KVM: MMU: Simplify kvm_mmu_free_page() a tiny bit

[mirror_ubuntu-bionic-kernel.git] / drivers / 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 <linux/types.h>
#include <linux/string.h>
#include <asm/page.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/module.h>

#include "vmx.h"
#include "kvm.h"

#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 = 1;
#endif

#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 PT64_PT_BITS 9
#define PT64_ENT_PER_PAGE (1 << PT64_PT_BITS)
#define PT32_PT_BITS 10
#define PT32_ENT_PER_PAGE (1 << PT32_PT_BITS)

#define PT_WRITABLE_SHIFT 1

#define PT_PRESENT_MASK (1ULL << 0)
#define PT_WRITABLE_MASK (1ULL << PT_WRITABLE_SHIFT)
#define PT_USER_MASK (1ULL << 2)
#define PT_PWT_MASK (1ULL << 3)
#define PT_PCD_MASK (1ULL << 4)
#define PT_ACCESSED_MASK (1ULL << 5)
#define PT_DIRTY_MASK (1ULL << 6)
#define PT_PAGE_SIZE_MASK (1ULL << 7)
#define PT_PAT_MASK (1ULL << 7)
#define PT_GLOBAL_MASK (1ULL << 8)
#define PT64_NX_MASK (1ULL << 63)

#define PT_PAT_SHIFT 7
#define PT_DIR_PAT_SHIFT 12
#define PT_DIR_PAT_MASK (1ULL << PT_DIR_PAT_SHIFT)

#define PT32_DIR_PSE36_SIZE 4
#define PT32_DIR_PSE36_SHIFT 13
#define PT32_DIR_PSE36_MASK (((1ULL << PT32_DIR_PSE36_SIZE) - 1) << PT32_DIR_PSE36_SHIFT)


#define PT32_PTE_COPY_MASK \
        (PT_PRESENT_MASK | PT_ACCESSED_MASK | PT_DIRTY_MASK | PT_GLOBAL_MASK)

#define PT64_PTE_COPY_MASK (PT64_NX_MASK | PT32_PTE_COPY_MASK)

#define PT_FIRST_AVAIL_BITS_SHIFT 9
#define PT64_SECOND_AVAIL_BITS_SHIFT 52

#define PT_SHADOW_PS_MARK (1ULL << PT_FIRST_AVAIL_BITS_SHIFT)
#define PT_SHADOW_IO_MARK (1ULL << PT_FIRST_AVAIL_BITS_SHIFT)

#define PT_SHADOW_WRITABLE_SHIFT (PT_FIRST_AVAIL_BITS_SHIFT + 1)
#define PT_SHADOW_WRITABLE_MASK (1ULL << PT_SHADOW_WRITABLE_SHIFT)

#define PT_SHADOW_USER_SHIFT (PT_SHADOW_WRITABLE_SHIFT + 1)
#define PT_SHADOW_USER_MASK (1ULL << (PT_SHADOW_USER_SHIFT))

#define PT_SHADOW_BITS_OFFSET (PT_SHADOW_WRITABLE_SHIFT - PT_WRITABLE_SHIFT)

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


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

#define PT64_ROOT_LEVEL 4
#define PT32_ROOT_LEVEL 2
#define PT32E_ROOT_LEVEL 3

#define PT_DIRECTORY_LEVEL 2
#define PT_PAGE_TABLE_LEVEL 1

#define RMAP_EXT 4

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

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

static int is_write_protection(struct kvm_vcpu *vcpu)
{
        return vcpu->cr0 & CR0_WP_MASK;
}

static int is_cpuid_PSE36(void)
{
        return 1;
}

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

static int is_present_pte(unsigned long pte)
{
        return pte & PT_PRESENT_MASK;
}

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

static int is_io_pte(unsigned long pte)
{
        return pte & PT_SHADOW_IO_MARK;
}

static int is_rmap_pte(u64 pte)
{
        return (pte & (PT_WRITABLE_MASK | PT_PRESENT_MASK))
                == (PT_WRITABLE_MASK | PT_PRESENT_MASK);
}

