5045 use atomic_{inc,dec}_* instead of atomic_add_*

[illumos-gate.git] / usr / src / uts / i86pc / vm / hat_i86.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 1992, 2010, Oracle and/or its affiliates. All rights reserved.
 */
/*
 * Copyright (c) 2010, Intel Corporation.
 * All rights reserved.
 */
/*
 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
 */

/*
 * VM - Hardware Address Translation management for i386 and amd64
 *
 * Implementation of the interfaces described in <common/vm/hat.h>
 *
 * Nearly all the details of how the hardware is managed should not be
 * visible outside this layer except for misc. machine specific functions
 * that work in conjunction with this code.
 *
 * Routines used only inside of i86pc/vm start with hati_ for HAT Internal.
 */

#include <sys/machparam.h>
#include <sys/machsystm.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <sys/cpuvar.h>
#include <sys/thread.h>
#include <sys/proc.h>
#include <sys/cpu.h>
#include <sys/kmem.h>
#include <sys/disp.h>
#include <sys/shm.h>
#include <sys/sysmacros.h>
#include <sys/machparam.h>
#include <sys/vmem.h>
#include <sys/vmsystm.h>
#include <sys/promif.h>
#include <sys/var.h>
#include <sys/x86_archext.h>
#include <sys/atomic.h>
#include <sys/bitmap.h>
#include <sys/controlregs.h>
#include <sys/bootconf.h>
#include <sys/bootsvcs.h>
#include <sys/bootinfo.h>
#include <sys/archsystm.h>

#include <vm/seg_kmem.h>
#include <vm/hat_i86.h>
#include <vm/as.h>
#include <vm/seg.h>
#include <vm/page.h>
#include <vm/seg_kp.h>
#include <vm/seg_kpm.h>
#include <vm/vm_dep.h>
#ifdef __xpv
#include <sys/hypervisor.h>
#endif
#include <vm/kboot_mmu.h>
#include <vm/seg_spt.h>

#include <sys/cmn_err.h>

/*
 * Basic parameters for hat operation.
 */
struct hat_mmu_info mmu;

/*
 * The page that is the kernel's top level pagetable.
 *
 * For 32 bit PAE support on i86pc, the kernel hat will use the 1st 4 entries
 * on this 4K page for its top level page table. The remaining groups of
 * 4 entries are used for per processor copies of user VLP pagetables for
 * running threads.  See hat_switch() and reload_pae32() for details.
 *
 * vlp_page[0..3] - level==2 PTEs for kernel HAT
 * vlp_page[4..7] - level==2 PTEs for user thread on cpu 0
 * vlp_page[8..11]  - level==2 PTE for user thread on cpu 1
 * etc...
 */
static x86pte_t *vlp_page;

/*
 * forward declaration of internal utility routines
 */
static x86pte_t hati_update_pte(htable_t *ht, uint_t entry, x86pte_t expected,
        x86pte_t new);

/*
 * The kernel address space exists in all HATs. To implement this the
 * kernel reserves a fixed number of entries in the topmost level(s) of page
 * tables. The values are setup during startup and then copied to every user
 * hat created by hat_alloc(). This means that kernelbase must be:
 *
 *        4Meg aligned for 32 bit kernels
 *      512Gig aligned for x86_64 64 bit kernel
 *
 * The hat_kernel_range_ts describe what needs to be copied from kernel hat
 * to each user hat.
 */
typedef struct hat_kernel_range {
        level_t         hkr_level;
        uintptr_t       hkr_start_va;
        uintptr_t       hkr_end_va;     /* zero means to end of memory */
} hat_kernel_range_t;
#define NUM_KERNEL_RANGE 2
static hat_kernel_range_t kernel_ranges[NUM_KERNEL_RANGE];
static int num_kernel_ranges;

uint_t use_boot_reserve = 1;    /* cleared after early boot process */
uint_t can_steal_post_boot = 0; /* set late in boot to enable stealing */

/*
 * enable_1gpg: controls 1g page support for user applications.
 * By default, 1g pages are exported to user applications. enable_1gpg can
 * be set to 0 to not export.
 */
int     enable_1gpg = 1;

/*
 * AMD shanghai processors provide better management of 1gb ptes in its tlb.
 * By default, 1g page support will be disabled for pre-shanghai AMD
 * processors that don't have optimal tlb support for the 1g page size.
 * chk_optimal_1gtlb can be set to 0 to force 1g page support on sub-optimal
 * processors.
 */
int     chk_optimal_1gtlb = 1;


#ifdef DEBUG
uint_t  map1gcnt;
#endif


/*
 * A cpuset for all cpus. This is used for kernel address cross calls, since
 * the kernel addresses apply to all cpus.
 */
cpuset_t khat_cpuset;

/*
 * management stuff for hat structures
 */
kmutex_t        hat_list_lock;
kcondvar_t      hat_list_cv;
kmem_cache_t    *hat_cache;
kmem_cache_t    *hat_hash_cache;
kmem_cache_t    *vlp_hash_cache;

/*
 * Simple statistics
 */
struct hatstats hatstat;

/*
 * Some earlier hypervisor versions do not emulate cmpxchg of PTEs
 * correctly.  For such hypervisors we must set PT_USER for kernel
 * entries ourselves (normally the emulation would set PT_USER for
 * kernel entries and PT_USER|PT_GLOBAL for user entries).  pt_kern is
 * thus set appropriately.  Note that dboot/kbm is OK, as only the full
 * HAT uses cmpxchg() and the other paths (hypercall etc.) were never
 * incorrect.
 */
int pt_kern;

/*
 * useful stuff for atomic access/clearing/setting REF/MOD/RO bits in page_t's.
 */
extern void atomic_orb(uchar_t *addr, uchar_t val);
extern void atomic_andb(uchar_t *addr, uchar_t val);

#ifndef __xpv
extern pfn_t memseg_get_start(struct memseg *);
#endif

#define PP_GETRM(pp, rmmask)    (pp->p_nrm & rmmask)
#define PP_ISMOD(pp)            PP_GETRM(pp, P_MOD)
#define PP_ISREF(pp)            PP_GETRM(pp, P_REF)
#define PP_ISRO(pp)             PP_GETRM(pp, P_RO)

#define PP_SETRM(pp, rm)        atomic_orb(&(pp->p_nrm), rm)
#define PP_SETMOD(pp)           PP_SETRM(pp, P_MOD)
#define PP_SETREF(pp)           PP_SETRM(pp, P_REF)
#define PP_SETRO(pp)            PP_SETRM(pp, P_RO)

#define PP_CLRRM(pp, rm)        atomic_andb(&(pp->p_nrm), ~(rm))
#define PP_CLRMOD(pp)           PP_CLRRM(pp, P_MOD)
#define PP_CLRREF(pp)           PP_CLRRM(pp, P_REF)
#define PP_CLRRO(pp)            PP_CLRRM(pp, P_RO)
#define PP_CLRALL(pp)           PP_CLRRM(pp, P_MOD | P_REF | P_RO)

/*
 * kmem cache constructor for struct hat
 */
/*ARGSUSED*/
static int
hati_constructor(void *buf, void *handle, int kmflags)
{
        hat_t   *hat = buf;

        mutex_init(&hat->hat_mutex, NULL, MUTEX_DEFAULT, NULL);
        bzero(hat->hat_pages_mapped,
            sizeof (pgcnt_t) * (mmu.max_page_level + 1));
        hat->hat_ism_pgcnt = 0;
        hat->hat_stats = 0;
        hat->hat_flags = 0;
        CPUSET_ZERO(hat->hat_cpus);
        hat->hat_htable = NULL;
        hat->hat_ht_hash = NULL;
        return (0);
}

/*
 * Allocate a hat structure for as. We also create the top level
 * htable and initialize it to contain the kernel hat entries.
 */
hat_t *
hat_alloc(struct as *as)
{
        hat_t                   *hat;
        htable_t                *ht;    /* top level htable */
        uint_t                  use_vlp;
        uint_t                  r;
        hat_kernel_range_t      *rp;
        uintptr_t               va;
        uintptr_t               eva;
        uint_t                  start;
        uint_t                  cnt;
        htable_t                *src;

        /*
         * Once we start creating user process HATs we can enable
         * the htable_steal() code.
         */
        if (can_steal_post_boot == 0)
                can_steal_post_boot = 1;

        ASSERT(AS_WRITE_HELD(as, &as->a_lock));
        hat = kmem_cache_alloc(hat_cache, KM_SLEEP);
        hat->hat_as = as;
        mutex_init(&hat->hat_mutex, NULL, MUTEX_DEFAULT, NULL);
        ASSERT(hat->hat_flags == 0);

#if defined(__xpv)
        /*
         * No VLP stuff on the hypervisor due to the 64-bit split top level
         * page tables.  On 32-bit it's not needed as the hypervisor takes
         * care of copying the top level PTEs to a below 4Gig page.
         */
        use_vlp = 0;
#else   /* __xpv */
        /* 32 bit processes uses a VLP style hat when running with PAE */
#if defined(__amd64)
        use_vlp = (ttoproc(curthread)->p_model == DATAMODEL_ILP32);
#elif defined(__i386)
        use_vlp = mmu.pae_hat;
#endif
#endif  /* __xpv */
        if (use_vlp) {
                hat->hat_flags = HAT_VLP;
                bzero(hat->hat_vlp_ptes, VLP_SIZE);
        }

        /*
         * Allocate the htable hash
         */
        if ((hat->hat_flags & HAT_VLP)) {
                hat->hat_num_hash = mmu.vlp_hash_cnt;
                hat->hat_ht_hash = kmem_cache_alloc(vlp_hash_cache, KM_SLEEP);
        } else {
                hat->hat_num_hash = mmu.hash_cnt;
                hat->hat_ht_hash = kmem_cache_alloc(hat_hash_cache, KM_SLEEP);
        }
        bzero(hat->hat_ht_hash, hat->hat_num_hash * sizeof (htable_t *));

        /*
         * Initialize Kernel HAT entries at the top of the top level page
         * tables for the new hat.
         */
        hat->hat_htable = NULL;
        hat->hat_ht_cached = NULL;
        XPV_DISALLOW_MIGRATE();
        ht = htable_create(hat, (uintptr_t)0, TOP_LEVEL(hat), NULL);
        hat->hat_htable = ht;

#if defined(__amd64)
        if (hat->hat_flags & HAT_VLP)
                goto init_done;
#endif

        for (r = 0; r < num_kernel_ranges; ++r) {
                rp = &kernel_ranges[r];
                for (va = rp->hkr_start_va; va != rp->hkr_end_va;
                    va += cnt * LEVEL_SIZE(rp->hkr_level)) {

                        if (rp->hkr_level == TOP_LEVEL(hat))
                                ht = hat->hat_htable;
                        else
                                ht = htable_create(hat, va, rp->hkr_level,
                                    NULL);

                        start = htable_va2entry(va, ht);
                        cnt = HTABLE_NUM_PTES(ht) - start;
                        eva = va +
                            ((uintptr_t)cnt << LEVEL_SHIFT(rp->hkr_level));
                        if (rp->hkr_end_va != 0 &&
                            (eva > rp->hkr_end_va || eva == 0))
                                cnt = htable_va2entry(rp->hkr_end_va, ht) -
                                    start;

#if defined(__i386) && !defined(__xpv)
                        if (ht->ht_flags & HTABLE_VLP) {
                                bcopy(&vlp_page[start],
                                    &hat->hat_vlp_ptes[start],
                                    cnt * sizeof (x86pte_t));
                                continue;
                        }
#endif
                        src = htable_lookup(kas.a_hat, va, rp->hkr_level);
                        ASSERT(src != NULL);
                        x86pte_copy(src, ht, start, cnt);
                        htable_release(src);
                }
        }

init_done:

#if defined(__xpv)
        /*
         * Pin top level page tables after initializing them
         */
        xen_pin(hat->hat_htable->ht_pfn, mmu.max_level);
#if defined(__amd64)
        xen_pin(hat->hat_user_ptable, mmu.max_level);
#endif
#endif
        XPV_ALLOW_MIGRATE();

        /*
         * Put it at the start of the global list of all hats (used by stealing)
         *
         * kas.a_hat is not in the list but is instead used to find the
         * first and last items in the list.
         *
         * - kas.a_hat->hat_next points to the start of the user hats.
         *   The list ends where hat->hat_next == NULL
         *
         * - kas.a_hat->hat_prev points to the last of the user hats.
         *   The list begins where hat->hat_prev == NULL
         */
        mutex_enter(&hat_list_lock);
        hat->hat_prev = NULL;
        hat->hat_next = kas.a_hat->hat_next;
        if (hat->hat_next)
                hat->hat_next->hat_prev = hat;
        else
                kas.a_hat->hat_prev = hat;
        kas.a_hat->hat_next = hat;
        mutex_exit(&hat_list_lock);

        return (hat);
}

/*
 * process has finished executing but as has not been cleaned up yet.
 */
/*ARGSUSED*/
void
hat_free_start(hat_t *hat)
{
        ASSERT(AS_WRITE_HELD(hat->hat_as, &hat->hat_as->a_lock));

        /*
         * If the hat is currently a stealing victim, wait for the stealing
         * to finish.  Once we mark it as HAT_FREEING, htable_steal()
         * won't look at its pagetables anymore.
         */
        mutex_enter(&hat_list_lock);
        while (hat->hat_flags & HAT_VICTIM)
                cv_wait(&hat_list_cv, &hat_list_lock);
        hat->hat_flags |= HAT_FREEING;
        mutex_exit(&hat_list_lock);
}

/*
 * An address space is being destroyed, so we destroy the associated hat.
 */
void
hat_free_end(hat_t *hat)
{
        kmem_cache_t *cache;

        ASSERT(hat->hat_flags & HAT_FREEING);

        /*
         * must not be running on the given hat
         */
        ASSERT(CPU->cpu_current_hat != hat);

        /*
         * Remove it from the list of HATs
         */
        mutex_enter(&hat_list_lock);
        if (hat->hat_prev)
                hat->hat_prev->hat_next = hat->hat_next;
        else
                kas.a_hat->hat_next = hat->hat_next;
        if (hat->hat_next)
                hat->hat_next->hat_prev = hat->hat_prev;
        else
                kas.a_hat->hat_prev = hat->hat_prev;
        mutex_exit(&hat_list_lock);
        hat->hat_next = hat->hat_prev = NULL;

#if defined(__xpv)
        /*
         * On the hypervisor, unpin top level page table(s)
         */
        xen_unpin(hat->hat_htable->ht_pfn);
#if defined(__amd64)
        xen_unpin(hat->hat_user_ptable);
#endif
#endif

        /*
         * Make a pass through the htables freeing them all up.
         */
        htable_purge_hat(hat);

        /*
         * Decide which kmem cache the hash table came from, then free it.
         */
        if (hat->hat_flags & HAT_VLP)
                cache = vlp_hash_cache;
        else
                cache = hat_hash_cache;
        kmem_cache_free(cache, hat->hat_ht_hash);
        hat->hat_ht_hash = NULL;

        hat->hat_flags = 0;
        kmem_cache_free(hat_cache, hat);
}

/*
 * round kernelbase down to a supported value to use for _userlimit
 *
 * userlimit must be aligned down to an entry in the top level htable.
 * The one exception is for 32 bit HAT's running PAE.
 */
uintptr_t
hat_kernelbase(uintptr_t va)
{
#if defined(__i386)
        va &= LEVEL_MASK(1);
#endif
        if (IN_VA_HOLE(va))
                panic("_userlimit %p will fall in VA hole\n", (void *)va);
        return (va);
}

/*
 *
 */
static void
set_max_page_level()
{
        level_t lvl;

        if (!kbm_largepage_support) {
                lvl = 0;
        } else {
                if (is_x86_feature(x86_featureset, X86FSET_1GPG)) {
                        lvl = 2;
                        if (chk_optimal_1gtlb &&
                            cpuid_opteron_erratum(CPU, 6671130)) {
                                lvl = 1;
                        }
                        if (plat_mnode_xcheck(LEVEL_SIZE(2) >>
                            LEVEL_SHIFT(0))) {
                                lvl = 1;
                        }
                } else {
                        lvl = 1;
                }
        }
        mmu.max_page_level = lvl;

        if ((lvl == 2) && (enable_1gpg == 0))
                mmu.umax_page_level = 1;
        else
                mmu.umax_page_level = lvl;
}

/*
 * Initialize hat data structures based on processor MMU information.
 */
void
mmu_init(void)
{
        uint_t max_htables;
        uint_t pa_bits;
        uint_t va_bits;
        int i;

        /*
         * If CPU enabled the page table global bit, use it for the kernel
         * This is bit 7 in CR4 (PGE - Page Global Enable).
         */
        if (is_x86_feature(x86_featureset, X86FSET_PGE) &&
            (getcr4() & CR4_PGE) != 0)
                mmu.pt_global = PT_GLOBAL;

        /*
         * Detect NX and PAE usage.
         */
        mmu.pae_hat = kbm_pae_support;
        if (kbm_nx_support)
                mmu.pt_nx = PT_NX;
        else
                mmu.pt_nx = 0;

        /*
         * Use CPU info to set various MMU parameters
         */
        cpuid_get_addrsize(CPU, &pa_bits, &va_bits);

        if (va_bits < sizeof (void *) * NBBY) {
                mmu.hole_start = (1ul << (va_bits - 1));
                mmu.hole_end = 0ul - mmu.hole_start - 1;
        } else {
                mmu.hole_end = 0;
                mmu.hole_start = mmu.hole_end - 1;
        }
#if defined(OPTERON_ERRATUM_121)
        /*
         * If erratum 121 has already been detected at this time, hole_start
         * contains the value to be subtracted from mmu.hole_start.
         */
        ASSERT(hole_start == 0 || opteron_erratum_121 != 0);
        hole_start = mmu.hole_start - hole_start;
#else
        hole_start = mmu.hole_start;
#endif
        hole_end = mmu.hole_end;

        mmu.highest_pfn = mmu_btop((1ull << pa_bits) - 1);
        if (mmu.pae_hat == 0 && pa_bits > 32)
                mmu.highest_pfn = PFN_4G - 1;

        if (mmu.pae_hat) {
                mmu.pte_size = 8;       /* 8 byte PTEs */
                mmu.pte_size_shift = 3;
        } else {
                mmu.pte_size = 4;       /* 4 byte PTEs */
                mmu.pte_size_shift = 2;
        }

        if (mmu.pae_hat && !is_x86_feature(x86_featureset, X86FSET_PAE))
                panic("Processor does not support PAE");

        if (!is_x86_feature(x86_featureset, X86FSET_CX8))
                panic("Processor does not support cmpxchg8b instruction");

