kernel: Correctly handle fake pages

[dragonfly.git] / sys / platform / vkernel64 / platform / pmap.c

/*
 * (MPSAFE)
 *
 * Copyright (c) 1991 Regents of the University of California.
 * Copyright (c) 1994 John S. Dyson
 * Copyright (c) 1994 David Greenman
 * Copyright (c) 2003 Peter Wemm
 * Copyright (c) 2005-2008 Alan L. Cox <alc@cs.rice.edu>
 * Copyright (c) 2008, 2009 The DragonFly Project.
 * Copyright (c) 2008, 2009 Jordan Gordeev.
 * 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
 * $FreeBSD: src/sys/i386/i386/pmap.c,v 1.250.2.18 2002/03/06 22:48:53 silby Exp $
 */

/*
 * Manages physical address maps.
 */

#if JG
#include "opt_pmap.h"
#endif
#include "opt_msgbuf.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/msgbuf.h>
#include <sys/vmmeter.h>
#include <sys/mman.h>
#include <sys/vmspace.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <sys/sysctl.h>
#include <sys/lock.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_zone.h>

#include <sys/user.h>
#include <sys/thread2.h>
#include <sys/sysref2.h>
#include <sys/spinlock2.h>

#include <machine/cputypes.h>
#include <machine/md_var.h>
#include <machine/specialreg.h>
#include <machine/smp.h>
#include <machine/globaldata.h>
#include <machine/pmap.h>
#include <machine/pmap_inval.h>

#include <ddb/ddb.h>

#include <stdio.h>
#include <assert.h>
#include <stdlib.h>

#define PMAP_KEEP_PDIRS
#ifndef PMAP_SHPGPERPROC
#define PMAP_SHPGPERPROC 1000
#endif

#if defined(DIAGNOSTIC)
#define PMAP_DIAGNOSTIC
#endif

#define MINPV 2048

#if !defined(PMAP_DIAGNOSTIC)
#define PMAP_INLINE __inline
#else
#define PMAP_INLINE
#endif

/*
 * Get PDEs and PTEs for user/kernel address space
 */
static pd_entry_t *pmap_pde(pmap_t pmap, vm_offset_t va);
#define pdir_pde(m, v) (m[(vm_offset_t)(v) >> PDRSHIFT])

#define pmap_pde_v(pte)         ((*(pd_entry_t *)pte & VPTE_V) != 0)
#define pmap_pte_w(pte)         ((*(pt_entry_t *)pte & VPTE_WIRED) != 0)
#define pmap_pte_m(pte)         ((*(pt_entry_t *)pte & VPTE_M) != 0)
#define pmap_pte_u(pte)         ((*(pt_entry_t *)pte & VPTE_A) != 0)
#define pmap_pte_v(pte)         ((*(pt_entry_t *)pte & VPTE_V) != 0)

/*
 * Given a map and a machine independent protection code,
 * convert to a vax protection code.
 */
#define pte_prot(m, p)          \
        (protection_codes[p & (VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE)])
static int protection_codes[8];

struct pmap kernel_pmap;
static TAILQ_HEAD(,pmap)        pmap_list = TAILQ_HEAD_INITIALIZER(pmap_list);

static boolean_t pmap_initialized = FALSE;      /* Has pmap_init completed? */

static vm_object_t kptobj;

static int nkpt;

static uint64_t KPDphys;        /* phys addr of kernel level 2 */
uint64_t                KPDPphys;       /* phys addr of kernel level 3 */
uint64_t                KPML4phys;      /* phys addr of kernel level 4 */


/*
 * Data for the pv entry allocation mechanism
 */
static vm_zone_t pvzone;
static struct vm_zone pvzone_store;
static struct vm_object pvzone_obj;
static int pv_entry_count=0, pv_entry_max=0, pv_entry_high_water=0;
static int pmap_pagedaemon_waken = 0;
static struct pv_entry *pvinit;

/*
 * All those kernel PT submaps that BSD is so fond of
 */
pt_entry_t *CMAP1 = NULL, *ptmmap;
caddr_t CADDR1 = NULL;
static pt_entry_t *msgbufmap;

uint64_t KPTphys;

static PMAP_INLINE void free_pv_entry (pv_entry_t pv);
static pv_entry_t get_pv_entry (void);
static void     i386_protection_init (void);
static __inline void    pmap_clearbit (vm_page_t m, int bit);

static void     pmap_remove_all (vm_page_t m);
static int pmap_remove_pte (struct pmap *pmap, pt_entry_t *ptq,
                                vm_offset_t sva);
static void pmap_remove_page (struct pmap *pmap, vm_offset_t va);
static int pmap_remove_entry (struct pmap *pmap, vm_page_t m,
                                vm_offset_t va);
static boolean_t pmap_testbit (vm_page_t m, int bit);
static void pmap_insert_entry (pmap_t pmap, vm_offset_t va,
                vm_page_t mpte, vm_page_t m);

static vm_page_t pmap_allocpte (pmap_t pmap, vm_offset_t va);

static int pmap_release_free_page (pmap_t pmap, vm_page_t p);
static vm_page_t _pmap_allocpte (pmap_t pmap, vm_pindex_t ptepindex);
#if JGPMAP32
static pt_entry_t * pmap_pte_quick (pmap_t pmap, vm_offset_t va);
#endif
static vm_page_t pmap_page_lookup (vm_object_t object, vm_pindex_t pindex);
static int pmap_unuse_pt (pmap_t, vm_offset_t, vm_page_t);

/*
 * pmap_pte_quick:
 *
 *      Super fast pmap_pte routine best used when scanning the pv lists.
 *      This eliminates many course-grained invltlb calls.  Note that many of
 *      the pv list scans are across different pmaps and it is very wasteful
 *      to do an entire invltlb when checking a single mapping.
 *
 *      Should only be called while in a critical section.
 */
#if JGPMAP32
static __inline pt_entry_t *pmap_pte(pmap_t pmap, vm_offset_t va);

static pt_entry_t *
pmap_pte_quick(pmap_t pmap, vm_offset_t va)
{
        return pmap_pte(pmap, va);
}
#endif

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

/* Return various clipped indexes for a given VA */
static __inline vm_pindex_t
pmap_pte_index(vm_offset_t va)
{

        return ((va >> PAGE_SHIFT) & ((1ul << NPTEPGSHIFT) - 1));
}

static __inline vm_pindex_t
pmap_pde_index(vm_offset_t va)
{

        return ((va >> PDRSHIFT) & ((1ul << NPDEPGSHIFT) - 1));
}

static __inline vm_pindex_t
pmap_pdpe_index(vm_offset_t va)
{

        return ((va >> PDPSHIFT) & ((1ul << NPDPEPGSHIFT) - 1));
}

static __inline vm_pindex_t
pmap_pml4e_index(vm_offset_t va)
{

        return ((va >> PML4SHIFT) & ((1ul << NPML4EPGSHIFT) - 1));
}

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

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

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

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

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

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

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

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

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

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

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

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

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

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


#if JGV
PMAP_INLINE pt_entry_t *
vtopte(vm_offset_t va)
{
        uint64_t mask = ((1ul << (NPTEPGSHIFT + NPDEPGSHIFT +
                                  NPDPEPGSHIFT + NPML4EPGSHIFT)) - 1);

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

static __inline pd_entry_t *
vtopde(vm_offset_t va)
{
        uint64_t mask = ((1ul << (NPDEPGSHIFT + NPDPEPGSHIFT +
                                  NPML4EPGSHIFT)) - 1);

        return (PDmap + ((va >> PDRSHIFT) & mask));
}
#else
static PMAP_INLINE pt_entry_t *
vtopte(vm_offset_t va)
{
        pt_entry_t *x;
        x = pmap_pte(&kernel_pmap, va);
        assert(x != NULL);
        return x;
}

static __inline pd_entry_t *
vtopde(vm_offset_t va)
{
        pd_entry_t *x;
        x = pmap_pde(&kernel_pmap, va);
        assert(x != NULL);
        return x;
}
#endif

static uint64_t
allocpages(vm_paddr_t *firstaddr, int n)
{
        uint64_t ret;

        ret = *firstaddr;
#if JGV
        bzero((void *)ret, n * PAGE_SIZE);
#endif
        *firstaddr += n * PAGE_SIZE;
        return (ret);
}

static void
create_pagetables(vm_paddr_t *firstaddr, int64_t ptov_offset)
{
        int i;
        pml4_entry_t *KPML4virt;
        pdp_entry_t *KPDPvirt;
        pd_entry_t *KPDvirt;
        pt_entry_t *KPTvirt;
        int kpml4i = pmap_pml4e_index(ptov_offset);
        int kpdpi = pmap_pdpe_index(ptov_offset);

        /*
         * Calculate NKPT - number of kernel page tables.  We have to
         * accomodoate prealloction of the vm_page_array, dump bitmap,
         * MSGBUF_SIZE, and other stuff.  Be generous.
         *
         * Maxmem is in pages.
         */
        nkpt = (Maxmem * (sizeof(struct vm_page) * 2) + MSGBUF_SIZE) / NBPDR;

        /*
         * Allocate pages
         */
        KPML4phys = allocpages(firstaddr, 1);
        KPDPphys = allocpages(firstaddr, NKPML4E);
        KPDphys = allocpages(firstaddr, NKPDPE);
        KPTphys = allocpages(firstaddr, nkpt);

        KPML4virt = (pml4_entry_t *)PHYS_TO_DMAP(KPML4phys);
        KPDPvirt = (pdp_entry_t *)PHYS_TO_DMAP(KPDPphys);
        KPDvirt = (pd_entry_t *)PHYS_TO_DMAP(KPDphys);
        KPTvirt = (pt_entry_t *)PHYS_TO_DMAP(KPTphys);

        bzero(KPML4virt, 1 * PAGE_SIZE);
        bzero(KPDPvirt, NKPML4E * PAGE_SIZE);
        bzero(KPDvirt, NKPDPE * PAGE_SIZE);
        bzero(KPTvirt, nkpt * PAGE_SIZE);

        /* Now map the page tables at their location within PTmap */
        for (i = 0; i < nkpt; i++) {
                KPDvirt[i] = KPTphys + (i << PAGE_SHIFT);
                KPDvirt[i] |= VPTE_R | VPTE_W | VPTE_V;
        }

        /* And connect up the PD to the PDP */
        for (i = 0; i < NKPDPE; i++) {
                KPDPvirt[i + kpdpi] = KPDphys + (i << PAGE_SHIFT);
                KPDPvirt[i + kpdpi] |= VPTE_R | VPTE_W | VPTE_V;
        }

        /* And recursively map PML4 to itself in order to get PTmap */
        KPML4virt[PML4PML4I] = KPML4phys;
        KPML4virt[PML4PML4I] |= VPTE_R | VPTE_W | VPTE_V;

        /* Connect the KVA slot up to the PML4 */
        KPML4virt[kpml4i] = KPDPphys;
        KPML4virt[kpml4i] |= VPTE_R | VPTE_W | VPTE_V;
}

/*
 * Typically used to initialize a fictitious page by vm/device_pager.c
 */
void
pmap_page_init(struct vm_page *m)
{
        vm_page_init(m);
        TAILQ_INIT(&m->md.pv_list);
}

/*
 *      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, int64_t ptov_offset)
{
        vm_offset_t va;
        pt_entry_t *pte;

