_lock_queues();
                        if (m->dirty || pmap_is_modified(m))
                                val |= MINCORE_MODIFIED_OTHER;
                        vm_page_unlock_queues();
                }
                /*
                 * Referenced by us
                 */
                if (pte & PG_A)
                        val |= MINCORE_REFERENCED|MINCORE_REFERENCED_OTHER;
                else {
                        /*
                         * Referenced by someone else
                         */
                        vm_page_lock_queues();
                        if ((m->flags & PG_REFERENCED) ||
                            pmap_ts_referenced(m)) {
                                val |= MINCORE_REFERENCED_OTHER;
                                vm_page_flag_set(m, PG_REFERENCED);
                        }
                        vm_page_unlock_queues();
                }
        } 
        return val;
}

void
pmap_activate(struct thread *td)
{
        pmap_t  pmap, oldpmap;
        u_int32_t  cr3;

        critical_enter();
        pmap = vmspace_pmap(td->td_proc->p_vmspace);
        oldpmap = PCPU_GET(curpmap);
#if defined(SMP)
        atomic_clear_int(&oldpmap->pm_active, PCPU_GET(cpumask));
        atomic_set_int(&pmap->pm_active, PCPU_GET(cpumask));
#else
        oldpmap->pm_active &= ~1;
        pmap->pm_active |= 1;
#endif
#ifdef PAE
        cr3 = vtophys(pmap->pm_pdpt);
#else
        cr3 = vtophys(pmap->pm_pdir);
#endif
        /*
         * pmap_activate is for the current thread on the current cpu
         */
        td->td_pcb->pcb_cr3 = cr3;
        load_cr3(cr3);
        PCPU_SET(curpmap, pmap);
        critical_exit();
}

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

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


#if defined(PMAP_DEBUG)
pmap_pid_dump(int pid)
{
        pmap_t pmap;
        struct proc *p;
        int npte = 0;
        int index;

        sx_slock(&allproc_lock);
        FOREACH_PROC_IN_SYSTEM(p) {
                if (p->p_pid != pid)
                        continue;

                if (p->p_vmspace) {
                        int i,j;
                        index = 0;
                        pmap = vmspace_pmap(p->p_vmspace);
                        for (i = 0; i < NPDEPTD; i++) {
                                pd_entry_t *pde;
                                pt_entry_t *pte;
                                vm_offset_t base = i << PDRSHIFT;
                                
                                pde = &pmap->pm_pdir[i];
                                if (pde && pmap_pde_v(pde)) {
                                        for (j = 0; j < NPTEPG; j++) {
                                                vm_offset_t va = base + (j << PAGE_SHIFT);
                                                if (va >= (vm_offset_t) VM_MIN_KERNEL_ADDRESS) {
                                                        if (index) {
                                                                index = 0;
                                                                printf("\n");
                                                        }
                                                        sx_sunlock(&allproc_lock);
                                                        return npte;
                                                }
                                                pte = pmap_pte(pmap, va);
                                                if (pte && pmap_pte_v(pte)) {
                                                        pt_entry_t pa;
                                                        vm_page_t m;
                                                        pa = *pte;
                                                        m = PHYS_TO_VM_PAGE(pa & PG_FRAME);
                                                        printf("va: 0x%x, pt: 0x%x, h: %d, w: %d, f: 0x%x",
                                                                va, pa, m->hold_count, m->wire_count, m->flags);
                                                        npte++;
                                                        index++;
                                                        if (index >= 2) {
                                                                index = 0;
                                                                printf("\n");
                                                        } else {
                                                                printf(" ");
                                                        }
                                                }
                                        }
                                }
                        }
                }
        }
        sx_sunlock(&allproc_lock);
        return npte;
}
#endif

#if defined(DEBUG)

static void     pads(pmap_t pm);
void            pmap_pvdump(vm_offset_t pa);

/* print address space of pmap*/
static void
pads(pmap_t pm)
{
        int i, j;
        vm_paddr_t va;
        pt_entry_t *ptep;

        if (pm == kernel_pmap)
                return;
        for (i = 0; i < NPDEPTD; i++)
                if (pm->pm_pdir[i])
                        for (j = 0; j < NPTEPG; j++) {
                                va = (i << PDRSHIFT) + (j << PAGE_SHIFT);
                                if (pm == kernel_pmap && va < KERNBASE)
                                        continue;
                                if (pm != kernel_pmap && va > UPT_MAX_ADDRESS)
                                        continue;
                                ptep = pmap_pte(pm, va);
                                if (pmap_pte_v(ptep))
                                        printf("%x:%x ", va, *ptep);
                        };

}

void
pmap_pvdump(vm_paddr_t pa)
{
        pv_entry_t pv;
        pmap_t pmap;
        vm_page_t m;

        printf("pa %x", pa);
        m = PHYS_TO_VM_PAGE(pa);
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                pmap = PV_PMAP(pv);
                printf(" -> pmap %p, va %x", (void *)pmap, pv->pv_va);
                pads(pmap);
        }
        printf(" ");
}
#endif