#if defined(__amd64)

        mmu.num_level = 4;
        mmu.max_level = 3;
        mmu.ptes_per_table = 512;
        mmu.top_level_count = 512;

        mmu.level_shift[0] = 12;
        mmu.level_shift[1] = 21;
        mmu.level_shift[2] = 30;
        mmu.level_shift[3] = 39;

#elif defined(__i386)

        if (mmu.pae_hat) {
                mmu.num_level = 3;
                mmu.max_level = 2;
                mmu.ptes_per_table = 512;
                mmu.top_level_count = 4;

                mmu.level_shift[0] = 12;
                mmu.level_shift[1] = 21;
                mmu.level_shift[2] = 30;

        } else {
                mmu.num_level = 2;
                mmu.max_level = 1;
                mmu.ptes_per_table = 1024;
                mmu.top_level_count = 1024;

                mmu.level_shift[0] = 12;
                mmu.level_shift[1] = 22;
        }

#endif  /* __i386 */

        for (i = 0; i < mmu.num_level; ++i) {
                mmu.level_size[i] = 1UL << mmu.level_shift[i];
                mmu.level_offset[i] = mmu.level_size[i] - 1;
                mmu.level_mask[i] = ~mmu.level_offset[i];
        }

        set_max_page_level();

        mmu_page_sizes = mmu.max_page_level + 1;
        mmu_exported_page_sizes = mmu.umax_page_level + 1;

        /* restrict legacy applications from using pagesizes 1g and above */
        mmu_legacy_page_sizes =
            (mmu_exported_page_sizes > 2) ? 2 : mmu_exported_page_sizes;


        for (i = 0; i <= mmu.max_page_level; ++i) {
                mmu.pte_bits[i] = PT_VALID | pt_kern;
                if (i > 0)
                        mmu.pte_bits[i] |= PT_PAGESIZE;
        }

        /*
         * NOTE Legacy 32 bit PAE mode only has the P_VALID bit at top level.
         */
        for (i = 1; i < mmu.num_level; ++i)
                mmu.ptp_bits[i] = PT_PTPBITS;

#if defined(__i386)
        mmu.ptp_bits[2] = PT_VALID;
#endif

        /*
         * Compute how many hash table entries to have per process for htables.
         * We start with 1 page's worth of entries.
         *
         * If physical memory is small, reduce the amount need to cover it.
         */
        max_htables = physmax / mmu.ptes_per_table;
        mmu.hash_cnt = MMU_PAGESIZE / sizeof (htable_t *);
        while (mmu.hash_cnt > 16 && mmu.hash_cnt >= max_htables)
                mmu.hash_cnt >>= 1;
        mmu.vlp_hash_cnt = mmu.hash_cnt;

#if defined(__amd64)
        /*
         * If running in 64 bits and physical memory is large,
         * increase the size of the cache to cover all of memory for
         * a 64 bit process.
         */
#define HASH_MAX_LENGTH 4
        while (mmu.hash_cnt * HASH_MAX_LENGTH < max_htables)
                mmu.hash_cnt <<= 1;
#endif
}


/*
 * initialize hat data structures
 */
void
hat_init()
{
#if defined(__i386)
        /*
         * _userlimit must be aligned correctly
         */
        if ((_userlimit & LEVEL_MASK(1)) != _userlimit) {
                prom_printf("hat_init(): _userlimit=%p, not aligned at %p\n",
                    (void *)_userlimit, (void *)LEVEL_SIZE(1));
                halt("hat_init(): Unable to continue");
        }
#endif

        cv_init(&hat_list_cv, NULL, CV_DEFAULT, NULL);

        /*
         * initialize kmem caches
         */
        htable_init();
        hment_init();

        hat_cache = kmem_cache_create("hat_t",
            sizeof (hat_t), 0, hati_constructor, NULL, NULL,
            NULL, 0, 0);

        hat_hash_cache = kmem_cache_create("HatHash",
            mmu.hash_cnt * sizeof (htable_t *), 0, NULL, NULL, NULL,
            NULL, 0, 0);

        /*
         * VLP hats can use a smaller hash table size on large memroy machines
         */
        if (mmu.hash_cnt == mmu.vlp_hash_cnt) {
                vlp_hash_cache = hat_hash_cache;
        } else {
                vlp_hash_cache = kmem_cache_create("HatVlpHash",
                    mmu.vlp_hash_cnt * sizeof (htable_t *), 0, NULL, NULL, NULL,
                    NULL, 0, 0);
        }

        /*
         * Set up the kernel's hat
         */
        AS_LOCK_ENTER(&kas, &kas.a_lock, RW_WRITER);
        kas.a_hat = kmem_cache_alloc(hat_cache, KM_NOSLEEP);
        mutex_init(&kas.a_hat->hat_mutex, NULL, MUTEX_DEFAULT, NULL);
        kas.a_hat->hat_as = &kas;
        kas.a_hat->hat_flags = 0;
        AS_LOCK_EXIT(&kas, &kas.a_lock);

        CPUSET_ZERO(khat_cpuset);
        CPUSET_ADD(khat_cpuset, CPU->cpu_id);

        /*
         * The kernel hat's next pointer serves as the head of the hat list .
         * The kernel hat's prev pointer tracks the last hat on the list for
         * htable_steal() to use.
         */
        kas.a_hat->hat_next = NULL;
        kas.a_hat->hat_prev = NULL;

        /*
         * Allocate an htable hash bucket for the kernel
         * XX64 - tune for 64 bit procs
         */
        kas.a_hat->hat_num_hash = mmu.hash_cnt;
        kas.a_hat->hat_ht_hash = kmem_cache_alloc(hat_hash_cache, KM_NOSLEEP);
        bzero(kas.a_hat->hat_ht_hash, mmu.hash_cnt * sizeof (htable_t *));

        /*
         * zero out the top level and cached htable pointers
         */
        kas.a_hat->hat_ht_cached = NULL;
        kas.a_hat->hat_htable = NULL;

        /*
         * Pre-allocate hrm_hashtab before enabling the collection of
         * refmod statistics.  Allocating on the fly would mean us
         * running the risk of suffering recursive mutex enters or
         * deadlocks.
         */
        hrm_hashtab = kmem_zalloc(HRM_HASHSIZE * sizeof (struct hrmstat *),
            KM_SLEEP);
}

/*
 * Prepare CPU specific pagetables for VLP processes on 64 bit kernels.
 *
 * Each CPU has a set of 2 pagetables that are reused for any 32 bit
 * process it runs. They are the top level pagetable, hci_vlp_l3ptes, and
 * the next to top level table for the bottom 512 Gig, hci_vlp_l2ptes.
 */
/*ARGSUSED*/
static void
hat_vlp_setup(struct cpu *cpu)
{
#if defined(__amd64) && !defined(__xpv)
        struct hat_cpu_info *hci = cpu->cpu_hat_info;
        pfn_t pfn;

        /*
         * allocate the level==2 page table for the bottom most
         * 512Gig of address space (this is where 32 bit apps live)
         */
        ASSERT(hci != NULL);
        hci->hci_vlp_l2ptes = kmem_zalloc(MMU_PAGESIZE, KM_SLEEP);

        /*
         * Allocate a top level pagetable and copy the kernel's
         * entries into it. Then link in hci_vlp_l2ptes in the 1st entry.
         */
        hci->hci_vlp_l3ptes = kmem_zalloc(MMU_PAGESIZE, KM_SLEEP);
        hci->hci_vlp_pfn =
            hat_getpfnum(kas.a_hat, (caddr_t)hci->hci_vlp_l3ptes);
        ASSERT(hci->hci_vlp_pfn != PFN_INVALID);
        bcopy(vlp_page, hci->hci_vlp_l3ptes, MMU_PAGESIZE);

        pfn = hat_getpfnum(kas.a_hat, (caddr_t)hci->hci_vlp_l2ptes);
        ASSERT(pfn != PFN_INVALID);
        hci->hci_vlp_l3ptes[0] = MAKEPTP(pfn, 2);
#endif /* __amd64 && !__xpv */
}

/*ARGSUSED*/
static void
hat_vlp_teardown(cpu_t *cpu)
{
#if defined(__amd64) && !defined(__xpv)
        struct hat_cpu_info *hci;

        if ((hci = cpu->cpu_hat_info) == NULL)
                return;
        if (hci->hci_vlp_l2ptes)
                kmem_free(hci->hci_vlp_l2ptes, MMU_PAGESIZE);
        if (hci->hci_vlp_l3ptes)
                kmem_free(hci->hci_vlp_l3ptes, MMU_PAGESIZE);
#endif
}

#define NEXT_HKR(r, l, s, e) {                  \
        kernel_ranges[r].hkr_level = l;         \
        kernel_ranges[r].hkr_start_va = s;      \
        kernel_ranges[r].hkr_end_va = e;        \
        ++r;                                    \
}

/*
 * Finish filling in the kernel hat.
 * Pre fill in all top level kernel page table entries for the kernel's
 * part of the address range.  From this point on we can't use any new
 * kernel large pages if they need PTE's at max_level
 *
 * create the kmap mappings.
 */
void
hat_init_finish(void)
{
        size_t          size;
        uint_t          r = 0;
        uintptr_t       va;
        hat_kernel_range_t *rp;


        /*
         * We are now effectively running on the kernel hat.
         * Clearing use_boot_reserve shuts off using the pre-allocated boot
         * reserve for all HAT allocations.  From here on, the reserves are
         * only used when avoiding recursion in kmem_alloc().
         */
        use_boot_reserve = 0;
        htable_adjust_reserve();

        /*
         * User HATs are initialized with copies of all kernel mappings in
         * higher level page tables. Ensure that those entries exist.
         */
#if defined(__amd64)

        NEXT_HKR(r, 3, kernelbase, 0);
#if defined(__xpv)
        NEXT_HKR(r, 3, HYPERVISOR_VIRT_START, HYPERVISOR_VIRT_END);
#endif

#elif defined(__i386)

#if !defined(__xpv)
        if (mmu.pae_hat) {
                va = kernelbase;
                if ((va & LEVEL_MASK(2)) != va) {
                        va = P2ROUNDUP(va, LEVEL_SIZE(2));
                        NEXT_HKR(r, 1, kernelbase, va);
                }
                if (va != 0)
                        NEXT_HKR(r, 2, va, 0);
        } else
#endif /* __xpv */
                NEXT_HKR(r, 1, kernelbase, 0);

#endif /* __i386 */

        num_kernel_ranges = r;

        /*
         * Create all the kernel pagetables that will have entries
         * shared to user HATs.
         */
        for (r = 0; r < num_kernel_ranges; ++r) {
                rp = &kernel_ranges[r];
                for (va = rp->hkr_start_va; va != rp->hkr_end_va;
                    va += LEVEL_SIZE(rp->hkr_level)) {
                        htable_t *ht;

                        if (IN_HYPERVISOR_VA(va))
                                continue;

                        /* can/must skip if a page mapping already exists */
                        if (rp->hkr_level <= mmu.max_page_level &&
                            (ht = htable_getpage(kas.a_hat, va, NULL)) !=
                            NULL) {
                                htable_release(ht);
                                continue;
                        }

                        (void) htable_create(kas.a_hat, va, rp->hkr_level - 1,
                            NULL);
                }
        }

        /*
         * 32 bit PAE metal kernels use only 4 of the 512 entries in the
         * page holding the top level pagetable. We use the remainder for
         * the "per CPU" page tables for VLP processes.
         * Map the top level kernel pagetable into the kernel to make
         * it easy to use bcopy access these tables.
         */
        if (mmu.pae_hat) {
                vlp_page = vmem_alloc(heap_arena, MMU_PAGESIZE, VM_SLEEP);
                hat_devload(kas.a_hat, (caddr_t)vlp_page, MMU_PAGESIZE,
                    kas.a_hat->hat_htable->ht_pfn,
#if !defined(__xpv)
                    PROT_WRITE |
#endif
                    PROT_READ | HAT_NOSYNC | HAT_UNORDERED_OK,
                    HAT_LOAD | HAT_LOAD_NOCONSIST);
        }
        hat_vlp_setup(CPU);

        /*
         * Create kmap (cached mappings of kernel PTEs)
         * for 32 bit we map from segmap_start .. ekernelheap
         * for 64 bit we map from segmap_start .. segmap_start + segmapsize;
         */
#if defined(__i386)
        size = (uintptr_t)ekernelheap - segmap_start;
#elif defined(__amd64)
        size = segmapsize;
#endif
        hat_kmap_init((uintptr_t)segmap_start, size);
}

/*
 * On 32 bit PAE mode, PTE's are 64 bits, but ordinary atomic memory references
 * are 32 bit, so for safety we must use atomic_cas_64() to install these.
 */
#ifdef __i386
static void
reload_pae32(hat_t *hat, cpu_t *cpu)
{
        x86pte_t *src;
        x86pte_t *dest;
        x86pte_t pte;
        int i;

        /*
         * Load the 4 entries of the level 2 page table into this
         * cpu's range of the vlp_page and point cr3 at them.
         */
        ASSERT(mmu.pae_hat);
        src = hat->hat_vlp_ptes;
        dest = vlp_page + (cpu->cpu_id + 1) * VLP_NUM_PTES;
        for (i = 0; i < VLP_NUM_PTES; ++i) {
                for (;;) {
                        pte = dest[i];
                        if (pte == src[i])
                                break;
                        if (atomic_cas_64(dest + i, pte, src[i]) != src[i])
                                break;
                }
        }
}
#endif

/*
 * Switch to a new active hat, maintaining bit masks to track active CPUs.
 *
 * On the 32-bit PAE hypervisor, %cr3 is a 64-bit value, on metal it
 * remains a 32-bit value.
 */
void
hat_switch(hat_t *hat)
{
        uint64_t        newcr3;
        cpu_t           *cpu = CPU;
        hat_t           *old = cpu->cpu_current_hat;

        /*
         * set up this information first, so we don't miss any cross calls
         */
        if (old != NULL) {
                if (old == hat)
                        return;
                if (old != kas.a_hat)
                        CPUSET_ATOMIC_DEL(old->hat_cpus, cpu->cpu_id);
        }

        /*
         * Add this CPU to the active set for this HAT.
         */
        if (hat != kas.a_hat) {
                CPUSET_ATOMIC_ADD(hat->hat_cpus, cpu->cpu_id);
        }
        cpu->cpu_current_hat = hat;

        /*
         * now go ahead and load cr3
         */
        if (hat->hat_flags & HAT_VLP) {
#if defined(__amd64)
                x86pte_t *vlpptep = cpu->cpu_hat_info->hci_vlp_l2ptes;

                VLP_COPY(hat->hat_vlp_ptes, vlpptep);
                newcr3 = MAKECR3(cpu->cpu_hat_info->hci_vlp_pfn);
#elif defined(__i386)
                reload_pae32(hat, cpu);
                newcr3 = MAKECR3(kas.a_hat->hat_htable->ht_pfn) +
                    (cpu->cpu_id + 1) * VLP_SIZE;
#endif
        } else {
                newcr3 = MAKECR3((uint64_t)hat->hat_htable->ht_pfn);
        }
#ifdef __xpv
        {
                struct mmuext_op t[2];
                uint_t retcnt;
                uint_t opcnt = 1;

                t[0].cmd = MMUEXT_NEW_BASEPTR;
                t[0].arg1.mfn = mmu_btop(pa_to_ma(newcr3));
#if defined(__amd64)
                /*
                 * There's an interesting problem here, as to what to
                 * actually specify when switching to the kernel hat.
                 * For now we'll reuse the kernel hat again.
                 */
                t[1].cmd = MMUEXT_NEW_USER_BASEPTR;
                if (hat == kas.a_hat)
                        t[1].arg1.mfn = mmu_btop(pa_to_ma(newcr3));
                else
                        t[1].arg1.mfn = pfn_to_mfn(hat->hat_user_ptable);
                ++opcnt;
#endif  /* __amd64 */
                if (HYPERVISOR_mmuext_op(t, opcnt, &retcnt, DOMID_SELF) < 0)
                        panic("HYPERVISOR_mmu_update() failed");
                ASSERT(retcnt == opcnt);

        }
#else
        setcr3(newcr3);
#endif
        ASSERT(cpu == CPU);
}

/*
 * Utility to return a valid x86pte_t from protections, pfn, and level number
 */
static x86pte_t
hati_mkpte(pfn_t pfn, uint_t attr, level_t level, uint_t flags)
{
        x86pte_t        pte;
        uint_t          cache_attr = attr & HAT_ORDER_MASK;

        pte = MAKEPTE(pfn, level);

        if (attr & PROT_WRITE)
                PTE_SET(pte, PT_WRITABLE);

        if (attr & PROT_USER)
                PTE_SET(pte, PT_USER);

        if (!(attr & PROT_EXEC))
                PTE_SET(pte, mmu.pt_nx);

        /*
         * Set the software bits used track ref/mod sync's and hments.
         * If not using REF/MOD, set them to avoid h/w rewriting PTEs.
         */
        if (flags & HAT_LOAD_NOCONSIST)
                PTE_SET(pte, PT_NOCONSIST | PT_REF | PT_MOD);
        else if (attr & HAT_NOSYNC)
                PTE_SET(pte, PT_NOSYNC | PT_REF | PT_MOD);