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

        virtual_start = KvaStart + *firstaddr;
        virtual_end = KvaEnd;

        /*
         * Initialize protection array.
         */
        i386_protection_init();

        /*
         * The kernel's pmap is statically allocated so we don't have to use
         * pmap_create, which is unlikely to work correctly at this part of
         * the boot sequence (XXX and which no longer exists).
         *
         * The kernel_pmap's pm_pteobj is used only for locking and not
         * for mmu pages.
         */
        kernel_pmap.pm_pml4 = (pml4_entry_t *)PHYS_TO_DMAP(KPML4phys);
        kernel_pmap.pm_count = 1;
        kernel_pmap.pm_active = (cpumask_t)-1;  /* don't allow deactivation */
        kernel_pmap.pm_pteobj = &kernel_object;
        TAILQ_INIT(&kernel_pmap.pm_pvlist);
        TAILQ_INIT(&kernel_pmap.pm_pvlist_free);
        lwkt_token_init(&kernel_pmap.pm_token, "kpmap_tok");
        spin_init(&kernel_pmap.pm_spin);

        /*
         * 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_start;
        pte = pmap_pte(&kernel_pmap, va);

        /*
         * CMAP1/CMAP2 are used for zeroing and copying pages.
         */
        SYSMAP(caddr_t, CMAP1, CADDR1, 1)

#if JGV
        /*
         * Crashdump maps.
         */
        SYSMAP(caddr_t, pt_crashdumpmap, crashdumpmap, MAXDUMPPGS);
#endif

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

        /*
         * msgbufp is used to map the system message buffer.
         * XXX msgbufmap is not used.
         */
        SYSMAP(struct msgbuf *, msgbufmap, msgbufp,
               atop(round_page(MSGBUF_SIZE)))

        virtual_start = va;

        *CMAP1 = 0;

        cpu_invltlb();
}

/*
 *      Initialize the pmap module.
 *      Called by vm_init, to initialize any structures that the pmap
 *      system needs to map virtual memory.
 *      pmap_init has been enhanced to support in a fairly consistant
 *      way, discontiguous physical memory.
 */
void
pmap_init(void)
{
        int i;
        int initial_pvs;

        /*
         * object for kernel page table pages
         */
        /* JG I think the number can be arbitrary */
        kptobj = vm_object_allocate(OBJT_DEFAULT, 5);

        /*
         * Allocate memory for random pmap data structures.  Includes the
         * pv_head_table.
         */

        for(i = 0; i < vm_page_array_size; i++) {
                vm_page_t m;

                m = &vm_page_array[i];
                TAILQ_INIT(&m->md.pv_list);
                m->md.pv_list_count = 0;
        }

        /*
         * init the pv free list
         */
        initial_pvs = vm_page_array_size;
        if (initial_pvs < MINPV)
                initial_pvs = MINPV;
        pvzone = &pvzone_store;
        pvinit = (struct pv_entry *) kmem_alloc(&kernel_map,
                initial_pvs * sizeof (struct pv_entry));
        zbootinit(pvzone, "PV ENTRY", sizeof (struct pv_entry), pvinit,
                initial_pvs);

        /*
         * Now it is safe to enable pv_table recording.
         */
        pmap_initialized = TRUE;
}

/*
 * 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.
 */
void
pmap_init2(void)
{
        int shpgperproc = PMAP_SHPGPERPROC;

        TUNABLE_INT_FETCH("vm.pmap.shpgperproc", &shpgperproc);
        pv_entry_max = shpgperproc * maxproc + vm_page_array_size;
        TUNABLE_INT_FETCH("vm.pmap.pv_entries", &pv_entry_max);
        pv_entry_high_water = 9 * (pv_entry_max / 10);
        zinitna(pvzone, &pvzone_obj, NULL, 0, pv_entry_max, ZONE_INTERRUPT, 1);
}


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

/*
 * The modification bit is not tracked for any pages in this range. XXX
 * such pages in this maps should always use pmap_k*() functions and not
 * be managed anyhow.
 *
 * XXX User and kernel address spaces are independant for virtual kernels,
 * this function only applies to the kernel pmap.
 */
static int
pmap_track_modified(pmap_t pmap, vm_offset_t va)
{
        if (pmap != &kernel_pmap)
                return 1;
        if ((va < clean_sva) || (va >= clean_eva))
                return 1;
        else
                return 0;
}

/*
 * Extract the physical page address associated with the map/VA pair.
 *
 * No requirements.
 */
vm_paddr_t
pmap_extract(pmap_t pmap, vm_offset_t va)
{
        vm_paddr_t rtval;
        pt_entry_t *pte;
        pd_entry_t pde, *pdep;

        lwkt_gettoken(&vm_token);
        rtval = 0;
        pdep = pmap_pde(pmap, va);
        if (pdep != NULL) {
                pde = *pdep;
                if (pde) {
                        if ((pde & VPTE_PS) != 0) {
                                /* JGV */
                                rtval = (pde & PG_PS_FRAME) | (va & PDRMASK);
                        } else {
                                pte = pmap_pde_to_pte(pdep, va);
                                rtval = (*pte & VPTE_FRAME) | (va & PAGE_MASK);
                        }
                }
        }
        lwkt_reltoken(&vm_token);
        return rtval;
}

/*
 *      Routine:        pmap_kextract
 *      Function:
 *              Extract the physical page address associated
 *              kernel virtual address.
 */
vm_paddr_t
pmap_kextract(vm_offset_t va)
{
        pd_entry_t pde;
        vm_paddr_t pa;

        KKASSERT(va >= KvaStart && va < KvaEnd);

        /*
         * The DMAP region is not included in [KvaStart, KvaEnd)
         */
#if 0
        if (va >= DMAP_MIN_ADDRESS && va < DMAP_MAX_ADDRESS) {
                pa = DMAP_TO_PHYS(va);
        } else {
#endif
                pde = *vtopde(va);
                if (pde & VPTE_PS) {
                        /* JGV */
                        pa = (pde & PG_PS_FRAME) | (va & PDRMASK);
                } else {
                        /*
                         * Beware of a concurrent promotion that changes the
                         * PDE at this point!  For example, vtopte() must not
                         * be used to access the PTE because it would use the
                         * new PDE.  It is, however, safe to use the old PDE
                         * because the page table page is preserved by the
                         * promotion.
                         */
                        pa = *pmap_pde_to_pte(&pde, va);
                        pa = (pa & VPTE_FRAME) | (va & PAGE_MASK);
                }
#if 0
        }
#endif
        return pa;
}

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

/*
 * Enter a mapping into kernel_pmap.  Mappings created in this fashion
 * are not managed.  Mappings must be immediately accessible on all cpus.
 *
 * Call pmap_inval_pte() to invalidate the virtual pte and clean out the
 * real pmap and handle related races before storing the new vpte.
 */
void
pmap_kenter(vm_offset_t va, vm_paddr_t pa)
{
        pt_entry_t *pte;
        pt_entry_t npte;

        KKASSERT(va >= KvaStart && va < KvaEnd);
        npte = pa | VPTE_R | VPTE_W | VPTE_V;
        pte = vtopte(va);
        if (*pte & VPTE_V)
                pmap_inval_pte(pte, &kernel_pmap, va);
        *pte = npte;
}

/*
 * Enter an unmanaged KVA mapping for the private use of the current
 * cpu only.  pmap_kenter_sync() may be called to make the mapping usable
 * by other cpus.
 *
 * It is illegal for the mapping to be accessed by other cpus unleess
 * pmap_kenter_sync*() is called.
 */
void
pmap_kenter_quick(vm_offset_t va, vm_paddr_t pa)
{
        pt_entry_t *pte;
        pt_entry_t npte;

        KKASSERT(va >= KvaStart && va < KvaEnd);

        npte = (vpte_t)pa | VPTE_R | VPTE_W | VPTE_V;
        pte = vtopte(va);
        if (*pte & VPTE_V)
                pmap_inval_pte_quick(pte, &kernel_pmap, va);
        *pte = npte;
        //cpu_invlpg((void *)va);
}

/*
 * Synchronize a kvm mapping originally made for the private use on
 * some other cpu so it can be used on all cpus.
 *
 * XXX add MADV_RESYNC to improve performance.
 */
void
pmap_kenter_sync(vm_offset_t va)
{
        madvise((void *)va, PAGE_SIZE, MADV_INVAL);
}

/*
 * Synchronize a kvm mapping originally made for the private use on
 * some other cpu so it can be used on our cpu.  Turns out to be the
 * same madvise() call, because we have to sync the real pmaps anyway.
 *
 * XXX add MADV_RESYNC to improve performance.
 */
void
pmap_kenter_sync_quick(vm_offset_t va)
{
        madvise((void *)va, PAGE_SIZE, MADV_INVAL);
}

/*
 * Remove an unmanaged mapping created with pmap_kenter*().
 */
void
pmap_kremove(vm_offset_t va)
{
        pt_entry_t *pte;

        KKASSERT(va >= KvaStart && va < KvaEnd);

        pte = vtopte(va);
        if (*pte & VPTE_V)
                pmap_inval_pte(pte, &kernel_pmap, va);
        *pte = 0;
}

/*
 * Remove an unmanaged mapping created with pmap_kenter*() but synchronize
 * only with this cpu.
 *
 * Unfortunately because we optimize new entries by testing VPTE_V later
 * on, we actually still have to synchronize with all the cpus.  XXX maybe
 * store a junk value and test against 0 in the other places instead?
 */
void
pmap_kremove_quick(vm_offset_t va)
{
        pt_entry_t *pte;

        KKASSERT(va >= KvaStart && va < KvaEnd);

        pte = vtopte(va);
        if (*pte & VPTE_V)
                pmap_inval_pte(pte, &kernel_pmap, va); /* NOT _quick */
        *pte = 0;
}

/*
 *      Used to map a range of physical addresses into kernel
 *      virtual address space.
 *
 *      For now, VM is already on, we only need to map the
 *      specified memory.
 */
vm_offset_t
pmap_map(vm_offset_t *virtp, vm_paddr_t start, vm_paddr_t end, int prot)
{
        return PHYS_TO_DMAP(start);
}


/*
 * Map a set of unmanaged VM pages into KVM.
 */
void
pmap_qenter(vm_offset_t va, vm_page_t *m, int count)
{
        vm_offset_t end_va;

        end_va = va + count * PAGE_SIZE;
        KKASSERT(va >= KvaStart && end_va < KvaEnd);

        while (va < end_va) {
                pt_entry_t *pte;

                pte = vtopte(va);
                if (*pte & VPTE_V)
                        pmap_inval_pte(pte, &kernel_pmap, va);
                *pte = VM_PAGE_TO_PHYS(*m) | VPTE_R | VPTE_W | VPTE_V;
                va += PAGE_SIZE;
                m++;
        }
}

/*
 * Undo the effects of pmap_qenter*().
 */
void
pmap_qremove(vm_offset_t va, int count)
{
        vm_offset_t end_va;

        end_va = va + count * PAGE_SIZE;
        KKASSERT(va >= KvaStart && end_va < KvaEnd);

        while (va < end_va) {
                pt_entry_t *pte;

                pte = vtopte(va);
                if (*pte & VPTE_V)
                        pmap_inval_pte(pte, &kernel_pmap, va);
                *pte = 0;
                va += PAGE_SIZE;
        }
}

