kernel - Greatly improve shared memory fault rate concurrency / shared tokens

[dragonfly.git] / sys / platform / pc64 / x86_64 / pmap.c

/*
 * 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.
 * Copyright (c) 2011 Matthew Dillon
 * 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.
 */
/*
 * Manage physical address maps for x86-64 systems.
 */

#if JG
#include "opt_disable_pse.h"
#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 <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 <vm/vm_page2.h>

#include <machine/cputypes.h>
#include <machine/md_var.h>
#include <machine/specialreg.h>
#include <machine/smp.h>
#include <machine_base/apic/apicreg.h>
#include <machine/globaldata.h>
#include <machine/pmap.h>
#include <machine/pmap_inval.h>
#include <machine/inttypes.h>

#include <ddb/ddb.h>

#define PMAP_KEEP_PDIRS
#ifndef PMAP_SHPGPERPROC
#define PMAP_SHPGPERPROC 2000
#endif

#if defined(DIAGNOSTIC)
#define PMAP_DIAGNOSTIC
#endif

#define MINPV 2048

/*
 * pmap debugging will report who owns a pv lock when blocking.
 */
#ifdef PMAP_DEBUG

#define PMAP_DEBUG_DECL         ,const char *func, int lineno
#define PMAP_DEBUG_ARGS         , __func__, __LINE__
#define PMAP_DEBUG_COPY         , func, lineno

#define pv_get(pmap, pindex)            _pv_get(pmap, pindex            \
                                                        PMAP_DEBUG_ARGS)
#define pv_lock(pv)                     _pv_lock(pv                     \
                                                        PMAP_DEBUG_ARGS)
#define pv_hold_try(pv)                 _pv_hold_try(pv                 \
                                                        PMAP_DEBUG_ARGS)
#define pv_alloc(pmap, pindex, isnewp)  _pv_alloc(pmap, pindex, isnewp  \
                                                        PMAP_DEBUG_ARGS)

#else

#define PMAP_DEBUG_DECL
#define PMAP_DEBUG_ARGS
#define PMAP_DEBUG_COPY

#define pv_get(pmap, pindex)            _pv_get(pmap, pindex)
#define pv_lock(pv)                     _pv_lock(pv)
#define pv_hold_try(pv)                 _pv_hold_try(pv)
#define pv_alloc(pmap, pindex, isnewp)  _pv_alloc(pmap, pindex, isnewp)

#endif

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

#define pmap_pde_v(pte)         ((*(pd_entry_t *)pte & PG_V) != 0)
#define pmap_pte_w(pte)         ((*(pt_entry_t *)pte & PG_W) != 0)
#define pmap_pte_m(pte)         ((*(pt_entry_t *)pte & PG_M) != 0)
#define pmap_pte_u(pte)         ((*(pt_entry_t *)pte & PG_A) != 0)
#define pmap_pte_v(pte)         ((*(pt_entry_t *)pte & PG_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);

vm_paddr_t avail_start;         /* PA of first available physical page */
vm_paddr_t avail_end;           /* PA of last available physical page */
vm_offset_t virtual2_start;     /* cutout free area prior to kernel start */
vm_offset_t virtual2_end;
vm_offset_t virtual_start;      /* VA of first avail page (after kernel bss) */
vm_offset_t virtual_end;        /* VA of last avail page (end of kernel AS) */
vm_offset_t KvaStart;           /* VA start of KVA space */
vm_offset_t KvaEnd;             /* VA end of KVA space (non-inclusive) */
vm_offset_t KvaSize;            /* max size of kernel virtual address space */
static boolean_t pmap_initialized = FALSE;      /* Has pmap_init completed? */
static int pgeflag;             /* PG_G or-in */
static int pseflag;             /* PG_PS or-in */

static int ndmpdp;
static vm_paddr_t dmaplimit;
static int nkpt;
vm_offset_t kernel_vm_end = VM_MIN_KERNEL_ADDRESS;

static uint64_t KPTbase;
static uint64_t KPTphys;
static uint64_t KPDphys;        /* phys addr of kernel level 2 */
static uint64_t KPDbase;        /* phys addr of kernel level 2 @ KERNBASE */
uint64_t KPDPphys;      /* phys addr of kernel level 3 */
uint64_t KPML4phys;     /* phys addr of kernel level 4 */

static uint64_t DMPDphys;       /* phys addr of direct mapped level 2 */
static uint64_t DMPDPphys;      /* phys addr of direct mapped level 3 */

/*
 * 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_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 = 0, *ptmmap;
caddr_t CADDR1 = 0, ptvmmap = 0;
static pt_entry_t *msgbufmap;
struct msgbuf *msgbufp=0;

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

static int pmap_yield_count = 64;
SYSCTL_INT(_machdep, OID_AUTO, pmap_yield_count, CTLFLAG_RW,
    &pmap_yield_count, 0, "Yield during init_pt/release");

#define DISABLE_PSE

static void pv_hold(pv_entry_t pv);
static int _pv_hold_try(pv_entry_t pv
                                PMAP_DEBUG_DECL);
static void pv_drop(pv_entry_t pv);
static void _pv_lock(pv_entry_t pv
                                PMAP_DEBUG_DECL);
static void pv_unlock(pv_entry_t pv);
static pv_entry_t _pv_alloc(pmap_t pmap, vm_pindex_t pindex, int *isnew
                                PMAP_DEBUG_DECL);
static pv_entry_t _pv_get(pmap_t pmap, vm_pindex_t pindex
                                PMAP_DEBUG_DECL);
static pv_entry_t pv_get_try(pmap_t pmap, vm_pindex_t pindex, int *errorp);
static pv_entry_t pv_find(pmap_t pmap, vm_pindex_t pindex);
static void pv_put(pv_entry_t pv);
static void pv_free(pv_entry_t pv);
static void *pv_pte_lookup(pv_entry_t pv, vm_pindex_t pindex);
static pv_entry_t pmap_allocpte(pmap_t pmap, vm_pindex_t ptepindex,
                      pv_entry_t *pvpp);
static void pmap_remove_pv_pte(pv_entry_t pv, pv_entry_t pvp,
                      struct pmap_inval_info *info);
static vm_page_t pmap_remove_pv_page(pv_entry_t pv, int holdpg);

static void pmap_remove_callback(pmap_t pmap, struct pmap_inval_info *info,
                      pv_entry_t pte_pv, pv_entry_t pt_pv, vm_offset_t va,
                      pt_entry_t *ptep, void *arg __unused);
static void pmap_protect_callback(pmap_t pmap, struct pmap_inval_info *info,
                      pv_entry_t pte_pv, pv_entry_t pt_pv, vm_offset_t va,
                      pt_entry_t *ptep, void *arg __unused);

static void i386_protection_init (void);
static void create_pagetables(vm_paddr_t *firstaddr);
static void pmap_remove_all (vm_page_t m);
static boolean_t pmap_testbit (vm_page_t m, int bit);

static pt_entry_t * pmap_pte_quick (pmap_t pmap, vm_offset_t va);
static vm_offset_t pmap_kmem_choose(vm_offset_t addr);

static unsigned pdir4mb;

static int
pv_entry_compare(pv_entry_t pv1, pv_entry_t pv2)
{
        if (pv1->pv_pindex < pv2->pv_pindex)
                return(-1);
        if (pv1->pv_pindex > pv2->pv_pindex)
                return(1);
        return(0);
}

RB_GENERATE2(pv_entry_rb_tree, pv_entry, pv_entry,
             pv_entry_compare, vm_pindex_t, pv_pindex);

/*
 * Move the kernel virtual free pointer to the next
 * 2MB.  This is used to help improve performance
 * by using a large (2MB) page for much of the kernel
 * (.text, .data, .bss)
 */
static
vm_offset_t
pmap_kmem_choose(vm_offset_t addr)
{
        vm_offset_t newaddr = addr;

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

/*
 * 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.
 */
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);
}

/*
 * Returns the pindex of a page table entry (representing a terminal page).
 * There are NUPTE_TOTAL page table entries possible (a huge number)
 *
 * x86-64 has a 48-bit address space, where bit 47 is sign-extended out.
 * We want to properly translate negative KVAs.
 */
static __inline
vm_pindex_t
pmap_pte_pindex(vm_offset_t va)
{
        return ((va >> PAGE_SHIFT) & (NUPTE_TOTAL - 1));
}

/*
 * Returns the pindex of a page table.
 */
static __inline
vm_pindex_t
pmap_pt_pindex(vm_offset_t va)
{
        return (NUPTE_TOTAL + ((va >> PDRSHIFT) & (NUPT_TOTAL - 1)));
}

/*
 * Returns the pindex of a page directory.
 */
static __inline
vm_pindex_t
pmap_pd_pindex(vm_offset_t va)
{
        return (NUPTE_TOTAL + NUPT_TOTAL +
                ((va >> PDPSHIFT) & (NUPD_TOTAL - 1)));
}

static __inline
vm_pindex_t
pmap_pdp_pindex(vm_offset_t va)
{
        return (NUPTE_TOTAL + NUPT_TOTAL + NUPD_TOTAL +
                ((va >> PML4SHIFT) & (NUPDP_TOTAL - 1)));
}

static __inline
vm_pindex_t
pmap_pml4_pindex(void)
{
        return (NUPTE_TOTAL + NUPT_TOTAL + NUPD_TOTAL + NUPDP_TOTAL);
}

/*
 * Return various clipped indexes for a given VA
 *
 * Returns the index of a pte in a page table, representing a terminal
 * page.
 */
static __inline
vm_pindex_t
pmap_pte_index(vm_offset_t va)
{
        return ((va >> PAGE_SHIFT) & ((1ul << NPTEPGSHIFT) - 1));
}

/*
 * Returns the index of a pt in a page directory, representing a page
 * table.
 */
static __inline
vm_pindex_t
pmap_pt_index(vm_offset_t va)
{
        return ((va >> PDRSHIFT) & ((1ul << NPDEPGSHIFT) - 1));
}

/*
 * Returns the index of a pd in a page directory page, representing a page
 * directory.
 */
static __inline
vm_pindex_t
pmap_pd_index(vm_offset_t va)
{
        return ((va >> PDPSHIFT) & ((1ul << NPDPEPGSHIFT) - 1));
}

/*
 * Returns the index of a pdp in the pml4 table, representing a page
 * directory page.
 */
static __inline
vm_pindex_t
pmap_pdp_index(vm_offset_t va)
{
        return ((va >> PML4SHIFT) & ((1ul << NPML4EPGSHIFT) - 1));
}

/*
 * Generic procedure to index a pte from a pt, pd, or pdp.
 */
static
void *
pv_pte_lookup(pv_entry_t pv, vm_pindex_t pindex)
{
        pt_entry_t *pte;

        pte = (pt_entry_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(pv->pv_m));
        return(&pte[pindex]);
}

/*
 * Return pointer to PDP slot in the PML4
 */
static __inline
pml4_entry_t *
pmap_pdp(pmap_t pmap, vm_offset_t va)
{
        return (&pmap->pm_pml4[pmap_pdp_index(va)]);
}

/*
 * Return pointer to PD slot in the PDP given a pointer to the PDP
 */
static __inline
pdp_entry_t *
pmap_pdp_to_pd(pml4_entry_t *pdp, vm_offset_t va)
{
        pdp_entry_t *pd;

        pd = (pdp_entry_t *)PHYS_TO_DMAP(*pdp & PG_FRAME);
        return (&pd[pmap_pd_index(va)]);
}

/*
 * Return pointer to PD slot in the PDP
 **/
static __inline
pdp_entry_t *
pmap_pd(pmap_t pmap, vm_offset_t va)
{
        pml4_entry_t *pdp;

        pdp = pmap_pdp(pmap, va);
        if ((*pdp & PG_V) == 0)
                return NULL;
        return (pmap_pdp_to_pd(pdp, va));
}

/*
 * Return pointer to PT slot in the PD given a pointer to the PD
 */
static __inline
pd_entry_t *
pmap_pd_to_pt(pdp_entry_t *pd, vm_offset_t va)
{
        pd_entry_t *pt;

        pt = (pd_entry_t *)PHYS_TO_DMAP(*pd & PG_FRAME);
        return (&pt[pmap_pt_index(va)]);
}

/*
 * Return pointer to PT slot in the PD
 */
static __inline
pd_entry_t *
pmap_pt(pmap_t pmap, vm_offset_t va)
{
        pdp_entry_t *pd;

        pd = pmap_pd(pmap, va);
        if (pd == NULL || (*pd & PG_V) == 0)
                 return NULL;
        return (pmap_pd_to_pt(pd, va));
}

/*
 * Return pointer to PTE slot in the PT given a pointer to the PT
 */
static __inline
pt_entry_t *
pmap_pt_to_pte(pd_entry_t *pt, vm_offset_t va)
{
        pt_entry_t *pte;

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

/*
 * Return pointer to PTE slot in the PT
 */
static __inline
pt_entry_t *
pmap_pte(pmap_t pmap, vm_offset_t va)
{
        pd_entry_t *pt;

        pt = pmap_pt(pmap, va);
        if (pt == NULL || (*pt & PG_V) == 0)
                 return NULL;
        if ((*pt & PG_PS) != 0)
                return ((pt_entry_t *)pt);
        return (pmap_pt_to_pte(pt, va));
}

/*
 * Of all the layers (PTE, PT, PD, PDP, PML4) the best one to cache is
 * the PT layer.  This will speed up core pmap operations considerably.
 */
static __inline
void
pv_cache(pv_entry_t pv, vm_pindex_t pindex)
{
        if (pindex >= pmap_pt_pindex(0) && pindex <= pmap_pd_pindex(0))
                pv->pv_pmap->pm_pvhint = pv;
}


