KVM: MMU: dont hold pagecount reference for mapped sptes pages

[deliverable/linux.git] / arch / x86 / kvm / mmu.c

/*
 * Kernel-based Virtual Machine driver for Linux
 *
 * This module enables machines with Intel VT-x extensions to run virtual
 * machines without emulation or binary translation.
 *
 * MMU support
 *
 * Copyright (C) 2006 Qumranet, Inc.
 *
 * Authors:
 *   Yaniv Kamay  <yaniv@qumranet.com>
 *   Avi Kivity   <avi@qumranet.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 */

#include "mmu.h"
#include "kvm_cache_regs.h"

#include <linux/kvm_host.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/module.h>
#include <linux/swap.h>
#include <linux/hugetlb.h>
#include <linux/compiler.h>

#include <asm/page.h>
#include <asm/cmpxchg.h>
#include <asm/io.h>
#include <asm/vmx.h>

/*
 * When setting this variable to true it enables Two-Dimensional-Paging
 * where the hardware walks 2 page tables:
 * 1. the guest-virtual to guest-physical
 * 2. while doing 1. it walks guest-physical to host-physical
 * If the hardware supports that we don't need to do shadow paging.
 */
bool tdp_enabled = false;

#undef MMU_DEBUG

#undef AUDIT

#ifdef AUDIT
static void kvm_mmu_audit(struct kvm_vcpu *vcpu, const char *msg);
#else
static void kvm_mmu_audit(struct kvm_vcpu *vcpu, const char *msg) {}
#endif

#ifdef MMU_DEBUG

#define pgprintk(x...) do { if (dbg) printk(x); } while (0)
#define rmap_printk(x...) do { if (dbg) printk(x); } while (0)

#else

#define pgprintk(x...) do { } while (0)
#define rmap_printk(x...) do { } while (0)

#endif

#if defined(MMU_DEBUG) || defined(AUDIT)
static int dbg = 0;
module_param(dbg, bool, 0644);
#endif

static int oos_shadow = 1;
module_param(oos_shadow, bool, 0644);

#ifndef MMU_DEBUG
#define ASSERT(x) do { } while (0)
#else
#define ASSERT(x)                                                       \
        if (!(x)) {                                                     \
                printk(KERN_WARNING "assertion failed %s:%d: %s\n",     \
                       __FILE__, __LINE__, #x);                         \
        }
#endif

#define PT_FIRST_AVAIL_BITS_SHIFT 9
#define PT64_SECOND_AVAIL_BITS_SHIFT 52

#define VALID_PAGE(x) ((x) != INVALID_PAGE)

#define PT64_LEVEL_BITS 9

#define PT64_LEVEL_SHIFT(level) \
                (PAGE_SHIFT + (level - 1) * PT64_LEVEL_BITS)

#define PT64_LEVEL_MASK(level) \
                (((1ULL << PT64_LEVEL_BITS) - 1) << PT64_LEVEL_SHIFT(level))

#define PT64_INDEX(address, level)\
        (((address) >> PT64_LEVEL_SHIFT(level)) & ((1 << PT64_LEVEL_BITS) - 1))


#define PT32_LEVEL_BITS 10

#define PT32_LEVEL_SHIFT(level) \
                (PAGE_SHIFT + (level - 1) * PT32_LEVEL_BITS)

#define PT32_LEVEL_MASK(level) \
                (((1ULL << PT32_LEVEL_BITS) - 1) << PT32_LEVEL_SHIFT(level))
#define PT32_LVL_OFFSET_MASK(level) \
        (PT32_BASE_ADDR_MASK & ((1ULL << (PAGE_SHIFT + (((level) - 1) \
                                                * PT32_LEVEL_BITS))) - 1))

#define PT32_INDEX(address, level)\
        (((address) >> PT32_LEVEL_SHIFT(level)) & ((1 << PT32_LEVEL_BITS) - 1))


#define PT64_BASE_ADDR_MASK (((1ULL << 52) - 1) & ~(u64)(PAGE_SIZE-1))
#define PT64_DIR_BASE_ADDR_MASK \
        (PT64_BASE_ADDR_MASK & ~((1ULL << (PAGE_SHIFT + PT64_LEVEL_BITS)) - 1))
#define PT64_LVL_ADDR_MASK(level) \
        (PT64_BASE_ADDR_MASK & ~((1ULL << (PAGE_SHIFT + (((level) - 1) \
                                                * PT64_LEVEL_BITS))) - 1))
#define PT64_LVL_OFFSET_MASK(level) \
        (PT64_BASE_ADDR_MASK & ((1ULL << (PAGE_SHIFT + (((level) - 1) \
                                                * PT64_LEVEL_BITS))) - 1))

#define PT32_BASE_ADDR_MASK PAGE_MASK
#define PT32_DIR_BASE_ADDR_MASK \
        (PAGE_MASK & ~((1ULL << (PAGE_SHIFT + PT32_LEVEL_BITS)) - 1))
#define PT32_LVL_ADDR_MASK(level) \
        (PAGE_MASK & ~((1ULL << (PAGE_SHIFT + (((level) - 1) \
                                            * PT32_LEVEL_BITS))) - 1))

#define PT64_PERM_MASK (PT_PRESENT_MASK | PT_WRITABLE_MASK | PT_USER_MASK \
                        | PT64_NX_MASK)

#define PFERR_PRESENT_MASK (1U << 0)
#define PFERR_WRITE_MASK (1U << 1)
#define PFERR_USER_MASK (1U << 2)
#define PFERR_RSVD_MASK (1U << 3)
#define PFERR_FETCH_MASK (1U << 4)

#define PT_PDPE_LEVEL 3
#define PT_DIRECTORY_LEVEL 2
#define PT_PAGE_TABLE_LEVEL 1

#define RMAP_EXT 4

#define ACC_EXEC_MASK    1
#define ACC_WRITE_MASK   PT_WRITABLE_MASK
#define ACC_USER_MASK    PT_USER_MASK
#define ACC_ALL          (ACC_EXEC_MASK | ACC_WRITE_MASK | ACC_USER_MASK)

#define CREATE_TRACE_POINTS
#include "mmutrace.h"

#define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)

struct kvm_rmap_desc {
        u64 *sptes[RMAP_EXT];
        struct kvm_rmap_desc *more;
};

struct kvm_shadow_walk_iterator {
        u64 addr;
        hpa_t shadow_addr;
        int level;
        u64 *sptep;
        unsigned index;
};

#define for_each_shadow_entry(_vcpu, _addr, _walker)    \
        for (shadow_walk_init(&(_walker), _vcpu, _addr);        \
             shadow_walk_okay(&(_walker));                      \
             shadow_walk_next(&(_walker)))


struct kvm_unsync_walk {
        int (*entry) (struct kvm_mmu_page *sp, struct kvm_unsync_walk *walk);
};

typedef int (*mmu_parent_walk_fn) (struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp);

static struct kmem_cache *pte_chain_cache;
static struct kmem_cache *rmap_desc_cache;
static struct kmem_cache *mmu_page_header_cache;

static u64 __read_mostly shadow_trap_nonpresent_pte;
static u64 __read_mostly shadow_notrap_nonpresent_pte;
static u64 __read_mostly shadow_base_present_pte;
static u64 __read_mostly shadow_nx_mask;
static u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
static u64 __read_mostly shadow_user_mask;
static u64 __read_mostly shadow_accessed_mask;
static u64 __read_mostly shadow_dirty_mask;

static inline u64 rsvd_bits(int s, int e)
{
        return ((1ULL << (e - s + 1)) - 1) << s;
}

void kvm_mmu_set_nonpresent_ptes(u64 trap_pte, u64 notrap_pte)
{
        shadow_trap_nonpresent_pte = trap_pte;
        shadow_notrap_nonpresent_pte = notrap_pte;
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_nonpresent_ptes);

void kvm_mmu_set_base_ptes(u64 base_pte)
{
        shadow_base_present_pte = base_pte;
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_base_ptes);

void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
                u64 dirty_mask, u64 nx_mask, u64 x_mask)
{
        shadow_user_mask = user_mask;
        shadow_accessed_mask = accessed_mask;
        shadow_dirty_mask = dirty_mask;
        shadow_nx_mask = nx_mask;
        shadow_x_mask = x_mask;
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes);

static int is_write_protection(struct kvm_vcpu *vcpu)
{
        return vcpu->arch.cr0 & X86_CR0_WP;
}

static int is_cpuid_PSE36(void)
{
        return 1;
}

static int is_nx(struct kvm_vcpu *vcpu)
{
        return vcpu->arch.shadow_efer & EFER_NX;
}

static int is_shadow_present_pte(u64 pte)
{
        return pte != shadow_trap_nonpresent_pte
                && pte != shadow_notrap_nonpresent_pte;
}

static int is_large_pte(u64 pte)
{
        return pte & PT_PAGE_SIZE_MASK;
}

static int is_writeble_pte(unsigned long pte)
{
        return pte & PT_WRITABLE_MASK;
}

static int is_dirty_gpte(unsigned long pte)
{
        return pte & PT_DIRTY_MASK;
}

static int is_rmap_spte(u64 pte)
{
        return is_shadow_present_pte(pte);
}

static int is_last_spte(u64 pte, int level)
{
        if (level == PT_PAGE_TABLE_LEVEL)
                return 1;
        if (is_large_pte(pte))
                return 1;
        return 0;
}

static pfn_t spte_to_pfn(u64 pte)
{
        return (pte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
}

static gfn_t pse36_gfn_delta(u32 gpte)
{
        int shift = 32 - PT32_DIR_PSE36_SHIFT - PAGE_SHIFT;

        return (gpte & PT32_DIR_PSE36_MASK) << shift;
}

static void __set_spte(u64 *sptep, u64 spte)
{
#ifdef CONFIG_X86_64
        set_64bit((unsigned long *)sptep, spte);
#else
        set_64bit((unsigned long long *)sptep, spte);
#endif
}

static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
                                  struct kmem_cache *base_cache, int min)
{
        void *obj;

        if (cache->nobjs >= min)
                return 0;
        while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
                obj = kmem_cache_zalloc(base_cache, GFP_KERNEL);
                if (!obj)
                        return -ENOMEM;
                cache->objects[cache->nobjs++] = obj;
        }
        return 0;
}

static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc)
{
        while (mc->nobjs)
                kfree(mc->objects[--mc->nobjs]);
}

static int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache,
                                       int min)
{
        struct page *page;

        if (cache->nobjs >= min)
                return 0;
        while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
                page = alloc_page(GFP_KERNEL);
                if (!page)
                        return -ENOMEM;
                set_page_private(page, 0);
                cache->objects[cache->nobjs++] = page_address(page);
        }
        return 0;
}

static void mmu_free_memory_cache_page(struct kvm_mmu_memory_cache *mc)
{
        while (mc->nobjs)
                free_page((unsigned long)mc->objects[--mc->nobjs]);
}

static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
{
        int r;

        r = mmu_topup_memory_cache(&vcpu->arch.mmu_pte_chain_cache,
                                   pte_chain_cache, 4);
        if (r)
                goto out;
        r = mmu_topup_memory_cache(&vcpu->arch.mmu_rmap_desc_cache,
                                   rmap_desc_cache, 4);
        if (r)
                goto out;
        r = mmu_topup_memory_cache_page(&vcpu->arch.mmu_page_cache, 8);
        if (r)
                goto out;
        r = mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
                                   mmu_page_header_cache, 4);
out:
        return r;
}

static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
{
        mmu_free_memory_cache(&vcpu->arch.mmu_pte_chain_cache);
        mmu_free_memory_cache(&vcpu->arch.mmu_rmap_desc_cache);
        mmu_free_memory_cache_page(&vcpu->arch.mmu_page_cache);
        mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache);
}

static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc,
                                    size_t size)
{
        void *p;