/*
 * This routine works like vm_page_lookup() but also blocks as long as the
 * page is busy.  This routine does not busy the page it returns.
 *
 * Unless the caller is managing objects whos pages are in a known state,
 * the call should be made with a critical section held so the page's object
 * association remains valid on return.
 */
static vm_page_t
pmap_page_lookup(vm_object_t object, vm_pindex_t pindex)
{
        vm_page_t m;

        ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
        m = vm_page_lookup_busy_wait(object, pindex, FALSE, "pplookp");

        return(m);
}

/*
 * Create a new thread and optionally associate it with a (new) process.
 * NOTE! the new thread's cpu may not equal the current cpu.
 */
void
pmap_init_thread(thread_t td)
{
        /* enforce pcb placement */
        td->td_pcb = (struct pcb *)(td->td_kstack + td->td_kstack_size) - 1;
        td->td_savefpu = &td->td_pcb->pcb_save;
        td->td_sp = (char *)td->td_pcb - 16; /* JG is -16 needed on x86_64? */
}

/*
 * This routine directly affects the fork perf for a process.
 */
void
pmap_init_proc(struct proc *p)
{
}

/***************************************************
 * Page table page management routines.....
 ***************************************************/

static __inline int pmap_unwire_pte_hold(pmap_t pmap, vm_offset_t va,
                        vm_page_t m);

/*
 * This routine unholds page table pages, and if the hold count
 * drops to zero, then it decrements the wire count.
 *
 * We must recheck that this is the last hold reference after busy-sleeping
 * on the page.
 */
static int
_pmap_unwire_pte_hold(pmap_t pmap, vm_offset_t va, vm_page_t m)
{
        vm_page_busy_wait(m, FALSE, "pmuwpt");
        KASSERT(m->queue == PQ_NONE,
                ("_pmap_unwire_pte_hold: %p->queue != PQ_NONE", m));

        if (m->hold_count == 1) {
                /*
                 * Unmap the page table page.
                 */
                //abort(); /* JG */
                /* pmap_inval_add(info, pmap, -1); */

                if (m->pindex >= (NUPDE + NUPDPE)) {
                        /* PDP page */
                        pml4_entry_t *pml4;
                        pml4 = pmap_pml4e(pmap, va);
                        *pml4 = 0;
                } else if (m->pindex >= NUPDE) {
                        /* PD page */
                        pdp_entry_t *pdp;
                        pdp = pmap_pdpe(pmap, va);
                        *pdp = 0;
                } else {
                        /* PT page */
                        pd_entry_t *pd;
                        pd = pmap_pde(pmap, va);
                        *pd = 0;
                }

                KKASSERT(pmap->pm_stats.resident_count > 0);
                --pmap->pm_stats.resident_count;

                if (pmap->pm_ptphint == m)
                        pmap->pm_ptphint = NULL;

                if (m->pindex < NUPDE) {
                        /* We just released a PT, unhold the matching PD */
                        vm_page_t pdpg;

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

                        pdppg = PHYS_TO_VM_PAGE(*pmap_pml4e(pmap, va) & VPTE_FRAME);
                        pmap_unwire_pte_hold(pmap, va, pdppg);
                }

                /*
                 * This was our last hold, the page had better be unwired
                 * after we decrement wire_count.
                 *
                 * FUTURE NOTE: shared page directory page could result in
                 * multiple wire counts.
                 */
                vm_page_unhold(m);
                --m->wire_count;
                KKASSERT(m->wire_count == 0);
                atomic_add_int(&vmstats.v_wire_count, -1);
                vm_page_flag_clear(m, PG_MAPPED | PG_WRITEABLE);
                vm_page_flash(m);
                vm_page_free_zero(m);
                return 1;
        } else {
                KKASSERT(m->hold_count > 1);
                vm_page_unhold(m);
                vm_page_wakeup(m);
                return 0;
        }
}

static __inline int
pmap_unwire_pte_hold(pmap_t pmap, vm_offset_t va, vm_page_t m)
{
        KKASSERT(m->hold_count > 0);
        if (m->hold_count > 1) {
                vm_page_unhold(m);
                return 0;
        } else {
                return _pmap_unwire_pte_hold(pmap, va, m);
        }
}

/*
 * 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 mpte)
{
        /* JG Use FreeBSD/amd64 or FreeBSD/i386 ptepde approaches? */
        vm_pindex_t ptepindex;

        ASSERT_LWKT_TOKEN_HELD(vm_object_token(pmap->pm_pteobj));

        if (mpte == NULL) {
                /*
                 * page table pages in the kernel_pmap are not managed.
                 */
                if (pmap == &kernel_pmap)
                        return(0);
                ptepindex = pmap_pde_pindex(va);
                if (pmap->pm_ptphint &&
                        (pmap->pm_ptphint->pindex == ptepindex)) {
                        mpte = pmap->pm_ptphint;
                } else {
                        mpte = pmap_page_lookup(pmap->pm_pteobj, ptepindex);
                        pmap->pm_ptphint = mpte;
                        vm_page_wakeup(mpte);
                }
        }

        return pmap_unwire_pte_hold(pmap, va, mpte);
}

/*
 * Initialize pmap0/vmspace0 .  Since process 0 never enters user mode we
 * just dummy it up so it works well enough for fork().
 *
 * In DragonFly, process pmaps may only be used to manipulate user address
 * space, never kernel address space.
 */
void
pmap_pinit0(struct pmap *pmap)
{
        pmap_pinit(pmap);
}

/*
 * Initialize a preallocated and zeroed pmap structure,
 * such as one in a vmspace structure.
 */
void
pmap_pinit(struct pmap *pmap)
{
        vm_page_t ptdpg;

        /*
         * No need to allocate page table space yet but we do need a valid
         * page directory table.
         */
        if (pmap->pm_pml4 == NULL) {
                pmap->pm_pml4 =
                    (pml4_entry_t *)kmem_alloc_pageable(&kernel_map, PAGE_SIZE);
        }

        /*
         * Allocate an object for the ptes
         */
        if (pmap->pm_pteobj == NULL)
                pmap->pm_pteobj = vm_object_allocate(OBJT_DEFAULT, NUPDE + NUPDPE + PML4PML4I + 1);

        /*
         * Allocate the page directory page, unless we already have
         * one cached.  If we used the cached page the wire_count will
         * already be set appropriately.
         */
        if ((ptdpg = pmap->pm_pdirm) == NULL) {
                ptdpg = vm_page_grab(pmap->pm_pteobj,
                                     NUPDE + NUPDPE + PML4PML4I,
                                     VM_ALLOC_NORMAL | VM_ALLOC_RETRY |
                                     VM_ALLOC_ZERO);
                pmap->pm_pdirm = ptdpg;
                vm_page_flag_clear(ptdpg, PG_MAPPED);
                vm_page_wire(ptdpg);
                vm_page_wakeup(ptdpg);
                pmap_kenter((vm_offset_t)pmap->pm_pml4, VM_PAGE_TO_PHYS(ptdpg));
        }
        pmap->pm_count = 1;
        pmap->pm_active = 0;
        pmap->pm_ptphint = NULL;
        TAILQ_INIT(&pmap->pm_pvlist);
        TAILQ_INIT(&pmap->pm_pvlist_free);
        spin_init(&pmap->pm_spin);
        lwkt_token_init(&pmap->pm_token, "pmap_tok");
        bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
        pmap->pm_stats.resident_count = 1;
}

/*
 * Clean up a pmap structure so it can be physically freed.  This routine
 * is called by the vmspace dtor function.  A great deal of pmap data is
 * left passively mapped to improve vmspace management so we have a bit
 * of cleanup work to do here.
 *
 * No requirements.
 */
void
pmap_puninit(pmap_t pmap)
{
        vm_page_t p;

        KKASSERT(pmap->pm_active == 0);
        if ((p = pmap->pm_pdirm) != NULL) {
                KKASSERT(pmap->pm_pml4 != NULL);
                pmap_kremove((vm_offset_t)pmap->pm_pml4);
                vm_page_busy_wait(p, FALSE, "pgpun");
                p->wire_count--;
                atomic_add_int(&vmstats.v_wire_count, -1);
                vm_page_free_zero(p);
                pmap->pm_pdirm = NULL;
        }
        if (pmap->pm_pml4) {
                kmem_free(&kernel_map, (vm_offset_t)pmap->pm_pml4, PAGE_SIZE);
                pmap->pm_pml4 = NULL;
        }
        if (pmap->pm_pteobj) {
                vm_object_deallocate(pmap->pm_pteobj);
                pmap->pm_pteobj = NULL;
        }
}

/*
 * Wire in kernel global address entries.  To avoid a race condition
 * between pmap initialization and pmap_growkernel, this procedure
 * adds the pmap to the master list (which growkernel scans to update),
 * then copies the template.
 *
 * In a virtual kernel there are no kernel global address entries.
 *
 * No requirements.
 */
void
pmap_pinit2(struct pmap *pmap)
{
        spin_lock(&pmap_spin);
        TAILQ_INSERT_TAIL(&pmap_list, pmap, pm_pmnode);
        spin_unlock(&pmap_spin);
}

/*
 * Attempt to release and free a vm_page in a pmap.  Returns 1 on success,
 * 0 on failure (if the procedure had to sleep).
 *
 * When asked to remove the page directory page itself, we actually just
 * leave it cached so we do not have to incur the SMP inval overhead of
 * removing the kernel mapping.  pmap_puninit() will take care of it.
 */
static int
pmap_release_free_page(struct pmap *pmap, vm_page_t p)
{
        /*
         * This code optimizes the case of freeing non-busy
         * page-table pages.  Those pages are zero now, and
         * might as well be placed directly into the zero queue.
         */
        if (vm_page_busy_try(p, FALSE)) {
                vm_page_sleep_busy(p, FALSE, "pmaprl");
                return 0;
        }

        /*
         * Remove the page table page from the processes address space.
         */
        if (p->pindex == NUPDE + NUPDPE + PML4PML4I) {
                /*
                 * We are the pml4 table itself.
                 */
                /* XXX anything to do here? */
        } else if (p->pindex >= (NUPDE + NUPDPE)) {
                /*
                 * We are a PDP page.
                 * We look for the PML4 entry that points to us.
                 */
                vm_page_t m4 = vm_page_lookup(pmap->pm_pteobj, NUPDE + NUPDPE + PML4PML4I);
                KKASSERT(m4 != NULL);
                pml4_entry_t *pml4 = (pml4_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m4));
                int idx = (p->pindex - (NUPDE + NUPDPE)) % NPML4EPG;
                KKASSERT(pml4[idx] != 0);
                pml4[idx] = 0;
                m4->hold_count--;
                /* JG What about wire_count? */
        } else if (p->pindex >= NUPDE) {
                /*
                 * We are a PD page.
                 * We look for the PDP entry that points to us.
                 */
                vm_page_t m3 = vm_page_lookup(pmap->pm_pteobj, NUPDE + NUPDPE + (p->pindex - NUPDE) / NPDPEPG);
                KKASSERT(m3 != NULL);
                pdp_entry_t *pdp = (pdp_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m3));
                int idx = (p->pindex - NUPDE) % NPDPEPG;
                KKASSERT(pdp[idx] != 0);
                pdp[idx] = 0;
                m3->hold_count--;
                /* JG What about wire_count? */
        } else {
                /* We are a PT page.
                 * We look for the PD entry that points to us.
                 */
                vm_page_t m2 = vm_page_lookup(pmap->pm_pteobj, NUPDE + p->pindex / NPDEPG);
                KKASSERT(m2 != NULL);
                pd_entry_t *pd = (pd_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m2));
                int idx = p->pindex % NPDEPG;
                pd[idx] = 0;
                m2->hold_count--;
                /* JG What about wire_count? */
        }
        KKASSERT(pmap->pm_stats.resident_count > 0);
        --pmap->pm_stats.resident_count;

        if (p->hold_count)  {
                panic("pmap_release: freeing held page table page");
        }
        if (pmap->pm_ptphint && (pmap->pm_ptphint->pindex == p->pindex))
                pmap->pm_ptphint = NULL;