/*
 * KVM - return address of PT slot in PD
 */
static __inline
pd_entry_t *
vtopt(vm_offset_t va)
{
        uint64_t mask = ((1ul << (NPDEPGSHIFT + NPDPEPGSHIFT +
                                  NPML4EPGSHIFT)) - 1);

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

/*
 * KVM - return address of PTE slot in PT
 */
static __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 uint64_t
allocpages(vm_paddr_t *firstaddr, long n)
{
        uint64_t ret;

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

static
void
create_pagetables(vm_paddr_t *firstaddr)
{
        long i;         /* must be 64 bits */
        long nkpt_base;
        long nkpt_phys;
        int j;

        /*
         * We are running (mostly) V=P at this point
         *
         * 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.
         *
         * ndmpdp is the number of 1GB pages we wish to map.
         */
        ndmpdp = (ptoa(Maxmem) + NBPDP - 1) >> PDPSHIFT;
        if (ndmpdp < 4)         /* Minimum 4GB of dirmap */
                ndmpdp = 4;
        KKASSERT(ndmpdp <= NKPDPE * NPDEPG);

        /*
         * Starting at the beginning of kvm (not KERNBASE).
         */
        nkpt_phys = (Maxmem * sizeof(struct vm_page) + NBPDR - 1) / NBPDR;
        nkpt_phys += (Maxmem * sizeof(struct pv_entry) + NBPDR - 1) / NBPDR;
        nkpt_phys += ((nkpt + nkpt + 1 + NKPML4E + NKPDPE + NDMPML4E +
                       ndmpdp) + 511) / 512;
        nkpt_phys += 128;

        /*
         * Starting at KERNBASE - map 2G worth of page table pages.
         * KERNBASE is offset -2G from the end of kvm.
         */
        nkpt_base = (NPDPEPG - KPDPI) * NPTEPG; /* typically 2 x 512 */

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

        /*
         * Calculate the page directory base for KERNBASE,
         * that is where we start populating the page table pages.
         * Basically this is the end - 2.
         */
        KPDbase = KPDphys + ((NKPDPE - (NPDPEPG - KPDPI)) << PAGE_SHIFT);

        DMPDPphys = allocpages(firstaddr, NDMPML4E);
        if ((amd_feature & AMDID_PAGE1GB) == 0)
                DMPDphys = allocpages(firstaddr, ndmpdp);
        dmaplimit = (vm_paddr_t)ndmpdp << PDPSHIFT;

        /*
         * Fill in the underlying page table pages for the area around
         * KERNBASE.  This remaps low physical memory to KERNBASE.
         *
         * Read-only from zero to physfree
         * XXX not fully used, underneath 2M pages
         */
        for (i = 0; (i << PAGE_SHIFT) < *firstaddr; i++) {
                ((pt_entry_t *)KPTbase)[i] = i << PAGE_SHIFT;
                ((pt_entry_t *)KPTbase)[i] |= PG_RW | PG_V | PG_G;
        }

        /*
         * Now map the initial kernel page tables.  One block of page
         * tables is placed at the beginning of kernel virtual memory,
         * and another block is placed at KERNBASE to map the kernel binary,
         * data, bss, and initial pre-allocations.
         */
        for (i = 0; i < nkpt_base; i++) {
                ((pd_entry_t *)KPDbase)[i] = KPTbase + (i << PAGE_SHIFT);
                ((pd_entry_t *)KPDbase)[i] |= PG_RW | PG_V;
        }
        for (i = 0; i < nkpt_phys; i++) {
                ((pd_entry_t *)KPDphys)[i] = KPTphys + (i << PAGE_SHIFT);
                ((pd_entry_t *)KPDphys)[i] |= PG_RW | PG_V;
        }

        /*
         * Map from zero to end of allocations using 2M pages as an
         * optimization.  This will bypass some of the KPTBase pages
         * above in the KERNBASE area.
         */
        for (i = 0; (i << PDRSHIFT) < *firstaddr; i++) {
                ((pd_entry_t *)KPDbase)[i] = i << PDRSHIFT;
                ((pd_entry_t *)KPDbase)[i] |= PG_RW | PG_V | PG_PS | PG_G;
        }

        /*
         * And connect up the PD to the PDP.  The kernel pmap is expected
         * to pre-populate all of its PDs.  See NKPDPE in vmparam.h.
         */
        for (i = 0; i < NKPDPE; i++) {
                ((pdp_entry_t *)KPDPphys)[NPDPEPG - NKPDPE + i] =
                                KPDphys + (i << PAGE_SHIFT);
                ((pdp_entry_t *)KPDPphys)[NPDPEPG - NKPDPE + i] |=
                                PG_RW | PG_V | PG_U;
        }

        /*
         * Now set up the direct map space using either 2MB or 1GB pages
         * Preset PG_M and PG_A because demotion expects it.
         *
         * When filling in entries in the PD pages make sure any excess
         * entries are set to zero as we allocated enough PD pages
         */
        if ((amd_feature & AMDID_PAGE1GB) == 0) {
                for (i = 0; i < NPDEPG * ndmpdp; i++) {
                        ((pd_entry_t *)DMPDphys)[i] = i << PDRSHIFT;
                        ((pd_entry_t *)DMPDphys)[i] |= PG_RW | PG_V | PG_PS |
                                                       PG_G | PG_M | PG_A;
                }

                /*
                 * And the direct map space's PDP
                 */
                for (i = 0; i < ndmpdp; i++) {
                        ((pdp_entry_t *)DMPDPphys)[i] = DMPDphys +
                                                        (i << PAGE_SHIFT);
                        ((pdp_entry_t *)DMPDPphys)[i] |= PG_RW | PG_V | PG_U;
                }
        } else {
                for (i = 0; i < ndmpdp; i++) {
                        ((pdp_entry_t *)DMPDPphys)[i] =
                                                (vm_paddr_t)i << PDPSHIFT;
                        ((pdp_entry_t *)DMPDPphys)[i] |= PG_RW | PG_V | PG_PS |
                                                         PG_G | PG_M | PG_A;
                }
        }

        /* And recursively map PML4 to itself in order to get PTmap */
        ((pdp_entry_t *)KPML4phys)[PML4PML4I] = KPML4phys;
        ((pdp_entry_t *)KPML4phys)[PML4PML4I] |= PG_RW | PG_V | PG_U;

        /*
         * Connect the Direct Map slots up to the PML4
         */
        for (j = 0; j < NDMPML4E; ++j) {
                ((pdp_entry_t *)KPML4phys)[DMPML4I + j] =
                        (DMPDPphys + ((vm_paddr_t)j << PML4SHIFT)) |
                        PG_RW | PG_V | PG_U;
        }

        /*
         * Connect the KVA slot up to the PML4
         */
        ((pdp_entry_t *)KPML4phys)[KPML4I] = KPDPphys;
        ((pdp_entry_t *)KPML4phys)[KPML4I] |= PG_RW | PG_V | PG_U;
}

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

        KvaStart = VM_MIN_KERNEL_ADDRESS;
        KvaEnd = VM_MAX_KERNEL_ADDRESS;
        KvaSize = KvaEnd - KvaStart;

        avail_start = *firstaddr;

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

        virtual2_start = KvaStart;
        virtual2_end = PTOV_OFFSET;

        virtual_start = (vm_offset_t) PTOV_OFFSET + *firstaddr;
        virtual_start = pmap_kmem_choose(virtual_start);

        virtual_end = VM_MAX_KERNEL_ADDRESS;

        /* XXX do %cr0 as well */
        load_cr4(rcr4() | CR4_PGE | CR4_PSE);
        load_cr3(KPML4phys);

        /*
         * 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).
         */
        kernel_pmap.pm_pml4 = (pdp_entry_t *) (PTOV_OFFSET + KPML4phys);
        kernel_pmap.pm_count = 1;
        kernel_pmap.pm_active = (cpumask_t)-1 & ~CPUMASK_LOCK;
        RB_INIT(&kernel_pmap.pm_pvroot);
        spin_init(&kernel_pmap.pm_spin);
        lwkt_token_init(&kernel_pmap.pm_token, "kpmap_tok");

        /*
         * 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 = vtopte(va);

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

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

        /*
         * 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;

        /*
         * PG_G is terribly broken on SMP because we IPI invltlb's in some
         * cases rather then invl1pg.  Actually, I don't even know why it
         * works under UP because self-referential page table mappings
         */
#ifdef SMP
        pgeflag = 0;
#else
        if (cpu_feature & CPUID_PGE)
                pgeflag = PG_G;
#endif
        
/*
 * Initialize the 4MB page size flag
 */
        pseflag = 0;
/*
 * The 4MB page version of the initial
 * kernel page mapping.
 */
        pdir4mb = 0;

#if !defined(DISABLE_PSE)
        if (cpu_feature & CPUID_PSE) {
                pt_entry_t ptditmp;
                /*
                 * Note that we have enabled PSE mode
                 */
                pseflag = PG_PS;
                ptditmp = *(PTmap + x86_64_btop(KERNBASE));
                ptditmp &= ~(NBPDR - 1);
                ptditmp |= PG_V | PG_RW | PG_PS | PG_U | pgeflag;
                pdir4mb = ptditmp;

#ifndef SMP
                /*
                 * Enable the PSE mode.  If we are SMP we can't do this
                 * now because the APs will not be able to use it when
                 * they boot up.
                 */
                load_cr4(rcr4() | CR4_PSE);

                /*
                 * We can do the mapping here for the single processor
                 * case.  We simply ignore the old page table page from
                 * now on.
                 */
                /*
                 * For SMP, we still need 4K pages to bootstrap APs,
                 * PSE will be enabled as soon as all APs are up.
                 */
                PTD[KPTDI] = (pd_entry_t)ptditmp;
                cpu_invltlb();
#endif
        }
#endif

        /*
         * We need to finish setting up the globaldata page for the BSP.
         * locore has already populated the page table for the mdglobaldata
         * portion.
         */
        pg = MDGLOBALDATA_BASEALLOC_PAGES;
        gd = &CPU_prvspace[0].mdglobaldata;

        cpu_invltlb();
}

#ifdef SMP
/*
 * Set 4mb pdir for mp startup
 */
void
pmap_set_opt(void)
{
        if (pseflag && (cpu_feature & CPUID_PSE)) {
                load_cr4(rcr4() | CR4_PSE);
                if (pdir4mb && mycpu->gd_cpuid == 0) {  /* only on BSP */
                        cpu_invltlb();
                }
        }
}
#endif

/*
 *      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;

        /*
         * 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);
        }

        /*
         * init the pv free list
         */
        initial_pvs = vm_page_array_size;
        if (initial_pvs < MINPV)
                initial_pvs = MINPV;
        pvzone = &pvzone_store;
        pvinit = (void *)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;
        int entry_max;

        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);

        /*
         * Subtract out pages already installed in the zone (hack)
         */
        entry_max = pv_entry_max - vm_page_array_size;
        if (entry_max <= 0)
                entry_max = 1;

        zinitna(pvzone, &pvzone_obj, NULL, 0, entry_max, ZONE_INTERRUPT, 1);
}


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

#if defined(PMAP_DIAGNOSTIC)

/*
 * This code checks for non-writeable/modified pages.
 * This should be an invalid condition.
 */
static
int
pmap_nw_modified(pt_entry_t pte)
{
        if ((pte & (PG_M|PG_RW)) == PG_M)
                return 1;
        else
                return 0;
}
#endif


/*
 * this routine defines the region(s) of memory that should
 * not be tested for the modified bit.
 */
static __inline
int
pmap_track_modified(vm_pindex_t pindex)
{
        vm_offset_t va = (vm_offset_t)pindex << PAGE_SHIFT;
        if ((va < clean_sva) || (va >= clean_eva)) 
                return 1;
        else
                return 0;
}

/*
 * Extract the physical page address associated with the map/VA pair.
 * The page must be wired for this to work reliably.
 *
 * XXX for the moment we're using pv_find() instead of pv_get(), as
 *     callers might be expecting non-blocking operation.
 */
vm_paddr_t 
pmap_extract(pmap_t pmap, vm_offset_t va)
{
        vm_paddr_t rtval;
        pv_entry_t pt_pv;
        pt_entry_t *ptep;

        rtval = 0;
        if (va >= VM_MAX_USER_ADDRESS) {
                /*
                 * Kernel page directories might be direct-mapped and
                 * there is typically no PV tracking of pte's
                 */
                pd_entry_t *pt;

                pt = pmap_pt(pmap, va);
                if (pt && (*pt & PG_V)) {
                        if (*pt & PG_PS) {
                                rtval = *pt & PG_PS_FRAME;
                                rtval |= va & PDRMASK;
                        } else {
                                ptep = pmap_pt_to_pte(pt, va);
                                if (*pt & PG_V) {
                                        rtval = *ptep & PG_FRAME;
                                        rtval |= va & PAGE_MASK;
                                }
                        }
                }
        } else {
                /*
                 * User pages currently do not direct-map the page directory
                 * and some pages might not used managed PVs.  But all PT's
                 * will have a PV.
                 */
                pt_pv = pv_find(pmap, pmap_pt_pindex(va));
                if (pt_pv) {
                        ptep = pv_pte_lookup(pt_pv, pmap_pte_index(va));
                        if (*ptep & PG_V) {
                                rtval = *ptep & PG_FRAME;
                                rtval |= va & PAGE_MASK;
                        }
                        pv_drop(pt_pv);
                }
        }
        return rtval;
}

