xref: /titanic_44/usr/src/uts/i86pc/vm/hat_i86.c (revision 39c23413b8df94a95f67b34cfd4a4dfc3fd0b48d)

/*
 * 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 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

/*
 * 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 <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>

#include <sys/cmn_err.h>


/*
 * Basic parameters for hat operation.
 */
struct hat_mmu_info mmu;
uint_t force_pae_off = 0;	/* for testing, change with kernel debugger */
uint_t force_pae_on = 0;	/* for testing, change with kernel debugger */

/*
 * The page that is the kernel's top level pagetable.
 *
 * For 32 bit VLP support, 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] - 0th level==2 PTE for kernel HAT (will be zero)
 * vlp_page[1] - 1st level==2 PTE for kernel HAT (will be zero)
 * vlp_page[2] - 2nd level==2 PTE for kernel HAT (zero for small memory)
 * vlp_page[3] - 3rd level==2 PTE for kernel
 *
 * vlp_page[4] - 0th level==2 PTE for user thread on cpu 0
 * vlp_page[5] - 1st level==2 PTE for user thread on cpu 0
 * vlp_page[6] - 2nd level==2 PTE for user thread on cpu 0
 * vlp_page[7] - probably copy of kernel PTE
 *
 * vlp_page[8]  - 0th level==2 PTE for user thread on cpu 1
 * vlp_page[9]  - 1st level==2 PTE for user thread on cpu 1
 * vlp_page[10] - 2nd level==2 PTE for user thread on cpu 1
 * vlp_page[11] - probably copy of kernel PTE
 * ...
 *
 * when / where the kernel PTE's are (entry 2 or 3 or none) depends
 * on kernelbase.
 */
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 every topmost level page
 * table. The values are setup in hat_init() and then copied to every 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 PAE 32 bit hat is handled as a special case. Otherwise requiring 1Gig
 * alignment would use too much VA for the kernel.
 *
 */
static uint_t	khat_start;	/* index of 1st entry in kernel's top ptable */
static uint_t	khat_entries;	/* number of entries in kernel's top ptable */

#if defined(__i386)

static htable_t	*khat_pae32_htable = NULL;
static uint_t	khat_pae32_start;
static uint_t	khat_pae32_entries;

#endif

/*
 * Locks, etc. to control use of the hat reserves when recursively
 * allocating pagetables for the hat data structures.
 */
static kmutex_t hat_reserves_lock;
static kcondvar_t hat_reserves_cv;
kthread_t *hat_reserves_thread;
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 */

/*
 * 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;

/*
 * macros to detect addresses in use by kernel only during boot
 */
#if defined(__amd64)

#define	BOOT_VA(va) ((va) < kernelbase ||			\
	((va) >= BOOT_DOUBLEMAP_BASE &&				\
	(va) < BOOT_DOUBLEMAP_BASE + BOOT_DOUBLEMAP_SIZE))

#elif defined(__i386)

#define	BOOT_VA(va) ((va) < kernelbase)

#endif	/* __i386 */

/*
 * 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);

#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)

/*
 * some useful tracing macros
 */

int hattrace = 0;
#ifdef DEBUG

#define	HATIN(r, h, a, l)	\
	if (hattrace) prom_printf("->%s hat=%p, adr=%p, len=%lx\n", #r, h, a, l)

#define	HATOUT(r, h, a)		\
	if (hattrace) prom_printf("<-%s hat=%p, adr=%p\n", #r, h, a)
#else

#define	HATIN(r, h, a, l)
#define	HATOUT(r, h, a)

#endif


/*
 * 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_stats = 0;
	hat->hat_flags = 0;
	mutex_init(&hat->hat_switch_mutex, NULL, MUTEX_DRIVER,
	    (void *)ipltospl(DISP_LEVEL));
	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;

	/*
	 * 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);

	/*
	 * a 32 bit process uses a VLP style hat when using PAE
	 */
#if defined(__amd64)
	use_vlp = (ttoproc(curthread)->p_model == DATAMODEL_ILP32);
#elif defined(__i386)
	use_vlp = mmu.pae_hat;
#endif
	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
	 * table for the new hat.
	 *
	 * Note that we don't call htable_release() for the top level, that
	 * happens when the hat is destroyed in hat_free_end()
	 */
	hat->hat_htable = NULL;
	hat->hat_ht_cached = NULL;
	ht = htable_create(hat, (uintptr_t)0, TOP_LEVEL(hat), NULL);
	if (!(hat->hat_flags & HAT_VLP))
		x86pte_copy(kas.a_hat->hat_htable, ht, khat_start,
		    khat_entries);
#if defined(__i386)
	else if (khat_entries > 0)
		bcopy(vlp_page + khat_start, hat->hat_vlp_ptes + khat_start,
		    khat_entries * sizeof (x86pte_t));
#endif
	hat->hat_htable = ht;

#if defined(__i386)
	/*
	 * PAE32 HAT alignment is less restrictive than the others to keep
	 * the kernel from using too much VA. Because of this we may need
	 * one layer further down when kernelbase isn't 1Gig aligned.
	 * See hat_free_end() for the htable_release() that goes with this
	 * htable_create()
	 */
	if (khat_pae32_htable != NULL) {
		ht = htable_create(hat, kernelbase,
		    khat_pae32_htable->ht_level, NULL);
		x86pte_copy(khat_pae32_htable, ht, khat_pae32_start,
		    khat_pae32_entries);
		ht->ht_valid_cnt = khat_pae32_entries;
	}
#endif