        BUG_ON(!mc->nobjs);
        p = mc->objects[--mc->nobjs];
        return p;
}

static struct kvm_pte_chain *mmu_alloc_pte_chain(struct kvm_vcpu *vcpu)
{
        return mmu_memory_cache_alloc(&vcpu->arch.mmu_pte_chain_cache,
                                      sizeof(struct kvm_pte_chain));
}

static void mmu_free_pte_chain(struct kvm_pte_chain *pc)
{
        kfree(pc);
}

static struct kvm_rmap_desc *mmu_alloc_rmap_desc(struct kvm_vcpu *vcpu)
{
        return mmu_memory_cache_alloc(&vcpu->arch.mmu_rmap_desc_cache,
                                      sizeof(struct kvm_rmap_desc));
}

static void mmu_free_rmap_desc(struct kvm_rmap_desc *rd)
{
        kfree(rd);
}

/*
 * Return the pointer to the largepage write count for a given
 * gfn, handling slots that are not large page aligned.
 */
static int *slot_largepage_idx(gfn_t gfn,
                               struct kvm_memory_slot *slot,
                               int level)
{
        unsigned long idx;

        idx = (gfn / KVM_PAGES_PER_HPAGE(level)) -
              (slot->base_gfn / KVM_PAGES_PER_HPAGE(level));
        return &slot->lpage_info[level - 2][idx].write_count;
}

static void account_shadowed(struct kvm *kvm, gfn_t gfn)
{
        struct kvm_memory_slot *slot;
        int *write_count;
        int i;

        gfn = unalias_gfn(kvm, gfn);

        slot = gfn_to_memslot_unaliased(kvm, gfn);
        for (i = PT_DIRECTORY_LEVEL;
             i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
                write_count   = slot_largepage_idx(gfn, slot, i);
                *write_count += 1;
        }
}

static void unaccount_shadowed(struct kvm *kvm, gfn_t gfn)
{
        struct kvm_memory_slot *slot;
        int *write_count;
        int i;

        gfn = unalias_gfn(kvm, gfn);
        for (i = PT_DIRECTORY_LEVEL;
             i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
                slot          = gfn_to_memslot_unaliased(kvm, gfn);
                write_count   = slot_largepage_idx(gfn, slot, i);
                *write_count -= 1;
                WARN_ON(*write_count < 0);
        }
}

static int has_wrprotected_page(struct kvm *kvm,
                                gfn_t gfn,
                                int level)
{
        struct kvm_memory_slot *slot;
        int *largepage_idx;

        gfn = unalias_gfn(kvm, gfn);
        slot = gfn_to_memslot_unaliased(kvm, gfn);
        if (slot) {
                largepage_idx = slot_largepage_idx(gfn, slot, level);
                return *largepage_idx;
        }

        return 1;
}

static int host_mapping_level(struct kvm *kvm, gfn_t gfn)
{
        unsigned long page_size = PAGE_SIZE;
        struct vm_area_struct *vma;
        unsigned long addr;
        int i, ret = 0;

        addr = gfn_to_hva(kvm, gfn);
        if (kvm_is_error_hva(addr))
                return page_size;

        down_read(&current->mm->mmap_sem);
        vma = find_vma(current->mm, addr);
        if (!vma)
                goto out;

        page_size = vma_kernel_pagesize(vma);

out:
        up_read(&current->mm->mmap_sem);

        for (i = PT_PAGE_TABLE_LEVEL;
             i < (PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES); ++i) {
                if (page_size >= KVM_HPAGE_SIZE(i))
                        ret = i;
                else
                        break;
        }

        return ret;
}

static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn)
{
        struct kvm_memory_slot *slot;
        int host_level;
        int level = PT_PAGE_TABLE_LEVEL;

        slot = gfn_to_memslot(vcpu->kvm, large_gfn);
        if (slot && slot->dirty_bitmap)
                return PT_PAGE_TABLE_LEVEL;

        host_level = host_mapping_level(vcpu->kvm, large_gfn);

        if (host_level == PT_PAGE_TABLE_LEVEL)
                return host_level;

        for (level = PT_DIRECTORY_LEVEL; level <= host_level; ++level) {

                if (has_wrprotected_page(vcpu->kvm, large_gfn, level))
                        break;
        }

        return level - 1;
}

/*
 * Take gfn and return the reverse mapping to it.
 * Note: gfn must be unaliased before this function get called
 */

static unsigned long *gfn_to_rmap(struct kvm *kvm, gfn_t gfn, int level)
{
        struct kvm_memory_slot *slot;
        unsigned long idx;

        slot = gfn_to_memslot(kvm, gfn);
        if (likely(level == PT_PAGE_TABLE_LEVEL))
                return &slot->rmap[gfn - slot->base_gfn];

        idx = (gfn / KVM_PAGES_PER_HPAGE(level)) -
                (slot->base_gfn / KVM_PAGES_PER_HPAGE(level));

        return &slot->lpage_info[level - 2][idx].rmap_pde;
}

/*
 * Reverse mapping data structures:
 *
 * If rmapp bit zero is zero, then rmapp point to the shadw page table entry
 * that points to page_address(page).
 *
 * If rmapp bit zero is one, (then rmap & ~1) points to a struct kvm_rmap_desc
 * containing more mappings.
 *
 * Returns the number of rmap entries before the spte was added or zero if
 * the spte was not added.
 *
 */
static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
{
        struct kvm_mmu_page *sp;
        struct kvm_rmap_desc *desc;
        unsigned long *rmapp;
        int i, count = 0;

        if (!is_rmap_spte(*spte))
                return count;
        gfn = unalias_gfn(vcpu->kvm, gfn);
        sp = page_header(__pa(spte));
        sp->gfns[spte - sp->spt] = gfn;
        rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level);
        if (!*rmapp) {
                rmap_printk("rmap_add: %p %llx 0->1\n", spte, *spte);
                *rmapp = (unsigned long)spte;
        } else if (!(*rmapp & 1)) {
                rmap_printk("rmap_add: %p %llx 1->many\n", spte, *spte);
                desc = mmu_alloc_rmap_desc(vcpu);
                desc->sptes[0] = (u64 *)*rmapp;
                desc->sptes[1] = spte;
                *rmapp = (unsigned long)desc | 1;
        } else {
                rmap_printk("rmap_add: %p %llx many->many\n", spte, *spte);
                desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
                while (desc->sptes[RMAP_EXT-1] && desc->more) {
                        desc = desc->more;
                        count += RMAP_EXT;
                }
                if (desc->sptes[RMAP_EXT-1]) {
                        desc->more = mmu_alloc_rmap_desc(vcpu);
                        desc = desc->more;
                }
                for (i = 0; desc->sptes[i]; ++i)
                        ;
                desc->sptes[i] = spte;
        }
        return count;
}

static void rmap_desc_remove_entry(unsigned long *rmapp,
                                   struct kvm_rmap_desc *desc,
                                   int i,
                                   struct kvm_rmap_desc *prev_desc)
{
        int j;

        for (j = RMAP_EXT - 1; !desc->sptes[j] && j > i; --j)
                ;
        desc->sptes[i] = desc->sptes[j];
        desc->sptes[j] = NULL;
        if (j != 0)
                return;
        if (!prev_desc && !desc->more)
                *rmapp = (unsigned long)desc->sptes[0];
        else
                if (prev_desc)
                        prev_desc->more = desc->more;
                else
                        *rmapp = (unsigned long)desc->more | 1;
        mmu_free_rmap_desc(desc);
}

static void rmap_remove(struct kvm *kvm, u64 *spte)
{
        struct kvm_rmap_desc *desc;
        struct kvm_rmap_desc *prev_desc;
        struct kvm_mmu_page *sp;
        pfn_t pfn;
        unsigned long *rmapp;
        int i;

        if (!is_rmap_spte(*spte))
                return;
        sp = page_header(__pa(spte));
        pfn = spte_to_pfn(*spte);
        if (*spte & shadow_accessed_mask)
                kvm_set_pfn_accessed(pfn);
        if (is_writeble_pte(*spte))
                kvm_set_pfn_dirty(pfn);
        rmapp = gfn_to_rmap(kvm, sp->gfns[spte - sp->spt], sp->role.level);
        if (!*rmapp) {
                printk(KERN_ERR "rmap_remove: %p %llx 0->BUG\n", spte, *spte);
                BUG();
        } else if (!(*rmapp & 1)) {
                rmap_printk("rmap_remove:  %p %llx 1->0\n", spte, *spte);
                if ((u64 *)*rmapp != spte) {
                        printk(KERN_ERR "rmap_remove:  %p %llx 1->BUG\n",
                               spte, *spte);
                        BUG();
                }
                *rmapp = 0;
        } else {
                rmap_printk("rmap_remove:  %p %llx many->many\n", spte, *spte);
                desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
                prev_desc = NULL;
                while (desc) {
                        for (i = 0; i < RMAP_EXT && desc->sptes[i]; ++i)
                                if (desc->sptes[i] == spte) {
                                        rmap_desc_remove_entry(rmapp,
                                                               desc, i,
                                                               prev_desc);
                                        return;
                                }
                        prev_desc = desc;
                        desc = desc->more;
                }
                BUG();
        }
}

static u64 *rmap_next(struct kvm *kvm, unsigned long *rmapp, u64 *spte)
{
        struct kvm_rmap_desc *desc;
        struct kvm_rmap_desc *prev_desc;
        u64 *prev_spte;
        int i;

        if (!*rmapp)
                return NULL;
        else if (!(*rmapp & 1)) {
                if (!spte)
                        return (u64 *)*rmapp;
                return NULL;
        }
        desc = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
        prev_desc = NULL;
        prev_spte = NULL;
        while (desc) {
                for (i = 0; i < RMAP_EXT && desc->sptes[i]; ++i) {
                        if (prev_spte == spte)
                                return desc->sptes[i];
                        prev_spte = desc->sptes[i];
                }
                desc = desc->more;
        }
        return NULL;
}

static int rmap_write_protect(struct kvm *kvm, u64 gfn)
{
        unsigned long *rmapp;
        u64 *spte;
        int i, write_protected = 0;

        gfn = unalias_gfn(kvm, gfn);
        rmapp = gfn_to_rmap(kvm, gfn, PT_PAGE_TABLE_LEVEL);

        spte = rmap_next(kvm, rmapp, NULL);
        while (spte) {
                BUG_ON(!spte);
                BUG_ON(!(*spte & PT_PRESENT_MASK));
                rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
                if (is_writeble_pte(*spte)) {
                        __set_spte(spte, *spte & ~PT_WRITABLE_MASK);
                        write_protected = 1;
                }
                spte = rmap_next(kvm, rmapp, spte);
        }
        if (write_protected) {
                pfn_t pfn;

                spte = rmap_next(kvm, rmapp, NULL);
                pfn = spte_to_pfn(*spte);
                kvm_set_pfn_dirty(pfn);
        }

        /* check for huge page mappings */
        for (i = PT_DIRECTORY_LEVEL;
             i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
                rmapp = gfn_to_rmap(kvm, gfn, i);
                spte = rmap_next(kvm, rmapp, NULL);
                while (spte) {
                        BUG_ON(!spte);
                        BUG_ON(!(*spte & PT_PRESENT_MASK));
                        BUG_ON((*spte & (PT_PAGE_SIZE_MASK|PT_PRESENT_MASK)) != (PT_PAGE_SIZE_MASK|PT_PRESENT_MASK));
                        pgprintk("rmap_write_protect(large): spte %p %llx %lld\n", spte, *spte, gfn);
                        if (is_writeble_pte(*spte)) {
                                rmap_remove(kvm, spte);
                                --kvm->stat.lpages;
                                __set_spte(spte, shadow_trap_nonpresent_pte);
                                spte = NULL;
                                write_protected = 1;
                        }
                        spte = rmap_next(kvm, rmapp, spte);
                }
        }

        return write_protected;
}

static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp)
{
        u64 *spte;
        int need_tlb_flush = 0;

        while ((spte = rmap_next(kvm, rmapp, NULL))) {
                BUG_ON(!(*spte & PT_PRESENT_MASK));
                rmap_printk("kvm_rmap_unmap_hva: spte %p %llx\n", spte, *spte);
                rmap_remove(kvm, spte);
                __set_spte(spte, shadow_trap_nonpresent_pte);
                need_tlb_flush = 1;
        }
        return need_tlb_flush;
}

static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
                          int (*handler)(struct kvm *kvm, unsigned long *rmapp))
{
        int i, j;
        int retval = 0;

        /*
         * If mmap_sem isn't taken, we can look the memslots with only
         * the mmu_lock by skipping over the slots with userspace_addr == 0.
         */
        for (i = 0; i < kvm->nmemslots; i++) {
                struct kvm_memory_slot *memslot = &kvm->memslots[i];
                unsigned long start = memslot->userspace_addr;
                unsigned long end;

                /* mmu_lock protects userspace_addr */
                if (!start)
                        continue;

                end = start + (memslot->npages << PAGE_SHIFT);
                if (hva >= start && hva < end) {
                        gfn_t gfn_offset = (hva - start) >> PAGE_SHIFT;

                        retval |= handler(kvm, &memslot->rmap[gfn_offset]);

                        for (j = 0; j < KVM_NR_PAGE_SIZES - 1; ++j) {
                                int idx = gfn_offset;
                                idx /= KVM_PAGES_PER_HPAGE(PT_DIRECTORY_LEVEL + j);
                                retval |= handler(kvm,
                                        &memslot->lpage_info[j][idx].rmap_pde);
                        }
                }
        }

        return retval;
}

int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
{
        return kvm_handle_hva(kvm, hva, kvm_unmap_rmapp);
}

static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp)
{
        u64 *spte;
        int young = 0;

        /* always return old for EPT */
        if (!shadow_accessed_mask)
                return 0;

        spte = rmap_next(kvm, rmapp, NULL);
        while (spte) {
                int _young;
                u64 _spte = *spte;
                BUG_ON(!(_spte & PT_PRESENT_MASK));
                _young = _spte & PT_ACCESSED_MASK;
                if (_young) {
                        young = 1;
                        clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte);
                }
                spte = rmap_next(kvm, rmapp, spte);
        }
        return young;
}

#define RMAP_RECYCLE_THRESHOLD 1000

static void rmap_recycle(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
{
        unsigned long *rmapp;
        struct kvm_mmu_page *sp;

        sp = page_header(__pa(spte));

        gfn = unalias_gfn(vcpu->kvm, gfn);
        rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level);

        kvm_unmap_rmapp(vcpu->kvm, rmapp);
        kvm_flush_remote_tlbs(vcpu->kvm);
}

int kvm_age_hva(struct kvm *kvm, unsigned long hva)
{
        return kvm_handle_hva(kvm, hva, kvm_age_rmapp);
}