/*
 * Extract the physical page address associated kernel virtual address.
 */
vm_paddr_t
pmap_kextract(vm_offset_t va)
{
        pd_entry_t pt;          /* pt entry in pd */
        vm_paddr_t pa;

        if (va >= DMAP_MIN_ADDRESS && va < DMAP_MAX_ADDRESS) {
                pa = DMAP_TO_PHYS(va);
        } else {
                pt = *vtopt(va);
                if (pt & PG_PS) {
                        pa = (pt & 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_pt_to_pte(&pt, va);
                        pa = (pa & PG_FRAME) | (va & PAGE_MASK);
                }
        }
        return pa;
}

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

/*
 * Routine: pmap_kenter
 * Function:
 *      Add a wired page to the KVA
 *      NOTE! note that in order for the mapping to take effect -- you
 *      should do an invltlb after doing the pmap_kenter().
 */
void 
pmap_kenter(vm_offset_t va, vm_paddr_t pa)
{
        pt_entry_t *pte;
        pt_entry_t npte;
        pmap_inval_info info;

        pmap_inval_init(&info);                         /* XXX remove */
        npte = pa | PG_RW | PG_V | pgeflag;
        pte = vtopte(va);
        pmap_inval_interlock(&info, &kernel_pmap, va);  /* XXX remove */
        *pte = npte;
        pmap_inval_deinterlock(&info, &kernel_pmap);    /* XXX remove */
        pmap_inval_done(&info);                         /* XXX remove */
}

/*
 * Routine: pmap_kenter_quick
 * Function:
 *      Similar to pmap_kenter(), except we only invalidate the
 *      mapping on the current CPU.
 */
void
pmap_kenter_quick(vm_offset_t va, vm_paddr_t pa)
{
        pt_entry_t *pte;
        pt_entry_t npte;

        npte = pa | PG_RW | PG_V | pgeflag;
        pte = vtopte(va);
        *pte = npte;
        cpu_invlpg((void *)va);
}

void
pmap_kenter_sync(vm_offset_t va)
{
        pmap_inval_info info;

        pmap_inval_init(&info);
        pmap_inval_interlock(&info, &kernel_pmap, va);
        pmap_inval_deinterlock(&info, &kernel_pmap);
        pmap_inval_done(&info);
}

void
pmap_kenter_sync_quick(vm_offset_t va)
{
        cpu_invlpg((void *)va);
}

/*
 * remove a page from the kernel pagetables
 */
void
pmap_kremove(vm_offset_t va)
{
        pt_entry_t *pte;
        pmap_inval_info info;

        pmap_inval_init(&info);
        pte = vtopte(va);
        pmap_inval_interlock(&info, &kernel_pmap, va);
        *pte = 0;
        pmap_inval_deinterlock(&info, &kernel_pmap);
        pmap_inval_done(&info);
}

void
pmap_kremove_quick(vm_offset_t va)
{
        pt_entry_t *pte;
        pte = vtopte(va);
        *pte = 0;
        cpu_invlpg((void *)va);
}

/*
 * XXX these need to be recoded.  They are not used in any critical path.
 */
void
pmap_kmodify_rw(vm_offset_t va)
{
        atomic_set_long(vtopte(va), PG_RW);
        cpu_invlpg((void *)va);
}

void
pmap_kmodify_nc(vm_offset_t va)
{
        atomic_set_long(vtopte(va), PG_N);
        cpu_invlpg((void *)va);
}

/*
 * Used to map a range of physical addresses into kernel virtual
 * address space during the low level boot, typically to map the
 * dump bitmap, message buffer, and vm_page_array.
 *
 * These mappings are typically made at some pointer after the end of the
 * kernel text+data.
 *
 * We could return PHYS_TO_DMAP(start) here and not allocate any
 * via (*virtp), but then kmem from userland and kernel dumps won't
 * have access to the related pointers.
 */
vm_offset_t
pmap_map(vm_offset_t *virtp, vm_paddr_t start, vm_paddr_t end, int prot)
{
        vm_offset_t va;
        vm_offset_t va_start;

        /*return PHYS_TO_DMAP(start);*/

        va_start = *virtp;
        va = va_start;

        while (start < end) {
                pmap_kenter_quick(va, start);
                va += PAGE_SIZE;
                start += PAGE_SIZE;
        }
        *virtp = va;
        return va_start;
}


/*
 * Add a list of wired pages to the kva
 * this routine is only used for temporary
 * kernel mappings that do not need to have
 * page modification or references recorded.
 * Note that old mappings are simply written
 * over.  The page *must* be wired.
 */
void
pmap_qenter(vm_offset_t va, vm_page_t *m, int count)
{
        vm_offset_t end_va;

        end_va = va + count * PAGE_SIZE;
                
        while (va < end_va) {
                pt_entry_t *pte;

                pte = vtopte(va);
                *pte = VM_PAGE_TO_PHYS(*m) | PG_RW | PG_V | pgeflag;
                cpu_invlpg((void *)va);
                va += PAGE_SIZE;
                m++;
        }
        smp_invltlb();
}

/*
 * This routine jerks page mappings from the
 * kernel -- it is meant only for temporary mappings.
 *
 * MPSAFE, INTERRUPT SAFE (cluster callback)
 */
void
pmap_qremove(vm_offset_t va, int count)
{
        vm_offset_t end_va;

        end_va = va + count * PAGE_SIZE;

        while (va < end_va) {
                pt_entry_t *pte;

                pte = vtopte(va);
                *pte = 0;
                cpu_invlpg((void *)va);
                va += PAGE_SIZE;
        }
        smp_invltlb();
}

/*
 * 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 & alignment */
        td->td_pcb = (struct pcb *)(td->td_kstack + td->td_kstack_size) - 1;
        td->td_pcb = (struct pcb *)((intptr_t)td->td_pcb & ~(intptr_t)0xF);
        td->td_savefpu = &td->td_pcb->pcb_save;
        td->td_sp = (char *)td->td_pcb; /* no -16 */
}

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

/*
 * Initialize pmap0/vmspace0.  This pmap is not added to pmap_list because
 * it, and IdlePTD, represents the template used to update all other pmaps.
 *
 * On architectures where the kernel pmap is not integrated into the user
 * process pmap, this pmap represents the process pmap, not the kernel pmap.
 * kernel_pmap should be used to directly access the kernel_pmap.
 */
void
pmap_pinit0(struct pmap *pmap)
{
        pmap->pm_pml4 = (pml4_entry_t *)(PTOV_OFFSET + KPML4phys);
        pmap->pm_count = 1;
        pmap->pm_active = 0;
        pmap->pm_pvhint = NULL;
        RB_INIT(&pmap->pm_pvroot);
        spin_init(&pmap->pm_spin);
        lwkt_token_init(&pmap->pm_token, "pmap_tok");
        bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
}

/*
 * Initialize a preallocated and zeroed pmap structure,
 * such as one in a vmspace structure.
 */
void
pmap_pinit(struct pmap *pmap)
{
        pv_entry_t pv;
        int j;

        /*
         * Misc initialization
         */
        pmap->pm_count = 1;
        pmap->pm_active = 0;
        pmap->pm_pvhint = NULL;
        if (pmap->pm_pmlpv == NULL) {
                RB_INIT(&pmap->pm_pvroot);
                bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
                spin_init(&pmap->pm_spin);
                lwkt_token_init(&pmap->pm_token, "pmap_tok");
        }

        /*
         * 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 the page directory page, which wires it even though
         * it isn't being entered into some higher level page table (it
         * being the highest level).  If one is already cached we don't
         * have to do anything.
         */
        if ((pv = pmap->pm_pmlpv) == NULL) {
                pv = pmap_allocpte(pmap, pmap_pml4_pindex(), NULL);
                pmap->pm_pmlpv = pv;
                pmap_kenter((vm_offset_t)pmap->pm_pml4,
                            VM_PAGE_TO_PHYS(pv->pv_m));
                pv_put(pv);

                /*
                 * Install DMAP and KMAP.
                 */
                for (j = 0; j < NDMPML4E; ++j) {
                        pmap->pm_pml4[DMPML4I + j] =
                                (DMPDPphys + ((vm_paddr_t)j << PML4SHIFT)) |
                                PG_RW | PG_V | PG_U;
                }
                pmap->pm_pml4[KPML4I] = KPDPphys | PG_RW | PG_V | PG_U;

                /*
                 * install self-referential address mapping entry
                 */
                pmap->pm_pml4[PML4PML4I] = VM_PAGE_TO_PHYS(pv->pv_m) |
                                           PG_V | PG_RW | PG_A | PG_M;
        } else {
                KKASSERT(pv->pv_m->flags & PG_MAPPED);
                KKASSERT(pv->pv_m->flags & PG_WRITEABLE);
        }
}

/*
 * 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.
 */
void
pmap_puninit(pmap_t pmap)
{
        pv_entry_t pv;
        vm_page_t p;

        KKASSERT(pmap->pm_active == 0);
        if ((pv = pmap->pm_pmlpv) != NULL) {
                if (pv_hold_try(pv) == 0)
                        pv_lock(pv);
                p = pmap_remove_pv_page(pv, 1);
                pv_free(pv);
                pmap_kremove((vm_offset_t)pmap->pm_pml4);
                vm_page_busy_wait(p, FALSE, "pgpun");
                vm_page_unhold(p);
                KKASSERT(p->flags & (PG_FICTITIOUS|PG_UNMANAGED));
                vm_page_unwire(p, 0);
                vm_page_flag_clear(p, PG_MAPPED | PG_WRITEABLE);

                /*
                 * XXX eventually clean out PML4 static entries and
                 * use vm_page_free_zero()
                 */
                vm_page_free(p);
                pmap->pm_pmlpv = NULL;
        }
        if (pmap->pm_pml4) {
                KKASSERT(pmap->pm_pml4 != (void *)(PTOV_OFFSET + KPML4phys));
                kmem_free(&kernel_map, (vm_offset_t)pmap->pm_pml4, PAGE_SIZE);
                pmap->pm_pml4 = NULL;
        }
        KKASSERT(pmap->pm_stats.resident_count == 0);
        KKASSERT(pmap->pm_stats.wired_count == 0);
}

/*
 * 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.
 */
void
pmap_pinit2(struct pmap *pmap)
{
        /*
         * XXX copies current process, does not fill in MPPTDI
         */
        spin_lock(&pmap_spin);
        TAILQ_INSERT_TAIL(&pmap_list, pmap, pm_pmnode);
        spin_unlock(&pmap_spin);
}

/*
 * This routine is called when various levels in the page table need to
 * be populated.  This routine cannot fail.
 *
 * This function returns two locked pv_entry's, one representing the
 * requested pv and one representing the requested pv's parent pv.  If
 * the pv did not previously exist it will be mapped into its parent
 * and wired, otherwise no additional wire count will be added.
 */
static
pv_entry_t
pmap_allocpte(pmap_t pmap, vm_pindex_t ptepindex, pv_entry_t *pvpp)
{
        pt_entry_t *ptep;
        pv_entry_t pv;
        pv_entry_t pvp;
        vm_pindex_t pt_pindex;
        vm_page_t m;
        int isnew;

        /*
         * If the pv already exists and we aren't being asked for the
         * parent page table page we can just return it.  A locked+held pv
         * is returned.
         */
        pv = pv_alloc(pmap, ptepindex, &isnew);
        if (isnew == 0 && pvpp == NULL)
                return(pv);

        /*
         * This is a new PV, we have to resolve its parent page table and
         * add an additional wiring to the page if necessary.
         */

        /*
         * Special case terminal PVs.  These are not page table pages so
         * no vm_page is allocated (the caller supplied the vm_page).  If
         * pvpp is non-NULL we are being asked to also removed the pt_pv
         * for this pv.
         *
         * Note that pt_pv's are only returned for user VAs. We assert that
         * a pt_pv is not being requested for kernel VAs.
         */
        if (ptepindex < pmap_pt_pindex(0)) {
                if (ptepindex >= NUPTE_USER)
                        KKASSERT(pvpp == NULL);
                else
                        KKASSERT(pvpp != NULL);
                if (pvpp) {
                        pt_pindex = NUPTE_TOTAL + (ptepindex >> NPTEPGSHIFT);
                        pvp = pmap_allocpte(pmap, pt_pindex, NULL);
                        if (isnew)
                                vm_page_wire_quick(pvp->pv_m);
                        *pvpp = pvp;
                } else {
                        pvp = NULL;
                }
                return(pv);
        }

        /*
         * Non-terminal PVs allocate a VM page to represent the page table,
         * so we have to resolve pvp and calculate ptepindex for the pvp
         * and then for the page table entry index in the pvp for
         * fall-through.
         */
        if (ptepindex < pmap_pd_pindex(0)) {
                /*
                 * pv is PT, pvp is PD
                 */
                ptepindex = (ptepindex - pmap_pt_pindex(0)) >> NPDEPGSHIFT;
                ptepindex += NUPTE_TOTAL + NUPT_TOTAL;
                pvp = pmap_allocpte(pmap, ptepindex, NULL);
                if (!isnew)
                        goto notnew;

                /*
                 * PT index in PD
                 */
                ptepindex = pv->pv_pindex - pmap_pt_pindex(0);
                ptepindex &= ((1ul << NPDEPGSHIFT) - 1);
        } else if (ptepindex < pmap_pdp_pindex(0)) {
                /*
                 * pv is PD, pvp is PDP
                 */
                ptepindex = (ptepindex - pmap_pd_pindex(0)) >> NPDPEPGSHIFT;
                ptepindex += NUPTE_TOTAL + NUPT_TOTAL + NUPD_TOTAL;
                pvp = pmap_allocpte(pmap, ptepindex, NULL);
                if (!isnew)
                        goto notnew;