	/*
	 * 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)
{
	int i;
	kmem_cache_t *cache;

#ifdef DEBUG
	for (i = 0; i <= mmu.max_page_level; i++)
		ASSERT(hat->hat_pages_mapped[i] == 0);
#endif
	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;

	/*
	 * 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);
}

/*
 * 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 ((x86_feature & X86_PGE) != 0 && (getcr4() & 0x80) != 0)
		mmu.pt_global = PT_GLOBAL;

	/*
	 * We use PAE except when we aren't on an AMD64 and this is
	 * a 32 bit kernel with all physical addresses less than 4 Gig.
	 */
	mmu.pae_hat = 1;
	if (x86_feature & X86_NX) {
		mmu.pt_nx = PT_NX;
	} else {
		mmu.pt_nx = 0;
#if defined(__i386)
		if (!PFN_ABOVE4G(physmax))
			mmu.pae_hat = 0;
#endif
	}

#if defined(__i386)
	/*
	 * Setting one of these two lets you force testing of the different
	 * hat modes for 32 bit, regardless of the hardware setup.
	 */
	if (force_pae_on) {
		mmu.pae_hat = 1;
	} else if (force_pae_off) {
		mmu.pae_hat = 0;
		mmu.pt_nx = 0;
	}
#endif

	/*
	 * 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 && (x86_feature & X86_PAE) == 0)
		panic("Processor does not support PAE");

	if ((x86_feature & X86_CX8) == 0)
		panic("Processor does not support cmpxchg8b instruction");

	/*
	 * Initialize parameters based on the 64 or 32 bit kernels and
	 * for the 32 bit kernel decide if we should use PAE.
	 */
	if (x86_feature & X86_LARGEPAGE)
		mmu.max_page_level = 1;
	else
		mmu.max_page_level = 0;
	mmu_page_sizes = mmu.max_page_level + 1;
	mmu_exported_page_sizes = mmu_page_sizes;

#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];
	}

	mmu.pte_bits[0] = PT_VALID;
	for (i = 1; i <= mmu.max_page_level; ++i)
		mmu.pte_bits[i] = PT_VALID | 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

	/*
	 * This code knows that there are only 2 pagesizes.
	 * We ignore 4MB (non-PAE) for now. The value is only used
	 * for optimizing demaps across large ranges.
	 * These return zero if no information is known.
	 */
	mmu.tlb_entries[0] = cpuid_get_dtlb_nent(NULL, MMU_PAGESIZE);
	mmu.tlb_entries[1] = cpuid_get_dtlb_nent(NULL, 2 * 1024 * 1024);
}


/*
 * 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)
	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 + khat_start, hci->hci_vlp_l3ptes + khat_start,
	    khat_entries * sizeof (x86pte_t));

	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 */
}

/*
 * 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
 */
void
hat_init_finish(void)
{
	htable_t	*top = kas.a_hat->hat_htable;
	htable_t	*ht;
	uint_t		e;
	x86pte_t	pte;
	uintptr_t	va = kernelbase;


#if defined(__i386)
	ASSERT((va & LEVEL_MASK(1)) == va);

	/*
	 * Deal with kernelbase not 1Gig aligned for 32 bit PAE hats.
	 */
	if (!mmu.pae_hat || (va & LEVEL_OFFSET(mmu.max_level)) == 0) {
		khat_pae32_htable = NULL;
	} else {
		ASSERT(mmu.max_level == 2);
		ASSERT((va & LEVEL_OFFSET(mmu.max_level - 1)) == 0);
		khat_pae32_htable =
		    htable_create(kas.a_hat, va, mmu.max_level - 1, NULL);
		khat_pae32_start = htable_va2entry(va, khat_pae32_htable);
		khat_pae32_entries = mmu.ptes_per_table - khat_pae32_start;
		for (e = khat_pae32_start; e < mmu.ptes_per_table;
		    ++e, va += LEVEL_SIZE(mmu.max_level - 1)) {
			pte = x86pte_get(khat_pae32_htable, e);
			if (PTE_ISVALID(pte))
				continue;
			ht = htable_create(kas.a_hat, va, mmu.max_level - 2,
			    NULL);
			ASSERT(ht != NULL);
		}
	}
#endif

	/*
	 * The kernel hat will need fixed values in the highest level
	 * ptable for copying to all other hat's. This implies
	 * alignment restrictions on _userlimit.
	 *
	 * Note we don't htable_release() these htables. This keeps them
	 * from ever being stolen or free'd.
	 *
	 * top_level_count is used instead of ptes_per_table, since
	 * on 32-bit PAE we only have 4 usable entries at the top level ptable.
	 */
	if (va == 0)
		khat_start = mmu.top_level_count;
	else
		khat_start = htable_va2entry(va, kas.a_hat->hat_htable);
	khat_entries = mmu.top_level_count - khat_start;
	for (e = khat_start; e < mmu.top_level_count;
	    ++e, va += LEVEL_SIZE(mmu.max_level)) {
		pte = x86pte_get(top, e);
		if (PTE_ISVALID(pte))
			continue;
		ht = htable_create(kas.a_hat, va, mmu.max_level - 1, NULL);
		ASSERT(ht != NULL);
	}

	/*
	 * 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 mapping in memory for the hat's own allocations.
	 */
	use_boot_reserve = 0;
	htable_adjust_reserve();