        /*
         * Set the caching attributes in the PTE. The combination
         * of attributes are poorly defined, so we pay attention
         * to them in the given order.
         *
         * The test for HAT_STRICTORDER is different because it's defined
         * as "0" - which was a stupid thing to do, but is too late to change!
         */
        if (cache_attr == HAT_STRICTORDER) {
                PTE_SET(pte, PT_NOCACHE);
        /*LINTED [Lint hates empty ifs, but it's the obvious way to do this] */
        } else if (cache_attr & (HAT_UNORDERED_OK | HAT_STORECACHING_OK)) {
                /* nothing to set */;
        } else if (cache_attr & (HAT_MERGING_OK | HAT_LOADCACHING_OK)) {
                PTE_SET(pte, PT_NOCACHE);
                if (is_x86_feature(x86_featureset, X86FSET_PAT))
                        PTE_SET(pte, (level == 0) ? PT_PAT_4K : PT_PAT_LARGE);
                else
                        PTE_SET(pte, PT_WRITETHRU);
        } else {
                panic("hati_mkpte(): bad caching attributes: %x\n", cache_attr);
        }

        return (pte);
}

/*
 * Duplicate address translations of the parent to the child.
 * This function really isn't used anymore.
 */
/*ARGSUSED*/
int
hat_dup(hat_t *old, hat_t *new, caddr_t addr, size_t len, uint_t flag)
{
        ASSERT((uintptr_t)addr < kernelbase);
        ASSERT(new != kas.a_hat);
        ASSERT(old != kas.a_hat);
        return (0);
}

/*
 * Allocate any hat resources required for a process being swapped in.
 */
/*ARGSUSED*/
void
hat_swapin(hat_t *hat)
{
        /* do nothing - we let everything fault back in */
}

/*
 * Unload all translations associated with an address space of a process
 * that is being swapped out.
 */
void
hat_swapout(hat_t *hat)
{
        uintptr_t       vaddr = (uintptr_t)0;
        uintptr_t       eaddr = _userlimit;
        htable_t        *ht = NULL;
        level_t         l;

        XPV_DISALLOW_MIGRATE();
        /*
         * We can't just call hat_unload(hat, 0, _userlimit...)  here, because
         * seg_spt and shared pagetables can't be swapped out.
         * Take a look at segspt_shmswapout() - it's a big no-op.
         *
         * Instead we'll walk through all the address space and unload
         * any mappings which we are sure are not shared, not locked.
         */
        ASSERT(IS_PAGEALIGNED(vaddr));
        ASSERT(IS_PAGEALIGNED(eaddr));
        ASSERT(AS_LOCK_HELD(hat->hat_as, &hat->hat_as->a_lock));
        if ((uintptr_t)hat->hat_as->a_userlimit < eaddr)
                eaddr = (uintptr_t)hat->hat_as->a_userlimit;

        while (vaddr < eaddr) {
                (void) htable_walk(hat, &ht, &vaddr, eaddr);
                if (ht == NULL)
                        break;

                ASSERT(!IN_VA_HOLE(vaddr));

                /*
                 * If the page table is shared skip its entire range.
                 */
                l = ht->ht_level;
                if (ht->ht_flags & HTABLE_SHARED_PFN) {
                        vaddr = ht->ht_vaddr + LEVEL_SIZE(l + 1);
                        htable_release(ht);
                        ht = NULL;
                        continue;
                }

                /*
                 * If the page table has no locked entries, unload this one.
                 */
                if (ht->ht_lock_cnt == 0)
                        hat_unload(hat, (caddr_t)vaddr, LEVEL_SIZE(l),
                            HAT_UNLOAD_UNMAP);

                /*
                 * If we have a level 0 page table with locked entries,
                 * skip the entire page table, otherwise skip just one entry.
                 */
                if (ht->ht_lock_cnt > 0 && l == 0)
                        vaddr = ht->ht_vaddr + LEVEL_SIZE(1);
                else
                        vaddr += LEVEL_SIZE(l);
        }
        if (ht)
                htable_release(ht);

        /*
         * We're in swapout because the system is low on memory, so
         * go back and flush all the htables off the cached list.
         */
        htable_purge_hat(hat);
        XPV_ALLOW_MIGRATE();
}

/*
 * returns number of bytes that have valid mappings in hat.
 */
size_t
hat_get_mapped_size(hat_t *hat)
{
        size_t total = 0;
        int l;

        for (l = 0; l <= mmu.max_page_level; l++)
                total += (hat->hat_pages_mapped[l] << LEVEL_SHIFT(l));
        total += hat->hat_ism_pgcnt;

        return (total);
}

/*
 * enable/disable collection of stats for hat.
 */
int
hat_stats_enable(hat_t *hat)
{
        atomic_inc_32(&hat->hat_stats);
        return (1);
}

void
hat_stats_disable(hat_t *hat)
{
        atomic_dec_32(&hat->hat_stats);
}

/*
 * Utility to sync the ref/mod bits from a page table entry to the page_t
 * We must be holding the mapping list lock when this is called.
 */
static void
hati_sync_pte_to_page(page_t *pp, x86pte_t pte, level_t level)
{
        uint_t  rm = 0;
        pgcnt_t pgcnt;

        if (PTE_GET(pte, PT_SOFTWARE) >= PT_NOSYNC)
                return;

        if (PTE_GET(pte, PT_REF))
                rm |= P_REF;

        if (PTE_GET(pte, PT_MOD))
                rm |= P_MOD;

        if (rm == 0)
                return;

        /*
         * sync to all constituent pages of a large page
         */
        ASSERT(x86_hm_held(pp));
        pgcnt = page_get_pagecnt(level);
        ASSERT(IS_P2ALIGNED(pp->p_pagenum, pgcnt));
        for (; pgcnt > 0; --pgcnt) {
                /*
                 * hat_page_demote() can't decrease
                 * pszc below this mapping size
                 * since this large mapping existed after we
                 * took mlist lock.
                 */
                ASSERT(pp->p_szc >= level);
                hat_page_setattr(pp, rm);
                ++pp;
        }
}

/*
 * This the set of PTE bits for PFN, permissions and caching
 * that are allowed to change on a HAT_LOAD_REMAP
 */
#define PT_REMAP_BITS                                                   \
        (PT_PADDR | PT_NX | PT_WRITABLE | PT_WRITETHRU |                \
        PT_NOCACHE | PT_PAT_4K | PT_PAT_LARGE | PT_IGNORE | PT_REF | PT_MOD)

#define REMAPASSERT(EX) if (!(EX)) panic("hati_pte_map: " #EX)
/*
 * Do the low-level work to get a mapping entered into a HAT's pagetables
 * and in the mapping list of the associated page_t.
 */
static int
hati_pte_map(
        htable_t        *ht,
        uint_t          entry,
        page_t          *pp,
        x86pte_t        pte,
        int             flags,
        void            *pte_ptr)
{
        hat_t           *hat = ht->ht_hat;
        x86pte_t        old_pte;
        level_t         l = ht->ht_level;
        hment_t         *hm;
        uint_t          is_consist;
        uint_t          is_locked;
        int             rv = 0;

        /*
         * Is this a consistent (ie. need mapping list lock) mapping?
         */
        is_consist = (pp != NULL && (flags & HAT_LOAD_NOCONSIST) == 0);

        /*
         * Track locked mapping count in the htable.  Do this first,
         * as we track locking even if there already is a mapping present.
         */
        is_locked = (flags & HAT_LOAD_LOCK) != 0 && hat != kas.a_hat;
        if (is_locked)
                HTABLE_LOCK_INC(ht);

        /*
         * Acquire the page's mapping list lock and get an hment to use.
         * Note that hment_prepare() might return NULL.
         */
        if (is_consist) {
                x86_hm_enter(pp);
                hm = hment_prepare(ht, entry, pp);
        }

        /*
         * Set the new pte, retrieving the old one at the same time.
         */
        old_pte = x86pte_set(ht, entry, pte, pte_ptr);

        /*
         * Did we get a large page / page table collision?
         */
        if (old_pte == LPAGE_ERROR) {
                if (is_locked)
                        HTABLE_LOCK_DEC(ht);
                rv = -1;
                goto done;
        }

        /*
         * If the mapping didn't change there is nothing more to do.
         */
        if (PTE_EQUIV(pte, old_pte))
                goto done;

        /*
         * Install a new mapping in the page's mapping list
         */
        if (!PTE_ISVALID(old_pte)) {
                if (is_consist) {
                        hment_assign(ht, entry, pp, hm);
                        x86_hm_exit(pp);
                } else {
                        ASSERT(flags & HAT_LOAD_NOCONSIST);
                }
#if defined(__amd64)
                if (ht->ht_flags & HTABLE_VLP) {
                        cpu_t *cpu = CPU;
                        x86pte_t *vlpptep = cpu->cpu_hat_info->hci_vlp_l2ptes;
                        VLP_COPY(hat->hat_vlp_ptes, vlpptep);
                }
#endif
                HTABLE_INC(ht->ht_valid_cnt);
                PGCNT_INC(hat, l);
                return (rv);
        }

        /*
         * Remap's are more complicated:
         *  - HAT_LOAD_REMAP must be specified if changing the pfn.
         *    We also require that NOCONSIST be specified.
         *  - Otherwise only permission or caching bits may change.
         */
        if (!PTE_ISPAGE(old_pte, l))
                panic("non-null/page mapping pte=" FMT_PTE, old_pte);

        if (PTE2PFN(old_pte, l) != PTE2PFN(pte, l)) {
                REMAPASSERT(flags & HAT_LOAD_REMAP);
                REMAPASSERT(flags & HAT_LOAD_NOCONSIST);
                REMAPASSERT(PTE_GET(old_pte, PT_SOFTWARE) >= PT_NOCONSIST);
                REMAPASSERT(pf_is_memory(PTE2PFN(old_pte, l)) ==
                    pf_is_memory(PTE2PFN(pte, l)));
                REMAPASSERT(!is_consist);
        }

        /*
         * We only let remaps change the certain bits in the PTE.
         */
        if (PTE_GET(old_pte, ~PT_REMAP_BITS) != PTE_GET(pte, ~PT_REMAP_BITS))
                panic("remap bits changed: old_pte="FMT_PTE", pte="FMT_PTE"\n",
                    old_pte, pte);

        /*
         * We don't create any mapping list entries on a remap, so release
         * any allocated hment after we drop the mapping list lock.
         */
done:
        if (is_consist) {
                x86_hm_exit(pp);
                if (hm != NULL)
                        hment_free(hm);
        }
        return (rv);
}

/*
 * Internal routine to load a single page table entry. This only fails if
 * we attempt to overwrite a page table link with a large page.
 */
static int
hati_load_common(
        hat_t           *hat,
        uintptr_t       va,
        page_t          *pp,
        uint_t          attr,
        uint_t          flags,
        level_t         level,
        pfn_t           pfn)
{
        htable_t        *ht;
        uint_t          entry;
        x86pte_t        pte;
        int             rv = 0;

        /*
         * The number 16 is arbitrary and here to catch a recursion problem
         * early before we blow out the kernel stack.
         */
        ++curthread->t_hatdepth;
        ASSERT(curthread->t_hatdepth < 16);

        ASSERT(hat == kas.a_hat ||
            AS_LOCK_HELD(hat->hat_as, &hat->hat_as->a_lock));

        if (flags & HAT_LOAD_SHARE)
                hat->hat_flags |= HAT_SHARED;

        /*
         * Find the page table that maps this page if it already exists.
         */
        ht = htable_lookup(hat, va, level);

        /*
         * We must have HAT_LOAD_NOCONSIST if page_t is NULL.
         */
        if (pp == NULL)
                flags |= HAT_LOAD_NOCONSIST;

        if (ht == NULL) {
                ht = htable_create(hat, va, level, NULL);
                ASSERT(ht != NULL);
        }
        entry = htable_va2entry(va, ht);

        /*
         * a bunch of paranoid error checking
         */
        ASSERT(ht->ht_busy > 0);
        if (ht->ht_vaddr > va || va > HTABLE_LAST_PAGE(ht))
                panic("hati_load_common: bad htable %p, va %p",
                    (void *)ht, (void *)va);
        ASSERT(ht->ht_level == level);

        /*
         * construct the new PTE
         */
        if (hat == kas.a_hat)
                attr &= ~PROT_USER;
        pte = hati_mkpte(pfn, attr, level, flags);
        if (hat == kas.a_hat && va >= kernelbase)
                PTE_SET(pte, mmu.pt_global);

        /*
         * establish the mapping
         */
        rv = hati_pte_map(ht, entry, pp, pte, flags, NULL);

        /*
         * release the htable and any reserves
         */
        htable_release(ht);
        --curthread->t_hatdepth;
        return (rv);
}

/*
 * special case of hat_memload to deal with some kernel addrs for performance
 */
static void
hat_kmap_load(
        caddr_t         addr,
        page_t          *pp,
        uint_t          attr,
        uint_t          flags)
{
        uintptr_t       va = (uintptr_t)addr;
        x86pte_t        pte;
        pfn_t           pfn = page_pptonum(pp);
        pgcnt_t         pg_off = mmu_btop(va - mmu.kmap_addr);
        htable_t        *ht;
        uint_t          entry;
        void            *pte_ptr;

        /*
         * construct the requested PTE
         */
        attr &= ~PROT_USER;
        attr |= HAT_STORECACHING_OK;
        pte = hati_mkpte(pfn, attr, 0, flags);
        PTE_SET(pte, mmu.pt_global);

        /*
         * Figure out the pte_ptr and htable and use common code to finish up
         */
        if (mmu.pae_hat)
                pte_ptr = mmu.kmap_ptes + pg_off;
        else
                pte_ptr = (x86pte32_t *)mmu.kmap_ptes + pg_off;
        ht = mmu.kmap_htables[(va - mmu.kmap_htables[0]->ht_vaddr) >>
            LEVEL_SHIFT(1)];
        entry = htable_va2entry(va, ht);
        ++curthread->t_hatdepth;
        ASSERT(curthread->t_hatdepth < 16);
        (void) hati_pte_map(ht, entry, pp, pte, flags, pte_ptr);
        --curthread->t_hatdepth;
}

/*
 * hat_memload() - load a translation to the given page struct
 *
 * Flags for hat_memload/hat_devload/hat_*attr.
 *
 *      HAT_LOAD        Default flags to load a translation to the page.
 *
 *      HAT_LOAD_LOCK   Lock down mapping resources; hat_map(), hat_memload(),
 *                      and hat_devload().
 *
 *      HAT_LOAD_NOCONSIST Do not add mapping to page_t mapping list.
 *                      sets PT_NOCONSIST
 *
 *      HAT_LOAD_SHARE  A flag to hat_memload() to indicate h/w page tables
 *                      that map some user pages (not kas) is shared by more
 *                      than one process (eg. ISM).
 *
 *      HAT_LOAD_REMAP  Reload a valid pte with a different page frame.
 *
 *      HAT_NO_KALLOC   Do not kmem_alloc while creating the mapping; at this
 *                      point, it's setting up mapping to allocate internal
 *                      hat layer data structures.  This flag forces hat layer
 *                      to tap its reserves in order to prevent infinite
 *                      recursion.
 *
 * The following is a protection attribute (like PROT_READ, etc.)
 *
 *      HAT_NOSYNC      set PT_NOSYNC - this mapping's ref/mod bits
 *                      are never cleared.
 *
 * Installing new valid PTE's and creation of the mapping list
 * entry are controlled under the same lock. It's derived from the
 * page_t being mapped.
 */
static uint_t supported_memload_flags =
        HAT_LOAD | HAT_LOAD_LOCK | HAT_LOAD_ADV | HAT_LOAD_NOCONSIST |
        HAT_LOAD_SHARE | HAT_NO_KALLOC | HAT_LOAD_REMAP | HAT_LOAD_TEXT;

void
hat_memload(
        hat_t           *hat,
        caddr_t         addr,
        page_t          *pp,
        uint_t          attr,
        uint_t          flags)
{
        uintptr_t       va = (uintptr_t)addr;
        level_t         level = 0;
        pfn_t           pfn = page_pptonum(pp);

        XPV_DISALLOW_MIGRATE();
        ASSERT(IS_PAGEALIGNED(va));
        ASSERT(hat == kas.a_hat || va < _userlimit);
        ASSERT(hat == kas.a_hat ||
            AS_LOCK_HELD(hat->hat_as, &hat->hat_as->a_lock));
        ASSERT((flags & supported_memload_flags) == flags);

        ASSERT(!IN_VA_HOLE(va));
        ASSERT(!PP_ISFREE(pp));

        /*
         * kernel address special case for performance.
         */
        if (mmu.kmap_addr <= va && va < mmu.kmap_eaddr) {
                ASSERT(hat == kas.a_hat);
                hat_kmap_load(addr, pp, attr, flags);
                XPV_ALLOW_MIGRATE();
                return;
        }

        /*
         * This is used for memory with normal caching enabled, so
         * always set HAT_STORECACHING_OK.
         */
        attr |= HAT_STORECACHING_OK;
        if (hati_load_common(hat, va, pp, attr, flags, level, pfn) != 0)
                panic("unexpected hati_load_common() failure");
        XPV_ALLOW_MIGRATE();
}

/* ARGSUSED */
void
hat_memload_region(struct hat *hat, caddr_t addr, struct page *pp,
    uint_t attr, uint_t flags, hat_region_cookie_t rcookie)
{
        hat_memload(hat, addr, pp, attr, flags);
}

/*
 * Load the given array of page structs using large pages when possible
 */
void
hat_memload_array(
        hat_t           *hat,
        caddr_t         addr,
        size_t          len,
        page_t          **pages,
        uint_t          attr,
        uint_t          flags)
{
        uintptr_t       va = (uintptr_t)addr;
        uintptr_t       eaddr = va + len;
        level_t         level;
        size_t          pgsize;
        pgcnt_t         pgindx = 0;
        pfn_t           pfn;
        pgcnt_t         i;