        /*
         * We leave the top-level page table page cached, wired, and mapped in
         * the pmap until the dtor function (pmap_puninit()) gets called.
         * However, still clean it up so we can set PG_ZERO.
         */
        if (p->pindex == NUPDE + NUPDPE + PML4PML4I) {
                bzero(pmap->pm_pml4, PAGE_SIZE);
                vm_page_flag_set(p, PG_ZERO);
                vm_page_wakeup(p);
        } else {
                abort();
                p->wire_count--;
                atomic_add_int(&vmstats.v_wire_count, -1);
                /* JG eventually revert to using vm_page_free_zero() */
                vm_page_free(p);
        }
        return 1;
}

/*
 * this routine is called if the page table page is not
 * mapped correctly.
 */
static vm_page_t
_pmap_allocpte(pmap_t pmap, vm_pindex_t ptepindex)
{
        vm_page_t m, pdppg, pdpg;

        /*
         * Find or fabricate a new pagetable page.  Handle allocation
         * races by checking m->valid.
         */
        m = vm_page_grab(pmap->pm_pteobj, ptepindex,
                         VM_ALLOC_NORMAL | VM_ALLOC_ZERO | VM_ALLOC_RETRY);

        KASSERT(m->queue == PQ_NONE,
                ("_pmap_allocpte: %p->queue != PQ_NONE", m));

        /*
         * Increment the hold count for the page we will be returning to
         * the caller.
         */
        m->hold_count++;
        vm_page_wire(m);

        /*
         * Map the pagetable page into the process address space, if
         * it isn't already there.
         */
        ++pmap->pm_stats.resident_count;

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

                /* Wire up a new PDP page */
                pml4index = ptepindex - (NUPDE + NUPDPE);
                pml4 = &pmap->pm_pml4[pml4index];
                *pml4 = VM_PAGE_TO_PHYS(m) | VPTE_R | VPTE_W | VPTE_V |
                        VPTE_A | VPTE_M;
        } else if (ptepindex >= NUPDE) {
                vm_pindex_t pml4index;
                vm_pindex_t pdpindex;
                pml4_entry_t *pml4;
                pdp_entry_t *pdp;

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

                pml4 = &pmap->pm_pml4[pml4index];
                if ((*pml4 & VPTE_V) == 0) {
                        /* Have to allocate a new PDP page, recurse */
                        if (_pmap_allocpte(pmap, NUPDE + NUPDPE + pml4index)
                             == NULL) {
                                --m->wire_count;
                                vm_page_free(m);
                                return (NULL);
                        }
                } else {
                        /* Add reference to the PDP page */
                        pdppg = PHYS_TO_VM_PAGE(*pml4 & VPTE_FRAME);
                        pdppg->hold_count++;
                }
                pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & VPTE_FRAME);

                /* Now find the pdp page */
                pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)];
                KKASSERT(*pdp == 0);    /* JG DEBUG64 */
                *pdp = VM_PAGE_TO_PHYS(m) | VPTE_R | VPTE_W | VPTE_V |
                       VPTE_A | VPTE_M;
        } else {
                vm_pindex_t pml4index;
                vm_pindex_t pdpindex;
                pml4_entry_t *pml4;
                pdp_entry_t *pdp;
                pd_entry_t *pd;

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

                /* First, find the pdp and check that its valid. */
                pml4 = &pmap->pm_pml4[pml4index];
                if ((*pml4 & VPTE_V) == 0) {
                        /* We miss a PDP page. We ultimately need a PD page.
                         * Recursively allocating a PD page will allocate
                         * the missing PDP page and will also allocate
                         * the PD page we need.
                         */
                        /* Have to allocate a new PD page, recurse */
                        if (_pmap_allocpte(pmap, NUPDE + pdpindex)
                             == NULL) {
                                --m->wire_count;
                                vm_page_free(m);
                                return (NULL);
                        }
                        pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & VPTE_FRAME);
                        pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)];
                } else {
                        pdp = (pdp_entry_t *)PHYS_TO_DMAP(*pml4 & VPTE_FRAME);
                        pdp = &pdp[pdpindex & ((1ul << NPDPEPGSHIFT) - 1)];
                        if ((*pdp & VPTE_V) == 0) {
                                /* Have to allocate a new PD page, recurse */
                                if (_pmap_allocpte(pmap, NUPDE + pdpindex)
                                     == NULL) {
                                        --m->wire_count;
                                        vm_page_free(m);
                                        return (NULL);
                                }
                        } else {
                                /* Add reference to the PD page */
                                pdpg = PHYS_TO_VM_PAGE(*pdp & VPTE_FRAME);
                                pdpg->hold_count++;
                        }
                }
                pd = (pd_entry_t *)PHYS_TO_DMAP(*pdp & VPTE_FRAME);

                /* Now we know where the page directory page is */
                pd = &pd[ptepindex & ((1ul << NPDEPGSHIFT) - 1)];
                KKASSERT(*pd == 0);     /* JG DEBUG64 */
                *pd = VM_PAGE_TO_PHYS(m) | VPTE_R | VPTE_W | VPTE_V |
                      VPTE_A | VPTE_M;
        }

        /*
         * Set the page table hint
         */
        pmap->pm_ptphint = m;
        vm_page_flag_set(m, PG_MAPPED);
        vm_page_wakeup(m);

        return m;
}

/*
 * Determine the page table page required to access the VA in the pmap
 * and allocate it if necessary.  Return a held vm_page_t for the page.
 *
 * Only used with user pmaps.
 */
static vm_page_t
pmap_allocpte(pmap_t pmap, vm_offset_t va)
{
        vm_pindex_t ptepindex;
        pd_entry_t *pd;
        vm_page_t m;

        ASSERT_LWKT_TOKEN_HELD(vm_object_token(pmap->pm_pteobj));

        /*
         * Calculate pagetable page index
         */
        ptepindex = pmap_pde_pindex(va);

        /*
         * Get the page directory entry
         */
        pd = pmap_pde(pmap, va);

        /*
         * This supports switching from a 2MB page to a
         * normal 4K page.
         */
        if (pd != NULL && (*pd & (VPTE_PS | VPTE_V)) == (VPTE_PS | VPTE_V)) {
                panic("no promotion/demotion yet");
                *pd = 0;
                pd = NULL;
                /*cpu_invltlb();*/
                /*smp_invltlb();*/
        }

        /*
         * If the page table page is mapped, we just increment the
         * hold count, and activate it.
         */
        if (pd != NULL && (*pd & VPTE_V) != 0) {
                /* YYY hint is used here on i386 */
                m = pmap_page_lookup(pmap->pm_pteobj, ptepindex);
                pmap->pm_ptphint = m;
                vm_page_hold(m);
                vm_page_wakeup(m);
                return m;
        }
        /*
         * Here if the pte page isn't mapped, or if it has been deallocated.
         */
        return _pmap_allocpte(pmap, ptepindex);
}


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

/*
 * Release any resources held by the given physical map.
 * Called when a pmap initialized by pmap_pinit is being released.
 * Should only be called if the map contains no valid mappings.
 *
 * Caller must hold pmap->pm_token
 */
static int pmap_release_callback(struct vm_page *p, void *data);

void
pmap_release(struct pmap *pmap)
{
        vm_object_t object = pmap->pm_pteobj;
        struct rb_vm_page_scan_info info;

        KKASSERT(pmap != &kernel_pmap);

#if defined(DIAGNOSTIC)
        if (object->ref_count != 1)
                panic("pmap_release: pteobj reference count != 1");
#endif

        info.pmap = pmap;
        info.object = object;

        spin_lock(&pmap_spin);
        TAILQ_REMOVE(&pmap_list, pmap, pm_pmnode);
        spin_unlock(&pmap_spin);

        vm_object_hold(object);
        do {
                info.error = 0;
                info.mpte = NULL;
                info.limit = object->generation;

                vm_page_rb_tree_RB_SCAN(&object->rb_memq, NULL,
                                        pmap_release_callback, &info);
                if (info.error == 0 && info.mpte) {
                        if (!pmap_release_free_page(pmap, info.mpte))
                                info.error = 1;
                }
        } while (info.error);
        vm_object_drop(object);
}

static int
pmap_release_callback(struct vm_page *p, void *data)
{
        struct rb_vm_page_scan_info *info = data;

        if (p->pindex == NUPDE + NUPDPE + PML4PML4I) {
                info->mpte = p;
                return(0);
        }
        if (!pmap_release_free_page(info->pmap, p)) {
                info->error = 1;
                return(-1);
        }
        if (info->object->generation != info->limit) {
                info->error = 1;
                return(-1);
        }
        return(0);
}

/*
 * Grow the number of kernel page table entries, if needed.
 *
 * No requirements.
 */
void
pmap_growkernel(vm_offset_t kstart, vm_offset_t kend)
{
        vm_offset_t addr;
        vm_paddr_t paddr;
        vm_offset_t ptppaddr;
        vm_page_t nkpg;
        pd_entry_t *pde, newpdir;
        pdp_entry_t newpdp;

        addr = kend;

        vm_object_hold(kptobj);
        if (kernel_vm_end == 0) {
                kernel_vm_end = KvaStart;
                nkpt = 0;
                while ((*pmap_pde(&kernel_pmap, kernel_vm_end) & VPTE_V) != 0) {
                        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) {
                pde = pmap_pde(&kernel_pmap, kernel_vm_end);
                if (pde == NULL) {
                        /* We need a new PDP entry */
                        nkpg = vm_page_alloc(kptobj, nkpt,
                                             VM_ALLOC_NORMAL | VM_ALLOC_SYSTEM
                                             | VM_ALLOC_INTERRUPT);
                        if (nkpg == NULL) {
                                panic("pmap_growkernel: no memory to "
                                      "grow kernel");
                        }
                        paddr = VM_PAGE_TO_PHYS(nkpg);
                        if ((nkpg->flags & PG_ZERO) == 0)
                                pmap_zero_page(paddr);
                        vm_page_flag_clear(nkpg, PG_ZERO);
                        newpdp = (pdp_entry_t)(paddr | VPTE_V | VPTE_R |
                                               VPTE_W | VPTE_A | VPTE_M);
                        *pmap_pdpe(&kernel_pmap, kernel_vm_end) = newpdp;
                        nkpt++;
                        continue; /* try again */
                }
                if ((*pde & VPTE_V) != 0) {
                        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;
                }