	/*
	 * 32 bit kernels use only 4 of the 512 entries in its top level
	 * pagetable. We'll use the remainder for the "per CPU" page tables
	 * for VLP processes.
	 *
	 * We map the top level kernel pagetable into the kernel's AS to make
	 * it easy to use bcopy for kernel entry PTEs.
	 *
	 * We were guaranteed to get a physical address < 4Gig, since the 32 bit
	 * boot loader uses non-PAE page 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,
		    PROT_READ | PROT_WRITE | HAT_NOSYNC | HAT_UNORDERED_OK,
		    HAT_LOAD | HAT_LOAD_NOCONSIST);
	}
	hat_vlp_setup(CPU);
}

/*
 * On 32 bit PAE mode, PTE's are 64 bits, but ordinary atomic memory references
 * are 32 bit, so for safety we must use cas64() 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 (cas64(dest + i, pte, src[i]) != src[i])
				break;
		}
	}
}
#endif

/*
 * Switch to a new active hat, maintaining bit masks to track active CPUs.
 */
void
hat_switch(hat_t *hat)
{
	uintptr_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);
	}

	/*
	 * Wait for any in flight pagetable invalidates on this hat to finish.
	 * This is a spin lock at DISP_LEVEL
	 */
	if (hat != kas.a_hat) {
		mutex_enter(&hat->hat_switch_mutex);
		CPUSET_ATOMIC_ADD(hat->hat_cpus, cpu->cpu_id);
		mutex_exit(&hat->hat_switch_mutex);
	}
	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(hat->hat_htable->ht_pfn);
	}
	setcr3(newcr3);
	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 (attr & HAT_NOSYNC)
		PTE_SET(pte, PT_NOSYNC);
	if (flags & HAT_LOAD_NOCONSIST)
		PTE_SET(pte, PT_NOCONSIST | PT_NOSYNC);

	/*
	 * 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 (x86_feature & X86_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;

	/*
	 * 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.
		 * This code knows that only level 0 page tables are shared
		 */
		l = ht->ht_level;
		if (ht->ht_flags & HTABLE_SHARED_PFN) {
			ASSERT(l == 0);
			vaddr = ht->ht_vaddr + LEVEL_SIZE(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);
}

/*
 * 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));

	return (total);
}

/*
 * enable/disable collection of stats for hat.
 */
int
hat_stats_enable(hat_t *hat)
{
	atomic_add_32(&hat->hat_stats, 1);
	return (1);
}

void
hat_stats_disable(hat_t *hat)
{
	atomic_add_32(&hat->hat_stats, -1);
}

/*
 * 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_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 require a TLB flush (hat_demap) if changed 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)

#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 void
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;

	/*
	 * Is this a consistant (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.
	 */
	if ((flags & HAT_LOAD_LOCK) != 0 && hat != kas.a_hat)
		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);

	/*
	 * If the mapping didn't change there is nothing more to do.
	 */
	if (PTE_EQUIV(pte, old_pte)) {
		if (is_consist) {
			x86_hm_exit(pp);
			if (hm != NULL)
				hment_free(hm);
		}
		return;
	}

	/*
	 * 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);
		}
		HTABLE_INC(ht->ht_valid_cnt);
		PGCNT_INC(hat, l);
		return;
	}

	/*
	 * 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_NOCONSIST));
		REMAPASSERT(pf_is_memory(PTE2PFN(old_pte, l)) ==
		    pf_is_memory(PTE2PFN(pte, l)));
		REMAPASSERT(!is_consist);
	}

	/*
	 * We only let remaps change the bits for PFNs, permissions
	 * or caching type.
	 */
	ASSERT(PTE_GET(old_pte, ~(PT_REMAP_BITS | PT_REF | PT_MOD)) ==
	    PTE_GET(pte, ~PT_REMAP_BITS));

	/*
	 * A remap requires invalidating the TLBs, since remapping the
	 * same PFN requires NOCONSIST, we don't have to sync R/M bits.
	 */
	hat_demap(hat, htable_e2va(ht, entry));

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

/*
 * The t_hatdepth field is an 8-bit counter.  We use the lower seven bits
 * to track exactly how deep we are in the memload->kmem_alloc recursion.
 * If the depth is greater than 1, that indicates that we are performing a
 * hat operation to satisfy another hat operation.  To prevent infinite
 * recursion, we switch over to using pre-allocated "reserves" of htables
 * and hments.
 *
 * The uppermost bit is used to indicate that we are transitioning away
 * from being the reserves thread.  See hati_reserves_exit() for the
 * details.
 */
#define	EXITING_FLAG		(1 << 7)
#define	DEPTH_MASK		(~EXITING_FLAG)
#define	HAT_DEPTH(t)		((t)->t_hatdepth & DEPTH_MASK)
#define	EXITING_RESERVES(t)	((t)->t_hatdepth & EXITING_FLAG)

/*
 * Access to reserves for HAT_NO_KALLOC is single threaded.
 * If someone else is in the reserves, we'll politely wait for them
 * to finish. This keeps normal hat_memload()s from eating up
 * the mappings needed to replenish the reserve.
 */
static void
hati_reserves_enter(uint_t kmem_for_hat)
{
	/*
	 * 64 is an arbitrary number to catch serious problems.  I'm not
	 * sure what the absolute maximum depth is, but it should be
	 * substantially less than this.
	 */
	ASSERT(HAT_DEPTH(curthread) < 64);