                /*
                 * PD index in PDP
                 */
                ptepindex = pv->pv_pindex - pmap_pd_pindex(0);
                ptepindex &= ((1ul << NPDPEPGSHIFT) - 1);
        } else if (ptepindex < pmap_pml4_pindex()) {
                /*
                 * pv is PDP, pvp is the root pml4 table
                 */
                pvp = pmap_allocpte(pmap, pmap_pml4_pindex(), NULL);
                if (!isnew)
                        goto notnew;

                /*
                 * PDP index in PML4
                 */
                ptepindex = pv->pv_pindex - pmap_pdp_pindex(0);
                ptepindex &= ((1ul << NPML4EPGSHIFT) - 1);
        } else {
                /*
                 * pv represents the top-level PML4, there is no parent.
                 */
                pvp = NULL;
                if (!isnew)
                        goto notnew;
        }

        /*
         * This code is only reached if isnew is TRUE and this is not a
         * terminal PV.  We need to allocate a vm_page for the page table
         * at this level and enter it into the parent page table.
         *
         * page table pages are marked PG_WRITEABLE and PG_MAPPED.
         */
        for (;;) {
                m = vm_page_alloc(NULL, pv->pv_pindex,
                                  VM_ALLOC_NORMAL | VM_ALLOC_SYSTEM |
                                  VM_ALLOC_INTERRUPT);
                if (m)
                        break;
                vm_wait(0);
        }
        vm_page_spin_lock(m);
        TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
        pv->pv_m = m;
        vm_page_flag_set(m, PG_MAPPED | PG_WRITEABLE);
        vm_page_spin_unlock(m);
        vm_page_unmanage(m);    /* m must be spinunlocked */

        if ((m->flags & PG_ZERO) == 0) {
                pmap_zero_page(VM_PAGE_TO_PHYS(m));
        }
#ifdef PMAP_DEBUG
        else {
                pmap_page_assertzero(VM_PAGE_TO_PHYS(m));
        }
#endif
        m->valid = VM_PAGE_BITS_ALL;
        vm_page_flag_clear(m, PG_ZERO);
        vm_page_wire(m);        /* wire for mapping in parent */

        /*
         * Wire the page into pvp, bump the wire-count for pvp's page table
         * page.  Bump the resident_count for the pmap.  There is no pvp
         * for the top level, address the pm_pml4[] array directly.
         *
         * If the caller wants the parent we return it, otherwise
         * we just put it away.
         *
         * No interlock is needed for pte 0 -> non-zero.
         */
        if (pvp) {
                vm_page_wire_quick(pvp->pv_m);
                ptep = pv_pte_lookup(pvp, ptepindex);
                KKASSERT((*ptep & PG_V) == 0);
                *ptep = VM_PAGE_TO_PHYS(m) | (PG_U | PG_RW | PG_V |
                                              PG_A | PG_M);
        }
        vm_page_wakeup(m);
notnew:
        if (pvpp)
                *pvpp = pvp;
        else if (pvp)
                pv_put(pvp);
        return (pv);
}

/*
 * 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
 */
struct pmap_release_info {
        pmap_t  pmap;
        int     retry;
};

static int pmap_release_callback(pv_entry_t pv, void *data);

void
pmap_release(struct pmap *pmap)
{
        struct pmap_release_info info;

        KASSERT(pmap->pm_active == 0,
                ("pmap still active! %016jx", (uintmax_t)pmap->pm_active));

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

        /*
         * Pull pv's off the RB tree in order from low to high and release
         * each page.
         */
        info.pmap = pmap;
        do {
                info.retry = 0;
                spin_lock(&pmap->pm_spin);
                RB_SCAN(pv_entry_rb_tree, &pmap->pm_pvroot, NULL,
                        pmap_release_callback, &info);
                spin_unlock(&pmap->pm_spin);
        } while (info.retry);


        /*
         * One resident page (the pml4 page) should remain.
         * No wired pages should remain.
         */
        KKASSERT(pmap->pm_stats.resident_count == 1);
        KKASSERT(pmap->pm_stats.wired_count == 0);
}

static int
pmap_release_callback(pv_entry_t pv, void *data)
{
        struct pmap_release_info *info = data;
        pmap_t pmap = info->pmap;
        vm_page_t p;

        if (pv_hold_try(pv)) {
                spin_unlock(&pmap->pm_spin);
        } else {
                spin_unlock(&pmap->pm_spin);
                pv_lock(pv);
                if (pv->pv_pmap != pmap) {
                        pv_put(pv);
                        spin_lock(&pmap->pm_spin);
                        info->retry = 1;
                        return(-1);
                }
        }

        /*
         * The pmap is currently not spinlocked, pv is held+locked.
         * Remove the pv's page from its parent's page table.  The
         * parent's page table page's wire_count will be decremented.
         */
        pmap_remove_pv_pte(pv, NULL, NULL);

        /*
         * Terminal pvs are unhooked from their vm_pages.  Because
         * terminal pages aren't page table pages they aren't wired
         * by us, so we have to be sure not to unwire them either.
         */
        if (pv->pv_pindex < pmap_pt_pindex(0)) {
                pmap_remove_pv_page(pv, 0);
                goto skip;
        }

        /*
         * We leave the top-level page table page cached, wired, and
         * mapped in the pmap until the dtor function (pmap_puninit())
         * gets called.
         *
         * Since we are leaving the top-level pv intact we need
         * to break out of what would otherwise be an infinite loop.
         */
        if (pv->pv_pindex == pmap_pml4_pindex()) {
                pv_put(pv);
                spin_lock(&pmap->pm_spin);
                return(-1);
        }

        /*
         * For page table pages (other than the top-level page),
         * remove and free the vm_page.  The representitive mapping
         * removed above by pmap_remove_pv_pte() did not undo the
         * last wire_count so we have to do that as well.
         */
        p = pmap_remove_pv_page(pv, 1);
        vm_page_busy_wait(p, FALSE, "pmaprl");
        vm_page_unhold(p);
        if (p->wire_count != 1) {
                kprintf("p->wire_count was %016lx %d\n",
                        pv->pv_pindex, p->wire_count);
        }
        KKASSERT(p->wire_count == 1);
        KKASSERT(p->flags & PG_UNMANAGED);

        vm_page_unwire(p, 0);
        KKASSERT(p->wire_count == 0);
        /* JG eventually revert to using vm_page_free_zero() */
        vm_page_free(p);
skip:
        pv_free(pv);
        spin_lock(&pmap->pm_spin);
        return(0);
}

/*
 * This function will remove the pte associated with a pv from its parent.
 * Terminal pv's are supported.  The removal will be interlocked if info
 * is non-NULL.  The caller must dispose of pv instead of just unlocking
 * it.
 *
 * The wire count will be dropped on the parent page table.  The wire
 * count on the page being removed (pv->pv_m) from the parent page table
 * is NOT touched.  Note that terminal pages will not have any additional
 * wire counts while page table pages will have at least one representing
 * the mapping, plus others representing sub-mappings.
 *
 * NOTE: Cannot be called on kernel page table pages, only KVM terminal
 *       pages and user page table and terminal pages.
 *
 * The pv must be locked.
 *
 * XXX must lock parent pv's if they exist to remove pte XXX
 */
static
void
pmap_remove_pv_pte(pv_entry_t pv, pv_entry_t pvp, struct pmap_inval_info *info)
{
        vm_pindex_t ptepindex = pv->pv_pindex;
        pmap_t pmap = pv->pv_pmap;
        vm_page_t p;
        int gotpvp = 0;

        KKASSERT(pmap);

        if (ptepindex == pmap_pml4_pindex()) {
                /*
                 * We are the top level pml4 table, there is no parent.
                 */
                p = pmap->pm_pmlpv->pv_m;
        } else if (ptepindex >= pmap_pdp_pindex(0)) {
                /*
                 * Remove a PDP page from the pml4e.  This can only occur
                 * with user page tables.  We do not have to lock the
                 * pml4 PV so just ignore pvp.
                 */
                vm_pindex_t pml4_pindex;
                vm_pindex_t pdp_index;
                pml4_entry_t *pdp;

                pdp_index = ptepindex - pmap_pdp_pindex(0);
                if (pvp == NULL) {
                        pml4_pindex = pmap_pml4_pindex();
                        pvp = pv_get(pv->pv_pmap, pml4_pindex);
                        gotpvp = 1;
                }
                pdp = &pmap->pm_pml4[pdp_index & ((1ul << NPML4EPGSHIFT) - 1)];
                KKASSERT((*pdp & PG_V) != 0);
                p = PHYS_TO_VM_PAGE(*pdp & PG_FRAME);
                *pdp = 0;
                KKASSERT(info == NULL);
        } else if (ptepindex >= pmap_pd_pindex(0)) {
                /*
                 *  Remove a PD page from the pdp
                 */
                vm_pindex_t pdp_pindex;
                vm_pindex_t pd_index;
                pdp_entry_t *pd;

                pd_index = ptepindex - pmap_pd_pindex(0);

                if (pvp == NULL) {
                        pdp_pindex = NUPTE_TOTAL + NUPT_TOTAL + NUPD_TOTAL +
                                     (pd_index >> NPML4EPGSHIFT);
                        pvp = pv_get(pv->pv_pmap, pdp_pindex);
                        gotpvp = 1;
                }
                pd = pv_pte_lookup(pvp, pd_index & ((1ul << NPDPEPGSHIFT) - 1));
                KKASSERT((*pd & PG_V) != 0);
                p = PHYS_TO_VM_PAGE(*pd & PG_FRAME);
                *pd = 0;
                KKASSERT(info == NULL);
        } else if (ptepindex >= pmap_pt_pindex(0)) {
                /*
                 *  Remove a PT page from the pd
                 */
                vm_pindex_t pd_pindex;
                vm_pindex_t pt_index;
                pd_entry_t *pt;

                pt_index = ptepindex - pmap_pt_pindex(0);

                if (pvp == NULL) {
                        pd_pindex = NUPTE_TOTAL + NUPT_TOTAL +
                                    (pt_index >> NPDPEPGSHIFT);
                        pvp = pv_get(pv->pv_pmap, pd_pindex);
                        gotpvp = 1;
                }
                pt = pv_pte_lookup(pvp, pt_index & ((1ul << NPDPEPGSHIFT) - 1));
                KKASSERT((*pt & PG_V) != 0);
                p = PHYS_TO_VM_PAGE(*pt & PG_FRAME);
                *pt = 0;
                KKASSERT(info == NULL);
        } else {
                /*
                 * Remove a PTE from the PT page
                 *
                 * NOTE: pv's must be locked bottom-up to avoid deadlocking.
                 *       pv is a pte_pv so we can safely lock pt_pv.
                 */
                vm_pindex_t pt_pindex;
                pt_entry_t *ptep;
                pt_entry_t pte;
                vm_offset_t va;

                pt_pindex = ptepindex >> NPTEPGSHIFT;
                va = (vm_offset_t)ptepindex << PAGE_SHIFT;

                if (ptepindex >= NUPTE_USER) {
                        ptep = vtopte(ptepindex << PAGE_SHIFT);
                        KKASSERT(pvp == NULL);
                } else {
                        if (pvp == NULL) {
                                pt_pindex = NUPTE_TOTAL +
                                            (ptepindex >> NPDPEPGSHIFT);
                                pvp = pv_get(pv->pv_pmap, pt_pindex);
                                gotpvp = 1;
                        }
                        ptep = pv_pte_lookup(pvp, ptepindex &
                                                  ((1ul << NPDPEPGSHIFT) - 1));
                }

                if (info)
                        pmap_inval_interlock(info, pmap, va);
                pte = pte_load_clear(ptep);
                if (info)
                        pmap_inval_deinterlock(info, pmap);

                /*
                 * Now update the vm_page_t
                 */
                if ((pte & (PG_MANAGED|PG_V)) != (PG_MANAGED|PG_V)) {
                        kprintf("remove_pte badpte %016lx %016lx %d\n",
                                pte, pv->pv_pindex,
                                pv->pv_pindex < pmap_pt_pindex(0));
                }
                /*KKASSERT((pte & (PG_MANAGED|PG_V)) == (PG_MANAGED|PG_V));*/
                p = PHYS_TO_VM_PAGE(pte & PG_FRAME);

                if (pte & PG_M) {
                        if (pmap_track_modified(ptepindex))
                                vm_page_dirty(p);
                }
                if (pte & PG_A) {
                        vm_page_flag_set(p, PG_REFERENCED);
                }
                if (pte & PG_W)
                        atomic_add_long(&pmap->pm_stats.wired_count, -1);
                if (pte & PG_G)
                        cpu_invlpg((void *)va);
        }

        /*
         * Unwire the parent page table page.  The wire_count cannot go below
         * 1 here because the parent page table page is itself still mapped.
         *
         * XXX remove the assertions later.
         */
        KKASSERT(pv->pv_m == p);
        if (pvp && vm_page_unwire_quick(pvp->pv_m))
                panic("pmap_remove_pv_pte: Insufficient wire_count");

        if (gotpvp)
                pv_put(pvp);
}

static
vm_page_t
pmap_remove_pv_page(pv_entry_t pv, int holdpg)
{
        vm_page_t m;

        m = pv->pv_m;
        if (holdpg)
                vm_page_hold(m);
        KKASSERT(m);
        vm_page_spin_lock(m);
        pv->pv_m = NULL;
        TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
        /*
        if (m->object)
                atomic_add_int(&m->object->agg_pv_list_count, -1);
        */
        if (TAILQ_EMPTY(&m->md.pv_list))
                vm_page_flag_clear(m, PG_MAPPED | PG_WRITEABLE);
        vm_page_spin_unlock(m);
        if (holdpg)
                return(m);
        return(NULL);
}