                /*
                 * This index is bogus, but out of the way
                 */
                nkpg = vm_page_alloc(kptobj, nkpt,
                                     VM_ALLOC_NORMAL |
                                     VM_ALLOC_SYSTEM |
                                     VM_ALLOC_INTERRUPT);
                if (nkpg == NULL)
                        panic("pmap_growkernel: no memory to grow kernel");

                vm_page_wire(nkpg);
                ptppaddr = VM_PAGE_TO_PHYS(nkpg);
                pmap_zero_page(ptppaddr);
                vm_page_flag_clear(nkpg, PG_ZERO);
                newpdir = (pd_entry_t)(ptppaddr | VPTE_V | VPTE_R |
                                       VPTE_W | VPTE_A | VPTE_M);
                *pmap_pde(&kernel_pmap, kernel_vm_end) = newpdir;
                nkpt++;

                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;
                }
        }
        vm_object_drop(kptobj);
}

/*
 * Add a reference to the specified pmap.
 *
 * No requirements.
 */
void
pmap_reference(pmap_t pmap)
{
        if (pmap) {
                lwkt_gettoken(&vm_token);
                ++pmap->pm_count;
                lwkt_reltoken(&vm_token);
        }
}

/************************************************************************
 *                      VMSPACE MANAGEMENT                              *
 ************************************************************************
 *
 * The VMSPACE management we do in our virtual kernel must be reflected
 * in the real kernel.  This is accomplished by making vmspace system
 * calls to the real kernel.
 */
void
cpu_vmspace_alloc(struct vmspace *vm)
{
        int r;
        void *rp;
        vpte_t vpte;

#define USER_SIZE       (VM_MAX_USER_ADDRESS - VM_MIN_USER_ADDRESS)

        if (vmspace_create(&vm->vm_pmap, 0, NULL) < 0)
                panic("vmspace_create() failed");

        rp = vmspace_mmap(&vm->vm_pmap, VM_MIN_USER_ADDRESS, USER_SIZE,
                          PROT_READ|PROT_WRITE,
                          MAP_FILE|MAP_SHARED|MAP_VPAGETABLE|MAP_FIXED,
                          MemImageFd, 0);
        if (rp == MAP_FAILED)
                panic("vmspace_mmap: failed");
        vmspace_mcontrol(&vm->vm_pmap, VM_MIN_USER_ADDRESS, USER_SIZE,
                         MADV_NOSYNC, 0);
        vpte = VM_PAGE_TO_PHYS(vmspace_pmap(vm)->pm_pdirm) | VPTE_R | VPTE_W | VPTE_V;
        r = vmspace_mcontrol(&vm->vm_pmap, VM_MIN_USER_ADDRESS, USER_SIZE,
                             MADV_SETMAP, vpte);
        if (r < 0)
                panic("vmspace_mcontrol: failed");
}

void
cpu_vmspace_free(struct vmspace *vm)
{
        if (vmspace_destroy(&vm->vm_pmap) < 0)
                panic("vmspace_destroy() failed");
}

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

/*
 * free the pv_entry back to the free list.  This function may be
 * called from an interrupt.
 */
static __inline void
free_pv_entry(pv_entry_t pv)
{
        pv_entry_count--;
        KKASSERT(pv_entry_count >= 0);
        zfree(pvzone, pv);
}

/*
 * get a new pv_entry, allocating a block from the system
 * when needed.  This function may be called from an interrupt.
 */
static pv_entry_t
get_pv_entry(void)
{
        pv_entry_count++;
        if (pv_entry_high_water &&
                (pv_entry_count > pv_entry_high_water) &&
                (pmap_pagedaemon_waken == 0)) {
                pmap_pagedaemon_waken = 1;
                wakeup(&vm_pages_needed);
        }
        return zalloc(pvzone);
}

/*
 * This routine is very drastic, but can save the system
 * in a pinch.
 *
 * No requirements.
 */
void
pmap_collect(void)
{
        int i;
        vm_page_t m;
        static int warningdone=0;

        if (pmap_pagedaemon_waken == 0)
                return;
        lwkt_gettoken(&vm_token);
        pmap_pagedaemon_waken = 0;

        if (warningdone < 5) {
                kprintf("pmap_collect: collecting pv entries -- suggest increasing PMAP_SHPGPERPROC\n");
                warningdone++;
        }

        for (i = 0; i < vm_page_array_size; i++) {
                m = &vm_page_array[i];
                if (m->wire_count || m->hold_count)
                        continue;
                if (vm_page_busy_try(m, TRUE) == 0) {
                        if (m->wire_count == 0 && m->hold_count == 0) {
                                pmap_remove_all(m);
                        }
                        vm_page_wakeup(m);
                }
        }
        lwkt_reltoken(&vm_token);
}


/*
 * If it is the first entry on the list, it is actually
 * in the header and we must copy the following entry up
 * to the header.  Otherwise we must search the list for
 * the entry.  In either case we free the now unused entry.
 *
 * caller must hold vm_token.
 */
static int
pmap_remove_entry(struct pmap *pmap, vm_page_t m, vm_offset_t va)
{
        pv_entry_t pv;
        int rtval;

        if (m->md.pv_list_count < pmap->pm_stats.resident_count) {
                TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                        if (pmap == pv->pv_pmap && va == pv->pv_va)
                                break;
                }
        } else {
                TAILQ_FOREACH(pv, &pmap->pm_pvlist, pv_plist) {
                        if (va == pv->pv_va)
                                break;
                }
        }

        /*
         * Note that pv_ptem is NULL if the page table page itself is not
         * managed, even if the page being removed IS managed.
         */
        rtval = 0;
        /* JGXXX When can 'pv' be NULL? */
        if (pv) {
                TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                m->md.pv_list_count--;
                atomic_add_int(&m->object->agg_pv_list_count, -1);
                KKASSERT(m->md.pv_list_count >= 0);
                if (TAILQ_EMPTY(&m->md.pv_list))
                        vm_page_flag_clear(m, PG_MAPPED | PG_WRITEABLE);
                TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
                ++pmap->pm_generation;
                KKASSERT(pmap->pm_pteobj != NULL);
                vm_object_hold(pmap->pm_pteobj);
                rtval = pmap_unuse_pt(pmap, va, pv->pv_ptem);
                vm_object_drop(pmap->pm_pteobj);
                free_pv_entry(pv);
        }
        return rtval;
}

/*
 * Create a pv entry for page at pa for (pmap, va).  If the page table page
 * holding the VA is managed, mpte will be non-NULL.
 */
static void
pmap_insert_entry(pmap_t pmap, vm_offset_t va, vm_page_t mpte, vm_page_t m)
{
        pv_entry_t pv;

        crit_enter();
        pv = get_pv_entry();
        pv->pv_va = va;
        pv->pv_pmap = pmap;
        pv->pv_ptem = mpte;

        TAILQ_INSERT_TAIL(&pmap->pm_pvlist, pv, pv_plist);
        TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
        m->md.pv_list_count++;
        atomic_add_int(&m->object->agg_pv_list_count, 1);

        crit_exit();
}

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

        oldpte = pmap_inval_loadandclear(ptq, pmap, va);
        if (oldpte & VPTE_WIRED)
                --pmap->pm_stats.wired_count;
        KKASSERT(pmap->pm_stats.wired_count >= 0);

#if 0
        /*
         * Machines that don't support invlpg, also don't support
         * PG_G.  XXX PG_G is disabled for SMP so don't worry about
         * the SMP case.
         */
        if (oldpte & PG_G)
                cpu_invlpg((void *)va);
#endif
        KKASSERT(pmap->pm_stats.resident_count > 0);
        --pmap->pm_stats.resident_count;
        if (oldpte & VPTE_MANAGED) {
                m = PHYS_TO_VM_PAGE(oldpte);
                if (oldpte & VPTE_M) {
#if defined(PMAP_DIAGNOSTIC)
                        if (pmap_nw_modified(oldpte)) {
                                kprintf("pmap_remove: modified page not "
                                        "writable: va: 0x%lx, pte: 0x%lx\n",
                                        va, oldpte);
                        }
#endif
                        if (pmap_track_modified(pmap, va))
                                vm_page_dirty(m);
                }
                if (oldpte & VPTE_A)
                        vm_page_flag_set(m, PG_REFERENCED);
                return pmap_remove_entry(pmap, m, va);
        } else {
                return pmap_unuse_pt(pmap, va, NULL);
        }

        return 0;
}

/*
 * pmap_remove_page:
 *
 *      Remove a single page from a process address space.
 *
 *      This function may not be called from an interrupt if the pmap is
 *      not kernel_pmap.
 */
static void
pmap_remove_page(struct pmap *pmap, vm_offset_t va)
{
        pt_entry_t *pte;

        pte = pmap_pte(pmap, va);
        if (pte == NULL)
                return;
        if ((*pte & VPTE_V) == 0)
                return;
        pmap_remove_pte(pmap, pte, 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.
 *
 * This function may not be called from an interrupt if the pmap is
 * not kernel_pmap.
 *
 * No requirements.
 */
void
pmap_remove(struct pmap *pmap, vm_offset_t sva, vm_offset_t eva)
{
        vm_offset_t va_next;
        pml4_entry_t *pml4e;
        pdp_entry_t *pdpe;
        pd_entry_t ptpaddr, *pde;
        pt_entry_t *pte;

        if (pmap == NULL)
                return;

        vm_object_hold(pmap->pm_pteobj);
        lwkt_gettoken(&vm_token);
        KKASSERT(pmap->pm_stats.resident_count >= 0);
        if (pmap->pm_stats.resident_count == 0) {
                lwkt_reltoken(&vm_token);
                vm_object_drop(pmap->pm_pteobj);
                return;
        }

        /*
         * special handling of removing one page.  a very
         * common operation and easy to short circuit some
         * code.
         */
        if (sva + PAGE_SIZE == eva) {
                pde = pmap_pde(pmap, sva);
                if (pde && (*pde & VPTE_PS) == 0) {
                        pmap_remove_page(pmap, sva);
                        lwkt_reltoken(&vm_token);
                        vm_object_drop(pmap->pm_pteobj);
                        return;
                }
        }

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

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

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

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

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

                /*
                 * Check for large page.
                 */
                if ((ptpaddr & VPTE_PS) != 0) {
                        /* JG FreeBSD has more complex treatment here */
                        KKASSERT(*pde != 0);
                        pmap_inval_pde(pde, pmap, sva);
                        pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                        continue;
                }

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

                /*
                 * NOTE: pmap_remove_pte() can block.
                 */
                for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
                    sva += PAGE_SIZE) {
                        if (*pte == 0)
                                continue;
                        if (pmap_remove_pte(pmap, pte, sva))
                                break;
                }
        }
        lwkt_reltoken(&vm_token);
        vm_object_drop(pmap->pm_pteobj);
}

/*
 * Removes this physical page from all physical maps in which it resides.
 * Reflects back modify bits to the pager.
 *
 * This routine may not be called from an interrupt.
 *
 * No requirements.
 */
static void
pmap_remove_all(vm_page_t m)
{
        pt_entry_t *pte, tpte;
        pv_entry_t pv;