	/*
	 * If we are doing a memload to satisfy a kmem operation, we enter
	 * the reserves immediately; we don't wait to recurse to a second
	 * level of memload.
	 */
	ASSERT(kmem_for_hat < 2);
	curthread->t_hatdepth += (1 + kmem_for_hat);

	if (hat_reserves_thread == curthread || use_boot_reserve)
		return;

	if (HAT_DEPTH(curthread) > 1 || hat_reserves_thread != NULL) {
		mutex_enter(&hat_reserves_lock);
		while (hat_reserves_thread != NULL)
			cv_wait(&hat_reserves_cv, &hat_reserves_lock);

		if (HAT_DEPTH(curthread) > 1)
			hat_reserves_thread = curthread;

		mutex_exit(&hat_reserves_lock);
	}
}

/*
 * If we are the reserves_thread and we've finally finished with all our
 * memloads (ie. no longer doing hat slabs), we can release our use of the
 * reserve.
 */
static void
hati_reserves_exit(uint_t kmem_for_hat)
{
	ASSERT(kmem_for_hat < 2);
	curthread->t_hatdepth -= (1 + kmem_for_hat);

	/*
	 * Simple case: either we are not the reserves thread, or we are
	 * the reserves thread and we are nested deeply enough that we
	 * should still be the reserves thread.
	 *
	 * Note: we may not become the reserves thread after we recursively
	 * enter our second HAT routine, but we don't stop being the
	 * reserves thread until we exit the toplevel HAT routine.  This is
	 * to work around vmem's inability to determine when an allocation
	 * should be satisfied from the hat_memload arena, which can lead
	 * to an infinite loop of memload->vmem_populate->memload->.
	 */
	if (curthread != hat_reserves_thread || HAT_DEPTH(curthread) > 0 ||
	    use_boot_reserve)
		return;

	mutex_enter(&hat_reserves_lock);
	ASSERT(hat_reserves_thread == curthread);
	hat_reserves_thread = NULL;
	cv_broadcast(&hat_reserves_cv);
	mutex_exit(&hat_reserves_lock);

	/*
	 * As we leave the reserves, we want to be sure the reserve lists
	 * aren't overstocked.  Freeing excess reserves requires that we
	 * call kmem_free(), which may require additional allocations,
	 * causing us to re-enter the reserves.  To avoid infinite
	 * recursion, we only try to adjust reserves at the very top level.
	 */
	if (!kmem_for_hat && !EXITING_RESERVES(curthread)) {
		curthread->t_hatdepth |= EXITING_FLAG;
		htable_adjust_reserve();
		hment_adjust_reserve();
		curthread->t_hatdepth &= (~EXITING_FLAG);
	}

	/*
	 * just in case something went wrong in doing adjust reserves
	 */
	ASSERT(hat_reserves_thread != curthread);
}

/*
 * Internal routine to load a single page table entry.
 */
static void
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;
	uint_t		kmem_for_hat = (flags & HAT_NO_KALLOC) ? 1 : 0;

	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);

	/*
	 * All threads go through hati_reserves_enter() to at least wait
	 * for any existing reserves user to finish. This helps reduce
	 * pressure on the reserves. In addition, if this thread needs
	 * to become the new reserve user it will.
	 */
	hati_reserves_enter(kmem_for_hat);

	ASSERT(HAT_DEPTH(curthread) == 1 || va >= kernelbase);

	/*
	 * Kernel memloads for HAT data should never use hments!
	 * If it did that would seriously complicate the reserves system, since
	 * hment_alloc() would need to know about HAT_NO_KALLOC.
	 *
	 * We also must have HAT_LOAD_NOCONSIST if page_t is NULL.
	 */
	if (HAT_DEPTH(curthread) > 1 || 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", 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
	 */
	hati_pte_map(ht, entry, pp, pte, flags, NULL);

	/*
	 * release the htable and any reserves
	 */
	htable_release(ht);
	hati_reserves_exit(kmem_for_hat);
}

/*
 * 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);
	hati_pte_map(ht, entry, pp, pte, flags, pte_ptr);
}

/*
 * 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 (soft bit)
 *
 *	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 (soft bit) - 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);

	HATIN(hat_memload, hat, addr, (size_t)MMU_PAGESIZE);
	ASSERT(IS_PAGEALIGNED(va));
	ASSERT(hat == kas.a_hat || va <= kernelbase);
	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);
		return;
	}

	/*
	 * This is used for memory with normal caching enabled, so
	 * always set HAT_STORECACHING_OK.
	 */
	attr |= HAT_STORECACHING_OK;
	hati_load_common(hat, va, pp, attr, flags, level, pfn);
	HATOUT(hat_memload, hat, addr);
}

/*
 * 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;

	HATIN(hat_memload_array, hat, addr, len);
	ASSERT(IS_PAGEALIGNED(va));
	ASSERT(hat == kas.a_hat || va + len <= kernelbase);
	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 << MMU_PAGESHIFT, 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))
					break;
			}
		}

		/*
		 * Shared page tables for DISM might have a pre-existing
		 * level 0 page table that wasn't unlinked from all the
		 * sharing hats. If we hit this for a large page, back off
		 * to using level 0 pages.
		 *
		 * This can't be made better (ie. use large pages) until we
		 * track all the htable's sharing and rewrite hat_pageunload().
		 * Note that would cost a pointer in htable_t for a rare case.
		 *
		 * Since the 32 bit kernel caches empty page tables, check
		 * the kernel too.
		 */
		if ((hat == kas.a_hat || (hat->hat_flags & HAT_SHARED)) &&
		    level > 0) {
			htable_t *lower;

			lower = htable_getpte(hat, va, NULL, NULL, level - 1);
			if (lower != NULL) {
				level = 0;
				pgsize = LEVEL_SIZE(0);
				htable_release(lower);
			}
		}