        XPV_DISALLOW_MIGRATE();
        ASSERT(IS_PAGEALIGNED(va));
        ASSERT(hat == kas.a_hat || va + len <= _userlimit);
        ASSERT(hat == kas.a_hat ||
            AS_LOCK_HELD(hat->hat_as, &hat->hat_as->a_lock));
        ASSERT((flags & supported_memload_flags) == flags);

        /*
         * memload is used for memory with full caching enabled, so
         * set HAT_STORECACHING_OK.
         */
        attr |= HAT_STORECACHING_OK;

        /*
         * handle all pages using largest possible pagesize
         */
        while (va < eaddr) {
                /*
                 * decide what level mapping to use (ie. pagesize)
                 */
                pfn = page_pptonum(pages[pgindx]);
                for (level = mmu.max_page_level; ; --level) {
                        pgsize = LEVEL_SIZE(level);
                        if (level == 0)
                                break;

                        if (!IS_P2ALIGNED(va, pgsize) ||
                            (eaddr - va) < pgsize ||
                            !IS_P2ALIGNED(pfn_to_pa(pfn), pgsize))
                                continue;

                        /*
                         * To use a large mapping of this size, all the
                         * pages we are passed must be sequential subpages
                         * of the large page.
                         * hat_page_demote() can't change p_szc because
                         * all pages are locked.
                         */
                        if (pages[pgindx]->p_szc >= level) {
                                for (i = 0; i < mmu_btop(pgsize); ++i) {
                                        if (pfn + i !=
                                            page_pptonum(pages[pgindx + i]))
                                                break;
                                        ASSERT(pages[pgindx + i]->p_szc >=
                                            level);
                                        ASSERT(pages[pgindx] + i ==
                                            pages[pgindx + i]);
                                }
                                if (i == mmu_btop(pgsize)) {
#ifdef DEBUG
                                        if (level == 2)
                                                map1gcnt++;
#endif
                                        break;
                                }
                        }
                }

                /*
                 * Load this page mapping. If the load fails, try a smaller
                 * pagesize.
                 */
                ASSERT(!IN_VA_HOLE(va));
                while (hati_load_common(hat, va, pages[pgindx], attr,
                    flags, level, pfn) != 0) {
                        if (level == 0)
                                panic("unexpected hati_load_common() failure");
                        --level;
                        pgsize = LEVEL_SIZE(level);
                }

                /*
                 * move to next page
                 */
                va += pgsize;
                pgindx += mmu_btop(pgsize);
        }
        XPV_ALLOW_MIGRATE();
}

/* ARGSUSED */
void
hat_memload_array_region(struct hat *hat, caddr_t addr, size_t len,
    struct page **pps, uint_t attr, uint_t flags,
    hat_region_cookie_t rcookie)
{
        hat_memload_array(hat, addr, len, pps, attr, flags);
}

/*
 * void hat_devload(hat, addr, len, pf, attr, flags)
 *      load/lock the given page frame number
 *
 * Advisory ordering attributes. Apply only to device mappings.
 *
 * HAT_STRICTORDER: the CPU must issue the references in order, as the
 *      programmer specified.  This is the default.
 * HAT_UNORDERED_OK: the CPU may reorder the references (this is all kinds
 *      of reordering; store or load with store or load).
 * HAT_MERGING_OK: merging and batching: the CPU may merge individual stores
 *      to consecutive locations (for example, turn two consecutive byte
 *      stores into one halfword store), and it may batch individual loads
 *      (for example, turn two consecutive byte loads into one halfword load).
 *      This also implies re-ordering.
 * HAT_LOADCACHING_OK: the CPU may cache the data it fetches and reuse it
 *      until another store occurs.  The default is to fetch new data
 *      on every load.  This also implies merging.
 * HAT_STORECACHING_OK: the CPU may keep the data in the cache and push it to
 *      the device (perhaps with other data) at a later time.  The default is
 *      to push the data right away.  This also implies load caching.
 *
 * Equivalent of hat_memload(), but can be used for device memory where
 * there are no page_t's and we support additional flags (write merging, etc).
 * Note that we can have large page mappings with this interface.
 */
int supported_devload_flags = HAT_LOAD | HAT_LOAD_LOCK |
        HAT_LOAD_NOCONSIST | HAT_STRICTORDER | HAT_UNORDERED_OK |
        HAT_MERGING_OK | HAT_LOADCACHING_OK | HAT_STORECACHING_OK;

void
hat_devload(
        hat_t           *hat,
        caddr_t         addr,
        size_t          len,
        pfn_t           pfn,
        uint_t          attr,
        int             flags)
{
        uintptr_t       va = ALIGN2PAGE(addr);
        uintptr_t       eva = va + len;
        level_t         level;
        size_t          pgsize;
        page_t          *pp;
        int             f;      /* per PTE copy of flags  - maybe modified */
        uint_t          a;      /* per PTE copy of attr */

        XPV_DISALLOW_MIGRATE();
        ASSERT(IS_PAGEALIGNED(va));
        ASSERT(hat == kas.a_hat || eva <= _userlimit);
        ASSERT(hat == kas.a_hat ||
            AS_LOCK_HELD(hat->hat_as, &hat->hat_as->a_lock));
        ASSERT((flags & supported_devload_flags) == flags);

        /*
         * handle all pages
         */
        while (va < eva) {

                /*
                 * decide what level mapping to use (ie. pagesize)
                 */
                for (level = mmu.max_page_level; ; --level) {
                        pgsize = LEVEL_SIZE(level);
                        if (level == 0)
                                break;
                        if (IS_P2ALIGNED(va, pgsize) &&
                            (eva - va) >= pgsize &&
                            IS_P2ALIGNED(pfn, mmu_btop(pgsize))) {
#ifdef DEBUG
                                if (level == 2)
                                        map1gcnt++;
#endif
                                break;
                        }
                }

                /*
                 * If this is just memory then allow caching (this happens
                 * for the nucleus pages) - though HAT_PLAT_NOCACHE can be used
                 * to override that. If we don't have a page_t then make sure
                 * NOCONSIST is set.
                 */
                a = attr;
                f = flags;
                if (!pf_is_memory(pfn))
                        f |= HAT_LOAD_NOCONSIST;
                else if (!(a & HAT_PLAT_NOCACHE))
                        a |= HAT_STORECACHING_OK;

                if (f & HAT_LOAD_NOCONSIST)
                        pp = NULL;
                else
                        pp = page_numtopp_nolock(pfn);

                /*
                 * Check to make sure we are really trying to map a valid
                 * memory page. The caller wishing to intentionally map
                 * free memory pages will have passed the HAT_LOAD_NOCONSIST
                 * flag, then pp will be NULL.
                 */
                if (pp != NULL) {
                        if (PP_ISFREE(pp)) {
                                panic("hat_devload: loading "
                                    "a mapping to free page %p", (void *)pp);
                        }

                        if (!PAGE_LOCKED(pp) && !PP_ISNORELOC(pp)) {
                                panic("hat_devload: loading a mapping "
                                    "to an unlocked page %p",
                                    (void *)pp);
                        }
                }

                /*
                 * load this page mapping
                 */
                ASSERT(!IN_VA_HOLE(va));
                while (hati_load_common(hat, va, pp, a, f, level, pfn) != 0) {
                        if (level == 0)
                                panic("unexpected hati_load_common() failure");
                        --level;
                        pgsize = LEVEL_SIZE(level);
                }

                /*
                 * move to next page
                 */
                va += pgsize;
                pfn += mmu_btop(pgsize);
        }
        XPV_ALLOW_MIGRATE();
}

/*
 * void hat_unlock(hat, addr, len)
 *      unlock the mappings to a given range of addresses
 *
 * Locks are tracked by ht_lock_cnt in the htable.
 */
void
hat_unlock(hat_t *hat, caddr_t addr, size_t len)
{
        uintptr_t       vaddr = (uintptr_t)addr;
        uintptr_t       eaddr = vaddr + len;
        htable_t        *ht = NULL;

        /*
         * kernel entries are always locked, we don't track lock counts
         */
        ASSERT(hat == kas.a_hat || eaddr <= _userlimit);
        ASSERT(IS_PAGEALIGNED(vaddr));
        ASSERT(IS_PAGEALIGNED(eaddr));
        if (hat == kas.a_hat)
                return;
        if (eaddr > _userlimit)
                panic("hat_unlock() address out of range - above _userlimit");

        XPV_DISALLOW_MIGRATE();
        ASSERT(AS_LOCK_HELD(hat->hat_as, &hat->hat_as->a_lock));
        while (vaddr < eaddr) {
                (void) htable_walk(hat, &ht, &vaddr, eaddr);
                if (ht == NULL)
                        break;

                ASSERT(!IN_VA_HOLE(vaddr));

                if (ht->ht_lock_cnt < 1)
                        panic("hat_unlock(): lock_cnt < 1, "
                            "htable=%p, vaddr=%p\n", (void *)ht, (void *)vaddr);
                HTABLE_LOCK_DEC(ht);

                vaddr += LEVEL_SIZE(ht->ht_level);
        }
        if (ht)
                htable_release(ht);
        XPV_ALLOW_MIGRATE();
}

/* ARGSUSED */
void
hat_unlock_region(struct hat *hat, caddr_t addr, size_t len,
    hat_region_cookie_t rcookie)
{
        panic("No shared region support on x86");
}

#if !defined(__xpv)
/*
 * Cross call service routine to demap a virtual page on
 * the current CPU or flush all mappings in TLB.
 */
/*ARGSUSED*/
static int
hati_demap_func(xc_arg_t a1, xc_arg_t a2, xc_arg_t a3)
{
        hat_t   *hat = (hat_t *)a1;
        caddr_t addr = (caddr_t)a2;

        /*
         * If the target hat isn't the kernel and this CPU isn't operating
         * in the target hat, we can ignore the cross call.
         */
        if (hat != kas.a_hat && hat != CPU->cpu_current_hat)
                return (0);

        /*
         * For a normal address, we just flush one page mapping
         */
        if ((uintptr_t)addr != DEMAP_ALL_ADDR) {
                mmu_tlbflush_entry(addr);
                return (0);
        }

        /*
         * Otherwise we reload cr3 to effect a complete TLB flush.
         *
         * A reload of cr3 on a VLP process also means we must also recopy in
         * the pte values from the struct hat
         */
        if (hat->hat_flags & HAT_VLP) {
#if defined(__amd64)
                x86pte_t *vlpptep = CPU->cpu_hat_info->hci_vlp_l2ptes;

                VLP_COPY(hat->hat_vlp_ptes, vlpptep);
#elif defined(__i386)
                reload_pae32(hat, CPU);
#endif
        }
        reload_cr3();
        return (0);
}

/*
 * Flush all TLB entries, including global (ie. kernel) ones.
 */
static void
flush_all_tlb_entries(void)
{
        ulong_t cr4 = getcr4();

        if (cr4 & CR4_PGE) {
                setcr4(cr4 & ~(ulong_t)CR4_PGE);
                setcr4(cr4);

                /*
                 * 32 bit PAE also needs to always reload_cr3()
                 */
                if (mmu.max_level == 2)
                        reload_cr3();
        } else {
                reload_cr3();
        }
}

#define TLB_CPU_HALTED  (01ul)
#define TLB_INVAL_ALL   (02ul)
#define CAS_TLB_INFO(cpu, old, new)     \
        atomic_cas_ulong((ulong_t *)&(cpu)->cpu_m.mcpu_tlb_info, (old), (new))

/*
 * Record that a CPU is going idle
 */
void
tlb_going_idle(void)
{
        atomic_or_ulong((ulong_t *)&CPU->cpu_m.mcpu_tlb_info, TLB_CPU_HALTED);
}

/*
 * Service a delayed TLB flush if coming out of being idle.
 * It will be called from cpu idle notification with interrupt disabled.
 */
void
tlb_service(void)
{
        ulong_t tlb_info;
        ulong_t found;

        /*
         * We only have to do something if coming out of being idle.
         */
        tlb_info = CPU->cpu_m.mcpu_tlb_info;
        if (tlb_info & TLB_CPU_HALTED) {
                ASSERT(CPU->cpu_current_hat == kas.a_hat);

                /*
                 * Atomic clear and fetch of old state.
                 */
                while ((found = CAS_TLB_INFO(CPU, tlb_info, 0)) != tlb_info) {
                        ASSERT(found & TLB_CPU_HALTED);
                        tlb_info = found;
                        SMT_PAUSE();
                }
                if (tlb_info & TLB_INVAL_ALL)
                        flush_all_tlb_entries();
        }
}
#endif /* !__xpv */

/*
 * Internal routine to do cross calls to invalidate a range of pages on
 * all CPUs using a given hat.
 */
void
hat_tlb_inval(hat_t *hat, uintptr_t va)
{
        extern int      flushes_require_xcalls; /* from mp_startup.c */
        cpuset_t        justme;
        cpuset_t        cpus_to_shootdown;
#ifndef __xpv
        cpuset_t        check_cpus;
        cpu_t           *cpup;
        int             c;
#endif

        /*
         * If the hat is being destroyed, there are no more users, so
         * demap need not do anything.
         */
        if (hat->hat_flags & HAT_FREEING)
                return;

        /*
         * If demapping from a shared pagetable, we best demap the
         * entire set of user TLBs, since we don't know what addresses
         * these were shared at.
         */
        if (hat->hat_flags & HAT_SHARED) {
                hat = kas.a_hat;
                va = DEMAP_ALL_ADDR;
        }

        /*
         * if not running with multiple CPUs, don't use cross calls
         */
        if (panicstr || !flushes_require_xcalls) {
#ifdef __xpv
                if (va == DEMAP_ALL_ADDR)
                        xen_flush_tlb();
                else
                        xen_flush_va((caddr_t)va);
#else
                (void) hati_demap_func((xc_arg_t)hat, (xc_arg_t)va, NULL);
#endif
                return;
        }


        /*
         * Determine CPUs to shootdown. Kernel changes always do all CPUs.
         * Otherwise it's just CPUs currently executing in this hat.
         */
        kpreempt_disable();
        CPUSET_ONLY(justme, CPU->cpu_id);
        if (hat == kas.a_hat)
                cpus_to_shootdown = khat_cpuset;
        else
                cpus_to_shootdown = hat->hat_cpus;

#ifndef __xpv
        /*
         * If any CPUs in the set are idle, just request a delayed flush
         * and avoid waking them up.
         */
        check_cpus = cpus_to_shootdown;
        for (c = 0; c < NCPU && !CPUSET_ISNULL(check_cpus); ++c) {
                ulong_t tlb_info;

                if (!CPU_IN_SET(check_cpus, c))
                        continue;
                CPUSET_DEL(check_cpus, c);
                cpup = cpu[c];
                if (cpup == NULL)
                        continue;

                tlb_info = cpup->cpu_m.mcpu_tlb_info;
                while (tlb_info == TLB_CPU_HALTED) {
                        (void) CAS_TLB_INFO(cpup, TLB_CPU_HALTED,
                            TLB_CPU_HALTED | TLB_INVAL_ALL);
                        SMT_PAUSE();
                        tlb_info = cpup->cpu_m.mcpu_tlb_info;
                }
                if (tlb_info == (TLB_CPU_HALTED | TLB_INVAL_ALL)) {
                        HATSTAT_INC(hs_tlb_inval_delayed);
                        CPUSET_DEL(cpus_to_shootdown, c);
                }
        }
#endif

        if (CPUSET_ISNULL(cpus_to_shootdown) ||
            CPUSET_ISEQUAL(cpus_to_shootdown, justme)) {

#ifdef __xpv
                if (va == DEMAP_ALL_ADDR)
                        xen_flush_tlb();
                else
                        xen_flush_va((caddr_t)va);
#else
                (void) hati_demap_func((xc_arg_t)hat, (xc_arg_t)va, NULL);
#endif

        } else {

                CPUSET_ADD(cpus_to_shootdown, CPU->cpu_id);
#ifdef __xpv
                if (va == DEMAP_ALL_ADDR)
                        xen_gflush_tlb(cpus_to_shootdown);
                else
                        xen_gflush_va((caddr_t)va, cpus_to_shootdown);
#else
                xc_call((xc_arg_t)hat, (xc_arg_t)va, NULL,
                    CPUSET2BV(cpus_to_shootdown), hati_demap_func);
#endif

        }
        kpreempt_enable();
}

/*
 * Interior routine for HAT_UNLOADs from hat_unload_callback(),
 * hat_kmap_unload() OR from hat_steal() code.  This routine doesn't
 * handle releasing of the htables.
 */
void
hat_pte_unmap(
        htable_t        *ht,
        uint_t          entry,
        uint_t          flags,
        x86pte_t        old_pte,
        void            *pte_ptr)
{
        hat_t           *hat = ht->ht_hat;
        hment_t         *hm = NULL;
        page_t          *pp = NULL;
        level_t         l = ht->ht_level;
        pfn_t           pfn;

        /*
         * We always track the locking counts, even if nothing is unmapped
         */
        if ((flags & HAT_UNLOAD_UNLOCK) != 0 && hat != kas.a_hat) {
                ASSERT(ht->ht_lock_cnt > 0);
                HTABLE_LOCK_DEC(ht);
        }

        /*
         * Figure out which page's mapping list lock to acquire using the PFN
         * passed in "old" PTE. We then attempt to invalidate the PTE.
         * If another thread, probably a hat_pageunload, has asynchronously
         * unmapped/remapped this address we'll loop here.
         */
        ASSERT(ht->ht_busy > 0);
        while (PTE_ISVALID(old_pte)) {
                pfn = PTE2PFN(old_pte, l);
                if (PTE_GET(old_pte, PT_SOFTWARE) >= PT_NOCONSIST) {
                        pp = NULL;
                } else {
#ifdef __xpv
                        if (pfn == PFN_INVALID)
                                panic("Invalid PFN, but not PT_NOCONSIST");
#endif
                        pp = page_numtopp_nolock(pfn);
                        if (pp == NULL) {
                                panic("no page_t, not NOCONSIST: old_pte="
                                    FMT_PTE " ht=%lx entry=0x%x pte_ptr=%lx",
                                    old_pte, (uintptr_t)ht, entry,
                                    (uintptr_t)pte_ptr);
                        }
                        x86_hm_enter(pp);
                }

                old_pte = x86pte_inval(ht, entry, old_pte, pte_ptr);