#if defined(PMAP_DIAGNOSTIC)
        /*
         * XXX this makes pmap_page_protect(NONE) illegal for non-managed
         * pages!
         */
        if (!pmap_initialized || (m->flags & PG_FICTITIOUS)) {
                panic("pmap_page_protect: illegal for unmanaged page, va: 0x%08llx", (long long)VM_PAGE_TO_PHYS(m));
        }
#endif

        lwkt_gettoken(&vm_token);
        while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                KKASSERT(pv->pv_pmap->pm_stats.resident_count > 0);
                --pv->pv_pmap->pm_stats.resident_count;

                pte = pmap_pte(pv->pv_pmap, pv->pv_va);
                KKASSERT(pte != NULL);

                tpte = pmap_inval_loadandclear(pte, pv->pv_pmap, pv->pv_va);
                if (tpte & VPTE_WIRED)
                        pv->pv_pmap->pm_stats.wired_count--;
                KKASSERT(pv->pv_pmap->pm_stats.wired_count >= 0);

                if (tpte & VPTE_A)
                        vm_page_flag_set(m, PG_REFERENCED);

                /*
                 * Update the vm_page_t clean and reference bits.
                 */
                if (tpte & VPTE_M) {
#if defined(PMAP_DIAGNOSTIC)
                        if (pmap_nw_modified(tpte)) {
                                kprintf(
        "pmap_remove_all: modified page not writable: va: 0x%lx, pte: 0x%lx\n",
                                    pv->pv_va, tpte);
                        }
#endif
                        if (pmap_track_modified(pv->pv_pmap, pv->pv_va))
                                vm_page_dirty(m);
                }
                TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                TAILQ_REMOVE(&pv->pv_pmap->pm_pvlist, pv, pv_plist);
                ++pv->pv_pmap->pm_generation;
                m->md.pv_list_count--;
                atomic_add_int(&m->object->agg_pv_list_count, -1);
                KKASSERT(m->md.pv_list_count >= 0);
                if (TAILQ_EMPTY(&m->md.pv_list))
                        vm_page_flag_clear(m, PG_MAPPED | PG_WRITEABLE);
                vm_object_hold(pv->pv_pmap->pm_pteobj);
                pmap_unuse_pt(pv->pv_pmap, pv->pv_va, pv->pv_ptem);
                vm_object_drop(pv->pv_pmap->pm_pteobj);
                free_pv_entry(pv);
        }
        KKASSERT((m->flags & (PG_MAPPED|PG_WRITEABLE)) == 0);
        lwkt_reltoken(&vm_token);
}

/*
 * Set the physical protection on the specified range of this map
 * as requested.
 *
 * This function may not be called from an interrupt if the map is
 * not the kernel_pmap.
 *
 * No requirements.
 */
void
pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
{
        vm_offset_t va_next;
        pml4_entry_t *pml4e;
        pdp_entry_t *pdpe;
        pd_entry_t ptpaddr, *pde;
        pt_entry_t *pte;

        /* JG review for NX */

        if (pmap == NULL)
                return;

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

        if (prot & VM_PROT_WRITE)
                return;

        lwkt_gettoken(&vm_token);

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

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

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

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

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

                /*
                 * Check for large page.
                 */
                if ((ptpaddr & VPTE_PS) != 0) {
                        /* JG correct? */
                        pmap_clean_pde(pde, pmap, sva);
                        pmap->pm_stats.resident_count -= NBPDR / PAGE_SIZE;
                        continue;
                }

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

                if (va_next > eva)
                        va_next = eva;

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

                        /*
                         * Clean managed pages and also check the accessed
                         * bit.  Just remove write perms for unmanaged
                         * pages.  Be careful of races, turning off write
                         * access will force a fault rather then setting
                         * the modified bit at an unexpected time.
                         */
                        if (*pte & VPTE_MANAGED) {
                                pbits = pmap_clean_pte(pte, pmap, sva);
                                m = NULL;
                                if (pbits & VPTE_A) {
                                        m = PHYS_TO_VM_PAGE(pbits & VPTE_FRAME);
                                        vm_page_flag_set(m, PG_REFERENCED);
                                        atomic_clear_long(pte, VPTE_A);
                                }
                                if (pbits & VPTE_M) {
                                        if (pmap_track_modified(pmap, sva)) {
                                                if (m == NULL)
                                                        m = PHYS_TO_VM_PAGE(pbits & VPTE_FRAME);
                                                vm_page_dirty(m);
                                        }
                                }
                        } else {
                                pbits = pmap_setro_pte(pte, pmap, sva);
                        }
                }
        }
        lwkt_reltoken(&vm_token);
}

/*
 * Enter a managed page into a pmap.  If the page is not wired related pmap
 * data can be destroyed at any time for later demand-operation.
 *
 * Insert the vm_page (m) at virtual address (v) in (pmap), with the
 * specified protection, and wire the mapping if requested.
 *
 * NOTE: This routine may not lazy-evaluate or lose information.  The
 * page must actually be inserted into the given map NOW.
 *
 * NOTE: When entering a page at a KVA address, the pmap must be the
 * kernel_pmap.
 *
 * No requirements.
 */
void
pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
           boolean_t wired, vm_map_entry_t entry __unused)
{
        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;

        if (pmap == NULL)
                return;

        va = trunc_page(va);

        vm_object_hold(pmap->pm_pteobj);
        lwkt_gettoken(&vm_token);

        /*
         * Get the page table page.   The kernel_pmap's page table pages
         * are preallocated and have no associated vm_page_t.
         */
        if (pmap == &kernel_pmap)
                mpte = NULL;
        else
                mpte = pmap_allocpte(pmap, va);

        pde = pmap_pde(pmap, va);
        if (pde != NULL && (*pde & VPTE_V) != 0) {
                if ((*pde & VPTE_PS) != 0)
                        panic("pmap_enter: attempted pmap_enter on 2MB page");
                pte = pmap_pde_to_pte(pde, va);
        } else {
                panic("pmap_enter: invalid page directory va=%#lx", va);
        }

        KKASSERT(pte != NULL);
        /*
         * Deal with races on the original mapping (though don't worry
         * about VPTE_A races) by cleaning it.  This will force a fault
         * if an attempt is made to write to the page.
         */
        pa = VM_PAGE_TO_PHYS(m);
        origpte = pmap_clean_pte(pte, pmap, va);
        opa = origpte & VPTE_FRAME;

        if (origpte & VPTE_PS)
                panic("pmap_enter: attempted pmap_enter on 2MB page");

        /*
         * 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 & VPTE_WIRED) == 0))
                        ++pmap->pm_stats.wired_count;
                else if (!wired && (origpte & VPTE_WIRED))
                        --pmap->pm_stats.wired_count;

                /*
                 * Remove the extra pte reference.  Note that we cannot
                 * optimize the RO->RW case because we have adjusted the
                 * wiring count above and may need to adjust the wiring
                 * bits below.
                 */
                if (mpte)
                        mpte->hold_count--;

                /*
                 * We might be turning off write access to the page,
                 * so we go ahead and sense modify status.
                 */
                if (origpte & VPTE_MANAGED) {
                        if ((origpte & VPTE_M) &&
                            pmap_track_modified(pmap, va)) {
                                vm_page_t om;
                                om = PHYS_TO_VM_PAGE(opa);
                                vm_page_dirty(om);
                        }
                        pa |= VPTE_MANAGED;
                        KKASSERT(m->flags & PG_MAPPED);
                }
                goto validate;
        }
        /*
         * Mapping has changed, invalidate old range and fall through to
         * handle validating new mapping.
         */
        if (opa) {
                int err;
                err = pmap_remove_pte(pmap, pte, va);
                if (err)
                        panic("pmap_enter: pte vanished, va: 0x%lx", va);
        }

        /*
         * Enter on the PV list if part of our managed memory. Note that we
         * raise IPL while manipulating pv_table since pmap_enter can be
         * called at interrupt time.
         */
        if (pmap_initialized &&
            (m->flags & (PG_FICTITIOUS|PG_UNMANAGED)) == 0) {
                pmap_insert_entry(pmap, va, mpte, m);
                pa |= VPTE_MANAGED;
                vm_page_flag_set(m, PG_MAPPED);
        }

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

validate:
        /*
         * Now validate mapping with desired protection/wiring.
         */
        newpte = (pt_entry_t) (pa | pte_prot(pmap, prot) | VPTE_V);

        if (wired)
                newpte |= VPTE_WIRED;
        if (pmap != &kernel_pmap)
                newpte |= VPTE_U;

        /*
         * If the mapping or permission bits are different from the
         * (now cleaned) original pte, an update is needed.  We've
         * already downgraded or invalidated the page so all we have
         * to do now is update the bits.
         *
         * XXX should we synchronize RO->RW changes to avoid another
         * fault?
         */
        if ((origpte & ~(VPTE_W|VPTE_M|VPTE_A)) != newpte) {
                *pte = newpte | VPTE_A;
                if (newpte & VPTE_W)
                        vm_page_flag_set(m, PG_WRITEABLE);
        }
        KKASSERT((newpte & VPTE_MANAGED) == 0 || (m->flags & PG_MAPPED));
        lwkt_reltoken(&vm_token);
        vm_object_drop(pmap->pm_pteobj);
}

/*
 * This code works like pmap_enter() but assumes VM_PROT_READ and not-wired.
 *
 * Currently this routine may only be used on user pmaps, not kernel_pmap.
 *
 * No requirements.
 */
void
pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m)
{
        pt_entry_t *pte;
        vm_paddr_t pa;
        vm_page_t mpte;
        vm_pindex_t ptepindex;
        pd_entry_t *ptepa;

        KKASSERT(pmap != &kernel_pmap);

        KKASSERT(va >= VM_MIN_USER_ADDRESS && va < VM_MAX_USER_ADDRESS);

        /*
         * Calculate pagetable page index
         */
        ptepindex = pmap_pde_pindex(va);

        vm_object_hold(pmap->pm_pteobj);
        lwkt_gettoken(&vm_token);

        do {
                /*
                 * Get the page directory entry
                 */
                ptepa = pmap_pde(pmap, va);

                /*
                 * If the page table page is mapped, we just increment
                 * the hold count, and activate it.
                 */
                if (ptepa && (*ptepa & VPTE_V) != 0) {
                        if (*ptepa & VPTE_PS)
                                panic("pmap_enter_quick: unexpected mapping into 2MB page");
                        if (pmap->pm_ptphint &&
                            (pmap->pm_ptphint->pindex == ptepindex)) {
                                mpte = pmap->pm_ptphint;
                        } else {
                                mpte = pmap_page_lookup( pmap->pm_pteobj, ptepindex);
                                pmap->pm_ptphint = mpte;
                                vm_page_wakeup(mpte);
                        }
                        if (mpte)
                                mpte->hold_count++;
                } else {
                        mpte = _pmap_allocpte(pmap, ptepindex);
                }
        } while (mpte == NULL);

        /*
         * Ok, now that the page table page has been validated, get the pte.
         * If the pte is already mapped undo mpte's hold_count and
         * just return.
         */
        pte = pmap_pte(pmap, va);
        if (*pte & VPTE_V) {
                KKASSERT(mpte != NULL);
                pmap_unwire_pte_hold(pmap, va, mpte);
                pa = VM_PAGE_TO_PHYS(m);
                KKASSERT(((*pte ^ pa) & VPTE_FRAME) == 0);
                lwkt_reltoken(&vm_token);
                vm_object_drop(pmap->pm_pteobj);
                return;
        }

        /*
         * Enter on the PV list if part of our managed memory
         */
        if ((m->flags & (PG_FICTITIOUS|PG_UNMANAGED)) == 0) {
                pmap_insert_entry(pmap, va, mpte, m);
                vm_page_flag_set(m, PG_MAPPED);
        }

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

        pa = VM_PAGE_TO_PHYS(m);