		/*
		 * load this page mapping
		 */
		ASSERT(!IN_VA_HOLE(va));
		hati_load_common(hat, va, pages[pgindx], attr, flags,
		    level, pfn);

		/*
		 * move to next page
		 */
		va += pgsize;
		pgindx += mmu_btop(pgsize);
	}
	HATOUT(hat_memload_array, hat, addr);
}

/*
 * 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 */

	HATIN(hat_devload, hat, addr, len);
	ASSERT(IS_PAGEALIGNED(va));
	ASSERT(hat == kas.a_hat || eva <= kernelbase);
	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)))
				break;
		}

		/*
		 * Some kernel addresses have permanently existing page tables,
		 * so be sure to use a compatible pagesize.
		 */
		if (hat == kas.a_hat && level > 0) {
			htable_t *lower;

			lower = htable_getpte(hat, va, NULL, NULL, level - 1);
			if (lower != NULL) {
				level = 0;
				pgsize = LEVEL_SIZE(0);
				htable_release(lower);
			}
		}

		/*
		 * If it is memory get page_t and 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, make sure
		 * NOCONSIST is set.
		 */
		a = attr;
		f = flags;
		if (pf_is_memory(pfn)) {
			if (!(a & HAT_PLAT_NOCACHE))
				a |= HAT_STORECACHING_OK;

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

		/*
		 * load this page mapping
		 */
		ASSERT(!IN_VA_HOLE(va));
		hati_load_common(hat, va, pp, a, f, level, pfn);

		/*
		 * move to next page
		 */
		va += pgsize;
		pfn += mmu_btop(pgsize);
	}
	HATOUT(hat_devload, hat, addr);
}

/*
 * 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 <= kernelbase);
	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");

	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", ht, (caddr_t)vaddr);
		HTABLE_LOCK_DEC(ht);

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

/*
 * 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((caddr_t)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);
}

/*
 * Internal routine to do cross calls to invalidate a range of pages on
 * all CPUs using a given hat.
 */
void
hat_demap(hat_t *hat, uintptr_t va)
{
	extern int	flushes_require_xcalls;	/* from mp_startup.c */
	cpuset_t	justme;

	/*
	 * 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) {
		(void) hati_demap_func((xc_arg_t)hat, (xc_arg_t)va, NULL);
		return;
	}


	/*
	 * All CPUs must see kernel hat changes.
	 */
	if (hat == kas.a_hat) {
		kpreempt_disable();
		xc_call((xc_arg_t)hat, (xc_arg_t)va, NULL,
		    X_CALL_HIPRI, khat_cpuset, hati_demap_func);
		kpreempt_enable();
		return;
	}

	/*
	 * Otherwise we notify CPUs currently running in this HAT
	 */
	mutex_enter(&hat->hat_switch_mutex);
	kpreempt_disable();
	CPUSET_ONLY(justme, CPU->cpu_id);
	if (CPUSET_ISEQUAL(hat->hat_cpus, justme))
		(void) hati_demap_func((xc_arg_t)hat, (xc_arg_t)va, NULL);
	else
		xc_call((xc_arg_t)hat, (xc_arg_t)va, NULL,
		    X_CALL_HIPRI, hat->hat_cpus, hati_demap_func);
	kpreempt_enable();
	mutex_exit(&hat->hat_switch_mutex);
}

/*
 * 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_NOCONSIST)) {
			pp = NULL;
		} else {
			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);
		}

		/*
		 * If freeing the address space, check that the PTE
		 * hasn't changed, as the mappings are no longer in use by
		 * any thread, invalidation is unnecessary.
		 * If not freeing, do a full invalidate.
		 */
		if (hat->hat_flags & HAT_FREEING)
			old_pte = x86pte_get(ht, entry);
		else
			old_pte =
			    x86pte_invalidate_pfn(ht, entry, pfn, 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_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_off;
	htable_t	*ht;
	uint_t		entry;
	void		*pte_ptr;
	x86pte_t	old_pte;

	for (; va < eva; va += MMU_PAGESIZE) {
		/*
		 * Get the PTE
		 */
		pg_off = mmu_btop(va - mmu.kmap_addr);
		if (mmu.pae_hat) {
			pte_ptr = mmu.kmap_ptes + pg_off;
			ATOMIC_LOAD64((x86pte_t *)pte_ptr, old_pte);
		} else {
			pte_ptr = (x86pte32_t *)mmu.kmap_ptes + pg_off;
			old_pte = *(x86pte32_t *)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;
	ASSERT(hat == kas.a_hat || va + len <= kernelbase);

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

/*
 * 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;

	HATIN(hat_unload_callback, hat, addr, len);
	ASSERT(hat == kas.a_hat || eaddr <= kernelbase);
	ASSERT(IS_PAGEALIGNED(vaddr));
	ASSERT(IS_PAGEALIGNED(eaddr));

	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);

	HATOUT(hat_unload_callback, hat, addr);
}

/*
 * 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 <= kernelbase);

	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_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_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);
}

/*
 * 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 < kernelbase);

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

	ht = htable_getpte(hat, vaddr, NULL, &pte, 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_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;

	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_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_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_NOSYNC))
				newpte &= ~PT_NOSYNC;

			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_NOSYNC))
				newpte &= ~PT_NOSYNC;