                /*
                 * If the page hadn't changed we've unmapped it and can proceed
                 */
                if (PTE_ISVALID(old_pte) && PTE2PFN(old_pte, l) == pfn)
                        break;

                /*
                 * Otherwise, we'll have to retry with the current old_pte.
                 * Drop the hment lock, since the pfn may have changed.
                 */
                if (pp != NULL) {
                        x86_hm_exit(pp);
                        pp = NULL;
                } else {
                        ASSERT(PTE_GET(old_pte, PT_SOFTWARE) >= PT_NOCONSIST);
                }
        }

        /*
         * If the old mapping wasn't valid, there's nothing more to do
         */
        if (!PTE_ISVALID(old_pte)) {
                if (pp != NULL)
                        x86_hm_exit(pp);
                return;
        }

        /*
         * Take care of syncing any MOD/REF bits and removing the hment.
         */
        if (pp != NULL) {
                if (!(flags & HAT_UNLOAD_NOSYNC))
                        hati_sync_pte_to_page(pp, old_pte, l);
                hm = hment_remove(pp, ht, entry);
                x86_hm_exit(pp);
                if (hm != NULL)
                        hment_free(hm);
        }

        /*
         * Handle book keeping in the htable and hat
         */
        ASSERT(ht->ht_valid_cnt > 0);
        HTABLE_DEC(ht->ht_valid_cnt);
        PGCNT_DEC(hat, l);
}

/*
 * very cheap unload implementation to special case some kernel addresses
 */
static void
hat_kmap_unload(caddr_t addr, size_t len, uint_t flags)
{
        uintptr_t       va = (uintptr_t)addr;
        uintptr_t       eva = va + len;
        pgcnt_t         pg_index;
        htable_t        *ht;
        uint_t          entry;
        x86pte_t        *pte_ptr;
        x86pte_t        old_pte;

        for (; va < eva; va += MMU_PAGESIZE) {
                /*
                 * Get the PTE
                 */
                pg_index = mmu_btop(va - mmu.kmap_addr);
                pte_ptr = PT_INDEX_PTR(mmu.kmap_ptes, pg_index);
                old_pte = GET_PTE(pte_ptr);

                /*
                 * get the htable / entry
                 */
                ht = mmu.kmap_htables[(va - mmu.kmap_htables[0]->ht_vaddr)
                    >> LEVEL_SHIFT(1)];
                entry = htable_va2entry(va, ht);

                /*
                 * use mostly common code to unmap it.
                 */
                hat_pte_unmap(ht, entry, flags, old_pte, pte_ptr);
        }
}


/*
 * unload a range of virtual address space (no callback)
 */
void
hat_unload(hat_t *hat, caddr_t addr, size_t len, uint_t flags)
{
        uintptr_t va = (uintptr_t)addr;

        XPV_DISALLOW_MIGRATE();
        ASSERT(hat == kas.a_hat || va + len <= _userlimit);

        /*
         * special case for performance.
         */
        if (mmu.kmap_addr <= va && va < mmu.kmap_eaddr) {
                ASSERT(hat == kas.a_hat);
                hat_kmap_unload(addr, len, flags);
        } else {
                hat_unload_callback(hat, addr, len, flags, NULL);
        }
        XPV_ALLOW_MIGRATE();
}

/*
 * Do the callbacks for ranges being unloaded.
 */
typedef struct range_info {
        uintptr_t       rng_va;
        ulong_t         rng_cnt;
        level_t         rng_level;
} range_info_t;

static void
handle_ranges(hat_callback_t *cb, uint_t cnt, range_info_t *range)
{
        /*
         * do callbacks to upper level VM system
         */
        while (cb != NULL && cnt > 0) {
                --cnt;
                cb->hcb_start_addr = (caddr_t)range[cnt].rng_va;
                cb->hcb_end_addr = cb->hcb_start_addr;
                cb->hcb_end_addr +=
                    range[cnt].rng_cnt << LEVEL_SIZE(range[cnt].rng_level);
                cb->hcb_function(cb);
        }
}

/*
 * Unload a given range of addresses (has optional callback)
 *
 * Flags:
 * define       HAT_UNLOAD              0x00
 * define       HAT_UNLOAD_NOSYNC       0x02
 * define       HAT_UNLOAD_UNLOCK       0x04
 * define       HAT_UNLOAD_OTHER        0x08 - not used
 * define       HAT_UNLOAD_UNMAP        0x10 - same as HAT_UNLOAD
 */
#define MAX_UNLOAD_CNT (8)
void
hat_unload_callback(
        hat_t           *hat,
        caddr_t         addr,
        size_t          len,
        uint_t          flags,
        hat_callback_t  *cb)
{
        uintptr_t       vaddr = (uintptr_t)addr;
        uintptr_t       eaddr = vaddr + len;
        htable_t        *ht = NULL;
        uint_t          entry;
        uintptr_t       contig_va = (uintptr_t)-1L;
        range_info_t    r[MAX_UNLOAD_CNT];
        uint_t          r_cnt = 0;
        x86pte_t        old_pte;

        XPV_DISALLOW_MIGRATE();
        ASSERT(hat == kas.a_hat || eaddr <= _userlimit);
        ASSERT(IS_PAGEALIGNED(vaddr));
        ASSERT(IS_PAGEALIGNED(eaddr));

        /*
         * Special case a single page being unloaded for speed. This happens
         * quite frequently, COW faults after a fork() for example.
         */
        if (cb == NULL && len == MMU_PAGESIZE) {
                ht = htable_getpte(hat, vaddr, &entry, &old_pte, 0);
                if (ht != NULL) {
                        if (PTE_ISVALID(old_pte))
                                hat_pte_unmap(ht, entry, flags, old_pte, NULL);
                        htable_release(ht);
                }
                XPV_ALLOW_MIGRATE();
                return;
        }

        while (vaddr < eaddr) {
                old_pte = htable_walk(hat, &ht, &vaddr, eaddr);
                if (ht == NULL)
                        break;

                ASSERT(!IN_VA_HOLE(vaddr));

                if (vaddr < (uintptr_t)addr)
                        panic("hat_unload_callback(): unmap inside large page");

                /*
                 * We'll do the call backs for contiguous ranges
                 */
                if (vaddr != contig_va ||
                    (r_cnt > 0 && r[r_cnt - 1].rng_level != ht->ht_level)) {
                        if (r_cnt == MAX_UNLOAD_CNT) {
                                handle_ranges(cb, r_cnt, r);
                                r_cnt = 0;
                        }
                        r[r_cnt].rng_va = vaddr;
                        r[r_cnt].rng_cnt = 0;
                        r[r_cnt].rng_level = ht->ht_level;
                        ++r_cnt;
                }

                /*
                 * Unload one mapping from the page tables.
                 */
                entry = htable_va2entry(vaddr, ht);
                hat_pte_unmap(ht, entry, flags, old_pte, NULL);
                ASSERT(ht->ht_level <= mmu.max_page_level);
                vaddr += LEVEL_SIZE(ht->ht_level);
                contig_va = vaddr;
                ++r[r_cnt - 1].rng_cnt;
        }
        if (ht)
                htable_release(ht);

        /*
         * handle last range for callbacks
         */
        if (r_cnt > 0)
                handle_ranges(cb, r_cnt, r);
        XPV_ALLOW_MIGRATE();
}

/*
 * Invalidate a virtual address translation on a slave CPU during
 * panic() dumps.
 */
void
hat_flush_range(hat_t *hat, caddr_t va, size_t size)
{
        ssize_t sz;
        caddr_t endva = va + size;

        while (va < endva) {
                sz = hat_getpagesize(hat, va);
                if (sz < 0) {
#ifdef __xpv
                        xen_flush_tlb();
#else
                        flush_all_tlb_entries();
#endif
                        break;
                }
#ifdef __xpv
                xen_flush_va(va);
#else
                mmu_tlbflush_entry(va);
#endif
                va += sz;
        }
}

/*
 * synchronize mapping with software data structures
 *
 * This interface is currently only used by the working set monitor
 * driver.
 */
/*ARGSUSED*/
void
hat_sync(hat_t *hat, caddr_t addr, size_t len, uint_t flags)
{
        uintptr_t       vaddr = (uintptr_t)addr;
        uintptr_t       eaddr = vaddr + len;
        htable_t        *ht = NULL;
        uint_t          entry;
        x86pte_t        pte;
        x86pte_t        save_pte;
        x86pte_t        new;
        page_t          *pp;

        ASSERT(!IN_VA_HOLE(vaddr));
        ASSERT(IS_PAGEALIGNED(vaddr));
        ASSERT(IS_PAGEALIGNED(eaddr));
        ASSERT(hat == kas.a_hat || eaddr <= _userlimit);

        XPV_DISALLOW_MIGRATE();
        for (; vaddr < eaddr; vaddr += LEVEL_SIZE(ht->ht_level)) {
try_again:
                pte = htable_walk(hat, &ht, &vaddr, eaddr);
                if (ht == NULL)
                        break;
                entry = htable_va2entry(vaddr, ht);

                if (PTE_GET(pte, PT_SOFTWARE) >= PT_NOSYNC ||
                    PTE_GET(pte, PT_REF | PT_MOD) == 0)
                        continue;

                /*
                 * We need to acquire the mapping list lock to protect
                 * against hat_pageunload(), hat_unload(), etc.
                 */
                pp = page_numtopp_nolock(PTE2PFN(pte, ht->ht_level));
                if (pp == NULL)
                        break;
                x86_hm_enter(pp);
                save_pte = pte;
                pte = x86pte_get(ht, entry);
                if (pte != save_pte) {
                        x86_hm_exit(pp);
                        goto try_again;
                }
                if (PTE_GET(pte, PT_SOFTWARE) >= PT_NOSYNC ||
                    PTE_GET(pte, PT_REF | PT_MOD) == 0) {
                        x86_hm_exit(pp);
                        continue;
                }

                /*
                 * Need to clear ref or mod bits. We may compete with
                 * hardware updating the R/M bits and have to try again.
                 */
                if (flags == HAT_SYNC_ZERORM) {
                        new = pte;
                        PTE_CLR(new, PT_REF | PT_MOD);
                        pte = hati_update_pte(ht, entry, pte, new);
                        if (pte != 0) {
                                x86_hm_exit(pp);
                                goto try_again;
                        }
                } else {
                        /*
                         * sync the PTE to the page_t
                         */
                        hati_sync_pte_to_page(pp, save_pte, ht->ht_level);
                }
                x86_hm_exit(pp);
        }
        if (ht)
                htable_release(ht);
        XPV_ALLOW_MIGRATE();
}

/*
 * void hat_map(hat, addr, len, flags)
 */
/*ARGSUSED*/
void
hat_map(hat_t *hat, caddr_t addr, size_t len, uint_t flags)
{
        /* does nothing */
}

/*
 * uint_t hat_getattr(hat, addr, *attr)
 *      returns attr for <hat,addr> in *attr.  returns 0 if there was a
 *      mapping and *attr is valid, nonzero if there was no mapping and
 *      *attr is not valid.
 */
uint_t
hat_getattr(hat_t *hat, caddr_t addr, uint_t *attr)
{
        uintptr_t       vaddr = ALIGN2PAGE(addr);
        htable_t        *ht = NULL;
        x86pte_t        pte;

        ASSERT(hat == kas.a_hat || vaddr <= _userlimit);

        if (IN_VA_HOLE(vaddr))
                return ((uint_t)-1);

        ht = htable_getpte(hat, vaddr, NULL, &pte, mmu.max_page_level);
        if (ht == NULL)
                return ((uint_t)-1);

        if (!PTE_ISVALID(pte) || !PTE_ISPAGE(pte, ht->ht_level)) {
                htable_release(ht);
                return ((uint_t)-1);
        }

        *attr = PROT_READ;
        if (PTE_GET(pte, PT_WRITABLE))
                *attr |= PROT_WRITE;
        if (PTE_GET(pte, PT_USER))
                *attr |= PROT_USER;
        if (!PTE_GET(pte, mmu.pt_nx))
                *attr |= PROT_EXEC;
        if (PTE_GET(pte, PT_SOFTWARE) >= PT_NOSYNC)
                *attr |= HAT_NOSYNC;
        htable_release(ht);
        return (0);
}

/*
 * hat_updateattr() applies the given attribute change to an existing mapping
 */
#define HAT_LOAD_ATTR           1
#define HAT_SET_ATTR            2
#define HAT_CLR_ATTR            3

static void
hat_updateattr(hat_t *hat, caddr_t addr, size_t len, uint_t attr, int what)
{
        uintptr_t       vaddr = (uintptr_t)addr;
        uintptr_t       eaddr = (uintptr_t)addr + len;
        htable_t        *ht = NULL;
        uint_t          entry;
        x86pte_t        oldpte, newpte;
        page_t          *pp;

        XPV_DISALLOW_MIGRATE();
        ASSERT(IS_PAGEALIGNED(vaddr));
        ASSERT(IS_PAGEALIGNED(eaddr));
        ASSERT(hat == kas.a_hat ||
            AS_LOCK_HELD(hat->hat_as, &hat->hat_as->a_lock));
        for (; vaddr < eaddr; vaddr += LEVEL_SIZE(ht->ht_level)) {
try_again:
                oldpte = htable_walk(hat, &ht, &vaddr, eaddr);
                if (ht == NULL)
                        break;
                if (PTE_GET(oldpte, PT_SOFTWARE) >= PT_NOCONSIST)
                        continue;

                pp = page_numtopp_nolock(PTE2PFN(oldpte, ht->ht_level));
                if (pp == NULL)
                        continue;
                x86_hm_enter(pp);

                newpte = oldpte;
                /*
                 * We found a page table entry in the desired range,
                 * figure out the new attributes.
                 */
                if (what == HAT_SET_ATTR || what == HAT_LOAD_ATTR) {
                        if ((attr & PROT_WRITE) &&
                            !PTE_GET(oldpte, PT_WRITABLE))
                                newpte |= PT_WRITABLE;

                        if ((attr & HAT_NOSYNC) &&
                            PTE_GET(oldpte, PT_SOFTWARE) < PT_NOSYNC)
                                newpte |= PT_NOSYNC;

                        if ((attr & PROT_EXEC) && PTE_GET(oldpte, mmu.pt_nx))
                                newpte &= ~mmu.pt_nx;
                }

                if (what == HAT_LOAD_ATTR) {
                        if (!(attr & PROT_WRITE) &&
                            PTE_GET(oldpte, PT_WRITABLE))
                                newpte &= ~PT_WRITABLE;

                        if (!(attr & HAT_NOSYNC) &&
                            PTE_GET(oldpte, PT_SOFTWARE) >= PT_NOSYNC)
                                newpte &= ~PT_SOFTWARE;

                        if (!(attr & PROT_EXEC) && !PTE_GET(oldpte, mmu.pt_nx))
                                newpte |= mmu.pt_nx;
                }

                if (what == HAT_CLR_ATTR) {
                        if ((attr & PROT_WRITE) && PTE_GET(oldpte, PT_WRITABLE))
                                newpte &= ~PT_WRITABLE;

                        if ((attr & HAT_NOSYNC) &&
                            PTE_GET(oldpte, PT_SOFTWARE) >= PT_NOSYNC)
                                newpte &= ~PT_SOFTWARE;

                        if ((attr & PROT_EXEC) && !PTE_GET(oldpte, mmu.pt_nx))
                                newpte |= mmu.pt_nx;
                }

                /*
                 * Ensure NOSYNC/NOCONSIST mappings have REF and MOD set.
                 * x86pte_set() depends on this.
                 */
                if (PTE_GET(newpte, PT_SOFTWARE) >= PT_NOSYNC)
                        newpte |= PT_REF | PT_MOD;

                /*
                 * what about PROT_READ or others? this code only handles:
                 * EXEC, WRITE, NOSYNC
                 */

                /*
                 * If new PTE really changed, update the table.
                 */
                if (newpte != oldpte) {
                        entry = htable_va2entry(vaddr, ht);
                        oldpte = hati_update_pte(ht, entry, oldpte, newpte);
                        if (oldpte != 0) {
                                x86_hm_exit(pp);
                                goto try_again;
                        }
                }
                x86_hm_exit(pp);
        }
        if (ht)
                htable_release(ht);
        XPV_ALLOW_MIGRATE();
}

/*
 * Various wrappers for hat_updateattr()
 */
void
hat_setattr(hat_t *hat, caddr_t addr, size_t len, uint_t attr)
{
        ASSERT(hat == kas.a_hat || (uintptr_t)addr + len <= _userlimit);
        hat_updateattr(hat, addr, len, attr, HAT_SET_ATTR);
}

void
hat_clrattr(hat_t *hat, caddr_t addr, size_t len, uint_t attr)
{
        ASSERT(hat == kas.a_hat || (uintptr_t)addr + len <= _userlimit);
        hat_updateattr(hat, addr, len, attr, HAT_CLR_ATTR);
}

void
hat_chgattr(hat_t *hat, caddr_t addr, size_t len, uint_t attr)
{
        ASSERT(hat == kas.a_hat || (uintptr_t)addr + len <= _userlimit);
        hat_updateattr(hat, addr, len, attr, HAT_LOAD_ATTR);
}

void
hat_chgprot(hat_t *hat, caddr_t addr, size_t len, uint_t vprot)
{
        ASSERT(hat == kas.a_hat || (uintptr_t)addr + len <= _userlimit);
        hat_updateattr(hat, addr, len, vprot & HAT_PROT_MASK, HAT_LOAD_ATTR);
}

/*
 * size_t hat_getpagesize(hat, addr)
 *      returns pagesize in bytes for <hat, addr>. returns -1 of there is
 *      no mapping. This is an advisory call.
 */
ssize_t
hat_getpagesize(hat_t *hat, caddr_t addr)
{
        uintptr_t       vaddr = ALIGN2PAGE(addr);
        htable_t        *ht;
        size_t          pagesize;