        /*
         * Now validate mapping with RO protection
         */
        if (m->flags & (PG_FICTITIOUS|PG_UNMANAGED))
                *pte = (vpte_t)pa | VPTE_V | VPTE_U;
        else
                *pte = (vpte_t)pa | VPTE_V | VPTE_U | VPTE_MANAGED;
        /*pmap_inval_add(&info, pmap, va); shouldn't be needed 0->valid */
        /*pmap_inval_flush(&info); don't need for vkernel */
        lwkt_reltoken(&vm_token);
        vm_object_drop(pmap->pm_pteobj);
}

/*
 * Make a temporary mapping for a physical address.  This is only intended
 * to be used for panic dumps.
 *
 * The caller is responsible for calling smp_invltlb().
 */
void *
pmap_kenter_temporary(vm_paddr_t pa, long i)
{
        pmap_kenter_quick(crashdumpmap + (i * PAGE_SIZE), pa);
        return ((void *)crashdumpmap);
}

#define MAX_INIT_PT (96)

/*
 * This routine preloads the ptes for a given object into the specified pmap.
 * This eliminates the blast of soft faults on process startup and
 * immediately after an mmap.
 *
 * No requirements.
 */
static int pmap_object_init_pt_callback(vm_page_t p, void *data);

void
pmap_object_init_pt(pmap_t pmap, vm_offset_t addr, vm_prot_t prot,
                    vm_object_t object, vm_pindex_t pindex,
                    vm_size_t size, int limit)
{
        struct rb_vm_page_scan_info info;
        struct lwp *lp;
        vm_size_t psize;

        /*
         * We can't preinit if read access isn't set or there is no pmap
         * or object.
         */
        if ((prot & VM_PROT_READ) == 0 || pmap == NULL || object == NULL)
                return;

        /*
         * We can't preinit if the pmap is not the current pmap
         */
        lp = curthread->td_lwp;
        if (lp == NULL || pmap != vmspace_pmap(lp->lwp_vmspace))
                return;

        psize = x86_64_btop(size);

        if ((object->type != OBJT_VNODE) ||
                ((limit & MAP_PREFAULT_PARTIAL) && (psize > MAX_INIT_PT) &&
                        (object->resident_page_count > MAX_INIT_PT))) {
                return;
        }

        if (psize + pindex > object->size) {
                if (object->size < pindex)
                        return;
                psize = object->size - pindex;
        }

        if (psize == 0)
                return;

        /*
         * Use a red-black scan to traverse the requested range and load
         * any valid pages found into the pmap.
         *
         * We cannot safely scan the object's memq unless we are in a
         * critical section since interrupts can remove pages from objects.
         */
        info.start_pindex = pindex;
        info.end_pindex = pindex + psize - 1;
        info.limit = limit;
        info.mpte = NULL;
        info.addr = addr;
        info.pmap = pmap;

        vm_object_hold_shared(object);
        vm_page_rb_tree_RB_SCAN(&object->rb_memq, rb_vm_page_scancmp,
                                pmap_object_init_pt_callback, &info);
        vm_object_drop(object);
}

static
int
pmap_object_init_pt_callback(vm_page_t p, void *data)
{
        struct rb_vm_page_scan_info *info = data;
        vm_pindex_t rel_index;
        /*
         * don't allow an madvise to blow away our really
         * free pages allocating pv entries.
         */
        if ((info->limit & MAP_PREFAULT_MADVISE) &&
                vmstats.v_free_count < vmstats.v_free_reserved) {
                    return(-1);
        }

        /*
         * Ignore list markers and ignore pages we cannot instantly
         * busy (while holding the object token).
         */
        if (p->flags & PG_MARKER)
                return 0;
        if (vm_page_busy_try(p, TRUE))
                return 0;
        if (((p->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) &&
            (p->flags & PG_FICTITIOUS) == 0) {
                if ((p->queue - p->pc) == PQ_CACHE)
                        vm_page_deactivate(p);
                rel_index = p->pindex - info->start_pindex;
                pmap_enter_quick(info->pmap,
                                 info->addr + x86_64_ptob(rel_index), p);
        }
        vm_page_wakeup(p);
        return(0);
}

/*
 * Return TRUE if the pmap is in shape to trivially
 * pre-fault the specified address.
 *
 * Returns FALSE if it would be non-trivial or if a
 * pte is already loaded into the slot.
 *
 * No requirements.
 */
int
pmap_prefault_ok(pmap_t pmap, vm_offset_t addr)
{
        pt_entry_t *pte;
        pd_entry_t *pde;
        int ret;

        lwkt_gettoken(&vm_token);
        pde = pmap_pde(pmap, addr);
        if (pde == NULL || *pde == 0) {
                ret = 0;
        } else {
                pte = pmap_pde_to_pte(pde, addr);
                ret = (*pte) ? 0 : 1;
        }
        lwkt_reltoken(&vm_token);
        return (ret);
}

/*
 * Change the wiring attribute for a map/virtual-address pair.
 *
 * The mapping must already exist in the pmap.
 * No other requirements.
 */
void
pmap_change_wiring(pmap_t pmap, vm_offset_t va, boolean_t wired,
                   vm_map_entry_t entry __unused)
{
        pt_entry_t *pte;

        if (pmap == NULL)
                return;

        lwkt_gettoken(&vm_token);
        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.  However, in an SMP environment we must use
         * a locked bus cycle to update the pte (if we are not using
         * the pmap_inval_*() API that is)... it's ok to do this for simple
         * wiring changes.
         */
        if (wired)
                atomic_set_long(pte, VPTE_WIRED);
        else
                atomic_clear_long(pte, VPTE_WIRED);
        lwkt_reltoken(&vm_token);
}

/*
 *      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)
{
        /*
         * XXX BUGGY.  Amoung other things srcmpte is assumed to remain
         * valid through blocking calls, and that's just not going to
         * be the case.
         *
         * FIXME!
         */
        return;
}

/*
 * pmap_zero_page:
 *
 *      Zero the specified physical page.
 *
 *      This function may be called from an interrupt and no locking is
 *      required.
 */
void
pmap_zero_page(vm_paddr_t phys)
{
        vm_offset_t va = PHYS_TO_DMAP(phys);

        bzero((void *)va, PAGE_SIZE);
}

/*
 * pmap_page_assertzero:
 *
 *      Assert that a page is empty, panic if it isn't.
 */
void
pmap_page_assertzero(vm_paddr_t phys)
{
        int i;

        crit_enter();
        vm_offset_t virt = PHYS_TO_DMAP(phys);

        for (i = 0; i < PAGE_SIZE; i += sizeof(int)) {
            if (*(int *)((char *)virt + i) != 0) {
                panic("pmap_page_assertzero() @ %p not zero!",
                    (void *)virt);
            }
        }
        crit_exit();
}

/*
 * pmap_zero_page:
 *
 *      Zero part of a physical page by mapping it into memory and clearing
 *      its contents with bzero.
 *
 *      off and size may not cover an area beyond a single hardware page.
 */
void
pmap_zero_page_area(vm_paddr_t phys, int off, int size)
{
        crit_enter();
        vm_offset_t virt = PHYS_TO_DMAP(phys);
        bzero((char *)virt + off, size);
        crit_exit();
}

/*
 * pmap_copy_page:
 *
 *      Copy the physical page from the source PA to the target PA.
 *      This function may be called from an interrupt.  No locking
 *      is required.
 */
void
pmap_copy_page(vm_paddr_t src, vm_paddr_t dst)
{
        vm_offset_t src_virt, dst_virt;

        crit_enter();
        src_virt = PHYS_TO_DMAP(src);
        dst_virt = PHYS_TO_DMAP(dst);
        bcopy((void *)src_virt, (void *)dst_virt, PAGE_SIZE);
        crit_exit();
}

/*
 * pmap_copy_page_frag:
 *
 *      Copy the physical page from the source PA to the target PA.
 *      This function may be called from an interrupt.  No locking
 *      is required.
 */
void
pmap_copy_page_frag(vm_paddr_t src, vm_paddr_t dst, size_t bytes)
{
        vm_offset_t src_virt, dst_virt;

        crit_enter();
        src_virt = PHYS_TO_DMAP(src);
        dst_virt = PHYS_TO_DMAP(dst);
        bcopy((char *)src_virt + (src & PAGE_MASK),
              (char *)dst_virt + (dst & PAGE_MASK),
              bytes);
        crit_exit();
}

/*
 * 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.
 *
 * No other requirements.
 */
boolean_t
pmap_page_exists_quick(pmap_t pmap, vm_page_t m)
{
        pv_entry_t pv;
        int loops = 0;

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

        crit_enter();
        lwkt_gettoken(&vm_token);

        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                if (pv->pv_pmap == pmap) {
                        lwkt_reltoken(&vm_token);
                        crit_exit();
                        return TRUE;
                }
                loops++;
                if (loops >= 16)
                        break;
        }
        lwkt_reltoken(&vm_token);
        crit_exit();
        return (FALSE);
}

/*
 * 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.
 *
 * No other requirements.
 */
void
pmap_remove_pages(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        pt_entry_t *pte, tpte;
        pv_entry_t pv, npv;
        vm_page_t m;
        int save_generation;

        if (pmap->pm_pteobj)
                vm_object_hold(pmap->pm_pteobj);
        lwkt_gettoken(&vm_token);

        for (pv = TAILQ_FIRST(&pmap->pm_pvlist); pv; pv = npv) {
                if (pv->pv_va >= eva || pv->pv_va < sva) {
                        npv = TAILQ_NEXT(pv, pv_plist);
                        continue;
                }

                KKASSERT(pmap == pv->pv_pmap);

                pte = pmap_pte(pmap, pv->pv_va);

                /*
                 * We cannot remove wired pages from a process' mapping
                 * at this time
                 */
                if (*pte & VPTE_WIRED) {
                        npv = TAILQ_NEXT(pv, pv_plist);
                        continue;
                }
                tpte = pmap_inval_loadandclear(pte, pmap, pv->pv_va);

                m = PHYS_TO_VM_PAGE(tpte & VPTE_FRAME);

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

                KKASSERT(pmap->pm_stats.resident_count > 0);
                --pmap->pm_stats.resident_count;

                /*
                 * Update the vm_page_t clean and reference bits.
                 */
                if (tpte & VPTE_M) {
                        vm_page_dirty(m);
                }

                npv = TAILQ_NEXT(pv, pv_plist);
                TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
                save_generation = ++pmap->pm_generation;

                m->md.pv_list_count--;
                atomic_add_int(&m->object->agg_pv_list_count, -1);
                TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
                if (TAILQ_EMPTY(&m->md.pv_list))
                        vm_page_flag_clear(m, PG_MAPPED | PG_WRITEABLE);

                pmap_unuse_pt(pmap, pv->pv_va, pv->pv_ptem);
                free_pv_entry(pv);

                /*
                 * Restart the scan if we blocked during the unuse or free
                 * calls and other removals were made.
                 */
                if (save_generation != pmap->pm_generation) {
                        kprintf("Warning: pmap_remove_pages race-A avoided\n");
                        npv = TAILQ_FIRST(&pmap->pm_pvlist);
                }
        }
        lwkt_reltoken(&vm_token);
        if (pmap->pm_pteobj)
                vm_object_drop(pmap->pm_pteobj);
}