/*
 * Grow the number of kernel page table entries, if needed.
 *
 * This routine is always called to validate any address space
 * beyond KERNBASE (for kldloads).  kernel_vm_end only governs the address
 * space below KERNBASE.
 */
void
pmap_growkernel(vm_offset_t kstart, vm_offset_t kend)
{
        vm_paddr_t paddr;
        vm_offset_t ptppaddr;
        vm_page_t nkpg;
        pd_entry_t *pt, newpt;
        pdp_entry_t newpd;
        int update_kernel_vm_end;

        /*
         * bootstrap kernel_vm_end on first real VM use
         */
        if (kernel_vm_end == 0) {
                kernel_vm_end = VM_MIN_KERNEL_ADDRESS;
                nkpt = 0;
                while ((*pmap_pt(&kernel_pmap, kernel_vm_end) & PG_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;                       
                        }
                }
        }

        /*
         * Fill in the gaps.  kernel_vm_end is only adjusted for ranges
         * below KERNBASE.  Ranges above KERNBASE are kldloaded and we
         * do not want to force-fill 128G worth of page tables.
         */
        if (kstart < KERNBASE) {
                if (kstart > kernel_vm_end)
                        kstart = kernel_vm_end;
                KKASSERT(kend <= KERNBASE);
                update_kernel_vm_end = 1;
        } else {
                update_kernel_vm_end = 0;
        }

        kstart = rounddown2(kstart, PAGE_SIZE * NPTEPG);
        kend = roundup2(kend, PAGE_SIZE * NPTEPG);

        if (kend - 1 >= kernel_map.max_offset)
                kend = kernel_map.max_offset;

        while (kstart < kend) {
                pt = pmap_pt(&kernel_pmap, kstart);
                if (pt == NULL) {
                        /* We need a new PDP entry */
                        nkpg = vm_page_alloc(NULL, 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);
                        newpd = (pdp_entry_t)
                                (paddr | PG_V | PG_RW | PG_A | PG_M);
                        *pmap_pd(&kernel_pmap, kstart) = newpd;
                        nkpt++;
                        continue; /* try again */
                }
                if ((*pt & PG_V) != 0) {
                        kstart = (kstart + PAGE_SIZE * NPTEPG) &
                                 ~(PAGE_SIZE * NPTEPG - 1);
                        if (kstart - 1 >= kernel_map.max_offset) {
                                kstart = kernel_map.max_offset;
                                break;                       
                        }
                        continue;
                }

                /*
                 * This index is bogus, but out of the way
                 */
                nkpg = vm_page_alloc(NULL, 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);
                newpt = (pd_entry_t) (ptppaddr | PG_V | PG_RW | PG_A | PG_M);
                *pmap_pt(&kernel_pmap, kstart) = newpt;
                nkpt++;

                kstart = (kstart + PAGE_SIZE * NPTEPG) &
                          ~(PAGE_SIZE * NPTEPG - 1);

                if (kstart - 1 >= kernel_map.max_offset) {
                        kstart = kernel_map.max_offset;
                        break;                       
                }
        }

        /*
         * Only update kernel_vm_end for areas below KERNBASE.
         */
        if (update_kernel_vm_end && kernel_vm_end < kstart)
                kernel_vm_end = kstart;
}

/*
 *      Retire the given physical map from service.
 *      Should only be called if the map contains
 *      no valid mappings.
 */
void
pmap_destroy(pmap_t pmap)
{
        int count;

        if (pmap == NULL)
                return;

        lwkt_gettoken(&pmap->pm_token);
        count = --pmap->pm_count;
        if (count == 0) {
                pmap_release(pmap);     /* eats pm_token */
                panic("destroying a pmap is not yet implemented");
        }
        lwkt_reltoken(&pmap->pm_token);
}

/*
 *      Add a reference to the specified pmap.
 */
void
pmap_reference(pmap_t pmap)
{
        if (pmap != NULL) {
                lwkt_gettoken(&pmap->pm_token);
                pmap->pm_count++;
                lwkt_reltoken(&pmap->pm_token);
        }
}

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

/*
 * Hold a pv without locking it
 */
static void
pv_hold(pv_entry_t pv)
{
        u_int count;

        if (atomic_cmpset_int(&pv->pv_hold, 0, 1))
                return;

        for (;;) {
                count = pv->pv_hold;
                cpu_ccfence();
                if (atomic_cmpset_int(&pv->pv_hold, count, count + 1))
                        return;
                /* retry */
        }
}

/*
 * Hold a pv_entry, preventing its destruction.  TRUE is returned if the pv
 * was successfully locked, FALSE if it wasn't.  The caller must dispose of
 * the pv properly.
 *
 * Either the pmap->pm_spin or the related vm_page_spin (if traversing a
 * pv list via its page) must be held by the caller.
 */
static int
_pv_hold_try(pv_entry_t pv PMAP_DEBUG_DECL)
{
        u_int count;

        if (atomic_cmpset_int(&pv->pv_hold, 0, PV_HOLD_LOCKED | 1)) {
#ifdef PMAP_DEBUG
                pv->pv_func = func;
                pv->pv_line = lineno;
#endif
                return TRUE;
        }

        for (;;) {
                count = pv->pv_hold;
                cpu_ccfence();
                if ((count & PV_HOLD_LOCKED) == 0) {
                        if (atomic_cmpset_int(&pv->pv_hold, count,
                                              (count + 1) | PV_HOLD_LOCKED)) {
#ifdef PMAP_DEBUG
                                pv->pv_func = func;
                                pv->pv_line = lineno;
#endif
                                return TRUE;
                        }
                } else {
                        if (atomic_cmpset_int(&pv->pv_hold, count, count + 1))
                                return FALSE;
                }
                /* retry */
        }
}

/*
 * Drop a previously held pv_entry which could not be locked, allowing its
 * destruction.
 *
 * Must not be called with a spinlock held as we might zfree() the pv if it
 * is no longer associated with a pmap and this was the last hold count.
 */
static void
pv_drop(pv_entry_t pv)
{
        u_int count;

        if (atomic_cmpset_int(&pv->pv_hold, 1, 0)) {
                if (pv->pv_pmap == NULL)
                        zfree(pvzone, pv);
                return;
        }

        for (;;) {
                count = pv->pv_hold;
                cpu_ccfence();
                KKASSERT((count & PV_HOLD_MASK) > 0);
                KKASSERT((count & (PV_HOLD_LOCKED | PV_HOLD_MASK)) !=
                         (PV_HOLD_LOCKED | 1));
                if (atomic_cmpset_int(&pv->pv_hold, count, count - 1)) {
                        if (count == 1 && pv->pv_pmap == NULL)
                                zfree(pvzone, pv);
                        return;
                }
                /* retry */
        }
}

/*
 * Find or allocate the requested PV entry, returning a locked pv
 */
static
pv_entry_t
_pv_alloc(pmap_t pmap, vm_pindex_t pindex, int *isnew PMAP_DEBUG_DECL)
{
        pv_entry_t pv;
        pv_entry_t pnew = NULL;

        spin_lock(&pmap->pm_spin);
        for (;;) {
                if ((pv = pmap->pm_pvhint) == NULL || pv->pv_pindex != pindex) {
                        pv = pv_entry_rb_tree_RB_LOOKUP(&pmap->pm_pvroot,
                                                        pindex);
                }
                if (pv == NULL) {
                        if (pnew == NULL) {
                                spin_unlock(&pmap->pm_spin);
                                pnew = zalloc(pvzone);
                                spin_lock(&pmap->pm_spin);
                                continue;
                        }
                        pnew->pv_pmap = pmap;
                        pnew->pv_pindex = pindex;
                        pnew->pv_hold = PV_HOLD_LOCKED | 1;
#ifdef PMAP_DEBUG
                        pnew->pv_func = func;
                        pnew->pv_line = lineno;
#endif
                        pv_entry_rb_tree_RB_INSERT(&pmap->pm_pvroot, pnew);
                        atomic_add_long(&pmap->pm_stats.resident_count, 1);
                        spin_unlock(&pmap->pm_spin);
                        *isnew = 1;
                        return(pnew);
                }
                if (pnew) {
                        spin_unlock(&pmap->pm_spin);
                        zfree(pvzone, pnew);
                        pnew = NULL;
                        spin_lock(&pmap->pm_spin);
                        continue;
                }
                if (_pv_hold_try(pv PMAP_DEBUG_COPY)) {
                        spin_unlock(&pmap->pm_spin);
                        *isnew = 0;
                        return(pv);
                }
                spin_unlock(&pmap->pm_spin);
                _pv_lock(pv PMAP_DEBUG_COPY);
                if (pv->pv_pmap == pmap && pv->pv_pindex == pindex) {
                        *isnew = 0;
                        return(pv);
                }
                pv_put(pv);
                spin_lock(&pmap->pm_spin);
        }


}

/*
 * Find the requested PV entry, returning a locked+held pv or NULL
 */
static
pv_entry_t
_pv_get(pmap_t pmap, vm_pindex_t pindex PMAP_DEBUG_DECL)
{
        pv_entry_t pv;

        spin_lock(&pmap->pm_spin);
        for (;;) {
                /*
                 * Shortcut cache
                 */
                if ((pv = pmap->pm_pvhint) == NULL || pv->pv_pindex != pindex) {
                        pv = pv_entry_rb_tree_RB_LOOKUP(&pmap->pm_pvroot,
                                                        pindex);
                }
                if (pv == NULL) {
                        spin_unlock(&pmap->pm_spin);
                        return NULL;
                }
                if (_pv_hold_try(pv PMAP_DEBUG_COPY)) {
                        pv_cache(pv, pindex);
                        spin_unlock(&pmap->pm_spin);
                        return(pv);
                }
                spin_unlock(&pmap->pm_spin);
                _pv_lock(pv PMAP_DEBUG_COPY);
                if (pv->pv_pmap == pmap && pv->pv_pindex == pindex)
                        return(pv);
                pv_put(pv);
                spin_lock(&pmap->pm_spin);
        }
}

/*
 * Lookup, hold, and attempt to lock (pmap,pindex).
 *
 * If the entry does not exist NULL is returned and *errorp is set to 0
 *
 * If the entry exists and could be successfully locked it is returned and
 * errorp is set to 0.
 *
 * If the entry exists but could NOT be successfully locked it is returned
 * held and *errorp is set to 1.
 */
static
pv_entry_t
pv_get_try(pmap_t pmap, vm_pindex_t pindex, int *errorp)
{
        pv_entry_t pv;

        spin_lock(&pmap->pm_spin);
        if ((pv = pmap->pm_pvhint) == NULL || pv->pv_pindex != pindex)
                pv = pv_entry_rb_tree_RB_LOOKUP(&pmap->pm_pvroot, pindex);
        if (pv == NULL) {
                spin_unlock(&pmap->pm_spin);
                *errorp = 0;
                return NULL;
        }
        if (pv_hold_try(pv)) {
                pv_cache(pv, pindex);
                spin_unlock(&pmap->pm_spin);
                *errorp = 0;
                return(pv);     /* lock succeeded */
        }
        spin_unlock(&pmap->pm_spin);
        *errorp = 1;
        return (pv);            /* lock failed */
}

/*
 * Find the requested PV entry, returning a held pv or NULL
 */
static
pv_entry_t
pv_find(pmap_t pmap, vm_pindex_t pindex)
{
        pv_entry_t pv;

        spin_lock(&pmap->pm_spin);

        if ((pv = pmap->pm_pvhint) == NULL || pv->pv_pindex != pindex)
                pv = pv_entry_rb_tree_RB_LOOKUP(&pmap->pm_pvroot, pindex);
        if (pv == NULL) {
                spin_unlock(&pmap->pm_spin);
                return NULL;
        }
        pv_hold(pv);
        pv_cache(pv, pindex);
        spin_unlock(&pmap->pm_spin);
        return(pv);
}

/*
 * Lock a held pv, keeping the hold count
 */
static
void
_pv_lock(pv_entry_t pv PMAP_DEBUG_DECL)
{
        u_int count;

        for (;;) {
                count = pv->pv_hold;
                cpu_ccfence();
                if ((count & PV_HOLD_LOCKED) == 0) {
                        if (atomic_cmpset_int(&pv->pv_hold, count,
                                              count | PV_HOLD_LOCKED)) {
#ifdef PMAP_DEBUG
                                pv->pv_func = func;
                                pv->pv_line = lineno;
#endif
                                return;
                        }
                        continue;
                }
                tsleep_interlock(pv, 0);
                if (atomic_cmpset_int(&pv->pv_hold, count,
                                      count | PV_HOLD_WAITING)) {
#ifdef PMAP_DEBUG
                        kprintf("pv waiting on %s:%d\n",
                                        pv->pv_func, pv->pv_line);
#endif
                        tsleep(pv, PINTERLOCKED, "pvwait", hz);
                }
                /* retry */
        }
}

/*
 * Unlock a held and locked pv, keeping the hold count.
 */
static
void
pv_unlock(pv_entry_t pv)
{
        u_int count;

        if (atomic_cmpset_int(&pv->pv_hold, PV_HOLD_LOCKED | 1, 1))
                return;

        for (;;) {
                count = pv->pv_hold;
                cpu_ccfence();
                KKASSERT((count & (PV_HOLD_LOCKED|PV_HOLD_MASK)) >=
                         (PV_HOLD_LOCKED | 1));
                if (atomic_cmpset_int(&pv->pv_hold, count,
                                      count &
                                      ~(PV_HOLD_LOCKED | PV_HOLD_WAITING))) {
                        if (count & PV_HOLD_WAITING)
                                wakeup(pv);
                        break;
                }
        }
}