#ifdef MMU_DEBUG
static int is_empty_shadow_page(u64 *spt)
{
        u64 *pos;
        u64 *end;

        for (pos = spt, end = pos + PAGE_SIZE / sizeof(u64); pos != end; pos++)
                if (is_shadow_present_pte(*pos)) {
                        printk(KERN_ERR "%s: %p %llx\n", __func__,
                               pos, *pos);
                        return 0;
                }
        return 1;
}
#endif

static void kvm_mmu_free_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        ASSERT(is_empty_shadow_page(sp->spt));
        list_del(&sp->link);
        __free_page(virt_to_page(sp->spt));
        __free_page(virt_to_page(sp->gfns));
        kfree(sp);
        ++kvm->arch.n_free_mmu_pages;
}

static unsigned kvm_page_table_hashfn(gfn_t gfn)
{
        return gfn & ((1 << KVM_MMU_HASH_SHIFT) - 1);
}

static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
                                               u64 *parent_pte)
{
        struct kvm_mmu_page *sp;

        sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache, sizeof *sp);
        sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache, PAGE_SIZE);
        sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache, PAGE_SIZE);
        set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
        list_add(&sp->link, &vcpu->kvm->arch.active_mmu_pages);
        INIT_LIST_HEAD(&sp->oos_link);
        bitmap_zero(sp->slot_bitmap, KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS);
        sp->multimapped = 0;
        sp->parent_pte = parent_pte;
        --vcpu->kvm->arch.n_free_mmu_pages;
        return sp;
}

static void mmu_page_add_parent_pte(struct kvm_vcpu *vcpu,
                                    struct kvm_mmu_page *sp, u64 *parent_pte)
{
        struct kvm_pte_chain *pte_chain;
        struct hlist_node *node;
        int i;

        if (!parent_pte)
                return;
        if (!sp->multimapped) {
                u64 *old = sp->parent_pte;

                if (!old) {
                        sp->parent_pte = parent_pte;
                        return;
                }
                sp->multimapped = 1;
                pte_chain = mmu_alloc_pte_chain(vcpu);
                INIT_HLIST_HEAD(&sp->parent_ptes);
                hlist_add_head(&pte_chain->link, &sp->parent_ptes);
                pte_chain->parent_ptes[0] = old;
        }
        hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link) {
                if (pte_chain->parent_ptes[NR_PTE_CHAIN_ENTRIES-1])
                        continue;
                for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i)
                        if (!pte_chain->parent_ptes[i]) {
                                pte_chain->parent_ptes[i] = parent_pte;
                                return;
                        }
        }
        pte_chain = mmu_alloc_pte_chain(vcpu);
        BUG_ON(!pte_chain);
        hlist_add_head(&pte_chain->link, &sp->parent_ptes);
        pte_chain->parent_ptes[0] = parent_pte;
}

static void mmu_page_remove_parent_pte(struct kvm_mmu_page *sp,
                                       u64 *parent_pte)
{
        struct kvm_pte_chain *pte_chain;
        struct hlist_node *node;
        int i;

        if (!sp->multimapped) {
                BUG_ON(sp->parent_pte != parent_pte);
                sp->parent_pte = NULL;
                return;
        }
        hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
                for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
                        if (!pte_chain->parent_ptes[i])
                                break;
                        if (pte_chain->parent_ptes[i] != parent_pte)
                                continue;
                        while (i + 1 < NR_PTE_CHAIN_ENTRIES
                                && pte_chain->parent_ptes[i + 1]) {
                                pte_chain->parent_ptes[i]
                                        = pte_chain->parent_ptes[i + 1];
                                ++i;
                        }
                        pte_chain->parent_ptes[i] = NULL;
                        if (i == 0) {
                                hlist_del(&pte_chain->link);
                                mmu_free_pte_chain(pte_chain);
                                if (hlist_empty(&sp->parent_ptes)) {
                                        sp->multimapped = 0;
                                        sp->parent_pte = NULL;
                                }
                        }
                        return;
                }
        BUG();
}


static void mmu_parent_walk(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
                            mmu_parent_walk_fn fn)
{
        struct kvm_pte_chain *pte_chain;
        struct hlist_node *node;
        struct kvm_mmu_page *parent_sp;
        int i;

        if (!sp->multimapped && sp->parent_pte) {
                parent_sp = page_header(__pa(sp->parent_pte));
                fn(vcpu, parent_sp);
                mmu_parent_walk(vcpu, parent_sp, fn);
                return;
        }
        hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
                for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
                        if (!pte_chain->parent_ptes[i])
                                break;
                        parent_sp = page_header(__pa(pte_chain->parent_ptes[i]));
                        fn(vcpu, parent_sp);
                        mmu_parent_walk(vcpu, parent_sp, fn);
                }
}

static void kvm_mmu_update_unsync_bitmap(u64 *spte)
{
        unsigned int index;
        struct kvm_mmu_page *sp = page_header(__pa(spte));

        index = spte - sp->spt;
        if (!__test_and_set_bit(index, sp->unsync_child_bitmap))
                sp->unsync_children++;
        WARN_ON(!sp->unsync_children);
}

static void kvm_mmu_update_parents_unsync(struct kvm_mmu_page *sp)
{
        struct kvm_pte_chain *pte_chain;
        struct hlist_node *node;
        int i;

        if (!sp->parent_pte)
                return;

        if (!sp->multimapped) {
                kvm_mmu_update_unsync_bitmap(sp->parent_pte);
                return;
        }

        hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
                for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
                        if (!pte_chain->parent_ptes[i])
                                break;
                        kvm_mmu_update_unsync_bitmap(pte_chain->parent_ptes[i]);
                }
}

static int unsync_walk_fn(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
        kvm_mmu_update_parents_unsync(sp);
        return 1;
}

static void kvm_mmu_mark_parents_unsync(struct kvm_vcpu *vcpu,
                                        struct kvm_mmu_page *sp)
{
        mmu_parent_walk(vcpu, sp, unsync_walk_fn);
        kvm_mmu_update_parents_unsync(sp);
}

static void nonpaging_prefetch_page(struct kvm_vcpu *vcpu,
                                    struct kvm_mmu_page *sp)
{
        int i;

        for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
                sp->spt[i] = shadow_trap_nonpresent_pte;
}

static int nonpaging_sync_page(struct kvm_vcpu *vcpu,
                               struct kvm_mmu_page *sp)
{
        return 1;
}

static void nonpaging_invlpg(struct kvm_vcpu *vcpu, gva_t gva)
{
}

#define KVM_PAGE_ARRAY_NR 16

struct kvm_mmu_pages {
        struct mmu_page_and_offset {
                struct kvm_mmu_page *sp;
                unsigned int idx;
        } page[KVM_PAGE_ARRAY_NR];
        unsigned int nr;
};

#define for_each_unsync_children(bitmap, idx)           \
        for (idx = find_first_bit(bitmap, 512);         \
             idx < 512;                                 \
             idx = find_next_bit(bitmap, 512, idx+1))

static int mmu_pages_add(struct kvm_mmu_pages *pvec, struct kvm_mmu_page *sp,
                         int idx)
{
        int i;

        if (sp->unsync)
                for (i=0; i < pvec->nr; i++)
                        if (pvec->page[i].sp == sp)
                                return 0;

        pvec->page[pvec->nr].sp = sp;
        pvec->page[pvec->nr].idx = idx;
        pvec->nr++;
        return (pvec->nr == KVM_PAGE_ARRAY_NR);
}

static int __mmu_unsync_walk(struct kvm_mmu_page *sp,
                           struct kvm_mmu_pages *pvec)
{
        int i, ret, nr_unsync_leaf = 0;

        for_each_unsync_children(sp->unsync_child_bitmap, i) {
                u64 ent = sp->spt[i];

                if (is_shadow_present_pte(ent) && !is_large_pte(ent)) {
                        struct kvm_mmu_page *child;
                        child = page_header(ent & PT64_BASE_ADDR_MASK);

                        if (child->unsync_children) {
                                if (mmu_pages_add(pvec, child, i))
                                        return -ENOSPC;

                                ret = __mmu_unsync_walk(child, pvec);
                                if (!ret)
                                        __clear_bit(i, sp->unsync_child_bitmap);
                                else if (ret > 0)
                                        nr_unsync_leaf += ret;
                                else
                                        return ret;
                        }

                        if (child->unsync) {
                                nr_unsync_leaf++;
                                if (mmu_pages_add(pvec, child, i))
                                        return -ENOSPC;
                        }
                }
        }

        if (find_first_bit(sp->unsync_child_bitmap, 512) == 512)
                sp->unsync_children = 0;

        return nr_unsync_leaf;
}

static int mmu_unsync_walk(struct kvm_mmu_page *sp,
                           struct kvm_mmu_pages *pvec)
{
        if (!sp->unsync_children)
                return 0;

        mmu_pages_add(pvec, sp, 0);
        return __mmu_unsync_walk(sp, pvec);
}

static struct kvm_mmu_page *kvm_mmu_lookup_page(struct kvm *kvm, gfn_t gfn)
{
        unsigned index;
        struct hlist_head *bucket;
        struct kvm_mmu_page *sp;
        struct hlist_node *node;

        pgprintk("%s: looking for gfn %lx\n", __func__, gfn);
        index = kvm_page_table_hashfn(gfn);
        bucket = &kvm->arch.mmu_page_hash[index];
        hlist_for_each_entry(sp, node, bucket, hash_link)
                if (sp->gfn == gfn && !sp->role.direct
                    && !sp->role.invalid) {
                        pgprintk("%s: found role %x\n",
                                 __func__, sp->role.word);
                        return sp;
                }
        return NULL;
}

static void kvm_unlink_unsync_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        WARN_ON(!sp->unsync);
        sp->unsync = 0;
        --kvm->stat.mmu_unsync;
}

static int kvm_mmu_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp);

static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
        if (sp->role.glevels != vcpu->arch.mmu.root_level) {
                kvm_mmu_zap_page(vcpu->kvm, sp);
                return 1;
        }

        trace_kvm_mmu_sync_page(sp);
        if (rmap_write_protect(vcpu->kvm, sp->gfn))
                kvm_flush_remote_tlbs(vcpu->kvm);
        kvm_unlink_unsync_page(vcpu->kvm, sp);
        if (vcpu->arch.mmu.sync_page(vcpu, sp)) {
                kvm_mmu_zap_page(vcpu->kvm, sp);
                return 1;
        }

        kvm_mmu_flush_tlb(vcpu);
        return 0;
}

struct mmu_page_path {
        struct kvm_mmu_page *parent[PT64_ROOT_LEVEL-1];
        unsigned int idx[PT64_ROOT_LEVEL-1];
};

#define for_each_sp(pvec, sp, parents, i)                       \
                for (i = mmu_pages_next(&pvec, &parents, -1),   \
                        sp = pvec.page[i].sp;                   \
                        i < pvec.nr && ({ sp = pvec.page[i].sp; 1;});   \
                        i = mmu_pages_next(&pvec, &parents, i))

static int mmu_pages_next(struct kvm_mmu_pages *pvec,
                          struct mmu_page_path *parents,
                          int i)
{
        int n;

        for (n = i+1; n < pvec->nr; n++) {
                struct kvm_mmu_page *sp = pvec->page[n].sp;

                if (sp->role.level == PT_PAGE_TABLE_LEVEL) {
                        parents->idx[0] = pvec->page[n].idx;
                        return n;
                }

                parents->parent[sp->role.level-2] = sp;
                parents->idx[sp->role.level-1] = pvec->page[n].idx;
        }

        return n;
}

static void mmu_pages_clear_parents(struct mmu_page_path *parents)
{
        struct kvm_mmu_page *sp;
        unsigned int level = 0;

        do {
                unsigned int idx = parents->idx[level];

                sp = parents->parent[level];
                if (!sp)
                        return;

                --sp->unsync_children;
                WARN_ON((int)sp->unsync_children < 0);
                __clear_bit(idx, sp->unsync_child_bitmap);
                level++;
        } while (level < PT64_ROOT_LEVEL-1 && !sp->unsync_children);
}

static void kvm_mmu_pages_init(struct kvm_mmu_page *parent,
                               struct mmu_page_path *parents,
                               struct kvm_mmu_pages *pvec)
{
        parents->parent[parent->role.level-1] = NULL;
        pvec->nr = 0;
}

static void mmu_sync_children(struct kvm_vcpu *vcpu,
                              struct kvm_mmu_page *parent)
{
        int i;
        struct kvm_mmu_page *sp;
        struct mmu_page_path parents;
        struct kvm_mmu_pages pages;

        kvm_mmu_pages_init(parent, &parents, &pages);
        while (mmu_unsync_walk(parent, &pages)) {
                int protected = 0;

                for_each_sp(pages, sp, parents, i)
                        protected |= rmap_write_protect(vcpu->kvm, sp->gfn);

                if (protected)
                        kvm_flush_remote_tlbs(vcpu->kvm);

                for_each_sp(pages, sp, parents, i) {
                        kvm_sync_page(vcpu, sp);
                        mmu_pages_clear_parents(&parents);
                }
                cond_resched_lock(&vcpu->kvm->mmu_lock);
                kvm_mmu_pages_init(parent, &parents, &pages);
        }
}

static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
                                             gfn_t gfn,
                                             gva_t gaddr,
                                             unsigned level,
                                             int direct,
                                             unsigned access,
                                             u64 *parent_pte)
{
        union kvm_mmu_page_role role;
        unsigned index;
        unsigned quadrant;
        struct hlist_head *bucket;
        struct kvm_mmu_page *sp;
        struct hlist_node *node, *tmp;

        role = vcpu->arch.mmu.base_role;
        role.level = level;
        role.direct = direct;
        role.access = access;
        if (vcpu->arch.mmu.root_level <= PT32_ROOT_LEVEL) {
                quadrant = gaddr >> (PAGE_SHIFT + (PT64_PT_BITS * level));
                quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1;
                role.quadrant = quadrant;
        }
        index = kvm_page_table_hashfn(gfn);
        bucket = &vcpu->kvm->arch.mmu_page_hash[index];
        hlist_for_each_entry_safe(sp, node, tmp, bucket, hash_link)
                if (sp->gfn == gfn) {
                        if (sp->unsync)
                                if (kvm_sync_page(vcpu, sp))
                                        continue;