/*
 * pmap_testbit tests bits in active mappings of a VM page.
 */
static boolean_t
pmap_testbit(vm_page_t m, int bit)
{
        pv_entry_t pv;
        pt_entry_t *pte;

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

        if (TAILQ_FIRST(&m->md.pv_list) == NULL)
                return FALSE;

        crit_enter();

        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                /*
                 * if the bit being tested is the modified bit, then
                 * mark clean_map and ptes as never
                 * modified.
                 */
                if (bit & (VPTE_A|VPTE_M)) {
                        if (!pmap_track_modified(pv->pv_pmap, pv->pv_va))
                                continue;
                }

#if defined(PMAP_DIAGNOSTIC)
                if (pv->pv_pmap == NULL) {
                        kprintf("Null pmap (tb) at va: 0x%lx\n", pv->pv_va);
                        continue;
                }
#endif
                pte = pmap_pte(pv->pv_pmap, pv->pv_va);
                if (*pte & bit) {
                        crit_exit();
                        return TRUE;
                }
        }
        crit_exit();
        return (FALSE);
}

/*
 * This routine is used to clear bits in ptes.  Certain bits require special
 * handling, in particular (on virtual kernels) the VPTE_M (modify) bit.
 *
 * This routine is only called with certain VPTE_* bit combinations.
 */
static __inline void
pmap_clearbit(vm_page_t m, int bit)
{
        pv_entry_t pv;
        pt_entry_t *pte;
        pt_entry_t pbits;

        if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                return;

        crit_enter();

        /*
         * Loop over all current mappings setting/clearing as appropos If
         * setting RO do we need to clear the VAC?
         */
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                /*
                 * don't write protect pager mappings
                 */
                if (bit == VPTE_W) {
                        if (!pmap_track_modified(pv->pv_pmap, pv->pv_va))
                                continue;
                }

#if defined(PMAP_DIAGNOSTIC)
                if (pv->pv_pmap == NULL) {
                        kprintf("Null pmap (cb) at va: 0x%lx\n", pv->pv_va);
                        continue;
                }
#endif

                /*
                 * Careful here.  We can use a locked bus instruction to
                 * clear VPTE_A or VPTE_M safely but we need to synchronize
                 * with the target cpus when we mess with VPTE_W.
                 *
                 * On virtual kernels we must force a new fault-on-write
                 * in the real kernel if we clear the Modify bit ourselves,
                 * otherwise the real kernel will not get a new fault and
                 * will never set our Modify bit again.
                 */
                pte = pmap_pte(pv->pv_pmap, pv->pv_va);
                if (*pte & bit) {
                        if (bit == VPTE_W) {
                                /*
                                 * We must also clear VPTE_M when clearing
                                 * VPTE_W
                                 */
                                pbits = pmap_clean_pte(pte, pv->pv_pmap,
                                                       pv->pv_va);
                                if (pbits & VPTE_M)
                                        vm_page_dirty(m);
                        } else if (bit == VPTE_M) {
                                /*
                                 * We do not have to make the page read-only
                                 * when clearing the Modify bit.  The real
                                 * kernel will make the real PTE read-only
                                 * or otherwise detect the write and set
                                 * our VPTE_M again simply by us invalidating
                                 * the real kernel VA for the pmap (as we did
                                 * above).  This allows the real kernel to
                                 * handle the write fault without forwarding
                                 * the fault to us.
                                 */
                                atomic_clear_long(pte, VPTE_M);
                        } else if ((bit & (VPTE_W|VPTE_M)) == (VPTE_W|VPTE_M)) {
                                /*
                                 * We've been asked to clear W & M, I guess
                                 * the caller doesn't want us to update
                                 * the dirty status of the VM page.
                                 */
                                pmap_clean_pte(pte, pv->pv_pmap, pv->pv_va);
                        } else {
                                /*
                                 * We've been asked to clear bits that do
                                 * not interact with hardware.
                                 */
                                atomic_clear_long(pte, bit);
                        }
                }
        }
        crit_exit();
}

/*
 * Lower the permission for all mappings to a given page.
 *
 * No other requirements.
 */
void
pmap_page_protect(vm_page_t m, vm_prot_t prot)
{
        /* JG NX support? */
        if ((prot & VM_PROT_WRITE) == 0) {
                lwkt_gettoken(&vm_token);
                if (prot & (VM_PROT_READ | VM_PROT_EXECUTE)) {
                        pmap_clearbit(m, VPTE_W);
                        vm_page_flag_clear(m, PG_WRITEABLE);
                } else {
                        pmap_remove_all(m);
                }
                lwkt_reltoken(&vm_token);
        }
}

vm_paddr_t
pmap_phys_address(vm_pindex_t ppn)
{
        return (x86_64_ptob(ppn));
}

/*
 * 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.
 *
 * No other requirements.
 */
int
pmap_ts_referenced(vm_page_t m)
{
        pv_entry_t pv, pvf, pvn;
        pt_entry_t *pte;
        int rtval = 0;

        if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
                return (rtval);

        crit_enter();
        lwkt_gettoken(&vm_token);

        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);

                        if (!pmap_track_modified(pv->pv_pmap, pv->pv_va))
                                continue;

                        pte = pmap_pte(pv->pv_pmap, pv->pv_va);

                        if (pte && (*pte & VPTE_A)) {
                                atomic_clear_long(pte, VPTE_A);
                                rtval++;
                                if (rtval > 4) {
                                        break;
                                }
                        }
                } while ((pv = pvn) != NULL && pv != pvf);
        }
        lwkt_reltoken(&vm_token);
        crit_exit();

        return (rtval);
}

/*
 * Return whether or not the specified physical page was modified
 * in any physical maps.
 *
 * No other requirements.
 */
boolean_t
pmap_is_modified(vm_page_t m)
{
        boolean_t res;

        lwkt_gettoken(&vm_token);
        res = pmap_testbit(m, VPTE_M);
        lwkt_reltoken(&vm_token);
        return (res);
}

/*
 * Clear the modify bits on the specified physical page.
 *
 * No other requirements.
 */
void
pmap_clear_modify(vm_page_t m)
{
        lwkt_gettoken(&vm_token);
        pmap_clearbit(m, VPTE_M);
        lwkt_reltoken(&vm_token);
}

/*
 * Clear the reference bit on the specified physical page.
 *
 * No other requirements.
 */
void
pmap_clear_reference(vm_page_t m)
{
        lwkt_gettoken(&vm_token);
        pmap_clearbit(m, VPTE_A);
        lwkt_reltoken(&vm_token);
}

/*
 * Miscellaneous support routines follow
 */

static void
i386_protection_init(void)
{
        int *kp, prot;

        kp = protection_codes;
        for (prot = 0; prot < 8; prot++) {
                if (prot & VM_PROT_READ)
                        *kp |= VPTE_R;
                if (prot & VM_PROT_WRITE)
                        *kp |= VPTE_W;
                if (prot & VM_PROT_EXECUTE)
                        *kp |= VPTE_X;
                ++kp;
        }
}

/*
 * Change the PAT attribute on an existing kernel memory map.  Caller
 * must ensure that the virtual memory in question is not accessed
 * during the adjustment.
 */
void
pmap_change_attr(vm_offset_t va, vm_size_t count, int mode)
{
        /* This is a vkernel, do nothing */
}

/*
 * Perform the pmap work for mincore
 *
 * No other requirements.
 */
int
pmap_mincore(pmap_t pmap, vm_offset_t addr)
{
        pt_entry_t *ptep, pte;
        vm_page_t m;
        int val = 0;

        lwkt_gettoken(&vm_token);
        ptep = pmap_pte(pmap, addr);

        if (ptep && (pte = *ptep) != 0) {
                vm_paddr_t pa;

                val = MINCORE_INCORE;
                if ((pte & VPTE_MANAGED) == 0)
                        goto done;

                pa = pte & VPTE_FRAME;

                m = PHYS_TO_VM_PAGE(pa);

                /*
                 * Modified by us
                 */
                if (pte & VPTE_M)
                        val |= MINCORE_MODIFIED|MINCORE_MODIFIED_OTHER;
                /*
                 * Modified by someone
                 */
                else if (m->dirty || pmap_is_modified(m))
                        val |= MINCORE_MODIFIED_OTHER;
                /*
                 * Referenced by us
                 */
                if (pte & VPTE_A)
                        val |= MINCORE_REFERENCED|MINCORE_REFERENCED_OTHER;

                /*
                 * Referenced by someone
                 */
                else if ((m->flags & PG_REFERENCED) || pmap_ts_referenced(m)) {
                        val |= MINCORE_REFERENCED_OTHER;
                        vm_page_flag_set(m, PG_REFERENCED);
                }
        }
done:
        lwkt_reltoken(&vm_token);
        return val;
}

/*
 * Replace p->p_vmspace with a new one.  If adjrefs is non-zero the new
 * vmspace will be ref'd and the old one will be deref'd.
 *
 * Caller must hold vmspace->vm_map.token for oldvm and newvm
 */
void
pmap_replacevm(struct proc *p, struct vmspace *newvm, int adjrefs)
{
        struct vmspace *oldvm;
        struct lwp *lp;

        crit_enter();
        oldvm = p->p_vmspace;
        if (oldvm != newvm) {
                p->p_vmspace = newvm;
                KKASSERT(p->p_nthreads == 1);
                lp = RB_ROOT(&p->p_lwp_tree);
                pmap_setlwpvm(lp, newvm);
                if (adjrefs) {
                        sysref_get(&newvm->vm_sysref);
                        sysref_put(&oldvm->vm_sysref);
                }
        }
        crit_exit();
}

/*
 * Set the vmspace for a LWP.  The vmspace is almost universally set the
 * same as the process vmspace, but virtual kernels need to swap out contexts
 * on a per-lwp basis.
 */
void
pmap_setlwpvm(struct lwp *lp, struct vmspace *newvm)
{
        struct vmspace *oldvm;
        struct pmap *pmap;

        crit_enter();
        oldvm = lp->lwp_vmspace;

        if (oldvm != newvm) {
                lp->lwp_vmspace = newvm;
                if (curthread->td_lwp == lp) {
                        pmap = vmspace_pmap(newvm);
                        atomic_set_cpumask(&pmap->pm_active, CPUMASK(mycpu->gd_cpuid));
#if defined(SWTCH_OPTIM_STATS)
                        tlb_flush_count++;
#endif
                        pmap = vmspace_pmap(oldvm);
                        atomic_clear_cpumask(&pmap->pm_active,
                                             CPUMASK(mycpu->gd_cpuid));
                }
        }
        crit_exit();
}

vm_offset_t
pmap_addr_hint(vm_object_t obj, vm_offset_t addr, vm_size_t size)
{

        if ((obj == NULL) || (size < NBPDR) || (obj->type != OBJT_DEVICE)) {
                return addr;
        }

        addr = (addr + (NBPDR - 1)) & ~(NBPDR - 1);
        return addr;
}

/*
 * Used by kmalloc/kfree, page already exists at va
 */
vm_page_t
pmap_kvtom(vm_offset_t va)
{
        vpte_t *ptep;

        KKASSERT(va >= KvaStart && va < KvaEnd);
        ptep = vtopte(va);
        return(PHYS_TO_VM_PAGE(*ptep & PG_FRAME));
}

void
pmap_object_init(vm_object_t object)
{
        /* empty */
}

void
pmap_object_free(vm_object_t object)
{
        /* empty */
}