/*
 * Unlock and drop a pv.  If the pv is no longer associated with a pmap
 * and the hold count drops to zero we will free it.
 *
 * Caller should not hold any spin locks.  We are protected from hold races
 * by virtue of holds only occuring only with a pmap_spin or vm_page_spin
 * lock held.  A pv cannot be located otherwise.
 */
static
void
pv_put(pv_entry_t pv)
{
        if (atomic_cmpset_int(&pv->pv_hold, PV_HOLD_LOCKED | 1, 0)) {
                if (pv->pv_pmap == NULL)
                        zfree(pvzone, pv);
                return;
        }
        pv_unlock(pv);
        pv_drop(pv);
}

/*
 * Unlock, drop, and free a pv, destroying it.  The pv is removed from its
 * pmap.  Any pte operations must have already been completed.
 */
static
void
pv_free(pv_entry_t pv)
{
        pmap_t pmap;

        KKASSERT(pv->pv_m == NULL);
        if ((pmap = pv->pv_pmap) != NULL) {
                spin_lock(&pmap->pm_spin);
                pv_entry_rb_tree_RB_REMOVE(&pmap->pm_pvroot, pv);
                if (pmap->pm_pvhint == pv)
                        pmap->pm_pvhint = NULL;
                atomic_add_long(&pmap->pm_stats.resident_count, -1);
                pv->pv_pmap = NULL;
                pv->pv_pindex = 0;
                spin_unlock(&pmap->pm_spin);
        }
        pv_put(pv);
}

/*
 * This routine is very drastic, but can save the system
 * in a pinch.
 */
void
pmap_collect(void)
{
        int i;
        vm_page_t m;
        static int warningdone=0;

        if (pmap_pagedaemon_waken == 0)
                return;
        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);
                }
        }
}

/*
 * Scan the pmap for active page table entries and issue a callback.
 * The callback must dispose of pte_pv.
 *
 * NOTE: Unmanaged page table entries will not have a pte_pv
 *
 * NOTE: Kernel page table entries will not have a pt_pv.  That is, wiring
 *       counts are not tracked in kernel page table pages.
 *
 * It is assumed that the start and end are properly rounded to the page size.
 */
static void
pmap_scan(struct pmap *pmap, vm_offset_t sva, vm_offset_t eva,
          void (*func)(pmap_t, struct pmap_inval_info *,
                       pv_entry_t, pv_entry_t, vm_offset_t,
                       pt_entry_t *, void *),
          void *arg)
{
        pv_entry_t pdp_pv;      /* A page directory page PV */
        pv_entry_t pd_pv;       /* A page directory PV */
        pv_entry_t pt_pv;       /* A page table PV */
        pv_entry_t pte_pv;      /* A page table entry PV */
        pt_entry_t *ptep;
        vm_offset_t va_next;
        struct pmap_inval_info info;
        int error;

        if (pmap == NULL)
                return;

        /*
         * Hold the token for stability; if the pmap is empty we have nothing
         * to do.
         */
        lwkt_gettoken(&pmap->pm_token);
#if 0
        if (pmap->pm_stats.resident_count == 0) {
                lwkt_reltoken(&pmap->pm_token);
                return;
        }
#endif

        pmap_inval_init(&info);

        /*
         * Special handling for removing one page, which is a very common
         * operation (it is?).
         * NOTE: Locks must be ordered bottom-up. pte,pt,pd,pdp,pml4
         */
        if (sva + PAGE_SIZE == eva) {
                if (sva >= VM_MAX_USER_ADDRESS) {
                        /*
                         * Kernel mappings do not track wire counts on
                         * page table pages.
                         */
                        pt_pv = NULL;
                        pte_pv = pv_get(pmap, pmap_pte_pindex(sva));
                        ptep = vtopte(sva);
                } else {
                        /*
                         * User mappings may or may not have a pte_pv but
                         * will always have a pt_pv if the page is present.
                         */
                        pte_pv = pv_get(pmap, pmap_pte_pindex(sva));
                        pt_pv = pv_get(pmap, pmap_pt_pindex(sva));
                        if (pt_pv == NULL) {
                                KKASSERT(pte_pv == NULL);
                                goto fast_skip;
                        }
                        ptep = pv_pte_lookup(pt_pv, pmap_pte_index(sva));
                }
                if (*ptep == 0) {
                        /*
                         * Unlike the pv_find() case below we actually
                         * acquired a locked pv in this case so any
                         * race should have been resolved.  It is expected
                         * to not exist.
                         */
                        KKASSERT(pte_pv == NULL);
                } else if (pte_pv) {
                        KASSERT((*ptep & (PG_MANAGED|PG_V)) == (PG_MANAGED|
                                                                PG_V),
                                ("bad *ptep %016lx sva %016lx pte_pv %p",
                                *ptep, sva, pte_pv));
                        func(pmap, &info, pte_pv, pt_pv, sva, ptep, arg);
                } else {
                        KASSERT((*ptep & (PG_MANAGED|PG_V)) == PG_V,
                                ("bad *ptep %016lx sva %016lx pte_pv NULL",
                                *ptep, sva));
                        func(pmap, &info, pte_pv, pt_pv, sva, ptep, arg);
                }
                if (pt_pv)
                        pv_put(pt_pv);
fast_skip:
                pmap_inval_done(&info);
                lwkt_reltoken(&pmap->pm_token);
                return;
        }

        /*
         * NOTE: kernel mappings do not track page table pages, only
         *       terminal pages.
         *
         * NOTE: Locks must be ordered bottom-up. pte,pt,pd,pdp,pml4.
         *       However, for the scan to be efficient we try to
         *       cache items top-down.
         */
        pdp_pv = NULL;
        pd_pv = NULL;
        pt_pv = NULL;

        for (; sva < eva; sva = va_next) {
                lwkt_yield();
                if (sva >= VM_MAX_USER_ADDRESS) {
                        if (pt_pv) {
                                pv_put(pt_pv);
                                pt_pv = NULL;
                        }
                        goto kernel_skip;
                }

                /*
                 * PDP cache
                 */
                if (pdp_pv == NULL) {
                        pdp_pv = pv_get(pmap, pmap_pdp_pindex(sva));
                } else if (pdp_pv->pv_pindex != pmap_pdp_pindex(sva)) {
                        pv_put(pdp_pv);
                        pdp_pv = pv_get(pmap, pmap_pdp_pindex(sva));
                }
                if (pdp_pv == NULL) {
                        va_next = (sva + NBPML4) & ~PML4MASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                /*
                 * PD cache
                 */
                if (pd_pv == NULL) {
                        if (pdp_pv) {
                                pv_put(pdp_pv);
                                pdp_pv = NULL;
                        }
                        pd_pv = pv_get(pmap, pmap_pd_pindex(sva));
                } else if (pd_pv->pv_pindex != pmap_pd_pindex(sva)) {
                        pv_put(pd_pv);
                        if (pdp_pv) {
                                pv_put(pdp_pv);
                                pdp_pv = NULL;
                        }
                        pd_pv = pv_get(pmap, pmap_pd_pindex(sva));
                }
                if (pd_pv == NULL) {
                        va_next = (sva + NBPDP) & ~PDPMASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                /*
                 * PT cache
                 */
                if (pt_pv == NULL) {
                        if (pdp_pv) {
                                pv_put(pdp_pv);
                                pdp_pv = NULL;
                        }
                        if (pd_pv) {
                                pv_put(pd_pv);
                                pd_pv = NULL;
                        }
                        pt_pv = pv_get(pmap, pmap_pt_pindex(sva));
                } else if (pt_pv->pv_pindex != pmap_pt_pindex(sva)) {
                        if (pdp_pv) {
                                pv_put(pdp_pv);
                                pdp_pv = NULL;
                        }
                        if (pd_pv) {
                                pv_put(pd_pv);
                                pd_pv = NULL;
                        }
                        pv_put(pt_pv);
                        pt_pv = pv_get(pmap, pmap_pt_pindex(sva));
                }

                /*
                 * We will scan or skip a page table page so adjust va_next
                 * either way.
                 */
                if (pt_pv == NULL) {
                        va_next = (sva + NBPDR) & ~PDRMASK;
                        if (va_next < sva)
                                va_next = eva;
                        continue;
                }

                /*
                 * From this point in the loop testing pt_pv for non-NULL
                 * means we are in UVM, else if it is NULL we are in KVM.
                 */
kernel_skip:
                va_next = (sva + NBPDR) & ~PDRMASK;
                if (va_next < sva)
                        va_next = eva;

                /*
                 * 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.
                 *
                 * Scan the page table for pages.  Some pages may not be
                 * managed (might not have a pv_entry).
                 *
                 * There is no page table management for kernel pages so
                 * pt_pv will be NULL in that case, but otherwise pt_pv
                 * is non-NULL, locked, and referenced.
                 */
                if (va_next > eva)
                        va_next = eva;

                /*
                 * At this point a non-NULL pt_pv means a UVA, and a NULL
                 * pt_pv means a KVA.
                 */
                if (pt_pv)
                        ptep = pv_pte_lookup(pt_pv, pmap_pte_index(sva));
                else
                        ptep = vtopte(sva);

                while (sva < va_next) {
                        /*
                         * Acquire the related pte_pv, if any.  If *ptep == 0
                         * the related pte_pv should not exist, but if *ptep
                         * is not zero the pte_pv may or may not exist (e.g.
                         * will not exist for an unmanaged page).
                         *
                         * However a multitude of races are possible here.
                         *
                         * In addition, the (pt_pv, pte_pv) lock order is
                         * backwards, so we have to be careful in aquiring
                         * a properly locked pte_pv.
                         */
                        lwkt_yield();
                        if (pt_pv) {
                                pte_pv = pv_get_try(pmap, pmap_pte_pindex(sva),
                                                    &error);
                                if (error) {
                                        if (pdp_pv) {
                                                pv_put(pdp_pv);
                                                pdp_pv = NULL;
                                        }
                                        if (pd_pv) {
                                                pv_put(pd_pv);
                                                pd_pv = NULL;
                                        }
                                        pv_put(pt_pv);   /* must be non-NULL */
                                        pt_pv = NULL;
                                        pv_lock(pte_pv); /* safe to block now */
                                        pv_put(pte_pv);
                                        pte_pv = NULL;
                                        pt_pv = pv_get(pmap,
                                                       pmap_pt_pindex(sva));
                                        continue;
                                }
                        } else {
                                pte_pv = pv_get(pmap, pmap_pte_pindex(sva));
                        }

                        /*
                         * Ok, if *ptep == 0 we had better NOT have a pte_pv.
                         */
                        if (*ptep == 0) {
                                if (pte_pv) {
                                        kprintf("Unexpected non-NULL pte_pv "
                                                "%p pt_pv %p *ptep = %016lx\n",
                                                pte_pv, pt_pv, *ptep);
                                        panic("Unexpected non-NULL pte_pv");
                                }
                                sva += PAGE_SIZE;
                                ++ptep;
                                continue;
                        }

                        /*
                         * Ready for the callback.  The locked pte_pv (if any)
                         * is consumed by the callback.  pte_pv will exist if
                         *  the page is managed, and will not exist if it
                         * isn't.
                         */
                        if (pte_pv) {
                                KASSERT((*ptep & (PG_MANAGED|PG_V)) ==
                                         (PG_MANAGED|PG_V),
                                        ("bad *ptep %016lx sva %016lx "
                                         "pte_pv %p",
                                         *ptep, sva, pte_pv));
                                func(pmap, &info, pte_pv, pt_pv, sva,
                                     ptep, arg);
                        } else {
                                KASSERT((*ptep & (PG_MANAGED|PG_V)) ==
                                         PG_V,
                                        ("bad *ptep %016lx sva %016lx "
                                         "pte_pv NULL",
                                         *ptep, sva));
                                func(pmap, &info, pte_pv, pt_pv, sva,
                                     ptep, arg);
                        }
                        pte_pv = NULL;
                        sva += PAGE_SIZE;
                        ++ptep;
                }
        }
        if (pdp_pv) {
                pv_put(pdp_pv);
                pdp_pv = NULL;
        }
        if (pd_pv) {
                pv_put(pd_pv);
                pd_pv = NULL;
        }
        if (pt_pv) {
                pv_put(pt_pv);
                pt_pv = NULL;
        }
        pmap_inval_done(&info);
        lwkt_reltoken(&pmap->pm_token);
}

void
pmap_remove(struct pmap *pmap, vm_offset_t sva, vm_offset_t eva)
{
        pmap_scan(pmap, sva, eva, pmap_remove_callback, NULL);
}

static void
pmap_remove_callback(pmap_t pmap, struct pmap_inval_info *info,
                     pv_entry_t pte_pv, pv_entry_t pt_pv, vm_offset_t va,
                     pt_entry_t *ptep, void *arg __unused)
{
        pt_entry_t pte;

        if (pte_pv) {
                /*
                 * This will also drop pt_pv's wire_count. Note that
                 * terminal pages are not wired based on mmu presence.
                 */
                pmap_remove_pv_pte(pte_pv, pt_pv, info);
                pmap_remove_pv_page(pte_pv, 0);
                pv_free(pte_pv);
        } else {
                /*
                 * pt_pv's wire_count is still bumped by unmanaged pages
                 * so we must decrement it manually.
                 */
                pmap_inval_interlock(info, pmap, va);
                pte = pte_load_clear(ptep);
                pmap_inval_deinterlock(info, pmap);
                if (pte & PG_W)
                        atomic_add_long(&pmap->pm_stats.wired_count, -1);
                atomic_add_long(&pmap->pm_stats.resident_count, -1);
                if (pt_pv && vm_page_unwire_quick(pt_pv->pv_m))
                        panic("pmap_remove: insufficient wirecount");
        }
}