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

		/*
		 * 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);
}

/*
 * 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 <= kernelbase);
	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 <= kernelbase);
	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 <= kernelbase);
	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 <= kernelbase);
	hat_updateattr(hat, addr, len, vprot & HAT_PROT_MASK, HAT_LOAD_ATTR);
}

/*ARGSUSED*/
void
hat_chgattr_pagedir(hat_t *hat, caddr_t addr, size_t len, uint_t attr)
{
	panic("hat_chgattr_pgdir() not supported - used by 80387 emulation");
}

/*
 * 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 < kernelbase);
	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 < kernelbase);
	if (khat_running == 0)
		panic("hat_getpfnum(): called too early\n");

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

	/*
	 * 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_off;

		pg_off = mmu_btop(vaddr - mmu.kmap_addr);
		if (mmu.pae_hat) {
			ATOMIC_LOAD64(mmu.kmap_ptes + pg_off, pte);
		} else {
			pte = ((x86pte32_t *)mmu.kmap_ptes)[pg_off];
		}
		if (!PTE_ISVALID(pte))
			return (PFN_INVALID);
		/*LINTED [use of constant 0 causes a silly lint warning] */
		return (PTE2PFN(pte, 0));
	}

	ht = htable_getpage(hat, vaddr, &entry);
	if (ht == NULL)
		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);
	return (pfn);
}

/*
 * hat_getkpfnum() is an obsolete DDI routine, and its use is discouraged.
 * Use hat_getpfnum(kas.a_hat, ...) instead.
 *
 * We'd like to return PFN_INVALID if the mappings have underlying page_t's
 * but can't right now due to the fact that some software has grown to use
 * this interface incorrectly. So for now when the interface is misused,
 * return a warning to the user that in the future it won't work in the
 * way they're abusing it, and carry on.
 *
 * Note that hat_getkpfnum() is never supported on amd64.
 */
#if !defined(__amd64)
pfn_t
hat_getkpfnum(caddr_t addr)
{
	pfn_t	pfn;
	int badcaller = 0;


	if (khat_running == 0)
		panic("hat_getkpfnum(): called too early\n");
	if ((uintptr_t)addr < kernelbase)
		return (PFN_INVALID);


	if (segkpm && IS_KPM_ADDR(addr)) {
		badcaller = 1;
		pfn = hat_kpm_va2pfn(addr);
	} else {
		pfn = hat_getpfnum(kas.a_hat, addr);
		badcaller = pf_is_memory(pfn);
	}

	if (badcaller)
		hat_getkpfnum_badcall(caller());
	return (pfn);
}
#endif /* __amd64 */

/*
 * 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 < kernelbase);
	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);
	if (ht == NULL)
		return (0);
	htable_release(ht);
	return (1);
}

/*
 * Simple implementation of ISM. hat_share() is just like hat_memload_array(),
 * except that we use the ism_hat's existing mappings to determine the pages
 * and protections to use for this hat. In case we find a properly aligned
 * and sized pagetable of 4K mappings, 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	pt_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;
	uint_t		valid_cnt;

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

	/*
	 * 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.
	 */
	HATIN(hat_share, hat, addr, len);
	ASSERT(IS_PAGEALIGNED(vaddr_start));
	ASSERT(IS_PAGEALIGNED(ism_addr_start));
	ASSERT(ism_hat->hat_flags & HAT_SHARED);
	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;

		/*
		 * Find the largest page size we can use, based on the
		 * ISM mapping size, our address alignment and the remaining
		 * map length.
		 */
		vaddr = vaddr_start + (ism_addr - ism_addr_start);
		for (l = ism_ht->ht_level; l > 0; --l) {
			if (LEVEL_SIZE(l) <= eaddr - vaddr &&
			    (vaddr & LEVEL_OFFSET(l)) == 0)
				break;
		}

		/*
		 * attempt to share the pagetable
		 *
		 * - only 4K pagetables are shared (ie. level == 0)
		 * - the hat_share() length must cover the whole pagetable
		 * - the shared address must align at level 1
		 * - a shared PTE for this address already exists OR
		 * - no page table for this address exists yet
		 */
		pt_vaddr =
		    vaddr_start + (ism_ht->ht_vaddr - ism_addr_start);
		if (ism_ht->ht_level == 0 &&
		    ism_ht->ht_vaddr + LEVEL_SIZE(1) <= e_ism_addr &&
		    (pt_vaddr & LEVEL_OFFSET(1)) == 0) {

			ht = htable_lookup(hat, pt_vaddr, 0);
			if (ht == NULL)
				ht = htable_create(hat, pt_vaddr, 0, ism_ht);

			if (ht->ht_level > 0 ||
			    !(ht->ht_flags & HTABLE_SHARED_PFN)) {

				htable_release(ht);

			} else {

				/*
				 * share the page table
				 */
				ASSERT(ht->ht_level == 0);
				ASSERT(ht->ht_shares == ism_ht);
				valid_cnt = ism_ht->ht_valid_cnt;
				atomic_add_long(&hat->hat_pages_mapped[0],
				    valid_cnt - ht->ht_valid_cnt);
				ht->ht_valid_cnt = valid_cnt;
				htable_release(ht);
				ism_addr = ism_ht->ht_vaddr + LEVEL_SIZE(1);
				htable_release(ism_ht);
				ism_ht = NULL;
				continue;
			}
		}

		/*
		 * Unable to share the page table. Instead we will
		 * create new mappings from the values in the ISM mappings.
		 *
		 * The ISM mapping might be larger than the share area,
		 * be careful to trunctate 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;