        ASSERT(hat == kas.a_hat || vaddr <= _userlimit);
        if (IN_VA_HOLE(vaddr))
                return (-1);
        ht = htable_getpage(hat, vaddr, NULL);
        if (ht == NULL)
                return (-1);
        pagesize = LEVEL_SIZE(ht->ht_level);
        htable_release(ht);
        return (pagesize);
}



/*
 * pfn_t hat_getpfnum(hat, addr)
 *      returns pfn for <hat, addr> or PFN_INVALID if mapping is invalid.
 */
pfn_t
hat_getpfnum(hat_t *hat, caddr_t addr)
{
        uintptr_t       vaddr = ALIGN2PAGE(addr);
        htable_t        *ht;
        uint_t          entry;
        pfn_t           pfn = PFN_INVALID;

        ASSERT(hat == kas.a_hat || vaddr <= _userlimit);
        if (khat_running == 0)
                return (PFN_INVALID);

        if (IN_VA_HOLE(vaddr))
                return (PFN_INVALID);

        XPV_DISALLOW_MIGRATE();
        /*
         * A very common use of hat_getpfnum() is from the DDI for kernel pages.
         * Use the kmap_ptes (which also covers the 32 bit heap) to speed
         * this up.
         */
        if (mmu.kmap_addr <= vaddr && vaddr < mmu.kmap_eaddr) {
                x86pte_t pte;
                pgcnt_t pg_index;

                pg_index = mmu_btop(vaddr - mmu.kmap_addr);
                pte = GET_PTE(PT_INDEX_PTR(mmu.kmap_ptes, pg_index));
                if (PTE_ISVALID(pte))
                        /*LINTED [use of constant 0 causes a lint warning] */
                        pfn = PTE2PFN(pte, 0);
                XPV_ALLOW_MIGRATE();
                return (pfn);
        }

        ht = htable_getpage(hat, vaddr, &entry);
        if (ht == NULL) {
                XPV_ALLOW_MIGRATE();
                return (PFN_INVALID);
        }
        ASSERT(vaddr >= ht->ht_vaddr);
        ASSERT(vaddr <= HTABLE_LAST_PAGE(ht));
        pfn = PTE2PFN(x86pte_get(ht, entry), ht->ht_level);
        if (ht->ht_level > 0)
                pfn += mmu_btop(vaddr & LEVEL_OFFSET(ht->ht_level));
        htable_release(ht);
        XPV_ALLOW_MIGRATE();
        return (pfn);
}

/*
 * int hat_probe(hat, addr)
 *      return 0 if no valid mapping is present.  Faster version
 *      of hat_getattr in certain architectures.
 */
int
hat_probe(hat_t *hat, caddr_t addr)
{
        uintptr_t       vaddr = ALIGN2PAGE(addr);
        uint_t          entry;
        htable_t        *ht;
        pgcnt_t         pg_off;

        ASSERT(hat == kas.a_hat || vaddr <= _userlimit);
        ASSERT(hat == kas.a_hat ||
            AS_LOCK_HELD(hat->hat_as, &hat->hat_as->a_lock));
        if (IN_VA_HOLE(vaddr))
                return (0);

        /*
         * Most common use of hat_probe is from segmap. We special case it
         * for performance.
         */
        if (mmu.kmap_addr <= vaddr && vaddr < mmu.kmap_eaddr) {
                pg_off = mmu_btop(vaddr - mmu.kmap_addr);
                if (mmu.pae_hat)
                        return (PTE_ISVALID(mmu.kmap_ptes[pg_off]));
                else
                        return (PTE_ISVALID(
                            ((x86pte32_t *)mmu.kmap_ptes)[pg_off]));
        }

        ht = htable_getpage(hat, vaddr, &entry);
        htable_release(ht);
        return (ht != NULL);
}

/*
 * Find out if the segment for hat_share()/hat_unshare() is DISM or locked ISM.
 */
static int
is_it_dism(hat_t *hat, caddr_t va)
{
        struct seg *seg;
        struct shm_data *shmd;
        struct spt_data *sptd;

        seg = as_findseg(hat->hat_as, va, 0);
        ASSERT(seg != NULL);
        ASSERT(seg->s_base <= va);
        shmd = (struct shm_data *)seg->s_data;
        ASSERT(shmd != NULL);
        sptd = (struct spt_data *)shmd->shm_sptseg->s_data;
        ASSERT(sptd != NULL);
        if (sptd->spt_flags & SHM_PAGEABLE)
                return (1);
        return (0);
}

/*
 * Simple implementation of ISM. hat_share() is similar to hat_memload_array(),
 * except that we use the ism_hat's existing mappings to determine the pages
 * and protections to use for this hat. If we find a full properly aligned
 * and sized pagetable, we will attempt to share the pagetable itself.
 */
/*ARGSUSED*/
int
hat_share(
        hat_t           *hat,
        caddr_t         addr,
        hat_t           *ism_hat,
        caddr_t         src_addr,
        size_t          len,    /* almost useless value, see below.. */
        uint_t          ismszc)
{
        uintptr_t       vaddr_start = (uintptr_t)addr;
        uintptr_t       vaddr;
        uintptr_t       eaddr = vaddr_start + len;
        uintptr_t       ism_addr_start = (uintptr_t)src_addr;
        uintptr_t       ism_addr = ism_addr_start;
        uintptr_t       e_ism_addr = ism_addr + len;
        htable_t        *ism_ht = NULL;
        htable_t        *ht;
        x86pte_t        pte;
        page_t          *pp;
        pfn_t           pfn;
        level_t         l;
        pgcnt_t         pgcnt;
        uint_t          prot;
        int             is_dism;
        int             flags;

        /*
         * We might be asked to share an empty DISM hat by as_dup()
         */
        ASSERT(hat != kas.a_hat);
        ASSERT(eaddr <= _userlimit);
        if (!(ism_hat->hat_flags & HAT_SHARED)) {
                ASSERT(hat_get_mapped_size(ism_hat) == 0);
                return (0);
        }
        XPV_DISALLOW_MIGRATE();

        /*
         * The SPT segment driver often passes us a size larger than there are
         * valid mappings. That's because it rounds the segment size up to a
         * large pagesize, even if the actual memory mapped by ism_hat is less.
         */
        ASSERT(IS_PAGEALIGNED(vaddr_start));
        ASSERT(IS_PAGEALIGNED(ism_addr_start));
        ASSERT(ism_hat->hat_flags & HAT_SHARED);
        is_dism = is_it_dism(hat, addr);
        while (ism_addr < e_ism_addr) {
                /*
                 * use htable_walk to get the next valid ISM mapping
                 */
                pte = htable_walk(ism_hat, &ism_ht, &ism_addr, e_ism_addr);
                if (ism_ht == NULL)
                        break;

                /*
                 * First check to see if we already share the page table.
                 */
                l = ism_ht->ht_level;
                vaddr = vaddr_start + (ism_addr - ism_addr_start);
                ht = htable_lookup(hat, vaddr, l);
                if (ht != NULL) {
                        if (ht->ht_flags & HTABLE_SHARED_PFN)
                                goto shared;
                        htable_release(ht);
                        goto not_shared;
                }

                /*
                 * Can't ever share top table.
                 */
                if (l == mmu.max_level)
                        goto not_shared;

                /*
                 * Avoid level mismatches later due to DISM faults.
                 */
                if (is_dism && l > 0)
                        goto not_shared;

                /*
                 * addresses and lengths must align
                 * table must be fully populated
                 * no lower level page tables
                 */
                if (ism_addr != ism_ht->ht_vaddr ||
                    (vaddr & LEVEL_OFFSET(l + 1)) != 0)
                        goto not_shared;

                /*
                 * The range of address space must cover a full table.
                 */
                if (e_ism_addr - ism_addr < LEVEL_SIZE(l + 1))
                        goto not_shared;

                /*
                 * All entries in the ISM page table must be leaf PTEs.
                 */
                if (l > 0) {
                        int e;

                        /*
                         * We know the 0th is from htable_walk() above.
                         */
                        for (e = 1; e < HTABLE_NUM_PTES(ism_ht); ++e) {
                                x86pte_t pte;
                                pte = x86pte_get(ism_ht, e);
                                if (!PTE_ISPAGE(pte, l))
                                        goto not_shared;
                        }
                }

                /*
                 * share the page table
                 */
                ht = htable_create(hat, vaddr, l, ism_ht);
shared:
                ASSERT(ht->ht_flags & HTABLE_SHARED_PFN);
                ASSERT(ht->ht_shares == ism_ht);
                hat->hat_ism_pgcnt +=
                    (ism_ht->ht_valid_cnt - ht->ht_valid_cnt) <<
                    (LEVEL_SHIFT(ht->ht_level) - MMU_PAGESHIFT);
                ht->ht_valid_cnt = ism_ht->ht_valid_cnt;
                htable_release(ht);
                ism_addr = ism_ht->ht_vaddr + LEVEL_SIZE(l + 1);
                htable_release(ism_ht);
                ism_ht = NULL;
                continue;

not_shared:
                /*
                 * Unable to share the page table. Instead we will
                 * create new mappings from the values in the ISM mappings.
                 * Figure out what level size mappings to use;
                 */
                for (l = ism_ht->ht_level; l > 0; --l) {
                        if (LEVEL_SIZE(l) <= eaddr - vaddr &&
                            (vaddr & LEVEL_OFFSET(l)) == 0)
                                break;
                }

                /*
                 * The ISM mapping might be larger than the share area,
                 * be careful to truncate it if needed.
                 */
                if (eaddr - vaddr >= LEVEL_SIZE(ism_ht->ht_level)) {
                        pgcnt = mmu_btop(LEVEL_SIZE(ism_ht->ht_level));
                } else {
                        pgcnt = mmu_btop(eaddr - vaddr);
                        l = 0;
                }

                pfn = PTE2PFN(pte, ism_ht->ht_level);
                ASSERT(pfn != PFN_INVALID);
                while (pgcnt > 0) {
                        /*
                         * Make a new pte for the PFN for this level.
                         * Copy protections for the pte from the ISM pte.
                         */
                        pp = page_numtopp_nolock(pfn);
                        ASSERT(pp != NULL);

                        prot = PROT_USER | PROT_READ | HAT_UNORDERED_OK;
                        if (PTE_GET(pte, PT_WRITABLE))
                                prot |= PROT_WRITE;
                        if (!PTE_GET(pte, PT_NX))
                                prot |= PROT_EXEC;

                        flags = HAT_LOAD;
                        if (!is_dism)
                                flags |= HAT_LOAD_LOCK | HAT_LOAD_NOCONSIST;
                        while (hati_load_common(hat, vaddr, pp, prot, flags,
                            l, pfn) != 0) {
                                if (l == 0)
                                        panic("hati_load_common() failure");
                                --l;
                        }

                        vaddr += LEVEL_SIZE(l);
                        ism_addr += LEVEL_SIZE(l);
                        pfn += mmu_btop(LEVEL_SIZE(l));
                        pgcnt -= mmu_btop(LEVEL_SIZE(l));
                }
        }
        if (ism_ht != NULL)
                htable_release(ism_ht);
        XPV_ALLOW_MIGRATE();
        return (0);
}


/*
 * hat_unshare() is similar to hat_unload_callback(), but
 * we have to look for empty shared pagetables. Note that
 * hat_unshare() is always invoked against an entire segment.
 */
/*ARGSUSED*/
void
hat_unshare(hat_t *hat, caddr_t addr, size_t len, uint_t ismszc)
{
        uint64_t        vaddr = (uintptr_t)addr;
        uintptr_t       eaddr = vaddr + len;
        htable_t        *ht = NULL;
        uint_t          need_demaps = 0;
        int             flags = HAT_UNLOAD_UNMAP;
        level_t         l;

        ASSERT(hat != kas.a_hat);
        ASSERT(eaddr <= _userlimit);
        ASSERT(IS_PAGEALIGNED(vaddr));
        ASSERT(IS_PAGEALIGNED(eaddr));
        XPV_DISALLOW_MIGRATE();

        /*
         * First go through and remove any shared pagetables.
         *
         * Note that it's ok to delay the TLB shootdown till the entire range is
         * finished, because if hat_pageunload() were to unload a shared
         * pagetable page, its hat_tlb_inval() will do a global TLB invalidate.
         */
        l = mmu.max_page_level;
        if (l == mmu.max_level)
                --l;
        for (; l >= 0; --l) {
                for (vaddr = (uintptr_t)addr; vaddr < eaddr;
                    vaddr = (vaddr & LEVEL_MASK(l + 1)) + LEVEL_SIZE(l + 1)) {
                        ASSERT(!IN_VA_HOLE(vaddr));
                        /*
                         * find a pagetable that maps the current address
                         */
                        ht = htable_lookup(hat, vaddr, l);
                        if (ht == NULL)
                                continue;
                        if (ht->ht_flags & HTABLE_SHARED_PFN) {
                                /*
                                 * clear page count, set valid_cnt to 0,
                                 * let htable_release() finish the job
                                 */
                                hat->hat_ism_pgcnt -= ht->ht_valid_cnt <<
                                    (LEVEL_SHIFT(ht->ht_level) - MMU_PAGESHIFT);
                                ht->ht_valid_cnt = 0;
                                need_demaps = 1;
                        }
                        htable_release(ht);
                }
        }

        /*
         * flush the TLBs - since we're probably dealing with MANY mappings
         * we do just one CR3 reload.
         */
        if (!(hat->hat_flags & HAT_FREEING) && need_demaps)
                hat_tlb_inval(hat, DEMAP_ALL_ADDR);

        /*
         * Now go back and clean up any unaligned mappings that
         * couldn't share pagetables.
         */
        if (!is_it_dism(hat, addr))
                flags |= HAT_UNLOAD_UNLOCK;
        hat_unload(hat, addr, len, flags);
        XPV_ALLOW_MIGRATE();
}


/*
 * hat_reserve() does nothing
 */
/*ARGSUSED*/
void
hat_reserve(struct as *as, caddr_t addr, size_t len)
{
}


/*
 * Called when all mappings to a page should have write permission removed.
 * Mostly stolen from hat_pagesync()
 */
static void
hati_page_clrwrt(struct page *pp)
{
        hment_t         *hm = NULL;
        htable_t        *ht;
        uint_t          entry;
        x86pte_t        old;
        x86pte_t        new;
        uint_t          pszc = 0;

        XPV_DISALLOW_MIGRATE();
next_size:
        /*
         * walk thru the mapping list clearing write permission
         */
        x86_hm_enter(pp);
        while ((hm = hment_walk(pp, &ht, &entry, hm)) != NULL) {
                if (ht->ht_level < pszc)
                        continue;
                old = x86pte_get(ht, entry);

                for (;;) {
                        /*
                         * Is this mapping of interest?
                         */
                        if (PTE2PFN(old, ht->ht_level) != pp->p_pagenum ||
                            PTE_GET(old, PT_WRITABLE) == 0)
                                break;

                        /*
                         * Clear ref/mod writable bits. This requires cross
                         * calls to ensure any executing TLBs see cleared bits.
                         */
                        new = old;
                        PTE_CLR(new, PT_REF | PT_MOD | PT_WRITABLE);
                        old = hati_update_pte(ht, entry, old, new);
                        if (old != 0)
                                continue;

                        break;
                }
        }
        x86_hm_exit(pp);
        while (pszc < pp->p_szc) {
                page_t *tpp;
                pszc++;
                tpp = PP_GROUPLEADER(pp, pszc);
                if (pp != tpp) {
                        pp = tpp;
                        goto next_size;
                }
        }
        XPV_ALLOW_MIGRATE();
}

/*
 * void hat_page_setattr(pp, flag)
 * void hat_page_clrattr(pp, flag)
 *      used to set/clr ref/mod bits.
 */
void
hat_page_setattr(struct page *pp, uint_t flag)
{
        vnode_t         *vp = pp->p_vnode;
        kmutex_t        *vphm = NULL;
        page_t          **listp;
        int             noshuffle;

        noshuffle = flag & P_NSH;
        flag &= ~P_NSH;

        if (PP_GETRM(pp, flag) == flag)
                return;

        if ((flag & P_MOD) != 0 && vp != NULL && IS_VMODSORT(vp) &&
            !noshuffle) {
                vphm = page_vnode_mutex(vp);
                mutex_enter(vphm);
        }

        PP_SETRM(pp, flag);

        if (vphm != NULL) {

                /*
                 * Some File Systems examine v_pages for NULL w/o
                 * grabbing the vphm mutex. Must not let it become NULL when
                 * pp is the only page on the list.
                 */
                if (pp->p_vpnext != pp) {
                        page_vpsub(&vp->v_pages, pp);
                        if (vp->v_pages != NULL)
                                listp = &vp->v_pages->p_vpprev->p_vpnext;
                        else
                                listp = &vp->v_pages;
                        page_vpadd(listp, pp);
                }
                mutex_exit(vphm);
        }
}

void
hat_page_clrattr(struct page *pp, uint_t flag)
{
        vnode_t         *vp = pp->p_vnode;
        ASSERT(!(flag & ~(P_MOD | P_REF | P_RO)));

        /*
         * Caller is expected to hold page's io lock for VMODSORT to work
         * correctly with pvn_vplist_dirty() and pvn_getdirty() when mod
         * bit is cleared.
         * We don't have assert to avoid tripping some existing third party
         * code. The dirty page is moved back to top of the v_page list
         * after IO is done in pvn_write_done().
         */
        PP_CLRRM(pp, flag);

        if ((flag & P_MOD) != 0 && vp != NULL && IS_VMODSORT(vp)) {

                /*
                 * VMODSORT works by removing write permissions and getting
                 * a fault when a page is made dirty. At this point
                 * we need to remove write permission from all mappings
                 * to this page.
                 */
                hati_page_clrwrt(pp);
        }
}