/*
 * 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.
 */
static
void
pmap_remove_all(vm_page_t m)
{
        struct pmap_inval_info info;
        pv_entry_t pv;

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

        pmap_inval_init(&info);
        vm_page_spin_lock(m);
        while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) {
                KKASSERT(pv->pv_m == m);
                if (pv_hold_try(pv)) {
                        vm_page_spin_unlock(m);
                } else {
                        vm_page_spin_unlock(m);
                        pv_lock(pv);
                        if (pv->pv_m != m) {
                                pv_put(pv);
                                vm_page_spin_lock(m);
                                continue;
                        }
                }
                /*
                 * Holding no spinlocks, pv is locked.
                 */
                pmap_remove_pv_pte(pv, NULL, &info);
                pmap_remove_pv_page(pv, 0);
                pv_free(pv);
                vm_page_spin_lock(m);
        }
        vm_page_spin_unlock(m);
        KKASSERT((m->flags & (PG_MAPPED|PG_WRITEABLE)) == 0);
        pmap_inval_done(&info);
}

/*
 * pmap_protect:
 *
 *      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.
 */
void
pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
{
        /* 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;
        pmap_scan(pmap, sva, eva, pmap_protect_callback, &prot);
}

static
void
pmap_protect_callback(pmap_t pmap, struct pmap_inval_info *info,
                      pv_entry_t pte_pv, pv_entry_t pt_pv, vm_offset_t va,
                      pt_entry_t *ptep, void *arg __unused)
{
        pt_entry_t pbits;
        pt_entry_t cbits;
        vm_page_t m;

        /*
         * XXX non-optimal.
         */
        pmap_inval_interlock(info, pmap, va);
again:
        pbits = *ptep;
        cbits = pbits;
        if (pte_pv) {
                m = NULL;
                if (pbits & PG_A) {
                        m = PHYS_TO_VM_PAGE(pbits & PG_FRAME);
                        KKASSERT(m == pte_pv->pv_m);
                        vm_page_flag_set(m, PG_REFERENCED);
                        cbits &= ~PG_A;
                }
                if (pbits & PG_M) {
                        if (pmap_track_modified(pte_pv->pv_pindex)) {
                                if (m == NULL)
                                        m = PHYS_TO_VM_PAGE(pbits & PG_FRAME);
                                vm_page_dirty(m);
                                cbits &= ~PG_M;
                        }
                }
        }
        cbits &= ~PG_RW;
        if (pbits != cbits && !atomic_cmpset_long(ptep, pbits, cbits)) {
                goto again;
        }
        pmap_inval_deinterlock(info, pmap);
        if (pte_pv)
                pv_put(pte_pv);
}

/*
 * Insert the vm_page (m) at the virtual address (va), replacing any prior
 * mapping at that address.  Set protection and wiring as requested.
 *
 * NOTE: This routine MUST insert the page into the pmap now, it cannot
 *       lazy-evaluate.
 */
void
pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot,
           boolean_t wired)
{
        pmap_inval_info info;
        pv_entry_t pt_pv;       /* page table */
        pv_entry_t pte_pv;      /* page table entry */
        pt_entry_t *ptep;
        vm_paddr_t opa;
        pt_entry_t origpte, newpte;
        vm_paddr_t pa;

        if (pmap == NULL)
                return;
        va = trunc_page(va);
#ifdef PMAP_DIAGNOSTIC
        if (va >= KvaEnd)
                panic("pmap_enter: toobig");
        if ((va >= UPT_MIN_ADDRESS) && (va < UPT_MAX_ADDRESS))
                panic("pmap_enter: invalid to pmap_enter page table "
                      "pages (va: 0x%lx)", va);
#endif
        if (va < UPT_MAX_ADDRESS && pmap == &kernel_pmap) {
                kprintf("Warning: pmap_enter called on UVA with "
                        "kernel_pmap\n");
#ifdef DDB
                db_print_backtrace();
#endif
        }
        if (va >= UPT_MAX_ADDRESS && pmap != &kernel_pmap) {
                kprintf("Warning: pmap_enter called on KVA without"
                        "kernel_pmap\n");
#ifdef DDB
                db_print_backtrace();
#endif
        }

        /*
         * Get locked PV entries for our new page table entry (pte_pv)
         * and for its parent page table (pt_pv).  We need the parent
         * so we can resolve the location of the ptep.
         *
         * Only hardware MMU actions can modify the ptep out from
         * under us.
         *
         * if (m) is fictitious or unmanaged we do not create a managing
         * pte_pv for it.  Any pre-existing page's management state must
         * match (avoiding code complexity).
         *
         * If the pmap is still being initialized we assume existing
         * page tables.
         *
         * Kernel mapppings do not track page table pages (i.e. pt_pv).
         * pmap_allocpte() checks the
         */
        if (pmap_initialized == FALSE) {
                pte_pv = NULL;
                pt_pv = NULL;
                ptep = vtopte(va);
        } else if (m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) {
                pte_pv = NULL;
                if (va >= VM_MAX_USER_ADDRESS) {
                        pt_pv = NULL;
                        ptep = vtopte(va);
                } else {
                        pt_pv = pmap_allocpte(pmap, pmap_pt_pindex(va), NULL);
                        ptep = pv_pte_lookup(pt_pv, pmap_pte_index(va));
                }
                KKASSERT(*ptep == 0 || (*ptep & PG_MANAGED) == 0);
        } else {
                if (va >= VM_MAX_USER_ADDRESS) {
                        pt_pv = NULL;
                        pte_pv = pmap_allocpte(pmap, pmap_pte_pindex(va), NULL);
                        ptep = vtopte(va);
                } else {
                        pte_pv = pmap_allocpte(pmap, pmap_pte_pindex(va),
                                               &pt_pv);
                        ptep = pv_pte_lookup(pt_pv, pmap_pte_index(va));
                }
                KKASSERT(*ptep == 0 || (*ptep & PG_MANAGED));
        }

        if ((prot & VM_PROT_NOSYNC) == 0)
                pmap_inval_init(&info);

        pa = VM_PAGE_TO_PHYS(m);
        origpte = *ptep;
        opa = origpte & PG_FRAME;

        /*
         * Mapping has not changed, must be protection or wiring change.
         */
        if (origpte && (opa == pa)) {
                /*
                 * Wiring change, just update stats. We don't worry about
                 * wiring PT pages as they remain resident as long as there
                 * are valid mappings in them. Hence, if a user page is wired,
                 * the PT page will be also.
                 */
                KKASSERT(pte_pv == NULL || m == pte_pv->pv_m);
                if (wired && ((origpte & PG_W) == 0))
                        atomic_add_long(&pmap->pm_stats.wired_count, 1);
                else if (!wired && (origpte & PG_W))
                        atomic_add_long(&pmap->pm_stats.wired_count, -1);

#if defined(PMAP_DIAGNOSTIC)
                if (pmap_nw_modified(origpte)) {
                        kprintf("pmap_enter: modified page not writable: "
                                "va: 0x%lx, pte: 0x%lx\n", va, origpte);
                }
#endif

                /*
                 * We might be turning off write access to the page,
                 * so we go ahead and sense modify status.
                 */
                if (pte_pv) {
                        if ((origpte & PG_M) &&
                            pmap_track_modified(pte_pv->pv_pindex)) {
                                vm_page_t om;
                                om = pte_pv->pv_m;
                                KKASSERT(PHYS_TO_VM_PAGE(opa) == om);
                                vm_page_dirty(om);
                        }
                        pa |= PG_MANAGED;
                }
                goto validate;
        } 

        /*
         * Mapping has changed, invalidate old range and fall through to
         * handle validating new mapping.
         *
         * We always interlock pte removals.
         */
        if (opa) {
                if (pte_pv) {
                        /* XXX pmap_remove_pv_pte() unwires pt_pv */
                        vm_page_wire_quick(pt_pv->pv_m);
                        if (prot & VM_PROT_NOSYNC)
                                pmap_remove_pv_pte(pte_pv, pt_pv, NULL);
                        else
                                pmap_remove_pv_pte(pte_pv, pt_pv, &info);
                        if (pte_pv->pv_m)
                                pmap_remove_pv_page(pte_pv, 0);
                } else if (prot & VM_PROT_NOSYNC) {
                        *ptep = 0;
                        cpu_invlpg((void *)va);
                        atomic_add_long(&pmap->pm_stats.resident_count, -1);
                } else {
                        pmap_inval_interlock(&info, pmap, va);
                        *ptep = 0;
                        pmap_inval_deinterlock(&info, pmap);
                        atomic_add_long(&pmap->pm_stats.resident_count, -1);
                }
                KKASSERT(*ptep == 0);
        }

        /*
         * Enter on the PV list if part of our managed memory.  Wiring is
         * handled automatically.
         */
        if (pte_pv) {
                KKASSERT(pte_pv->pv_m == NULL);
                vm_page_spin_lock(m);
                pte_pv->pv_m = m;
                TAILQ_INSERT_TAIL(&m->md.pv_list, pte_pv, pv_list);
                /*
                if (m->object)
                        atomic_add_int(&m->object->agg_pv_list_count, 1);
                */
                vm_page_flag_set(m, PG_MAPPED);
                vm_page_spin_unlock(m);
                pa |= PG_MANAGED;
        } else if (pt_pv && opa == 0) {
                vm_page_wire_quick(pt_pv->pv_m);
        }

        /*
         * Increment counters
         */
        if (wired)
                atomic_add_long(&pmap->pm_stats.wired_count, 1);

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

        if (wired)
                newpte |= PG_W;
        if (va < VM_MAX_USER_ADDRESS)
                newpte |= PG_U;
        if (pmap == &kernel_pmap)
                newpte |= pgeflag;

        /*
         * If the mapping or permission bits are different, we need
         * to update the pte.
         */
        if ((origpte & ~(PG_M|PG_A)) != newpte) {
#if 1
                if ((prot & VM_PROT_NOSYNC) == 0)
                        pmap_inval_interlock(&info, pmap, va);
#endif
                *ptep = newpte | PG_A;
#if 1
                if (prot & VM_PROT_NOSYNC)
                        cpu_invlpg((void *)va);
                else
                        pmap_inval_deinterlock(&info, pmap);
#endif
                if (newpte & PG_RW)
                        vm_page_flag_set(m, PG_WRITEABLE);
                if (pte_pv == NULL)
                        atomic_add_long(&pmap->pm_stats.resident_count, 1);
        }

        KKASSERT((newpte & PG_MANAGED) == 0 || (m->flags & PG_MAPPED));
        if ((prot & VM_PROT_NOSYNC) == 0)
                pmap_inval_done(&info);

        /*
         * Cleanup the pv entry, allowing other accessors.
         */
        if (pte_pv)
                pv_put(pte_pv);
        if (pt_pv)
                pv_put(pt_pv);
}

/*
 * This code works like pmap_enter() but assumes VM_PROT_READ and not-wired.
 * This code also assumes that the pmap has no pre-existing entry for this
 * VA.
 *
 * This code currently may only be used on user pmaps, not kernel_pmap.
 */
void
pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m)
{
        pmap_enter(pmap, va, m, VM_PROT_READ, FALSE);
}

/*
 * 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((vm_offset_t)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.
 */
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 (pindex + psize > 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 without holding the
         * object token.
         */
        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);
        }
        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);
        lwkt_yield();
        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.
 *
 * XXX This is safe only because page table pages are not freed.
 */
int
pmap_prefault_ok(pmap_t pmap, vm_offset_t addr)
{
        pt_entry_t *pte;

        /*spin_lock(&pmap->pm_spin);*/
        if ((pte = pmap_pte(pmap, addr)) != NULL) {
                if (*pte & PG_V) {
                        /*spin_unlock(&pmap->pm_spin);*/
                        return FALSE;
                }
        }
        /*spin_unlock(&pmap->pm_spin);*/
        return TRUE;
}

/*
 * Change the wiring attribute for a pmap/va pair.  The mapping must already
 * exist in the pmap.  The mapping may or may not be managed.
 */
void
pmap_change_wiring(pmap_t pmap, vm_offset_t va, boolean_t wired)
{
        pt_entry_t *ptep;
        pv_entry_t pv;

        if (pmap == NULL)
                return;
        lwkt_gettoken(&pmap->pm_token);
        pv = pmap_allocpte(pmap, pmap_pt_pindex(va), NULL);
        ptep = pv_pte_lookup(pv, pmap_pte_index(va));

        if (wired && !pmap_pte_w(ptep))
                atomic_add_long(&pmap->pm_stats.wired_count, 1);
        else if (!wired && pmap_pte_w(ptep))
                atomic_add_long(&pmap->pm_stats.wired_count, -1);

        /*
         * 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.
         */
#ifdef SMP
        if (wired)
                atomic_set_long(ptep, PG_W);
        else
                atomic_clear_long(ptep, PG_W);
#else
        if (wired)
                atomic_set_long_nonlocked(ptep, PG_W);
        else
                atomic_clear_long_nonlocked(ptep, PG_W);
#endif
        pv_put(pv);
        lwkt_reltoken(&pmap->pm_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)
{
}       