			/*
			 * XX64 -- can shm ever be written to swap?
			 * if not we could use HAT_NOSYNC here.
			 */
			hati_load_common(hat, vaddr, pp, prot,
			    HAT_LOAD, l, pfn);

			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);

	HATOUT(hat_share, hat, addr);
	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)
{
	uintptr_t	vaddr = (uintptr_t)addr;
	uintptr_t	eaddr = vaddr + len;
	htable_t	*ht = NULL;
	uint_t		need_demaps = 0;

	ASSERT(hat != kas.a_hat);
	ASSERT(eaddr <= kernelbase);
	HATIN(hat_unshare, hat, addr, len);
	ASSERT(IS_PAGEALIGNED(vaddr));
	ASSERT(IS_PAGEALIGNED(eaddr));

	/*
	 * First go through and remove any shared pagetables.
	 *
	 * Note that it's ok to delay the demap until the entire range is
	 * finished, because if hat_pageunload() were to unload a shared
	 * pagetable page, its hat_demap() will do a global user TLB invalidate.
	 */
	while (vaddr < eaddr) {
		ASSERT(!IN_VA_HOLE(vaddr));
		/*
		 * find the pagetable that would map the current address
		 */
		ht = htable_lookup(hat, vaddr, 0);
		if (ht != NULL) {
			if (ht->ht_flags & HTABLE_SHARED_PFN) {
				/*
				 * clear mapped pages count, set valid_cnt to 0
				 * and let htable_release() finish the job
				 */
				atomic_add_long(&hat->hat_pages_mapped[0],
				    -ht->ht_valid_cnt);
				ht->ht_valid_cnt = 0;
				need_demaps = 1;
			}
			htable_release(ht);
		}
		vaddr = (vaddr & LEVEL_MASK(1)) + LEVEL_SIZE(1);
	}

	/*
	 * 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_demap(hat, DEMAP_ALL_ADDR);

	/*
	 * Now go back and clean up any unaligned mappings that
	 * couldn't share pagetables.
	 */
	hat_unload(hat, addr, len, HAT_UNLOAD_UNMAP);

	HATOUT(hat_unshare, hat, addr);
}


/*
 * 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 stolem 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;

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;
		}
	}
}

/*
 * 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;

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

	if ((flag & P_MOD) != 0 && vp != NULL && IS_VMODSORT(vp)) {
		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 attributs
 *	then returns 0 if ALL atriibutes 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_invalidate_pfn(ht, entry, pfn, NULL);
	if (PTE2PFN(old_pte, ht->ht_level) != pfn) {
		panic("x86pte_invalidate_pfn() 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_NOSYNC) == 0)
		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;

#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)
					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);
		}
	}

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_NOSYNC) == 0)
			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);
			return (save_pp->p_nrm & nrmbits);
		}
	}
	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;
		}
	}
	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);
}

/*
 * 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);

	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);
	hat_switch(thd->t_procp->p_as->a_hat);
}

/*
 * 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)
{
	kpreempt_disable();

	hat_switch(hat);

	kpreempt_enable();
}

/*
 * 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.
 */
void *
hat_mempte_kern_setup(caddr_t addr, void *pt)
{
	uintptr_t	va = (uintptr_t)addr;
	htable_t	*ht;
	uint_t		entry;
	x86pte_t	oldpte;
	caddr_t		p = (caddr_t)pt;

	ASSERT(IS_PAGEALIGNED(va));
	ASSERT(!IN_VA_HOLE(va));
	ht = htable_getpte(kas.a_hat, va, &entry, &oldpte, 0);
	if (ht == NULL) {
		/*
		 * Note that we don't need a hat_reserves_exit() check
		 * for this htable_create(), since that'll be done by the
		 * hat_devload() just below.
		 */
		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, ht, entry, oldpte);

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

	/*
	 * now we need to map the page holding the pagetable for va into
	 * the kernel's address space.
	 */
	hat_devload(kas.a_hat, p, MMU_PAGESIZE, ht->ht_pfn,
	    PROT_READ | PROT_WRITE | HAT_NOSYNC | HAT_UNORDERED_OK,
	    HAT_LOAD | HAT_LOAD_NOCONSIST);

	/*
	 * return the PTE address to the caller.
	 */
	htable_release(ht);
	p += entry << mmu.pte_size_shift;
	return ((void *)p);
}

/*
 * Prepare for a CPU private mapping for the given address.
 */
void *
hat_mempte_setup(caddr_t addr)
{
	x86pte_t	*p;

	p = vmem_alloc(heap_arena, MMU_PAGESIZE, VM_SLEEP);
	return (hat_mempte_kern_setup(addr, p));
}

/*
 * Release a CPU private mapping for the given address.
 * We decrement the htable valid count so it might be destroyed.
 */
void
hat_mempte_release(caddr_t addr, void *pteptr)
{
	htable_t	*ht;
	uintptr_t	va = ALIGN2PAGE(pteptr);

	/*
	 * first invalidate any left over mapping and decrement the
	 * htable's mapping count
	 */
	if (mmu.pae_hat)
		*(x86pte_t *)pteptr = 0;
	else
		*(x86pte32_t *)pteptr = 0;
	mmu_tlbflush_entry(addr);
	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);

	/*
	 * now blow away the kernel mapping to the page table page
	 * XX64 -- see comment in hat_mempte_setup()
	 */
	hat_unload_callback(kas.a_hat, (caddr_t)va, MMU_PAGESIZE,
	    HAT_UNLOAD, NULL);
}