                        if (sp->role.word != role.word)
                                continue;

                        mmu_page_add_parent_pte(vcpu, sp, parent_pte);
                        if (sp->unsync_children) {
                                set_bit(KVM_REQ_MMU_SYNC, &vcpu->requests);
                                kvm_mmu_mark_parents_unsync(vcpu, sp);
                        }
                        trace_kvm_mmu_get_page(sp, false);
                        return sp;
                }
        ++vcpu->kvm->stat.mmu_cache_miss;
        sp = kvm_mmu_alloc_page(vcpu, parent_pte);
        if (!sp)
                return sp;
        sp->gfn = gfn;
        sp->role = role;
        hlist_add_head(&sp->hash_link, bucket);
        if (!direct) {
                if (rmap_write_protect(vcpu->kvm, gfn))
                        kvm_flush_remote_tlbs(vcpu->kvm);
                account_shadowed(vcpu->kvm, gfn);
        }
        if (shadow_trap_nonpresent_pte != shadow_notrap_nonpresent_pte)
                vcpu->arch.mmu.prefetch_page(vcpu, sp);
        else
                nonpaging_prefetch_page(vcpu, sp);
        trace_kvm_mmu_get_page(sp, true);
        return sp;
}

static void shadow_walk_init(struct kvm_shadow_walk_iterator *iterator,
                             struct kvm_vcpu *vcpu, u64 addr)
{
        iterator->addr = addr;
        iterator->shadow_addr = vcpu->arch.mmu.root_hpa;
        iterator->level = vcpu->arch.mmu.shadow_root_level;
        if (iterator->level == PT32E_ROOT_LEVEL) {
                iterator->shadow_addr
                        = vcpu->arch.mmu.pae_root[(addr >> 30) & 3];
                iterator->shadow_addr &= PT64_BASE_ADDR_MASK;
                --iterator->level;
                if (!iterator->shadow_addr)
                        iterator->level = 0;
        }
}

static bool shadow_walk_okay(struct kvm_shadow_walk_iterator *iterator)
{
        if (iterator->level < PT_PAGE_TABLE_LEVEL)
                return false;

        if (iterator->level == PT_PAGE_TABLE_LEVEL)
                if (is_large_pte(*iterator->sptep))
                        return false;

        iterator->index = SHADOW_PT_INDEX(iterator->addr, iterator->level);
        iterator->sptep = ((u64 *)__va(iterator->shadow_addr)) + iterator->index;
        return true;
}

static void shadow_walk_next(struct kvm_shadow_walk_iterator *iterator)
{
        iterator->shadow_addr = *iterator->sptep & PT64_BASE_ADDR_MASK;
        --iterator->level;
}

static void kvm_mmu_page_unlink_children(struct kvm *kvm,
                                         struct kvm_mmu_page *sp)
{
        unsigned i;
        u64 *pt;
        u64 ent;

        pt = sp->spt;

        for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
                ent = pt[i];

                if (is_shadow_present_pte(ent)) {
                        if (!is_last_spte(ent, sp->role.level)) {
                                ent &= PT64_BASE_ADDR_MASK;
                                mmu_page_remove_parent_pte(page_header(ent),
                                                           &pt[i]);
                        } else {
                                if (is_large_pte(ent))
                                        --kvm->stat.lpages;
                                rmap_remove(kvm, &pt[i]);
                        }
                }
                pt[i] = shadow_trap_nonpresent_pte;
        }
}

static void kvm_mmu_put_page(struct kvm_mmu_page *sp, u64 *parent_pte)
{
        mmu_page_remove_parent_pte(sp, parent_pte);
}

static void kvm_mmu_reset_last_pte_updated(struct kvm *kvm)
{
        int i;
        struct kvm_vcpu *vcpu;

        kvm_for_each_vcpu(i, vcpu, kvm)
                vcpu->arch.last_pte_updated = NULL;
}

static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        u64 *parent_pte;

        while (sp->multimapped || sp->parent_pte) {
                if (!sp->multimapped)
                        parent_pte = sp->parent_pte;
                else {
                        struct kvm_pte_chain *chain;

                        chain = container_of(sp->parent_ptes.first,
                                             struct kvm_pte_chain, link);
                        parent_pte = chain->parent_ptes[0];
                }
                BUG_ON(!parent_pte);
                kvm_mmu_put_page(sp, parent_pte);
                __set_spte(parent_pte, shadow_trap_nonpresent_pte);
        }
}

static int mmu_zap_unsync_children(struct kvm *kvm,
                                   struct kvm_mmu_page *parent)
{
        int i, zapped = 0;
        struct mmu_page_path parents;
        struct kvm_mmu_pages pages;

        if (parent->role.level == PT_PAGE_TABLE_LEVEL)
                return 0;

        kvm_mmu_pages_init(parent, &parents, &pages);
        while (mmu_unsync_walk(parent, &pages)) {
                struct kvm_mmu_page *sp;

                for_each_sp(pages, sp, parents, i) {
                        kvm_mmu_zap_page(kvm, sp);
                        mmu_pages_clear_parents(&parents);
                }
                zapped += pages.nr;
                kvm_mmu_pages_init(parent, &parents, &pages);
        }

        return zapped;
}

static int kvm_mmu_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        int ret;

        trace_kvm_mmu_zap_page(sp);
        ++kvm->stat.mmu_shadow_zapped;
        ret = mmu_zap_unsync_children(kvm, sp);
        kvm_mmu_page_unlink_children(kvm, sp);
        kvm_mmu_unlink_parents(kvm, sp);
        kvm_flush_remote_tlbs(kvm);
        if (!sp->role.invalid && !sp->role.direct)
                unaccount_shadowed(kvm, sp->gfn);
        if (sp->unsync)
                kvm_unlink_unsync_page(kvm, sp);
        if (!sp->root_count) {
                hlist_del(&sp->hash_link);
                kvm_mmu_free_page(kvm, sp);
        } else {
                sp->role.invalid = 1;
                list_move(&sp->link, &kvm->arch.active_mmu_pages);
                kvm_reload_remote_mmus(kvm);
        }
        kvm_mmu_reset_last_pte_updated(kvm);
        return ret;
}

/*
 * Changing the number of mmu pages allocated to the vm
 * Note: if kvm_nr_mmu_pages is too small, you will get dead lock
 */
void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages)
{
        int used_pages;

        used_pages = kvm->arch.n_alloc_mmu_pages - kvm->arch.n_free_mmu_pages;
        used_pages = max(0, used_pages);

        /*
         * If we set the number of mmu pages to be smaller be than the
         * number of actived pages , we must to free some mmu pages before we
         * change the value
         */

        if (used_pages > kvm_nr_mmu_pages) {
                while (used_pages > kvm_nr_mmu_pages) {
                        struct kvm_mmu_page *page;

                        page = container_of(kvm->arch.active_mmu_pages.prev,
                                            struct kvm_mmu_page, link);
                        kvm_mmu_zap_page(kvm, page);
                        used_pages--;
                }
                kvm->arch.n_free_mmu_pages = 0;
        }
        else
                kvm->arch.n_free_mmu_pages += kvm_nr_mmu_pages
                                         - kvm->arch.n_alloc_mmu_pages;

        kvm->arch.n_alloc_mmu_pages = kvm_nr_mmu_pages;
}

static int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn)
{
        unsigned index;
        struct hlist_head *bucket;
        struct kvm_mmu_page *sp;
        struct hlist_node *node, *n;
        int r;

        pgprintk("%s: looking for gfn %lx\n", __func__, gfn);
        r = 0;
        index = kvm_page_table_hashfn(gfn);
        bucket = &kvm->arch.mmu_page_hash[index];
        hlist_for_each_entry_safe(sp, node, n, bucket, hash_link)
                if (sp->gfn == gfn && !sp->role.direct) {
                        pgprintk("%s: gfn %lx role %x\n", __func__, gfn,
                                 sp->role.word);
                        r = 1;
                        if (kvm_mmu_zap_page(kvm, sp))
                                n = bucket->first;
                }
        return r;
}

static void mmu_unshadow(struct kvm *kvm, gfn_t gfn)
{
        unsigned index;
        struct hlist_head *bucket;
        struct kvm_mmu_page *sp;
        struct hlist_node *node, *nn;

        index = kvm_page_table_hashfn(gfn);
        bucket = &kvm->arch.mmu_page_hash[index];
        hlist_for_each_entry_safe(sp, node, nn, bucket, hash_link) {
                if (sp->gfn == gfn && !sp->role.direct
                    && !sp->role.invalid) {
                        pgprintk("%s: zap %lx %x\n",
                                 __func__, gfn, sp->role.word);
                        kvm_mmu_zap_page(kvm, sp);
                }
        }
}

static void page_header_update_slot(struct kvm *kvm, void *pte, gfn_t gfn)
{
        int slot = memslot_id(kvm, gfn_to_memslot(kvm, gfn));
        struct kvm_mmu_page *sp = page_header(__pa(pte));

        __set_bit(slot, sp->slot_bitmap);
}

static void mmu_convert_notrap(struct kvm_mmu_page *sp)
{
        int i;
        u64 *pt = sp->spt;

        if (shadow_trap_nonpresent_pte == shadow_notrap_nonpresent_pte)
                return;

        for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
                if (pt[i] == shadow_notrap_nonpresent_pte)
                        __set_spte(&pt[i], shadow_trap_nonpresent_pte);
        }
}

struct page *gva_to_page(struct kvm_vcpu *vcpu, gva_t gva)
{
        struct page *page;

        gpa_t gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, gva);

        if (gpa == UNMAPPED_GVA)
                return NULL;

        page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);

        return page;
}

/*
 * The function is based on mtrr_type_lookup() in
 * arch/x86/kernel/cpu/mtrr/generic.c
 */
static int get_mtrr_type(struct mtrr_state_type *mtrr_state,
                         u64 start, u64 end)
{
        int i;
        u64 base, mask;
        u8 prev_match, curr_match;
        int num_var_ranges = KVM_NR_VAR_MTRR;

        if (!mtrr_state->enabled)
                return 0xFF;

        /* Make end inclusive end, instead of exclusive */
        end--;

        /* Look in fixed ranges. Just return the type as per start */
        if (mtrr_state->have_fixed && (start < 0x100000)) {
                int idx;

                if (start < 0x80000) {
                        idx = 0;
                        idx += (start >> 16);
                        return mtrr_state->fixed_ranges[idx];
                } else if (start < 0xC0000) {
                        idx = 1 * 8;
                        idx += ((start - 0x80000) >> 14);
                        return mtrr_state->fixed_ranges[idx];
                } else if (start < 0x1000000) {
                        idx = 3 * 8;
                        idx += ((start - 0xC0000) >> 12);
                        return mtrr_state->fixed_ranges[idx];
                }
        }

        /*
         * Look in variable ranges
         * Look of multiple ranges matching this address and pick type
         * as per MTRR precedence
         */
        if (!(mtrr_state->enabled & 2))
                return mtrr_state->def_type;

        prev_match = 0xFF;
        for (i = 0; i < num_var_ranges; ++i) {
                unsigned short start_state, end_state;

                if (!(mtrr_state->var_ranges[i].mask_lo & (1 << 11)))
                        continue;

                base = (((u64)mtrr_state->var_ranges[i].base_hi) << 32) +
                       (mtrr_state->var_ranges[i].base_lo & PAGE_MASK);
                mask = (((u64)mtrr_state->var_ranges[i].mask_hi) << 32) +
                       (mtrr_state->var_ranges[i].mask_lo & PAGE_MASK);

                start_state = ((start & mask) == (base & mask));
                end_state = ((end & mask) == (base & mask));
                if (start_state != end_state)
                        return 0xFE;

                if ((start & mask) != (base & mask))
                        continue;

                curr_match = mtrr_state->var_ranges[i].base_lo & 0xff;
                if (prev_match == 0xFF) {
                        prev_match = curr_match;
                        continue;
                }

                if (prev_match == MTRR_TYPE_UNCACHABLE ||
                    curr_match == MTRR_TYPE_UNCACHABLE)
                        return MTRR_TYPE_UNCACHABLE;

                if ((prev_match == MTRR_TYPE_WRBACK &&
                     curr_match == MTRR_TYPE_WRTHROUGH) ||
                    (prev_match == MTRR_TYPE_WRTHROUGH &&
                     curr_match == MTRR_TYPE_WRBACK)) {
                        prev_match = MTRR_TYPE_WRTHROUGH;
                        curr_match = MTRR_TYPE_WRTHROUGH;
                }

                if (prev_match != curr_match)
                        return MTRR_TYPE_UNCACHABLE;
        }

        if (prev_match != 0xFF)
                return prev_match;

        return mtrr_state->def_type;
}

u8 kvm_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        u8 mtrr;

        mtrr = get_mtrr_type(&vcpu->arch.mtrr_state, gfn << PAGE_SHIFT,
                             (gfn << PAGE_SHIFT) + PAGE_SIZE);
        if (mtrr == 0xfe || mtrr == 0xff)
                mtrr = MTRR_TYPE_WRBACK;
        return mtrr;
}
EXPORT_SYMBOL_GPL(kvm_get_guest_memory_type);

static int kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
        unsigned index;
        struct hlist_head *bucket;
        struct kvm_mmu_page *s;
        struct hlist_node *node, *n;

        trace_kvm_mmu_unsync_page(sp);
        index = kvm_page_table_hashfn(sp->gfn);
        bucket = &vcpu->kvm->arch.mmu_page_hash[index];
        /* don't unsync if pagetable is shadowed with multiple roles */
        hlist_for_each_entry_safe(s, node, n, bucket, hash_link) {
                if (s->gfn != sp->gfn || s->role.direct)
                        continue;
                if (s->role.word != sp->role.word)
                        return 1;
        }
        ++vcpu->kvm->stat.mmu_unsync;
        sp->unsync = 1;

        kvm_mmu_mark_parents_unsync(vcpu, sp);

        mmu_convert_notrap(sp);
        return 0;
}

static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
                                  bool can_unsync)
{
        struct kvm_mmu_page *shadow;

        shadow = kvm_mmu_lookup_page(vcpu->kvm, gfn);
        if (shadow) {
                if (shadow->role.level != PT_PAGE_TABLE_LEVEL)
                        return 1;
                if (shadow->unsync)
                        return 0;
                if (can_unsync && oos_shadow)
                        return kvm_unsync_page(vcpu, shadow);
                return 1;
        }
        return 0;
}

static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                    unsigned pte_access, int user_fault,
                    int write_fault, int dirty, int level,
                    gfn_t gfn, pfn_t pfn, bool speculative,
                    bool can_unsync)
{
        u64 spte;
        int ret = 0;