/*
 *      If flag is specified, returns 0 if attribute is disabled
 *      and non zero if enabled.  If flag specifes multiple attributes
 *      then returns 0 if ALL attributes are disabled.  This is an advisory
 *      call.
 */
uint_t
hat_page_getattr(struct page *pp, uint_t flag)
{
        return (PP_GETRM(pp, flag));
}


/*
 * common code used by hat_pageunload() and hment_steal()
 */
hment_t *
hati_page_unmap(page_t *pp, htable_t *ht, uint_t entry)
{
        x86pte_t old_pte;
        pfn_t pfn = pp->p_pagenum;
        hment_t *hm;

        /*
         * We need to acquire a hold on the htable in order to
         * do the invalidate. We know the htable must exist, since
         * unmap's don't release the htable until after removing any
         * hment. Having x86_hm_enter() keeps that from proceeding.
         */
        htable_acquire(ht);

        /*
         * Invalidate the PTE and remove the hment.
         */
        old_pte = x86pte_inval(ht, entry, 0, NULL);
        if (PTE2PFN(old_pte, ht->ht_level) != pfn) {
                panic("x86pte_inval() failure found PTE = " FMT_PTE
                    " pfn being unmapped is %lx ht=0x%lx entry=0x%x",
                    old_pte, pfn, (uintptr_t)ht, entry);
        }

        /*
         * Clean up all the htable information for this mapping
         */
        ASSERT(ht->ht_valid_cnt > 0);
        HTABLE_DEC(ht->ht_valid_cnt);
        PGCNT_DEC(ht->ht_hat, ht->ht_level);

        /*
         * sync ref/mod bits to the page_t
         */
        if (PTE_GET(old_pte, PT_SOFTWARE) < PT_NOSYNC)
                hati_sync_pte_to_page(pp, old_pte, ht->ht_level);

        /*
         * Remove the mapping list entry for this page.
         */
        hm = hment_remove(pp, ht, entry);

        /*
         * drop the mapping list lock so that we might free the
         * hment and htable.
         */
        x86_hm_exit(pp);
        htable_release(ht);
        return (hm);
}

extern int      vpm_enable;
/*
 * Unload all translations to a page. If the page is a subpage of a large
 * page, the large page mappings are also removed.
 *
 * The forceflags are unused.
 */

/*ARGSUSED*/
static int
hati_pageunload(struct page *pp, uint_t pg_szcd, uint_t forceflag)
{
        page_t          *cur_pp = pp;
        hment_t         *hm;
        hment_t         *prev;
        htable_t        *ht;
        uint_t          entry;
        level_t         level;

        XPV_DISALLOW_MIGRATE();

        /*
         * prevent recursion due to kmem_free()
         */
        ++curthread->t_hatdepth;
        ASSERT(curthread->t_hatdepth < 16);

#if defined(__amd64)
        /*
         * clear the vpm ref.
         */
        if (vpm_enable) {
                pp->p_vpmref = 0;
        }
#endif
        /*
         * The loop with next_size handles pages with multiple pagesize mappings
         */
next_size:
        for (;;) {

                /*
                 * Get a mapping list entry
                 */
                x86_hm_enter(cur_pp);
                for (prev = NULL; ; prev = hm) {
                        hm = hment_walk(cur_pp, &ht, &entry, prev);
                        if (hm == NULL) {
                                x86_hm_exit(cur_pp);

                                /*
                                 * If not part of a larger page, we're done.
                                 */
                                if (cur_pp->p_szc <= pg_szcd) {
                                        ASSERT(curthread->t_hatdepth > 0);
                                        --curthread->t_hatdepth;
                                        XPV_ALLOW_MIGRATE();
                                        return (0);
                                }

                                /*
                                 * Else check the next larger page size.
                                 * hat_page_demote() may decrease p_szc
                                 * but that's ok we'll just take an extra
                                 * trip discover there're no larger mappings
                                 * and return.
                                 */
                                ++pg_szcd;
                                cur_pp = PP_GROUPLEADER(cur_pp, pg_szcd);
                                goto next_size;
                        }

                        /*
                         * If this mapping size matches, remove it.
                         */
                        level = ht->ht_level;
                        if (level == pg_szcd)
                                break;
                }

                /*
                 * Remove the mapping list entry for this page.
                 * Note this does the x86_hm_exit() for us.
                 */
                hm = hati_page_unmap(cur_pp, ht, entry);
                if (hm != NULL)
                        hment_free(hm);
        }
}

int
hat_pageunload(struct page *pp, uint_t forceflag)
{
        ASSERT(PAGE_EXCL(pp));
        return (hati_pageunload(pp, 0, forceflag));
}

/*
 * Unload all large mappings to pp and reduce by 1 p_szc field of every large
 * page level that included pp.
 *
 * pp must be locked EXCL. Even though no other constituent pages are locked
 * it's legal to unload large mappings to pp because all constituent pages of
 * large locked mappings have to be locked SHARED.  therefore if we have EXCL
 * lock on one of constituent pages none of the large mappings to pp are
 * locked.
 *
 * Change (always decrease) p_szc field starting from the last constituent
 * page and ending with root constituent page so that root's pszc always shows
 * the area where hat_page_demote() may be active.
 *
 * This mechanism is only used for file system pages where it's not always
 * possible to get EXCL locks on all constituent pages to demote the size code
 * (as is done for anonymous or kernel large pages).
 */
void
hat_page_demote(page_t *pp)
{
        uint_t          pszc;
        uint_t          rszc;
        uint_t          szc;
        page_t          *rootpp;
        page_t          *firstpp;
        page_t          *lastpp;
        pgcnt_t         pgcnt;

        ASSERT(PAGE_EXCL(pp));
        ASSERT(!PP_ISFREE(pp));
        ASSERT(page_szc_lock_assert(pp));

        if (pp->p_szc == 0)
                return;

        rootpp = PP_GROUPLEADER(pp, 1);
        (void) hati_pageunload(rootpp, 1, HAT_FORCE_PGUNLOAD);

        /*
         * all large mappings to pp are gone
         * and no new can be setup since pp is locked exclusively.
         *
         * Lock the root to make sure there's only one hat_page_demote()
         * outstanding within the area of this root's pszc.
         *
         * Second potential hat_page_demote() is already eliminated by upper
         * VM layer via page_szc_lock() but we don't rely on it and use our
         * own locking (so that upper layer locking can be changed without
         * assumptions that hat depends on upper layer VM to prevent multiple
         * hat_page_demote() to be issued simultaneously to the same large
         * page).
         */
again:
        pszc = pp->p_szc;
        if (pszc == 0)
                return;
        rootpp = PP_GROUPLEADER(pp, pszc);
        x86_hm_enter(rootpp);
        /*
         * If root's p_szc is different from pszc we raced with another
         * hat_page_demote().  Drop the lock and try to find the root again.
         * If root's p_szc is greater than pszc previous hat_page_demote() is
         * not done yet.  Take and release mlist lock of root's root to wait
         * for previous hat_page_demote() to complete.
         */
        if ((rszc = rootpp->p_szc) != pszc) {
                x86_hm_exit(rootpp);
                if (rszc > pszc) {
                        /* p_szc of a locked non free page can't increase */
                        ASSERT(pp != rootpp);

                        rootpp = PP_GROUPLEADER(rootpp, rszc);
                        x86_hm_enter(rootpp);
                        x86_hm_exit(rootpp);
                }
                goto again;
        }
        ASSERT(pp->p_szc == pszc);

        /*
         * Decrement by 1 p_szc of every constituent page of a region that
         * covered pp. For example if original szc is 3 it gets changed to 2
         * everywhere except in region 2 that covered pp. Region 2 that
         * covered pp gets demoted to 1 everywhere except in region 1 that
         * covered pp. The region 1 that covered pp is demoted to region
         * 0. It's done this way because from region 3 we removed level 3
         * mappings, from region 2 that covered pp we removed level 2 mappings
         * and from region 1 that covered pp we removed level 1 mappings.  All
         * changes are done from from high pfn's to low pfn's so that roots
         * are changed last allowing one to know the largest region where
         * hat_page_demote() is stil active by only looking at the root page.
         *
         * This algorithm is implemented in 2 while loops. First loop changes
         * p_szc of pages to the right of pp's level 1 region and second
         * loop changes p_szc of pages of level 1 region that covers pp
         * and all pages to the left of level 1 region that covers pp.
         * In the first loop p_szc keeps dropping with every iteration
         * and in the second loop it keeps increasing with every iteration.
         *
         * First loop description: Demote pages to the right of pp outside of
         * level 1 region that covers pp.  In every iteration of the while
         * loop below find the last page of szc region and the first page of
         * (szc - 1) region that is immediately to the right of (szc - 1)
         * region that covers pp.  From last such page to first such page
         * change every page's szc to szc - 1. Decrement szc and continue
         * looping until szc is 1. If pp belongs to the last (szc - 1) region
         * of szc region skip to the next iteration.
         */
        szc = pszc;
        while (szc > 1) {
                lastpp = PP_GROUPLEADER(pp, szc);
                pgcnt = page_get_pagecnt(szc);
                lastpp += pgcnt - 1;
                firstpp = PP_GROUPLEADER(pp, (szc - 1));
                pgcnt = page_get_pagecnt(szc - 1);
                if (lastpp - firstpp < pgcnt) {
                        szc--;
                        continue;
                }
                firstpp += pgcnt;
                while (lastpp != firstpp) {
                        ASSERT(lastpp->p_szc == pszc);
                        lastpp->p_szc = szc - 1;
                        lastpp--;
                }
                firstpp->p_szc = szc - 1;
                szc--;
        }

        /*
         * Second loop description:
         * First iteration changes p_szc to 0 of every
         * page of level 1 region that covers pp.
         * Subsequent iterations find last page of szc region
         * immediately to the left of szc region that covered pp
         * and first page of (szc + 1) region that covers pp.
         * From last to first page change p_szc of every page to szc.
         * Increment szc and continue looping until szc is pszc.
         * If pp belongs to the fist szc region of (szc + 1) region
         * skip to the next iteration.
         *
         */
        szc = 0;
        while (szc < pszc) {
                firstpp = PP_GROUPLEADER(pp, (szc + 1));
                if (szc == 0) {
                        pgcnt = page_get_pagecnt(1);
                        lastpp = firstpp + (pgcnt - 1);
                } else {
                        lastpp = PP_GROUPLEADER(pp, szc);
                        if (firstpp == lastpp) {
                                szc++;
                                continue;
                        }
                        lastpp--;
                        pgcnt = page_get_pagecnt(szc);
                }
                while (lastpp != firstpp) {
                        ASSERT(lastpp->p_szc == pszc);
                        lastpp->p_szc = szc;
                        lastpp--;
                }
                firstpp->p_szc = szc;
                if (firstpp == rootpp)
                        break;
                szc++;
        }
        x86_hm_exit(rootpp);
}

/*
 * get hw stats from hardware into page struct and reset hw stats
 * returns attributes of page
 * Flags for hat_pagesync, hat_getstat, hat_sync
 *
 * define       HAT_SYNC_ZERORM         0x01
 *
 * Additional flags for hat_pagesync
 *
 * define       HAT_SYNC_STOPON_REF     0x02
 * define       HAT_SYNC_STOPON_MOD     0x04
 * define       HAT_SYNC_STOPON_RM      0x06
 * define       HAT_SYNC_STOPON_SHARED  0x08
 */
uint_t
hat_pagesync(struct page *pp, uint_t flags)
{
        hment_t         *hm = NULL;
        htable_t        *ht;
        uint_t          entry;
        x86pte_t        old, save_old;
        x86pte_t        new;
        uchar_t         nrmbits = P_REF|P_MOD|P_RO;
        extern ulong_t  po_share;
        page_t          *save_pp = pp;
        uint_t          pszc = 0;

        ASSERT(PAGE_LOCKED(pp) || panicstr);

        if (PP_ISRO(pp) && (flags & HAT_SYNC_STOPON_MOD))
                return (pp->p_nrm & nrmbits);

        if ((flags & HAT_SYNC_ZERORM) == 0) {

                if ((flags & HAT_SYNC_STOPON_REF) != 0 && PP_ISREF(pp))
                        return (pp->p_nrm & nrmbits);

                if ((flags & HAT_SYNC_STOPON_MOD) != 0 && PP_ISMOD(pp))
                        return (pp->p_nrm & nrmbits);

                if ((flags & HAT_SYNC_STOPON_SHARED) != 0 &&
                    hat_page_getshare(pp) > po_share) {
                        if (PP_ISRO(pp))
                                PP_SETREF(pp);
                        return (pp->p_nrm & nrmbits);
                }
        }

        XPV_DISALLOW_MIGRATE();
next_size:
        /*
         * walk thru the mapping list syncing (and clearing) ref/mod bits.
         */
        x86_hm_enter(pp);
        while ((hm = hment_walk(pp, &ht, &entry, hm)) != NULL) {
                if (ht->ht_level < pszc)
                        continue;
                old = x86pte_get(ht, entry);
try_again:

                ASSERT(PTE2PFN(old, ht->ht_level) == pp->p_pagenum);

                if (PTE_GET(old, PT_REF | PT_MOD) == 0)
                        continue;

                save_old = old;
                if ((flags & HAT_SYNC_ZERORM) != 0) {

                        /*
                         * Need to clear ref or mod bits. Need to demap
                         * to make sure any executing TLBs see cleared bits.
                         */
                        new = old;
                        PTE_CLR(new, PT_REF | PT_MOD);
                        old = hati_update_pte(ht, entry, old, new);
                        if (old != 0)
                                goto try_again;

                        old = save_old;
                }

                /*
                 * Sync the PTE
                 */
                if (!(flags & HAT_SYNC_ZERORM) &&
                    PTE_GET(old, PT_SOFTWARE) <= PT_NOSYNC)
                        hati_sync_pte_to_page(pp, old, ht->ht_level);

                /*
                 * can stop short if we found a ref'd or mod'd page
                 */
                if ((flags & HAT_SYNC_STOPON_MOD) && PP_ISMOD(save_pp) ||
                    (flags & HAT_SYNC_STOPON_REF) && PP_ISREF(save_pp)) {
                        x86_hm_exit(pp);
                        goto done;
                }
        }
        x86_hm_exit(pp);
        while (pszc < pp->p_szc) {
                page_t *tpp;
                pszc++;
                tpp = PP_GROUPLEADER(pp, pszc);
                if (pp != tpp) {
                        pp = tpp;
                        goto next_size;
                }
        }
done:
        XPV_ALLOW_MIGRATE();
        return (save_pp->p_nrm & nrmbits);
}

/*
 * returns approx number of mappings to this pp.  A return of 0 implies
 * there are no mappings to the page.
 */
ulong_t
hat_page_getshare(page_t *pp)
{
        uint_t cnt;
        cnt = hment_mapcnt(pp);
#if defined(__amd64)
        if (vpm_enable && pp->p_vpmref) {
                cnt += 1;
        }
#endif
        return (cnt);
}

/*
 * Return 1 the number of mappings exceeds sh_thresh. Return 0
 * otherwise.
 */
int
hat_page_checkshare(page_t *pp, ulong_t sh_thresh)
{
        return (hat_page_getshare(pp) > sh_thresh);
}

/*
 * hat_softlock isn't supported anymore
 */
/*ARGSUSED*/
faultcode_t
hat_softlock(
        hat_t *hat,
        caddr_t addr,
        size_t *len,
        struct page **page_array,
        uint_t flags)
{
        return (FC_NOSUPPORT);
}



/*
 * Routine to expose supported HAT features to platform independent code.
 */
/*ARGSUSED*/
int
hat_supported(enum hat_features feature, void *arg)
{
        switch (feature) {

        case HAT_SHARED_PT:     /* this is really ISM */
                return (1);

        case HAT_DYNAMIC_ISM_UNMAP:
                return (0);

        case HAT_VMODSORT:
                return (1);

        case HAT_SHARED_REGIONS:
                return (0);

        default:
                panic("hat_supported() - unknown feature");
        }
        return (0);
}

/*
 * Called when a thread is exiting and has been switched to the kernel AS
 */
void
hat_thread_exit(kthread_t *thd)
{
        ASSERT(thd->t_procp->p_as == &kas);
        XPV_DISALLOW_MIGRATE();
        hat_switch(thd->t_procp->p_as->a_hat);
        XPV_ALLOW_MIGRATE();
}

/*
 * Setup the given brand new hat structure as the new HAT on this cpu's mmu.
 */
/*ARGSUSED*/
void
hat_setup(hat_t *hat, int flags)
{
        XPV_DISALLOW_MIGRATE();
        kpreempt_disable();

        hat_switch(hat);

        kpreempt_enable();
        XPV_ALLOW_MIGRATE();
}

/*
 * Prepare for a CPU private mapping for the given address.
 *
 * The address can only be used from a single CPU and can be remapped
 * using hat_mempte_remap().  Return the address of the PTE.
 *
 * We do the htable_create() if necessary and increment the valid count so
 * the htable can't disappear.  We also hat_devload() the page table into
 * kernel so that the PTE is quickly accessed.
 */
hat_mempte_t
hat_mempte_setup(caddr_t addr)
{
        uintptr_t       va = (uintptr_t)addr;
        htable_t        *ht;
        uint_t          entry;
        x86pte_t        oldpte;
        hat_mempte_t    p;

        ASSERT(IS_PAGEALIGNED(va));
        ASSERT(!IN_VA_HOLE(va));
        ++curthread->t_hatdepth;
        XPV_DISALLOW_MIGRATE();
        ht = htable_getpte(kas.a_hat, va, &entry, &oldpte, 0);
        if (ht == NULL) {
                ht = htable_create(kas.a_hat, va, 0, NULL);
                entry = htable_va2entry(va, ht);
                ASSERT(ht->ht_level == 0);
                oldpte = x86pte_get(ht, entry);
        }
        if (PTE_ISVALID(oldpte))
                panic("hat_mempte_setup(): address already mapped"
                    "ht=%p, entry=%d, pte=" FMT_PTE, (void *)ht, entry, oldpte);