/*
 * 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,
	void *pteptr,
	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);
	htable_release(ht);
#endif
	pte = hati_mkpte(pfn, attr, 0, flags);
	if (mmu.pae_hat)
		*(x86pte_t *)pteptr = pte;
	else
		*(x86pte32_t *)pteptr = (x86pte32_t)pte;
	mmu_tlbflush_entry(addr);
}



/*
 * 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);
}


/*
 * Used by hat_kern_setup() to create initial kernel HAT mappings from
 * the boot loader's mappings.
 *
 * - size is either PAGESIZE or some multiple of a level one pagesize
 * - there may not be page_t's for every pfn. (ie. the nucleus pages)
 * - pfn's are continguous for the given va range (va to va + size * cnt)
 */
void
hati_kern_setup_load(
	uintptr_t va,	/* starting va of range to map */
	size_t size,	/* either PAGESIZE or multiple of large page size */
	pfn_t pfn,	/* starting PFN */
	pgcnt_t cnt,	/* number of mappings, (cnt * size) == total size */
	uint_t prot)	/* protections (PROT_READ, PROT_WRITE, PROT_EXEC) */
{
	level_t level = (size == MMU_PAGESIZE ? 0 : 1);
	size_t bytes = size * cnt;
	size_t pgsize = LEVEL_SIZE(level);
	page_t *pp;
	uint_t flags = HAT_LOAD;

	/*
	 * We're only going to throw away mappings below kernelbase or in
	 * boot's special double-mapping region, so set noconsist to avoid
	 * using hments
	 */
	if (BOOT_VA(va))
		flags |= HAT_LOAD_NOCONSIST;

	prot |= HAT_STORECACHING_OK;
	while (bytes != 0) {
		ASSERT(bytes >= pgsize);

		pp = NULL;
		if (pf_is_memory(pfn) && !BOOT_VA(va) && level == 0)
			pp = page_numtopp_nolock(pfn);

		hati_load_common(kas.a_hat, va, pp, prot, flags, level, pfn);

		va += pgsize;
		pfn += mmu_btop(pgsize);
		bytes -= pgsize;
	}
}

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

/*
 * 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 kernelbase.
	 */
	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_set(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);

	/*
	 * cross call for a complete invalidate.
	 */
	hat_demap(kas.a_hat, DEMAP_ALL_ADDR);
}

/*
 * Initialize a special area in the kernel that always holds some PTEs for
 * faster performance. This always holds segmap's PTEs.
 * In the 32 bit kernel this maps the kernel heap too.
 */
void
hat_kmap_init(uintptr_t base, size_t len)
{
	uintptr_t map_addr;	/* base rounded down to large page size */
	uintptr_t map_eaddr;	/* base + len rounded up */
	size_t map_len;
	caddr_t ptes;		/* mapping area in kernel as for ptes */
	size_t window_size;	/* size of mapping area for ptes */
	ulong_t htable_cnt;	/* # of page tables to cover map_len */
	ulong_t i;
	htable_t *ht;

	/*
	 * we have to map in an area that matches an entire page table
	 */
	map_addr = base & LEVEL_MASK(1);
	map_eaddr = (base + len + LEVEL_SIZE(1) - 1) & LEVEL_MASK(1);
	map_len = map_eaddr - map_addr;
	window_size = mmu_btop(map_len) * mmu.pte_size;
	htable_cnt = mmu_btop(map_len) / mmu.ptes_per_table;

	/*
	 * allocate vmem for the kmap_ptes
	 */
	ptes = vmem_xalloc(heap_arena, window_size, MMU_PAGESIZE, 0,
	    0, NULL, NULL, VM_SLEEP);
	mmu.kmap_htables =
	    kmem_alloc(htable_cnt * sizeof (htable_t *), KM_SLEEP);

	/*
	 * Map the page tables that cover kmap into the allocated range.
	 * Note we don't ever htable_release() the kmap page tables - they
	 * can't ever be stolen, freed, etc.
	 */
	for (i = 0; i < htable_cnt; ++i) {
		ht = htable_create(kas.a_hat, map_addr + i * LEVEL_SIZE(1),
		    0, NULL);
		mmu.kmap_htables[i] = ht;

		hat_devload(kas.a_hat, ptes + i * MMU_PAGESIZE, MMU_PAGESIZE,
		    ht->ht_pfn,
		    PROT_READ | PROT_WRITE | HAT_NOSYNC | HAT_UNORDERED_OK,
		    HAT_LOAD | HAT_LOAD_NOCONSIST);

	}

	/*
	 * set information in mmu to activate handling of kmap
	 */
	mmu.kmap_addr = base;
	mmu.kmap_eaddr = base + len;
	mmu.kmap_ptes =
	    (x86pte_t *)(ptes + mmu.pte_size * mmu_btop(base - map_addr));
}

/*
 * 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_NOSYNC | PT_NOCONSIST) &&
	    PTE_GET(expected, PT_MOD | PT_REF) &&
	    (PTE_GET(new, PT_NOSYNC) || !PTE_GET(new, PT_WRITABLE) ||
		!PTE_GET(new, PT_MOD | PT_REF))) {

		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);
}

/*
 * 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
}

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

	ASSERT(kpm_enable);

	vaddr = (uintptr_t)kpm_vbase + mmu_ptob(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", hat, vaddr);

	return (0);
}

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

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