        /*
         * We don't set the accessed bit, since we sometimes want to see
         * whether the guest actually used the pte (in order to detect
         * demand paging).
         */
        spte = shadow_base_present_pte | shadow_dirty_mask;
        if (!speculative)
                spte |= shadow_accessed_mask;
        if (!dirty)
                pte_access &= ~ACC_WRITE_MASK;
        if (pte_access & ACC_EXEC_MASK)
                spte |= shadow_x_mask;
        else
                spte |= shadow_nx_mask;
        if (pte_access & ACC_USER_MASK)
                spte |= shadow_user_mask;
        if (level > PT_PAGE_TABLE_LEVEL)
                spte |= PT_PAGE_SIZE_MASK;
        if (tdp_enabled)
                spte |= kvm_x86_ops->get_mt_mask(vcpu, gfn,
                        kvm_is_mmio_pfn(pfn));

        spte |= (u64)pfn << PAGE_SHIFT;

        if ((pte_access & ACC_WRITE_MASK)
            || (write_fault && !is_write_protection(vcpu) && !user_fault)) {

                if (level > PT_PAGE_TABLE_LEVEL &&
                    has_wrprotected_page(vcpu->kvm, gfn, level)) {
                        ret = 1;
                        spte = shadow_trap_nonpresent_pte;
                        goto set_pte;
                }

                spte |= PT_WRITABLE_MASK;

                /*
                 * Optimization: for pte sync, if spte was writable the hash
                 * lookup is unnecessary (and expensive). Write protection
                 * is responsibility of mmu_get_page / kvm_sync_page.
                 * Same reasoning can be applied to dirty page accounting.
                 */
                if (!can_unsync && is_writeble_pte(*sptep))
                        goto set_pte;

                if (mmu_need_write_protect(vcpu, gfn, can_unsync)) {
                        pgprintk("%s: found shadow page for %lx, marking ro\n",
                                 __func__, gfn);
                        ret = 1;
                        pte_access &= ~ACC_WRITE_MASK;
                        if (is_writeble_pte(spte))
                                spte &= ~PT_WRITABLE_MASK;
                }
        }

        if (pte_access & ACC_WRITE_MASK)
                mark_page_dirty(vcpu->kvm, gfn);

set_pte:
        __set_spte(sptep, spte);
        return ret;
}

static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                         unsigned pt_access, unsigned pte_access,
                         int user_fault, int write_fault, int dirty,
                         int *ptwrite, int level, gfn_t gfn,
                         pfn_t pfn, bool speculative)
{
        int was_rmapped = 0;
        int was_writeble = is_writeble_pte(*sptep);
        int rmap_count;

        pgprintk("%s: spte %llx access %x write_fault %d"
                 " user_fault %d gfn %lx\n",
                 __func__, *sptep, pt_access,
                 write_fault, user_fault, gfn);

        if (is_rmap_spte(*sptep)) {
                /*
                 * If we overwrite a PTE page pointer with a 2MB PMD, unlink
                 * the parent of the now unreachable PTE.
                 */
                if (level > PT_PAGE_TABLE_LEVEL &&
                    !is_large_pte(*sptep)) {
                        struct kvm_mmu_page *child;
                        u64 pte = *sptep;

                        child = page_header(pte & PT64_BASE_ADDR_MASK);
                        mmu_page_remove_parent_pte(child, sptep);
                } else if (pfn != spte_to_pfn(*sptep)) {
                        pgprintk("hfn old %lx new %lx\n",
                                 spte_to_pfn(*sptep), pfn);
                        rmap_remove(vcpu->kvm, sptep);
                } else
                        was_rmapped = 1;
        }

        if (set_spte(vcpu, sptep, pte_access, user_fault, write_fault,
                      dirty, level, gfn, pfn, speculative, true)) {
                if (write_fault)
                        *ptwrite = 1;
                kvm_x86_ops->tlb_flush(vcpu);
        }

        pgprintk("%s: setting spte %llx\n", __func__, *sptep);
        pgprintk("instantiating %s PTE (%s) at %ld (%llx) addr %p\n",
                 is_large_pte(*sptep)? "2MB" : "4kB",
                 *sptep & PT_PRESENT_MASK ?"RW":"R", gfn,
                 *sptep, sptep);
        if (!was_rmapped && is_large_pte(*sptep))
                ++vcpu->kvm->stat.lpages;

        page_header_update_slot(vcpu->kvm, sptep, gfn);
        if (!was_rmapped) {
                rmap_count = rmap_add(vcpu, sptep, gfn);
                kvm_release_pfn_clean(pfn);
                if (rmap_count > RMAP_RECYCLE_THRESHOLD)
                        rmap_recycle(vcpu, sptep, gfn);
        } else {
                if (was_writeble)
                        kvm_release_pfn_dirty(pfn);
                else
                        kvm_release_pfn_clean(pfn);
        }
        if (speculative) {
                vcpu->arch.last_pte_updated = sptep;
                vcpu->arch.last_pte_gfn = gfn;
        }
}

static void nonpaging_new_cr3(struct kvm_vcpu *vcpu)
{
}

static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
                        int level, gfn_t gfn, pfn_t pfn)
{
        struct kvm_shadow_walk_iterator iterator;
        struct kvm_mmu_page *sp;
        int pt_write = 0;
        gfn_t pseudo_gfn;

        for_each_shadow_entry(vcpu, (u64)gfn << PAGE_SHIFT, iterator) {
                if (iterator.level == level) {
                        mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, ACC_ALL,
                                     0, write, 1, &pt_write,
                                     level, gfn, pfn, false);
                        ++vcpu->stat.pf_fixed;
                        break;
                }

                if (*iterator.sptep == shadow_trap_nonpresent_pte) {
                        pseudo_gfn = (iterator.addr & PT64_DIR_BASE_ADDR_MASK) >> PAGE_SHIFT;
                        sp = kvm_mmu_get_page(vcpu, pseudo_gfn, iterator.addr,
                                              iterator.level - 1,
                                              1, ACC_ALL, iterator.sptep);
                        if (!sp) {
                                pgprintk("nonpaging_map: ENOMEM\n");
                                kvm_release_pfn_clean(pfn);
                                return -ENOMEM;
                        }

                        __set_spte(iterator.sptep,
                                   __pa(sp->spt)
                                   | PT_PRESENT_MASK | PT_WRITABLE_MASK
                                   | shadow_user_mask | shadow_x_mask);
                }
        }
        return pt_write;
}

static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn)
{
        int r;
        int level;
        pfn_t pfn;
        unsigned long mmu_seq;

        level = mapping_level(vcpu, gfn);

        /*
         * This path builds a PAE pagetable - so we can map 2mb pages at
         * maximum. Therefore check if the level is larger than that.
         */
        if (level > PT_DIRECTORY_LEVEL)
                level = PT_DIRECTORY_LEVEL;

        gfn &= ~(KVM_PAGES_PER_HPAGE(level) - 1);

        mmu_seq = vcpu->kvm->mmu_notifier_seq;
        smp_rmb();
        pfn = gfn_to_pfn(vcpu->kvm, gfn);

        /* mmio */
        if (is_error_pfn(pfn)) {
                kvm_release_pfn_clean(pfn);
                return 1;
        }

        spin_lock(&vcpu->kvm->mmu_lock);
        if (mmu_notifier_retry(vcpu, mmu_seq))
                goto out_unlock;
        kvm_mmu_free_some_pages(vcpu);
        r = __direct_map(vcpu, v, write, level, gfn, pfn);
        spin_unlock(&vcpu->kvm->mmu_lock);


        return r;

out_unlock:
        spin_unlock(&vcpu->kvm->mmu_lock);
        kvm_release_pfn_clean(pfn);
        return 0;
}


static void mmu_free_roots(struct kvm_vcpu *vcpu)
{
        int i;
        struct kvm_mmu_page *sp;

        if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
                return;
        spin_lock(&vcpu->kvm->mmu_lock);
        if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_LEVEL) {
                hpa_t root = vcpu->arch.mmu.root_hpa;

                sp = page_header(root);
                --sp->root_count;
                if (!sp->root_count && sp->role.invalid)
                        kvm_mmu_zap_page(vcpu->kvm, sp);
                vcpu->arch.mmu.root_hpa = INVALID_PAGE;
                spin_unlock(&vcpu->kvm->mmu_lock);
                return;
        }
        for (i = 0; i < 4; ++i) {
                hpa_t root = vcpu->arch.mmu.pae_root[i];

                if (root) {
                        root &= PT64_BASE_ADDR_MASK;
                        sp = page_header(root);
                        --sp->root_count;
                        if (!sp->root_count && sp->role.invalid)
                                kvm_mmu_zap_page(vcpu->kvm, sp);
                }
                vcpu->arch.mmu.pae_root[i] = INVALID_PAGE;
        }
        spin_unlock(&vcpu->kvm->mmu_lock);
        vcpu->arch.mmu.root_hpa = INVALID_PAGE;
}

static int mmu_check_root(struct kvm_vcpu *vcpu, gfn_t root_gfn)
{
        int ret = 0;

        if (!kvm_is_visible_gfn(vcpu->kvm, root_gfn)) {
                set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
                ret = 1;
        }

        return ret;
}

static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
{
        int i;
        gfn_t root_gfn;
        struct kvm_mmu_page *sp;
        int direct = 0;
        u64 pdptr;

        root_gfn = vcpu->arch.cr3 >> PAGE_SHIFT;

        if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_LEVEL) {
                hpa_t root = vcpu->arch.mmu.root_hpa;

                ASSERT(!VALID_PAGE(root));
                if (tdp_enabled)
                        direct = 1;
                if (mmu_check_root(vcpu, root_gfn))
                        return 1;
                sp = kvm_mmu_get_page(vcpu, root_gfn, 0,
                                      PT64_ROOT_LEVEL, direct,
                                      ACC_ALL, NULL);
                root = __pa(sp->spt);
                ++sp->root_count;
                vcpu->arch.mmu.root_hpa = root;
                return 0;
        }
        direct = !is_paging(vcpu);
        if (tdp_enabled)
                direct = 1;
        for (i = 0; i < 4; ++i) {
                hpa_t root = vcpu->arch.mmu.pae_root[i];

                ASSERT(!VALID_PAGE(root));
                if (vcpu->arch.mmu.root_level == PT32E_ROOT_LEVEL) {
                        pdptr = kvm_pdptr_read(vcpu, i);
                        if (!is_present_gpte(pdptr)) {
                                vcpu->arch.mmu.pae_root[i] = 0;
                                continue;
                        }
                        root_gfn = pdptr >> PAGE_SHIFT;
                } else if (vcpu->arch.mmu.root_level == 0)
                        root_gfn = 0;
                if (mmu_check_root(vcpu, root_gfn))
                        return 1;
                sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30,
                                      PT32_ROOT_LEVEL, direct,
                                      ACC_ALL, NULL);
                root = __pa(sp->spt);
                ++sp->root_count;
                vcpu->arch.mmu.pae_root[i] = root | PT_PRESENT_MASK;
        }
        vcpu->arch.mmu.root_hpa = __pa(vcpu->arch.mmu.pae_root);
        return 0;
}

static void mmu_sync_roots(struct kvm_vcpu *vcpu)
{
        int i;
        struct kvm_mmu_page *sp;

        if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
                return;
        if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_LEVEL) {
                hpa_t root = vcpu->arch.mmu.root_hpa;
                sp = page_header(root);
                mmu_sync_children(vcpu, sp);
                return;
        }
        for (i = 0; i < 4; ++i) {
                hpa_t root = vcpu->arch.mmu.pae_root[i];

                if (root && VALID_PAGE(root)) {
                        root &= PT64_BASE_ADDR_MASK;
                        sp = page_header(root);
                        mmu_sync_children(vcpu, sp);
                }
        }
}

void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
{
        spin_lock(&vcpu->kvm->mmu_lock);
        mmu_sync_roots(vcpu);
        spin_unlock(&vcpu->kvm->mmu_lock);
}

static gpa_t nonpaging_gva_to_gpa(struct kvm_vcpu *vcpu, gva_t vaddr)
{
        return vaddr;
}

static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
                                u32 error_code)
{
        gfn_t gfn;
        int r;

        pgprintk("%s: gva %lx error %x\n", __func__, gva, error_code);
        r = mmu_topup_memory_caches(vcpu);
        if (r)
                return r;