        /*
         * increment ht_valid_cnt so that the pagetable can't disappear
         */
        HTABLE_INC(ht->ht_valid_cnt);

        /*
         * return the PTE physical address to the caller.
         */
        htable_release(ht);
        XPV_ALLOW_MIGRATE();
        p = PT_INDEX_PHYSADDR(pfn_to_pa(ht->ht_pfn), entry);
        --curthread->t_hatdepth;
        return (p);
}

/*
 * Release a CPU private mapping for the given address.
 * We decrement the htable valid count so it might be destroyed.
 */
/*ARGSUSED1*/
void
hat_mempte_release(caddr_t addr, hat_mempte_t pte_pa)
{
        htable_t        *ht;

        XPV_DISALLOW_MIGRATE();
        /*
         * invalidate any left over mapping and decrement the htable valid count
         */
#ifdef __xpv
        if (HYPERVISOR_update_va_mapping((uintptr_t)addr, 0,
            UVMF_INVLPG | UVMF_LOCAL))
                panic("HYPERVISOR_update_va_mapping() failed");
#else
        {
                x86pte_t *pteptr;

                pteptr = x86pte_mapin(mmu_btop(pte_pa),
                    (pte_pa & MMU_PAGEOFFSET) >> mmu.pte_size_shift, NULL);
                if (mmu.pae_hat)
                        *pteptr = 0;
                else
                        *(x86pte32_t *)pteptr = 0;
                mmu_tlbflush_entry(addr);
                x86pte_mapout();
        }
#endif

        ht = htable_getpte(kas.a_hat, ALIGN2PAGE(addr), NULL, NULL, 0);
        if (ht == NULL)
                panic("hat_mempte_release(): invalid address");
        ASSERT(ht->ht_level == 0);
        HTABLE_DEC(ht->ht_valid_cnt);
        htable_release(ht);
        XPV_ALLOW_MIGRATE();
}

/*
 * Apply a temporary CPU private mapping to a page. We flush the TLB only
 * on this CPU, so this ought to have been called with preemption disabled.
 */
void
hat_mempte_remap(
        pfn_t           pfn,
        caddr_t         addr,
        hat_mempte_t    pte_pa,
        uint_t          attr,
        uint_t          flags)
{
        uintptr_t       va = (uintptr_t)addr;
        x86pte_t        pte;

        /*
         * Remap the given PTE to the new page's PFN. Invalidate only
         * on this CPU.
         */
#ifdef DEBUG
        htable_t        *ht;
        uint_t          entry;

        ASSERT(IS_PAGEALIGNED(va));
        ASSERT(!IN_VA_HOLE(va));
        ht = htable_getpte(kas.a_hat, va, &entry, NULL, 0);
        ASSERT(ht != NULL);
        ASSERT(ht->ht_level == 0);
        ASSERT(ht->ht_valid_cnt > 0);
        ASSERT(ht->ht_pfn == mmu_btop(pte_pa));
        htable_release(ht);
#endif
        XPV_DISALLOW_MIGRATE();
        pte = hati_mkpte(pfn, attr, 0, flags);
#ifdef __xpv
        if (HYPERVISOR_update_va_mapping(va, pte, UVMF_INVLPG | UVMF_LOCAL))
                panic("HYPERVISOR_update_va_mapping() failed");
#else
        {
                x86pte_t *pteptr;

                pteptr = x86pte_mapin(mmu_btop(pte_pa),
                    (pte_pa & MMU_PAGEOFFSET) >> mmu.pte_size_shift, NULL);
                if (mmu.pae_hat)
                        *(x86pte_t *)pteptr = pte;
                else
                        *(x86pte32_t *)pteptr = (x86pte32_t)pte;
                mmu_tlbflush_entry(addr);
                x86pte_mapout();
        }
#endif
        XPV_ALLOW_MIGRATE();
}



/*
 * Hat locking functions
 * XXX - these two functions are currently being used by hatstats
 *      they can be removed by using a per-as mutex for hatstats.
 */
void
hat_enter(hat_t *hat)
{
        mutex_enter(&hat->hat_mutex);
}

void
hat_exit(hat_t *hat)
{
        mutex_exit(&hat->hat_mutex);
}

/*
 * HAT part of cpu initialization.
 */
void
hat_cpu_online(struct cpu *cpup)
{
        if (cpup != CPU) {
                x86pte_cpu_init(cpup);
                hat_vlp_setup(cpup);
        }
        CPUSET_ATOMIC_ADD(khat_cpuset, cpup->cpu_id);
}

/*
 * HAT part of cpu deletion.
 * (currently, we only call this after the cpu is safely passivated.)
 */
void
hat_cpu_offline(struct cpu *cpup)
{
        ASSERT(cpup != CPU);

        CPUSET_ATOMIC_DEL(khat_cpuset, cpup->cpu_id);
        hat_vlp_teardown(cpup);
        x86pte_cpu_fini(cpup);
}

/*
 * Function called after all CPUs are brought online.
 * Used to remove low address boot mappings.
 */
void
clear_boot_mappings(uintptr_t low, uintptr_t high)
{
        uintptr_t vaddr = low;
        htable_t *ht = NULL;
        level_t level;
        uint_t entry;
        x86pte_t pte;

        /*
         * On 1st CPU we can unload the prom mappings, basically we blow away
         * all virtual mappings under _userlimit.
         */
        while (vaddr < high) {
                pte = htable_walk(kas.a_hat, &ht, &vaddr, high);
                if (ht == NULL)
                        break;

                level = ht->ht_level;
                entry = htable_va2entry(vaddr, ht);
                ASSERT(level <= mmu.max_page_level);
                ASSERT(PTE_ISPAGE(pte, level));

                /*
                 * Unload the mapping from the page tables.
                 */
                (void) x86pte_inval(ht, entry, 0, NULL);
                ASSERT(ht->ht_valid_cnt > 0);
                HTABLE_DEC(ht->ht_valid_cnt);
                PGCNT_DEC(ht->ht_hat, ht->ht_level);

                vaddr += LEVEL_SIZE(ht->ht_level);
        }
        if (ht)
                htable_release(ht);
}

/*
 * Atomically update a new translation for a single page.  If the
 * currently installed PTE doesn't match the value we expect to find,
 * it's not updated and we return the PTE we found.
 *
 * If activating nosync or NOWRITE and the page was modified we need to sync
 * with the page_t. Also sync with page_t if clearing ref/mod bits.
 */
static x86pte_t
hati_update_pte(htable_t *ht, uint_t entry, x86pte_t expected, x86pte_t new)
{
        page_t          *pp;
        uint_t          rm = 0;
        x86pte_t        replaced;

        if (PTE_GET(expected, PT_SOFTWARE) < PT_NOSYNC &&
            PTE_GET(expected, PT_MOD | PT_REF) &&
            (PTE_GET(new, PT_NOSYNC) || !PTE_GET(new, PT_WRITABLE) ||
            !PTE_GET(new, PT_MOD | PT_REF))) {

                ASSERT(!pfn_is_foreign(PTE2PFN(expected, ht->ht_level)));
                pp = page_numtopp_nolock(PTE2PFN(expected, ht->ht_level));
                ASSERT(pp != NULL);
                if (PTE_GET(expected, PT_MOD))
                        rm |= P_MOD;
                if (PTE_GET(expected, PT_REF))
                        rm |= P_REF;
                PTE_CLR(new, PT_MOD | PT_REF);
        }

        replaced = x86pte_update(ht, entry, expected, new);
        if (replaced != expected)
                return (replaced);

        if (rm) {
                /*
                 * sync to all constituent pages of a large page
                 */
                pgcnt_t pgcnt = page_get_pagecnt(ht->ht_level);
                ASSERT(IS_P2ALIGNED(pp->p_pagenum, pgcnt));
                while (pgcnt-- > 0) {
                        /*
                         * hat_page_demote() can't decrease
                         * pszc below this mapping size
                         * since large mapping existed after we
                         * took mlist lock.
                         */
                        ASSERT(pp->p_szc >= ht->ht_level);
                        hat_page_setattr(pp, rm);
                        ++pp;
                }
        }

        return (0);
}

/* ARGSUSED */
void
hat_join_srd(struct hat *hat, vnode_t *evp)
{
}

/* ARGSUSED */
hat_region_cookie_t
hat_join_region(struct hat *hat,
    caddr_t r_saddr,
    size_t r_size,
    void *r_obj,
    u_offset_t r_objoff,
    uchar_t r_perm,
    uchar_t r_pgszc,
    hat_rgn_cb_func_t r_cb_function,
    uint_t flags)
{
        panic("No shared region support on x86");
        return (HAT_INVALID_REGION_COOKIE);
}

/* ARGSUSED */
void
hat_leave_region(struct hat *hat, hat_region_cookie_t rcookie, uint_t flags)
{
        panic("No shared region support on x86");
}

/* ARGSUSED */
void
hat_dup_region(struct hat *hat, hat_region_cookie_t rcookie)
{
        panic("No shared region support on x86");
}


/*
 * Kernel Physical Mapping (kpm) facility
 *
 * Most of the routines needed to support segkpm are almost no-ops on the
 * x86 platform.  We map in the entire segment when it is created and leave
 * it mapped in, so there is no additional work required to set up and tear
 * down individual mappings.  All of these routines were created to support
 * SPARC platforms that have to avoid aliasing in their virtually indexed
 * caches.
 *
 * Most of the routines have sanity checks in them (e.g. verifying that the
 * passed-in page is locked).  We don't actually care about most of these
 * checks on x86, but we leave them in place to identify problems in the
 * upper levels.
 */

/*
 * Map in a locked page and return the vaddr.
 */
/*ARGSUSED*/
caddr_t
hat_kpm_mapin(struct page *pp, struct kpme *kpme)
{
        caddr_t         vaddr;

#ifdef DEBUG
        if (kpm_enable == 0) {
                cmn_err(CE_WARN, "hat_kpm_mapin: kpm_enable not set\n");
                return ((caddr_t)NULL);
        }

        if (pp == NULL || PAGE_LOCKED(pp) == 0) {
                cmn_err(CE_WARN, "hat_kpm_mapin: pp zero or not locked\n");
                return ((caddr_t)NULL);
        }
#endif

        vaddr = hat_kpm_page2va(pp, 1);

        return (vaddr);
}

/*
 * Mapout a locked page.
 */
/*ARGSUSED*/
void
hat_kpm_mapout(struct page *pp, struct kpme *kpme, caddr_t vaddr)
{
#ifdef DEBUG
        if (kpm_enable == 0) {
                cmn_err(CE_WARN, "hat_kpm_mapout: kpm_enable not set\n");
                return;
        }

        if (IS_KPM_ADDR(vaddr) == 0) {
                cmn_err(CE_WARN, "hat_kpm_mapout: no kpm address\n");
                return;
        }

        if (pp == NULL || PAGE_LOCKED(pp) == 0) {
                cmn_err(CE_WARN, "hat_kpm_mapout: page zero or not locked\n");
                return;
        }
#endif
}

/*
 * hat_kpm_mapin_pfn is used to obtain a kpm mapping for physical
 * memory addresses that are not described by a page_t.  It can
 * also be used for normal pages that are not locked, but beware
 * this is dangerous - no locking is performed, so the identity of
 * the page could change.  hat_kpm_mapin_pfn is not supported when
 * vac_colors > 1, because the chosen va depends on the page identity,
 * which could change.
 * The caller must only pass pfn's for valid physical addresses; violation
 * of this rule will cause panic.
 */
caddr_t
hat_kpm_mapin_pfn(pfn_t pfn)
{
        caddr_t paddr, vaddr;

        if (kpm_enable == 0)
                return ((caddr_t)NULL);

        paddr = (caddr_t)ptob(pfn);
        vaddr = (uintptr_t)kpm_vbase + paddr;

        return ((caddr_t)vaddr);
}

/*ARGSUSED*/
void
hat_kpm_mapout_pfn(pfn_t pfn)
{
        /* empty */
}

/*
 * Return the kpm virtual address for a specific pfn
 */
caddr_t
hat_kpm_pfn2va(pfn_t pfn)
{
        uintptr_t vaddr = (uintptr_t)kpm_vbase + mmu_ptob(pfn);

        ASSERT(!pfn_is_foreign(pfn));
        return ((caddr_t)vaddr);
}

/*
 * Return the kpm virtual address for the page at pp.
 */
/*ARGSUSED*/
caddr_t
hat_kpm_page2va(struct page *pp, int checkswap)
{
        return (hat_kpm_pfn2va(pp->p_pagenum));
}

/*
 * Return the page frame number for the kpm virtual address vaddr.
 */
pfn_t
hat_kpm_va2pfn(caddr_t vaddr)
{
        pfn_t           pfn;

        ASSERT(IS_KPM_ADDR(vaddr));

        pfn = (pfn_t)btop(vaddr - kpm_vbase);

        return (pfn);
}


/*
 * Return the page for the kpm virtual address vaddr.
 */
page_t *
hat_kpm_vaddr2page(caddr_t vaddr)
{
        pfn_t           pfn;

        ASSERT(IS_KPM_ADDR(vaddr));

        pfn = hat_kpm_va2pfn(vaddr);

        return (page_numtopp_nolock(pfn));
}

/*
 * hat_kpm_fault is called from segkpm_fault when we take a page fault on a
 * KPM page.  This should never happen on x86
 */
int
hat_kpm_fault(hat_t *hat, caddr_t vaddr)
{
        panic("pagefault in seg_kpm.  hat: 0x%p  vaddr: 0x%p",
            (void *)hat, (void *)vaddr);

        return (0);
}

/*ARGSUSED*/
void
hat_kpm_mseghash_clear(int nentries)
{}

/*ARGSUSED*/
void
hat_kpm_mseghash_update(pgcnt_t inx, struct memseg *msp)
{}

#ifndef __xpv
void
hat_kpm_addmem_mseg_update(struct memseg *msp, pgcnt_t nkpmpgs,
        offset_t kpm_pages_off)
{
        _NOTE(ARGUNUSED(nkpmpgs, kpm_pages_off));
        pfn_t base, end;

        /*
         * kphysm_add_memory_dynamic() does not set nkpmpgs
         * when page_t memory is externally allocated.  That
         * code must properly calculate nkpmpgs in all cases
         * if nkpmpgs needs to be used at some point.
         */

        /*
         * The meta (page_t) pages for dynamically added memory are allocated
         * either from the incoming memory itself or from existing memory.
         * In the former case the base of the incoming pages will be different
         * than the base of the dynamic segment so call memseg_get_start() to
         * get the actual base of the incoming memory for each case.
         */

        base = memseg_get_start(msp);
        end = msp->pages_end;

        hat_devload(kas.a_hat, kpm_vbase + mmu_ptob(base),
            mmu_ptob(end - base), base, PROT_READ | PROT_WRITE,
            HAT_LOAD | HAT_LOAD_LOCK | HAT_LOAD_NOCONSIST);
}

void
hat_kpm_addmem_mseg_insert(struct memseg *msp)
{
        _NOTE(ARGUNUSED(msp));
}

void
hat_kpm_addmem_memsegs_update(struct memseg *msp)
{
        _NOTE(ARGUNUSED(msp));
}

/*
 * Return end of metadata for an already setup memseg.
 * X86 platforms don't need per-page meta data to support kpm.
 */
caddr_t
hat_kpm_mseg_reuse(struct memseg *msp)
{
        return ((caddr_t)msp->epages);
}

void
hat_kpm_delmem_mseg_update(struct memseg *msp, struct memseg **mspp)
{
        _NOTE(ARGUNUSED(msp, mspp));
        ASSERT(0);
}

void
hat_kpm_split_mseg_update(struct memseg *msp, struct memseg **mspp,
        struct memseg *lo, struct memseg *mid, struct memseg *hi)
{
        _NOTE(ARGUNUSED(msp, mspp, lo, mid, hi));
        ASSERT(0);
}

/*
 * Walk the memsegs chain, applying func to each memseg span.
 */
void
hat_kpm_walk(void (*func)(void *, void *, size_t), void *arg)
{
        pfn_t   pbase, pend;
        void    *base;
        size_t  size;
        struct memseg *msp;

        for (msp = memsegs; msp; msp = msp->next) {
                pbase = msp->pages_base;
                pend = msp->pages_end;
                base = ptob(pbase) + kpm_vbase;
                size = ptob(pend - pbase);
                func(arg, base, size);
        }
}

#else   /* __xpv */

/*
 * There are specific Hypervisor calls to establish and remove mappings
 * to grant table references and the privcmd driver. We have to ensure
 * that a page table actually exists.
 */
void
hat_prepare_mapping(hat_t *hat, caddr_t addr, uint64_t *pte_ma)
{
        maddr_t base_ma;
        htable_t *ht;
        uint_t entry;

        ASSERT(IS_P2ALIGNED((uintptr_t)addr, MMU_PAGESIZE));
        XPV_DISALLOW_MIGRATE();
        ht = htable_create(hat, (uintptr_t)addr, 0, NULL);

        /*
         * if an address for pte_ma is passed in, return the MA of the pte
         * for this specific address.  This address is only valid as long
         * as the htable stays locked.
         */
        if (pte_ma != NULL) {
                entry = htable_va2entry((uintptr_t)addr, ht);
                base_ma = pa_to_ma(ptob(ht->ht_pfn));
                *pte_ma = base_ma + (entry << mmu.pte_size_shift);
        }
        XPV_ALLOW_MIGRATE();
}

void
hat_release_mapping(hat_t *hat, caddr_t addr)
{
        htable_t *ht;

        ASSERT(IS_P2ALIGNED((uintptr_t)addr, MMU_PAGESIZE));
        XPV_DISALLOW_MIGRATE();
        ht = htable_lookup(hat, (uintptr_t)addr, 0);
        ASSERT(ht != NULL);
        ASSERT(ht->ht_busy >= 2);
        htable_release(ht);
        htable_release(ht);
        XPV_ALLOW_MIGRATE();
}
#endif  /* __xpv */