/*
 * 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);

        pagezero((void *)va);
}

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

        for (i = 0; i < PAGE_SIZE; i += sizeof(long)) {
                if (*(long *)((char *)va + i) != 0) {
                        panic("pmap_page_assertzero() @ %p not zero!\n",
                              (void *)(intptr_t)va);
                }
        }
}

/*
 * 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)
{
        vm_offset_t virt = PHYS_TO_DMAP(phys);

        bzero((char *)virt + off, size);
}

/*
 * 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;

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

/*
 * 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;

        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);
}

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

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

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

/*
 * Remove all pages from specified address space this aids process exit
 * speeds.  Also, this code may be special cased for the current process
 * only.
 */
void
pmap_remove_pages(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
        pmap_remove(pmap, sva, eva);
}

/*
 * pmap_testbit tests bits in pte's note that the testbit/clearbit
 * routines are inline, and a lot of things compile-time evaluate.
 */
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;
        vm_page_spin_lock(m);
        if (TAILQ_FIRST(&m->md.pv_list) == NULL) {
                vm_page_spin_unlock(m);
                return FALSE;
        }

        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 & (PG_A|PG_M)) {
                        if (!pmap_track_modified(pv->pv_pindex))
                                continue;
                }

#if defined(PMAP_DIAGNOSTIC)
                if (pv->pv_pmap == NULL) {
                        kprintf("Null pmap (tb) at pindex: %"PRIu64"\n",
                            pv->pv_pindex);
                        continue;
                }
#endif
                pte = pmap_pte_quick(pv->pv_pmap, pv->pv_pindex << PAGE_SHIFT);
                if (*pte & bit) {
                        vm_page_spin_unlock(m);
                        return TRUE;
                }
        }
        vm_page_spin_unlock(m);
        return (FALSE);
}

/*
 * This routine is used to modify bits in ptes.  Only one bit should be
 * specified.  PG_RW requires special handling.
 *
 * Caller must NOT hold any spin locks
 */
static __inline
void
pmap_clearbit(vm_page_t m, int bit)
{
        struct pmap_inval_info info;
        pv_entry_t pv;
        pt_entry_t *pte;
        pt_entry_t pbits;
        vm_pindex_t save_pindex;
        pmap_t save_pmap;

        if (bit == PG_RW)
                vm_page_flag_clear(m, PG_WRITEABLE);
        if (!pmap_initialized || (m->flags & PG_FICTITIOUS)) {
                return;
        }

        /*
         * PG_M or PG_A case
         *
         * Loop over all current mappings setting/clearing as appropos If
         * setting RO do we need to clear the VAC?
         *
         * NOTE: When clearing PG_M we could also (not implemented) drop
         *       through to the PG_RW code and clear PG_RW too, forcing
         *       a fault on write to redetect PG_M for virtual kernels, but
         *       it isn't necessary since virtual kernels invalidate the
         *       pte when they clear the VPTE_M bit in their virtual page
         *       tables.
         *
         * NOTE: Does not re-dirty the page when clearing only PG_M.
         */
        if ((bit & PG_RW) == 0) {
                vm_page_spin_lock(m);
                TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
        #if defined(PMAP_DIAGNOSTIC)
                        if (pv->pv_pmap == NULL) {
                                kprintf("Null pmap (cb) at pindex: %"PRIu64"\n",
                                    pv->pv_pindex);
                                continue;
                        }
        #endif
                        pte = pmap_pte_quick(pv->pv_pmap,
                                             pv->pv_pindex << PAGE_SHIFT);
                        pbits = *pte;
                        if (pbits & bit)
                                atomic_clear_long(pte, bit);
                }
                vm_page_spin_unlock(m);
                return;
        }

        /*
         * Clear PG_RW.  Also clears PG_M and marks the page dirty if PG_M
         * was set.
         */
        pmap_inval_init(&info);

restart:
        vm_page_spin_lock(m);
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                /*
                 * don't write protect pager mappings
                 */
                if (!pmap_track_modified(pv->pv_pindex))
                        continue;

#if defined(PMAP_DIAGNOSTIC)
                if (pv->pv_pmap == NULL) {
                        kprintf("Null pmap (cb) at pindex: %"PRIu64"\n",
                            pv->pv_pindex);
                        continue;
                }
#endif
                /*
                 * Skip pages which do not have PG_RW set.
                 */
                pte = pmap_pte_quick(pv->pv_pmap, pv->pv_pindex << PAGE_SHIFT);
                if ((*pte & PG_RW) == 0)
                        continue;

                /*
                 * Lock the PV
                 */
                if (pv_hold_try(pv) == 0) {
                        vm_page_spin_unlock(m);
                        pv_lock(pv);    /* held, now do a blocking lock */
                        pv_put(pv);     /* and release */
                        goto restart;   /* anything could have happened */
                }

                save_pmap = pv->pv_pmap;
                vm_page_spin_unlock(m);
                pmap_inval_interlock(&info, save_pmap,
                                     (vm_offset_t)save_pindex << PAGE_SHIFT);
                KKASSERT(pv->pv_pmap == save_pmap);
                for (;;) {
                        pbits = *pte;
                        cpu_ccfence();
                        if (atomic_cmpset_long(pte, pbits,
                                               pbits & ~(PG_RW|PG_M))) {
                                break;
                        }
                }
                pmap_inval_deinterlock(&info, save_pmap);
                vm_page_spin_lock(m);

                /*
                 * If PG_M was found to be set while we were clearing PG_RW
                 * we also clear PG_M (done above) and mark the page dirty.
                 * Callers expect this behavior.
                 */
                if (pbits & PG_M)
                        vm_page_dirty(m);
                pv_put(pv);
        }
        vm_page_spin_unlock(m);
        pmap_inval_done(&info);
}

/*
 * Lower the permission for all mappings to a given page.
 *
 * Page must be busied by caller.
 */
void
pmap_page_protect(vm_page_t m, vm_prot_t prot)
{
        /* JG NX support? */
        if ((prot & VM_PROT_WRITE) == 0) {
                if (prot & (VM_PROT_READ | VM_PROT_EXECUTE)) {
                        /*
                         * NOTE: pmap_clearbit(.. PG_RW) also clears
                         *       the PG_WRITEABLE flag in (m).
                         */
                        pmap_clearbit(m, PG_RW);
                } else {
                        pmap_remove_all(m);
                }
        }
}

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.
 *
 * This routine may not block.
 */
int
pmap_ts_referenced(vm_page_t m)
{
        pv_entry_t pv;
        pt_entry_t *pte;
        int rtval = 0;

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

        vm_page_spin_lock(m);
        TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
                if (!pmap_track_modified(pv->pv_pindex))
                        continue;
                pte = pmap_pte_quick(pv->pv_pmap, pv->pv_pindex << PAGE_SHIFT);
                if (pte && (*pte & PG_A)) {
#ifdef SMP
                        atomic_clear_long(pte, PG_A);
#else
                        atomic_clear_long_nonlocked(pte, PG_A);
#endif
                        rtval++;
                        if (rtval > 4)
                                break;
                }
        }
        vm_page_spin_unlock(m);
        return (rtval);
}

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

        res = pmap_testbit(m, PG_M);
        return (res);
}

/*
 *      Clear the modify bits on the specified physical page.
 */
void
pmap_clear_modify(vm_page_t m)
{
        pmap_clearbit(m, PG_M);
}

/*
 *      pmap_clear_reference:
 *
 *      Clear the reference bit on the specified physical page.
 */
void
pmap_clear_reference(vm_page_t m)
{
        pmap_clearbit(m, PG_A);
}

/*
 * Miscellaneous support routines follow
 */

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

        /* JG NX support may go here; No VM_PROT_EXECUTE ==> set NX bit  */
        kp = protection_codes;
        for (prot = 0; prot < 8; prot++) {
                switch (prot) {
                case VM_PROT_NONE | VM_PROT_NONE | VM_PROT_NONE:
                        /*
                         * Read access is also 0. There isn't any execute bit,
                         * so just make it readable.
                         */
                case VM_PROT_READ | VM_PROT_NONE | VM_PROT_NONE:
                case VM_PROT_READ | VM_PROT_NONE | VM_PROT_EXECUTE:
                case VM_PROT_NONE | VM_PROT_NONE | VM_PROT_EXECUTE:
                        *kp++ = 0;
                        break;
                case VM_PROT_NONE | VM_PROT_WRITE | VM_PROT_NONE:
                case VM_PROT_NONE | VM_PROT_WRITE | VM_PROT_EXECUTE:
                case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_NONE:
                case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE:
                        *kp++ = PG_RW;
                        break;
                }
        }
}

/*
 * Map a set of physical memory pages into the kernel virtual
 * address space. Return a pointer to where it is mapped. This
 * routine is intended to be used for mapping device memory,
 * NOT real memory.
 *
 * NOTE: we can't use pgeflag unless we invalidate the pages one at
 * a time.
 */
void *
pmap_mapdev(vm_paddr_t pa, vm_size_t size)
{
        vm_offset_t va, tmpva, offset;
        pt_entry_t *pte;

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

        va = kmem_alloc_nofault(&kernel_map, size, PAGE_SIZE);
        if (va == 0)
                panic("pmap_mapdev: Couldn't alloc kernel virtual memory");

        pa = pa & ~PAGE_MASK;
        for (tmpva = va; size > 0;) {
                pte = vtopte(tmpva);
                *pte = pa | PG_RW | PG_V; /* | pgeflag; */
                size -= PAGE_SIZE;
                tmpva += PAGE_SIZE;
                pa += PAGE_SIZE;
        }
        cpu_invltlb();
        smp_invltlb();

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

void *
pmap_mapdev_uncacheable(vm_paddr_t pa, vm_size_t size)
{
        vm_offset_t va, tmpva, offset;
        pt_entry_t *pte;

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

        va = kmem_alloc_nofault(&kernel_map, size, PAGE_SIZE);
        if (va == 0)
                panic("pmap_mapdev: Couldn't alloc kernel virtual memory");

        pa = pa & ~PAGE_MASK;
        for (tmpva = va; size > 0;) {
                pte = vtopte(tmpva);
                *pte = pa | PG_RW | PG_V | PG_N; /* | pgeflag; */
                size -= PAGE_SIZE;
                tmpva += PAGE_SIZE;
                pa += PAGE_SIZE;
        }
        cpu_invltlb();
        smp_invltlb();

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

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

        base = va & ~PAGE_MASK;
        offset = va & PAGE_MASK;
        size = roundup(offset + size, PAGE_SIZE);
        pmap_qremove(va, size >> PAGE_SHIFT);
        kmem_free(&kernel_map, base, size);
}

/*
 * perform the pmap work for mincore
 */
int
pmap_mincore(pmap_t pmap, vm_offset_t addr)
{
        pt_entry_t *ptep, pte;
        vm_page_t m;
        int val = 0;
        
        lwkt_gettoken(&pmap->pm_token);
        ptep = pmap_pte(pmap, addr);

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

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

                pa = pte & PG_FRAME;

                m = PHYS_TO_VM_PAGE(pa);

                /*
                 * Modified by us
                 */
                if (pte & PG_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 & PG_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(&pmap->pm_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.
 *
 * The vmspace for all lwps associated with the process will be adjusted
 * and cr3 will be reloaded if any lwp is the current lwp.
 *
 * The process must hold the 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;

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

/*
 * 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.
 *
 * Caller does not necessarily hold any vmspace tokens.  Caller must control
 * the lwp (typically be in the context of the lwp).  We use a critical
 * section to protect against statclock and hardclock (statistics collection).
 */
void
pmap_setlwpvm(struct lwp *lp, struct vmspace *newvm)
{
        struct vmspace *oldvm;
        struct pmap *pmap;

        oldvm = lp->lwp_vmspace;

        if (oldvm != newvm) {
                crit_enter();
                lp->lwp_vmspace = newvm;
                if (curthread->td_lwp == lp) {
                        pmap = vmspace_pmap(newvm);
#if defined(SMP)
                        atomic_set_cpumask(&pmap->pm_active, mycpu->gd_cpumask);
                        if (pmap->pm_active & CPUMASK_LOCK)
                                pmap_interlock_wait(newvm);
#else
                        pmap->pm_active |= 1;
#endif
#if defined(SWTCH_OPTIM_STATS)
                        tlb_flush_count++;
#endif
                        curthread->td_pcb->pcb_cr3 = vtophys(pmap->pm_pml4);
                        curthread->td_pcb->pcb_cr3 |= PG_RW | PG_U | PG_V;
                        load_cr3(curthread->td_pcb->pcb_cr3);
                        pmap = vmspace_pmap(oldvm);
#if defined(SMP)
                        atomic_clear_cpumask(&pmap->pm_active, mycpu->gd_cpumask);
#else
                        pmap->pm_active &= ~(cpumask_t)1;
#endif
                }
                crit_exit();
        }
}

#ifdef SMP

/*
 * Called when switching to a locked pmap, used to interlock against pmaps
 * undergoing modifications to prevent us from activating the MMU for the
 * target pmap until all such modifications have completed.  We have to do
 * this because the thread making the modifications has already set up its
 * SMP synchronization mask.
 *
 * No requirements.
 */
void
pmap_interlock_wait(struct vmspace *vm)
{
        struct pmap *pmap = &vm->vm_pmap;

        if (pmap->pm_active & CPUMASK_LOCK) {
                crit_enter();
                DEBUG_PUSH_INFO("pmap_interlock_wait");
                while (pmap->pm_active & CPUMASK_LOCK) {
                        cpu_ccfence();
                        lwkt_process_ipiq();
                }
                DEBUG_POP_INFO();
                crit_exit();
        }
}

#endif

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)
{
        return(PHYS_TO_VM_PAGE(*vtopte(va) & PG_FRAME));
}