        ASSERT(vcpu);
        ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa));

        gfn = gva >> PAGE_SHIFT;

        return nonpaging_map(vcpu, gva & PAGE_MASK,
                             error_code & PFERR_WRITE_MASK, gfn);
}

static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
                                u32 error_code)
{
        pfn_t pfn;
        int r;
        int level;
        gfn_t gfn = gpa >> PAGE_SHIFT;
        unsigned long mmu_seq;

        ASSERT(vcpu);
        ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa));

        r = mmu_topup_memory_caches(vcpu);
        if (r)
                return r;

        level = mapping_level(vcpu, gfn);

        gfn &= ~(KVM_PAGES_PER_HPAGE(level) - 1);

        mmu_seq = vcpu->kvm->mmu_notifier_seq;
        smp_rmb();
        pfn = gfn_to_pfn(vcpu->kvm, gfn);
        if (is_error_pfn(pfn)) {
                kvm_release_pfn_clean(pfn);
                return 1;
        }
        spin_lock(&vcpu->kvm->mmu_lock);
        if (mmu_notifier_retry(vcpu, mmu_seq))
                goto out_unlock;
        kvm_mmu_free_some_pages(vcpu);
        r = __direct_map(vcpu, gpa, error_code & PFERR_WRITE_MASK,
                         level, gfn, pfn);
        spin_unlock(&vcpu->kvm->mmu_lock);

        return r;

out_unlock:
        spin_unlock(&vcpu->kvm->mmu_lock);
        kvm_release_pfn_clean(pfn);
        return 0;
}

static void nonpaging_free(struct kvm_vcpu *vcpu)
{
        mmu_free_roots(vcpu);
}

static int nonpaging_init_context(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu *context = &vcpu->arch.mmu;

        context->new_cr3 = nonpaging_new_cr3;
        context->page_fault = nonpaging_page_fault;
        context->gva_to_gpa = nonpaging_gva_to_gpa;
        context->free = nonpaging_free;
        context->prefetch_page = nonpaging_prefetch_page;
        context->sync_page = nonpaging_sync_page;
        context->invlpg = nonpaging_invlpg;
        context->root_level = 0;
        context->shadow_root_level = PT32E_ROOT_LEVEL;
        context->root_hpa = INVALID_PAGE;
        return 0;
}

void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu)
{
        ++vcpu->stat.tlb_flush;
        kvm_x86_ops->tlb_flush(vcpu);
}

static void paging_new_cr3(struct kvm_vcpu *vcpu)
{
        pgprintk("%s: cr3 %lx\n", __func__, vcpu->arch.cr3);
        mmu_free_roots(vcpu);
}

static void inject_page_fault(struct kvm_vcpu *vcpu,
                              u64 addr,
                              u32 err_code)
{
        kvm_inject_page_fault(vcpu, addr, err_code);
}

static void paging_free(struct kvm_vcpu *vcpu)
{
        nonpaging_free(vcpu);
}

static bool is_rsvd_bits_set(struct kvm_vcpu *vcpu, u64 gpte, int level)
{
        int bit7;

        bit7 = (gpte >> 7) & 1;
        return (gpte & vcpu->arch.mmu.rsvd_bits_mask[bit7][level-1]) != 0;
}

#define PTTYPE 64
#include "paging_tmpl.h"
#undef PTTYPE

#define PTTYPE 32
#include "paging_tmpl.h"
#undef PTTYPE

static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu, int level)
{
        struct kvm_mmu *context = &vcpu->arch.mmu;
        int maxphyaddr = cpuid_maxphyaddr(vcpu);
        u64 exb_bit_rsvd = 0;

        if (!is_nx(vcpu))
                exb_bit_rsvd = rsvd_bits(63, 63);
        switch (level) {
        case PT32_ROOT_LEVEL:
                /* no rsvd bits for 2 level 4K page table entries */
                context->rsvd_bits_mask[0][1] = 0;
                context->rsvd_bits_mask[0][0] = 0;
                if (is_cpuid_PSE36())
                        /* 36bits PSE 4MB page */
                        context->rsvd_bits_mask[1][1] = rsvd_bits(17, 21);
                else
                        /* 32 bits PSE 4MB page */
                        context->rsvd_bits_mask[1][1] = rsvd_bits(13, 21);
                context->rsvd_bits_mask[1][0] = context->rsvd_bits_mask[1][0];
                break;
        case PT32E_ROOT_LEVEL:
                context->rsvd_bits_mask[0][2] =
                        rsvd_bits(maxphyaddr, 63) |
                        rsvd_bits(7, 8) | rsvd_bits(1, 2);      /* PDPTE */
                context->rsvd_bits_mask[0][1] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 62);      /* PDE */
                context->rsvd_bits_mask[0][0] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 62);      /* PTE */
                context->rsvd_bits_mask[1][1] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 62) |
                        rsvd_bits(13, 20);              /* large page */
                context->rsvd_bits_mask[1][0] = context->rsvd_bits_mask[1][0];
                break;
        case PT64_ROOT_LEVEL:
                context->rsvd_bits_mask[0][3] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
                context->rsvd_bits_mask[0][2] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
                context->rsvd_bits_mask[0][1] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51);
                context->rsvd_bits_mask[0][0] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51);
                context->rsvd_bits_mask[1][3] = context->rsvd_bits_mask[0][3];
                context->rsvd_bits_mask[1][2] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51) |
                        rsvd_bits(13, 29);
                context->rsvd_bits_mask[1][1] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51) |
                        rsvd_bits(13, 20);              /* large page */
                context->rsvd_bits_mask[1][0] = context->rsvd_bits_mask[1][0];
                break;
        }
}

static int paging64_init_context_common(struct kvm_vcpu *vcpu, int level)
{
        struct kvm_mmu *context = &vcpu->arch.mmu;

        ASSERT(is_pae(vcpu));
        context->new_cr3 = paging_new_cr3;
        context->page_fault = paging64_page_fault;
        context->gva_to_gpa = paging64_gva_to_gpa;
        context->prefetch_page = paging64_prefetch_page;
        context->sync_page = paging64_sync_page;
        context->invlpg = paging64_invlpg;
        context->free = paging_free;
        context->root_level = level;
        context->shadow_root_level = level;
        context->root_hpa = INVALID_PAGE;
        return 0;
}

static int paging64_init_context(struct kvm_vcpu *vcpu)
{
        reset_rsvds_bits_mask(vcpu, PT64_ROOT_LEVEL);
        return paging64_init_context_common(vcpu, PT64_ROOT_LEVEL);
}

static int paging32_init_context(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu *context = &vcpu->arch.mmu;

        reset_rsvds_bits_mask(vcpu, PT32_ROOT_LEVEL);
        context->new_cr3 = paging_new_cr3;
        context->page_fault = paging32_page_fault;
        context->gva_to_gpa = paging32_gva_to_gpa;
        context->free = paging_free;
        context->prefetch_page = paging32_prefetch_page;
        context->sync_page = paging32_sync_page;
        context->invlpg = paging32_invlpg;
        context->root_level = PT32_ROOT_LEVEL;
        context->shadow_root_level = PT32E_ROOT_LEVEL;
        context->root_hpa = INVALID_PAGE;
        return 0;
}

static int paging32E_init_context(struct kvm_vcpu *vcpu)
{
        reset_rsvds_bits_mask(vcpu, PT32E_ROOT_LEVEL);
        return paging64_init_context_common(vcpu, PT32E_ROOT_LEVEL);
}

static int init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu *context = &vcpu->arch.mmu;

        context->new_cr3 = nonpaging_new_cr3;
        context->page_fault = tdp_page_fault;
        context->free = nonpaging_free;
        context->prefetch_page = nonpaging_prefetch_page;
        context->sync_page = nonpaging_sync_page;
        context->invlpg = nonpaging_invlpg;
        context->shadow_root_level = kvm_x86_ops->get_tdp_level();
        context->root_hpa = INVALID_PAGE;

        if (!is_paging(vcpu)) {
                context->gva_to_gpa = nonpaging_gva_to_gpa;
                context->root_level = 0;
        } else if (is_long_mode(vcpu)) {
                reset_rsvds_bits_mask(vcpu, PT64_ROOT_LEVEL);
                context->gva_to_gpa = paging64_gva_to_gpa;
                context->root_level = PT64_ROOT_LEVEL;
        } else if (is_pae(vcpu)) {
                reset_rsvds_bits_mask(vcpu, PT32E_ROOT_LEVEL);
                context->gva_to_gpa = paging64_gva_to_gpa;
                context->root_level = PT32E_ROOT_LEVEL;
        } else {
                reset_rsvds_bits_mask(vcpu, PT32_ROOT_LEVEL);
                context->gva_to_gpa = paging32_gva_to_gpa;
                context->root_level = PT32_ROOT_LEVEL;
        }

        return 0;
}

static int init_kvm_softmmu(struct kvm_vcpu *vcpu)
{
        int r;

        ASSERT(vcpu);
        ASSERT(!VALID_PAGE(vcpu->arch.mmu.root_hpa));

        if (!is_paging(vcpu))
                r = nonpaging_init_context(vcpu);
        else if (is_long_mode(vcpu))
                r = paging64_init_context(vcpu);
        else if (is_pae(vcpu))
                r = paging32E_init_context(vcpu);
        else
                r = paging32_init_context(vcpu);

        vcpu->arch.mmu.base_role.glevels = vcpu->arch.mmu.root_level;

        return r;
}

static int init_kvm_mmu(struct kvm_vcpu *vcpu)
{
        vcpu->arch.update_pte.pfn = bad_pfn;

        if (tdp_enabled)
                return init_kvm_tdp_mmu(vcpu);
        else
                return init_kvm_softmmu(vcpu);
}

static void destroy_kvm_mmu(struct kvm_vcpu *vcpu)
{
        ASSERT(vcpu);
        if (VALID_PAGE(vcpu->arch.mmu.root_hpa)) {
                vcpu->arch.mmu.free(vcpu);
                vcpu->arch.mmu.root_hpa = INVALID_PAGE;
        }
}

int kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
{
        destroy_kvm_mmu(vcpu);
        return init_kvm_mmu(vcpu);
}
EXPORT_SYMBOL_GPL(kvm_mmu_reset_context);

int kvm_mmu_load(struct kvm_vcpu *vcpu)
{
        int r;

        r = mmu_topup_memory_caches(vcpu);
        if (r)
                goto out;
        spin_lock(&vcpu->kvm->mmu_lock);
        kvm_mmu_free_some_pages(vcpu);
        r = mmu_alloc_roots(vcpu);
        mmu_sync_roots(vcpu);
        spin_unlock(&vcpu->kvm->mmu_lock);
        if (r)
                goto out;
        /* set_cr3() should ensure TLB has been flushed */
        kvm_x86_ops->set_cr3(vcpu, vcpu->arch.mmu.root_hpa);
out:
        return r;
}
EXPORT_SYMBOL_GPL(kvm_mmu_load);

void kvm_mmu_unload(struct kvm_vcpu *vcpu)
{
        mmu_free_roots(vcpu);
}

static void mmu_pte_write_zap_pte(struct kvm_vcpu *vcpu,
                                  struct kvm_mmu_page *sp,
                                  u64 *spte)
{
        u64 pte;
        struct kvm_mmu_page *child;

        pte = *spte;
        if (is_shadow_present_pte(pte)) {
                if (is_last_spte(pte, sp->role.level))
                        rmap_remove(vcpu->kvm, spte);
                else {
                        child = page_header(pte & PT64_BASE_ADDR_MASK);
                        mmu_page_remove_parent_pte(child, spte);
                }
        }
        __set_spte(spte, shadow_trap_nonpresent_pte);
        if (is_large_pte(pte))
                --vcpu->kvm->stat.lpages;
}

static void mmu_pte_write_new_pte(struct kvm_vcpu *vcpu,
                                  struct kvm_mmu_page *sp,
                                  u64 *spte,
                                  const void *new)
{
        if (sp->role.level != PT_PAGE_TABLE_LEVEL) {
                ++vcpu->kvm->stat.mmu_pde_zapped;
                return;
        }

        ++vcpu->kvm->stat.mmu_pte_updated;
        if (sp->role.glevels == PT32_ROOT_LEVEL)
                paging32_update_pte(vcpu, sp, spte, new);
        else
                paging64_update_pte(vcpu, sp, spte, new);
}

static bool need_remote_flush(u64 old, u64 new)
{
        if (!is_shadow_present_pte(old))
                return false;
        if (!is_shadow_present_pte(new))
                return true;
        if ((old ^ new) & PT64_BASE_ADDR_MASK)
                return true;
        old ^= PT64_NX_MASK;
        new ^= PT64_NX_MASK;
        return (old & ~new & PT64_PERM_MASK) != 0;
}

static void mmu_pte_write_flush_tlb(struct kvm_vcpu *vcpu, u64 old, u64 new)
{
        if (need_remote_flush(old, new))
                kvm_flush_remote_tlbs(vcpu->kvm);
        else
                kvm_mmu_flush_tlb(vcpu);
}

static bool last_updated_pte_accessed(struct kvm_vcpu *vcpu)
{
        u64 *spte = vcpu->arch.last_pte_updated;

        return !!(spte && (*spte & shadow_accessed_mask));
}

static void mmu_guess_page_from_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
                                          const u8 *new, int bytes)
{
        gfn_t gfn;
        int r;
        u64 gpte = 0;
        pfn_t pfn;

        if (bytes != 4 && bytes != 8)
                return;

        /*
         * Assume that the pte write on a page table of the same type
         * as the current vcpu paging mode.  This is nearly always true
         * (might be false while changing modes).  Note it is verified later
         * by update_pte().
         */
        if (is_pae(vcpu)) {
                /* Handle a 32-bit guest writing two halves of a 64-bit gpte */
                if ((bytes == 4) && (gpa % 4 == 0)) {
                        r = kvm_read_guest(vcpu->kvm, gpa & ~(u64)7, &gpte, 8);
                        if (r)
                                return;
                        memcpy((void *)&gpte + (gpa % 8), new, 4);
                } else if ((bytes == 8) && (gpa % 8 == 0)) {
                        memcpy((void *)&gpte, new, 8);
                }
        } else {
                if ((bytes == 4) && (gpa % 4 == 0))
                        memcpy((void *)&gpte, new, 4);
        }
        if (!is_present_gpte(gpte))
                return;
        gfn = (gpte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;

        vcpu->arch.update_pte.mmu_seq = vcpu->kvm->mmu_notifier_seq;
        smp_rmb();
        pfn = gfn_to_pfn(vcpu->kvm, gfn);

        if (is_error_pfn(pfn)) {
                kvm_release_pfn_clean(pfn);
                return;
        }
        vcpu->arch.update_pte.gfn = gfn;
        vcpu->arch.update_pte.pfn = pfn;
}

static void kvm_mmu_access_page(struct kvm_vcpu *vcpu, gfn_t gfn)
{
        u64 *spte = vcpu->arch.last_pte_updated;

        if (spte
            && vcpu->arch.last_pte_gfn == gfn
            && shadow_accessed_mask
            && !(*spte & shadow_accessed_mask)
            && is_shadow_present_pte(*spte))
                set_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte);
}

void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
                       const u8 *new, int bytes,
                       bool guest_initiated)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        struct kvm_mmu_page *sp;
        struct hlist_node *node, *n;
        struct hlist_head *bucket;
        unsigned index;
        u64 entry, gentry;
        u64 *spte;
        unsigned offset = offset_in_page(gpa);
        unsigned pte_size;
        unsigned page_offset;
        unsigned misaligned;
        unsigned quadrant;
        int level;
        int flooded = 0;
        int npte;
        int r;

        pgprintk("%s: gpa %llx bytes %d\n", __func__, gpa, bytes);
        mmu_guess_page_from_pte_write(vcpu, gpa, new, bytes);
        spin_lock(&vcpu->kvm->mmu_lock);
        kvm_mmu_access_page(vcpu, gfn);
        kvm_mmu_free_some_pages(vcpu);
        ++vcpu->kvm->stat.mmu_pte_write;
        kvm_mmu_audit(vcpu, "pre pte write");
        if (guest_initiated) {
                if (gfn == vcpu->arch.last_pt_write_gfn
                    && !last_updated_pte_accessed(vcpu)) {
                        ++vcpu->arch.last_pt_write_count;
                        if (vcpu->arch.last_pt_write_count >= 3)
                                flooded = 1;
                } else {
                        vcpu->arch.last_pt_write_gfn = gfn;
                        vcpu->arch.last_pt_write_count = 1;
                        vcpu->arch.last_pte_updated = NULL;
                }
        }
        index = kvm_page_table_hashfn(gfn);
        bucket = &vcpu->kvm->arch.mmu_page_hash[index];
        hlist_for_each_entry_safe(sp, node, n, bucket, hash_link) {
                if (sp->gfn != gfn || sp->role.direct || sp->role.invalid)
                        continue;
                pte_size = sp->role.glevels == PT32_ROOT_LEVEL ? 4 : 8;
                misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1);
                misaligned |= bytes < 4;
                if (misaligned || flooded) {
                        /*
                         * Misaligned accesses are too much trouble to fix
                         * up; also, they usually indicate a page is not used
                         * as a page table.
                         *
                         * If we're seeing too many writes to a page,
                         * it may no longer be a page table, or we may be
                         * forking, in which case it is better to unmap the
                         * page.
                         */
                        pgprintk("misaligned: gpa %llx bytes %d role %x\n",
                                 gpa, bytes, sp->role.word);
                        if (kvm_mmu_zap_page(vcpu->kvm, sp))
                                n = bucket->first;
                        ++vcpu->kvm->stat.mmu_flooded;
                        continue;
                }
                page_offset = offset;
                level = sp->role.level;
                npte = 1;
                if (sp->role.glevels == PT32_ROOT_LEVEL) {
                        page_offset <<= 1;      /* 32->64 */
                        /*
                         * A 32-bit pde maps 4MB while the shadow pdes map
                         * only 2MB.  So we need to double the offset again
                         * and zap two pdes instead of one.
                         */
                        if (level == PT32_ROOT_LEVEL) {
                                page_offset &= ~7; /* kill rounding error */
                                page_offset <<= 1;
                                npte = 2;
                        }
                        quadrant = page_offset >> PAGE_SHIFT;
                        page_offset &= ~PAGE_MASK;
                        if (quadrant != sp->role.quadrant)
                                continue;
                }
                spte = &sp->spt[page_offset / sizeof(*spte)];
                if ((gpa & (pte_size - 1)) || (bytes < pte_size)) {
                        gentry = 0;
                        r = kvm_read_guest_atomic(vcpu->kvm,
                                                  gpa & ~(u64)(pte_size - 1),
                                                  &gentry, pte_size);
                        new = (const void *)&gentry;
                        if (r < 0)
                                new = NULL;
                }
                while (npte--) {
                        entry = *spte;
                        mmu_pte_write_zap_pte(vcpu, sp, spte);
                        if (new)
                                mmu_pte_write_new_pte(vcpu, sp, spte, new);
                        mmu_pte_write_flush_tlb(vcpu, entry, *spte);
                        ++spte;
                }
        }
        kvm_mmu_audit(vcpu, "post pte write");
        spin_unlock(&vcpu->kvm->mmu_lock);
        if (!is_error_pfn(vcpu->arch.update_pte.pfn)) {
                kvm_release_pfn_clean(vcpu->arch.update_pte.pfn);
                vcpu->arch.update_pte.pfn = bad_pfn;
        }
}

int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
{
        gpa_t gpa;
        int r;

        if (tdp_enabled)
                return 0;

        gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, gva);

        spin_lock(&vcpu->kvm->mmu_lock);
        r = kvm_mmu_unprotect_page(vcpu->kvm, gpa >> PAGE_SHIFT);
        spin_unlock(&vcpu->kvm->mmu_lock);
        return r;
}
EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page_virt);

void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
{
        while (vcpu->kvm->arch.n_free_mmu_pages < KVM_REFILL_PAGES &&
               !list_empty(&vcpu->kvm->arch.active_mmu_pages)) {
                struct kvm_mmu_page *sp;

                sp = container_of(vcpu->kvm->arch.active_mmu_pages.prev,
                                  struct kvm_mmu_page, link);
                kvm_mmu_zap_page(vcpu->kvm, sp);
                ++vcpu->kvm->stat.mmu_recycled;
        }
}

int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code)
{
        int r;
        enum emulation_result er;

        r = vcpu->arch.mmu.page_fault(vcpu, cr2, error_code);
        if (r < 0)
                goto out;

        if (!r) {
                r = 1;
                goto out;
        }

        r = mmu_topup_memory_caches(vcpu);
        if (r)
                goto out;

        er = emulate_instruction(vcpu, vcpu->run, cr2, error_code, 0);

        switch (er) {
        case EMULATE_DONE:
                return 1;
        case EMULATE_DO_MMIO:
                ++vcpu->stat.mmio_exits;
                return 0;
        case EMULATE_FAIL:
                vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
                vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
                return 0;
        default:
                BUG();
        }
out:
        return r;
}
EXPORT_SYMBOL_GPL(kvm_mmu_page_fault);

void kvm_mmu_invlpg(struct kvm_vcpu *vcpu, gva_t gva)
{
        vcpu->arch.mmu.invlpg(vcpu, gva);
        kvm_mmu_flush_tlb(vcpu);
        ++vcpu->stat.invlpg;
}
EXPORT_SYMBOL_GPL(kvm_mmu_invlpg);

void kvm_enable_tdp(void)
{
        tdp_enabled = true;
}
EXPORT_SYMBOL_GPL(kvm_enable_tdp);

void kvm_disable_tdp(void)
{
        tdp_enabled = false;
}
EXPORT_SYMBOL_GPL(kvm_disable_tdp);

static void free_mmu_pages(struct kvm_vcpu *vcpu)
{
        free_page((unsigned long)vcpu->arch.mmu.pae_root);
}

static int alloc_mmu_pages(struct kvm_vcpu *vcpu)
{
        struct page *page;
        int i;

        ASSERT(vcpu);

        /*
         * When emulating 32-bit mode, cr3 is only 32 bits even on x86_64.
         * Therefore we need to allocate shadow page tables in the first
         * 4GB of memory, which happens to fit the DMA32 zone.
         */
        page = alloc_page(GFP_KERNEL | __GFP_DMA32);
        if (!page)
                goto error_1;
        vcpu->arch.mmu.pae_root = page_address(page);
        for (i = 0; i < 4; ++i)
                vcpu->arch.mmu.pae_root[i] = INVALID_PAGE;

        return 0;

error_1:
        free_mmu_pages(vcpu);
        return -ENOMEM;
}

int kvm_mmu_create(struct kvm_vcpu *vcpu)
{
        ASSERT(vcpu);
        ASSERT(!VALID_PAGE(vcpu->arch.mmu.root_hpa));

        return alloc_mmu_pages(vcpu);
}

int kvm_mmu_setup(struct kvm_vcpu *vcpu)
{
        ASSERT(vcpu);
        ASSERT(!VALID_PAGE(vcpu->arch.mmu.root_hpa));

        return init_kvm_mmu(vcpu);
}

void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
{
        ASSERT(vcpu);

        destroy_kvm_mmu(vcpu);
        free_mmu_pages(vcpu);
        mmu_free_memory_caches(vcpu);
}

void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
{
        struct kvm_mmu_page *sp;

        list_for_each_entry(sp, &kvm->arch.active_mmu_pages, link) {
                int i;
                u64 *pt;

                if (!test_bit(slot, sp->slot_bitmap))
                        continue;

                pt = sp->spt;
                for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
                        /* avoid RMW */
                        if (pt[i] & PT_WRITABLE_MASK)
                                pt[i] &= ~PT_WRITABLE_MASK;
        }
        kvm_flush_remote_tlbs(kvm);
}

void kvm_mmu_zap_all(struct kvm *kvm)
{
        struct kvm_mmu_page *sp, *node;

        spin_lock(&kvm->mmu_lock);
        list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link)
                if (kvm_mmu_zap_page(kvm, sp))
                        node = container_of(kvm->arch.active_mmu_pages.next,
                                            struct kvm_mmu_page, link);
        spin_unlock(&kvm->mmu_lock);

        kvm_flush_remote_tlbs(kvm);
}

static void kvm_mmu_remove_one_alloc_mmu_page(struct kvm *kvm)
{
        struct kvm_mmu_page *page;

        page = container_of(kvm->arch.active_mmu_pages.prev,
                            struct kvm_mmu_page, link);
        kvm_mmu_zap_page(kvm, page);
}

static int mmu_shrink(int nr_to_scan, gfp_t gfp_mask)
{
        struct kvm *kvm;
        struct kvm *kvm_freed = NULL;
        int cache_count = 0;

        spin_lock(&kvm_lock);

        list_for_each_entry(kvm, &vm_list, vm_list) {
                int npages;

                if (!down_read_trylock(&kvm->slots_lock))
                        continue;
                spin_lock(&kvm->mmu_lock);
                npages = kvm->arch.n_alloc_mmu_pages -
                         kvm->arch.n_free_mmu_pages;
                cache_count += npages;
                if (!kvm_freed && nr_to_scan > 0 && npages > 0) {
                        kvm_mmu_remove_one_alloc_mmu_page(kvm);
                        cache_count--;
                        kvm_freed = kvm;
                }
                nr_to_scan--;

                spin_unlock(&kvm->mmu_lock);
                up_read(&kvm->slots_lock);
        }
        if (kvm_freed)
                list_move_tail(&kvm_freed->vm_list, &vm_list);

        spin_unlock(&kvm_lock);

        return cache_count;
}

static struct shrinker mmu_shrinker = {
        .shrink = mmu_shrink,
        .seeks = DEFAULT_SEEKS * 10,
};

static void mmu_destroy_caches(void)
{
        if (pte_chain_cache)
                kmem_cache_destroy(pte_chain_cache);
        if (rmap_desc_cache)
                kmem_cache_destroy(rmap_desc_cache);
        if (mmu_page_header_cache)
                kmem_cache_destroy(mmu_page_header_cache);
}

void kvm_mmu_module_exit(void)
{
        mmu_destroy_caches();
        unregister_shrinker(&mmu_shrinker);
}

int kvm_mmu_module_init(void)
{
        pte_chain_cache = kmem_cache_create("kvm_pte_chain",
                                            sizeof(struct kvm_pte_chain),
                                            0, 0, NULL);
        if (!pte_chain_cache)
                goto nomem;
        rmap_desc_cache = kmem_cache_create("kvm_rmap_desc",
                                            sizeof(struct kvm_rmap_desc),
                                            0, 0, NULL);
        if (!rmap_desc_cache)
                goto nomem;

        mmu_page_header_cache = kmem_cache_create("kvm_mmu_page_header",
                                                  sizeof(struct kvm_mmu_page),
                                                  0, 0, NULL);
        if (!mmu_page_header_cache)
                goto nomem;

        register_shrinker(&mmu_shrinker);

        return 0;

nomem:
        mmu_destroy_caches();
        return -ENOMEM;
}

/*
 * Caculate mmu pages needed for kvm.
 */
unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm)
{
        int i;
        unsigned int nr_mmu_pages;
        unsigned int  nr_pages = 0;

        for (i = 0; i < kvm->nmemslots; i++)
                nr_pages += kvm->memslots[i].npages;

        nr_mmu_pages = nr_pages * KVM_PERMILLE_MMU_PAGES / 1000;
        nr_mmu_pages = max(nr_mmu_pages,
                        (unsigned int) KVM_MIN_ALLOC_MMU_PAGES);

        return nr_mmu_pages;
}

static void *pv_mmu_peek_buffer(struct kvm_pv_mmu_op_buffer *buffer,
                                unsigned len)
{
        if (len > buffer->len)
                return NULL;
        return buffer->ptr;
}

static void *pv_mmu_read_buffer(struct kvm_pv_mmu_op_buffer *buffer,
                                unsigned len)
{
        void *ret;

        ret = pv_mmu_peek_buffer(buffer, len);
        if (!ret)
                return ret;
        buffer->ptr += len;
        buffer->len -= len;
        buffer->processed += len;
        return ret;
}

static int kvm_pv_mmu_write(struct kvm_vcpu *vcpu,
                             gpa_t addr, gpa_t value)
{
        int bytes = 8;
        int r;

        if (!is_long_mode(vcpu) && !is_pae(vcpu))
                bytes = 4;

        r = mmu_topup_memory_caches(vcpu);
        if (r)
                return r;

        if (!emulator_write_phys(vcpu, addr, &value, bytes))
                return -EFAULT;

        return 1;
}

static int kvm_pv_mmu_flush_tlb(struct kvm_vcpu *vcpu)
{
        kvm_set_cr3(vcpu, vcpu->arch.cr3);
        return 1;
}

static int kvm_pv_mmu_release_pt(struct kvm_vcpu *vcpu, gpa_t addr)
{
        spin_lock(&vcpu->kvm->mmu_lock);
        mmu_unshadow(vcpu->kvm, addr >> PAGE_SHIFT);
        spin_unlock(&vcpu->kvm->mmu_lock);
        return 1;
}

static int kvm_pv_mmu_op_one(struct kvm_vcpu *vcpu,
                             struct kvm_pv_mmu_op_buffer *buffer)
{
        struct kvm_mmu_op_header *header;

        header = pv_mmu_peek_buffer(buffer, sizeof *header);
        if (!header)
                return 0;
        switch (header->op) {
        case KVM_MMU_OP_WRITE_PTE: {
                struct kvm_mmu_op_write_pte *wpte;

                wpte = pv_mmu_read_buffer(buffer, sizeof *wpte);
                if (!wpte)
                        return 0;
                return kvm_pv_mmu_write(vcpu, wpte->pte_phys,
                                        wpte->pte_val);
        }
        case KVM_MMU_OP_FLUSH_TLB: {
                struct kvm_mmu_op_flush_tlb *ftlb;

                ftlb = pv_mmu_read_buffer(buffer, sizeof *ftlb);
                if (!ftlb)
                        return 0;
                return kvm_pv_mmu_flush_tlb(vcpu);
        }
        case KVM_MMU_OP_RELEASE_PT: {
                struct kvm_mmu_op_release_pt *rpt;

                rpt = pv_mmu_read_buffer(buffer, sizeof *rpt);
                if (!rpt)
                        return 0;
                return kvm_pv_mmu_release_pt(vcpu, rpt->pt_phys);
        }
        default: return 0;
        }
}

int kvm_pv_mmu_op(struct kvm_vcpu *vcpu, unsigned long bytes,
                  gpa_t addr, unsigned long *ret)
{
        int r;
        struct kvm_pv_mmu_op_buffer *buffer = &vcpu->arch.mmu_op_buffer;

        buffer->ptr = buffer->buf;
        buffer->len = min_t(unsigned long, bytes, sizeof buffer->buf);
        buffer->processed = 0;

        r = kvm_read_guest(vcpu->kvm, addr, buffer->buf, buffer->len);
        if (r)
                goto out;

        while (buffer->len) {
                r = kvm_pv_mmu_op_one(vcpu, buffer);
                if (r < 0)
                        goto out;
                if (r == 0)
                        break;
        }

        r = 1;
out:
        *ret = buffer->processed;
        return r;
}

int kvm_mmu_get_spte_hierarchy(struct kvm_vcpu *vcpu, u64 addr, u64 sptes[4])
{
        struct kvm_shadow_walk_iterator iterator;
        int nr_sptes = 0;

        spin_lock(&vcpu->kvm->mmu_lock);
        for_each_shadow_entry(vcpu, addr, iterator) {
                sptes[iterator.level-1] = *iterator.sptep;
                nr_sptes++;
                if (!is_shadow_present_pte(*iterator.sptep))
                        break;
        }
        spin_unlock(&vcpu->kvm->mmu_lock);

        return nr_sptes;
}
EXPORT_SYMBOL_GPL(kvm_mmu_get_spte_hierarchy);

#ifdef AUDIT

static const char *audit_msg;

static gva_t canonicalize(gva_t gva)
{
#ifdef CONFIG_X86_64
        gva = (long long)(gva << 16) >> 16;
#endif
        return gva;
}


typedef void (*inspect_spte_fn) (struct kvm *kvm, struct kvm_mmu_page *sp,
                                 u64 *sptep);

static void __mmu_spte_walk(struct kvm *kvm, struct kvm_mmu_page *sp,
                            inspect_spte_fn fn)
{
        int i;

        for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
                u64 ent = sp->spt[i];

                if (is_shadow_present_pte(ent)) {
                        if (!is_last_spte(ent, sp->role.level)) {
                                struct kvm_mmu_page *child;
                                child = page_header(ent & PT64_BASE_ADDR_MASK);
                                __mmu_spte_walk(kvm, child, fn);
                        } else
                                fn(kvm, sp, &sp->spt[i]);
                }
        }
}

static void mmu_spte_walk(struct kvm_vcpu *vcpu, inspect_spte_fn fn)
{
        int i;
        struct kvm_mmu_page *sp;

        if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
                return;
        if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_LEVEL) {
                hpa_t root = vcpu->arch.mmu.root_hpa;
                sp = page_header(root);
                __mmu_spte_walk(vcpu->kvm, sp, fn);
                return;
        }
        for (i = 0; i < 4; ++i) {
                hpa_t root = vcpu->arch.mmu.pae_root[i];

                if (root && VALID_PAGE(root)) {
                        root &= PT64_BASE_ADDR_MASK;
                        sp = page_header(root);
                        __mmu_spte_walk(vcpu->kvm, sp, fn);
                }
        }
        return;
}

static void audit_mappings_page(struct kvm_vcpu *vcpu, u64 page_pte,
                                gva_t va, int level)
{
        u64 *pt = __va(page_pte & PT64_BASE_ADDR_MASK);
        int i;
        gva_t va_delta = 1ul << (PAGE_SHIFT + 9 * (level - 1));

        for (i = 0; i < PT64_ENT_PER_PAGE; ++i, va += va_delta) {
                u64 ent = pt[i];

                if (ent == shadow_trap_nonpresent_pte)
                        continue;

                va = canonicalize(va);
                if (is_shadow_present_pte(ent) && !is_last_spte(ent, level))
                        audit_mappings_page(vcpu, ent, va, level - 1);
                else {
                        gpa_t gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, va);
                        gfn_t gfn = gpa >> PAGE_SHIFT;
                        pfn_t pfn = gfn_to_pfn(vcpu->kvm, gfn);
                        hpa_t hpa = (hpa_t)pfn << PAGE_SHIFT;

                        if (is_error_pfn(pfn)) {
                                kvm_release_pfn_clean(pfn);
                                continue;
                        }

                        if (is_shadow_present_pte(ent)
                            && (ent & PT64_BASE_ADDR_MASK) != hpa)
                                printk(KERN_ERR "xx audit error: (%s) levels %d"
                                       " gva %lx gpa %llx hpa %llx ent %llx %d\n",
                                       audit_msg, vcpu->arch.mmu.root_level,
                                       va, gpa, hpa, ent,
                                       is_shadow_present_pte(ent));
                        else if (ent == shadow_notrap_nonpresent_pte
                                 && !is_error_hpa(hpa))
                                printk(KERN_ERR "audit: (%s) notrap shadow,"
                                       " valid guest gva %lx\n", audit_msg, va);
                        kvm_release_pfn_clean(pfn);

                }
        }
}

static void audit_mappings(struct kvm_vcpu *vcpu)
{
        unsigned i;

        if (vcpu->arch.mmu.root_level == 4)
                audit_mappings_page(vcpu, vcpu->arch.mmu.root_hpa, 0, 4);
        else
                for (i = 0; i < 4; ++i)
                        if (vcpu->arch.mmu.pae_root[i] & PT_PRESENT_MASK)
                                audit_mappings_page(vcpu,
                                                    vcpu->arch.mmu.pae_root[i],
                                                    i << 30,
                                                    2);
}

static int count_rmaps(struct kvm_vcpu *vcpu)
{
        int nmaps = 0;
        int i, j, k;

        for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
                struct kvm_memory_slot *m = &vcpu->kvm->memslots[i];
                struct kvm_rmap_desc *d;

                for (j = 0; j < m->npages; ++j) {
                        unsigned long *rmapp = &m->rmap[j];

                        if (!*rmapp)
                                continue;
                        if (!(*rmapp & 1)) {
                                ++nmaps;
                                continue;
                        }
                        d = (struct kvm_rmap_desc *)(*rmapp & ~1ul);
                        while (d) {
                                for (k = 0; k < RMAP_EXT; ++k)
                                        if (d->sptes[k])
                                                ++nmaps;
                                        else
                                                break;
                                d = d->more;
                        }
                }
        }
        return nmaps;
}

void inspect_spte_has_rmap(struct kvm *kvm, struct kvm_mmu_page *sp, u64 *sptep)
{
        unsigned long *rmapp;
        struct kvm_mmu_page *rev_sp;
        gfn_t gfn;

        if (*sptep & PT_WRITABLE_MASK) {
                rev_sp = page_header(__pa(sptep));
                gfn = rev_sp->gfns[sptep - rev_sp->spt];

                if (!gfn_to_memslot(kvm, gfn)) {
                        if (!printk_ratelimit())
                                return;
                        printk(KERN_ERR "%s: no memslot for gfn %ld\n",
                                         audit_msg, gfn);
                        printk(KERN_ERR "%s: index %ld of sp (gfn=%lx)\n",
                                        audit_msg, sptep - rev_sp->spt,
                                        rev_sp->gfn);
                        dump_stack();
                        return;
                }

                rmapp = gfn_to_rmap(kvm, rev_sp->gfns[sptep - rev_sp->spt],
                                    is_large_pte(*sptep));
                if (!*rmapp) {
                        if (!printk_ratelimit())
                                return;
                        printk(KERN_ERR "%s: no rmap for writable spte %llx\n",
                                         audit_msg, *sptep);
                        dump_stack();
                }
        }

}

void audit_writable_sptes_have_rmaps(struct kvm_vcpu *vcpu)
{
        mmu_spte_walk(vcpu, inspect_spte_has_rmap);
}

static void check_writable_mappings_rmap(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_page *sp;
        int i;

        list_for_each_entry(sp, &vcpu->kvm->arch.active_mmu_pages, link) {
                u64 *pt = sp->spt;

                if (sp->role.level != PT_PAGE_TABLE_LEVEL)
                        continue;

                for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
                        u64 ent = pt[i];

                        if (!(ent & PT_PRESENT_MASK))
                                continue;
                        if (!(ent & PT_WRITABLE_MASK))
                                continue;
                        inspect_spte_has_rmap(vcpu->kvm, sp, &pt[i]);
                }
        }
        return;
}

static void audit_rmap(struct kvm_vcpu *vcpu)
{
        check_writable_mappings_rmap(vcpu);
        count_rmaps(vcpu);
}

static void audit_write_protection(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_page *sp;
        struct kvm_memory_slot *slot;
        unsigned long *rmapp;
        u64 *spte;
        gfn_t gfn;

        list_for_each_entry(sp, &vcpu->kvm->arch.active_mmu_pages, link) {
                if (sp->role.direct)
                        continue;
                if (sp->unsync)
                        continue;

                gfn = unalias_gfn(vcpu->kvm, sp->gfn);
                slot = gfn_to_memslot_unaliased(vcpu->kvm, sp->gfn);
                rmapp = &slot->rmap[gfn - slot->base_gfn];

                spte = rmap_next(vcpu->kvm, rmapp, NULL);
                while (spte) {
                        if (*spte & PT_WRITABLE_MASK)
                                printk(KERN_ERR "%s: (%s) shadow page has "
                                "writable mappings: gfn %lx role %x\n",
                               __func__, audit_msg, sp->gfn,
                               sp->role.word);
                        spte = rmap_next(vcpu->kvm, rmapp, spte);
                }
        }
}

static void kvm_mmu_audit(struct kvm_vcpu *vcpu, const char *msg)
{
        int olddbg = dbg;

        dbg = 0;
        audit_msg = msg;
        audit_rmap(vcpu);
        audit_write_protection(vcpu);
        if (strcmp("pre pte write", audit_msg) != 0)
                audit_mappings(vcpu);
        audit_writable_sptes_have_rmaps(vcpu);
        dbg = olddbg;
}

#endif