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

        if (cache->nobjs >= min)
                return 0;
        while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
                obj = kmem_cache_zalloc(base_cache, gfp_flags);
                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_caches(struct kvm_vcpu *vcpu, gfp_t gfp_flags)
{
        int r;

        r = mmu_topup_memory_cache(&vcpu->mmu_pte_chain_cache,
                                   pte_chain_cache, 4, gfp_flags);
        if (r)
                goto out;
        r = mmu_topup_memory_cache(&vcpu->mmu_rmap_desc_cache,
                                   rmap_desc_cache, 1, gfp_flags);
out:
        return r;
}

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

        r = __mmu_topup_memory_caches(vcpu, GFP_NOWAIT);
        if (r < 0) {
                spin_unlock(&vcpu->kvm->lock);
                kvm_arch_ops->vcpu_put(vcpu);
                r = __mmu_topup_memory_caches(vcpu, GFP_KERNEL);
                kvm_arch_ops->vcpu_load(vcpu);
                spin_lock(&vcpu->kvm->lock);
        }
        return r;
}

static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
{
        mmu_free_memory_cache(&vcpu->mmu_pte_chain_cache);
        mmu_free_memory_cache(&vcpu->mmu_rmap_desc_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];
        memset(p, 0, size);
        return p;
}

static void mmu_memory_cache_free(struct kvm_mmu_memory_cache *mc, void *obj)
{
        if (mc->nobjs < KVM_NR_MEM_OBJS)
                mc->objects[mc->nobjs++] = obj;
        else
                kfree(obj);
}

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

static void mmu_free_pte_chain(struct kvm_vcpu *vcpu,
                               struct kvm_pte_chain *pc)
{
        mmu_memory_cache_free(&vcpu->mmu_pte_chain_cache, pc);
}

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

static void mmu_free_rmap_desc(struct kvm_vcpu *vcpu,
                               struct kvm_rmap_desc *rd)
{
        mmu_memory_cache_free(&vcpu->mmu_rmap_desc_cache, rd);
}

/*
 * Reverse mapping data structures:
 *
 * If page->private bit zero is zero, then page->private points to the
 * shadow page table entry that points to page_address(page).
 *
 * If page->private bit zero is one, (then page->private & ~1) points
 * to a struct kvm_rmap_desc containing more mappings.
 */
static void rmap_add(struct kvm_vcpu *vcpu, u64 *spte)
{
        struct page *page;
        struct kvm_rmap_desc *desc;
        int i;

        if (!is_rmap_pte(*spte))
                return;
        page = pfn_to_page((*spte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT);
        if (!page_private(page)) {
                rmap_printk("rmap_add: %p %llx 0->1\n", spte, *spte);
                set_page_private(page,(unsigned long)spte);
        } else if (!(page_private(page) & 1)) {
                rmap_printk("rmap_add: %p %llx 1->many\n", spte, *spte);
                desc = mmu_alloc_rmap_desc(vcpu);
                desc->shadow_ptes[0] = (u64 *)page_private(page);
                desc->shadow_ptes[1] = spte;
                set_page_private(page,(unsigned long)desc | 1);
        } else {
                rmap_printk("rmap_add: %p %llx many->many\n", spte, *spte);
                desc = (struct kvm_rmap_desc *)(page_private(page) & ~1ul);
                while (desc->shadow_ptes[RMAP_EXT-1] && desc->more)
                        desc = desc->more;
                if (desc->shadow_ptes[RMAP_EXT-1]) {
                        desc->more = mmu_alloc_rmap_desc(vcpu);
                        desc = desc->more;
                }
                for (i = 0; desc->shadow_ptes[i]; ++i)
                        ;
                desc->shadow_ptes[i] = spte;
        }
}

static void rmap_desc_remove_entry(struct kvm_vcpu *vcpu,
                                   struct page *page,
                                   struct kvm_rmap_desc *desc,
                                   int i,
                                   struct kvm_rmap_desc *prev_desc)
{
        int j;

        for (j = RMAP_EXT - 1; !desc->shadow_ptes[j] && j > i; --j)
                ;
        desc->shadow_ptes[i] = desc->shadow_ptes[j];
        desc->shadow_ptes[j] = NULL;
        if (j != 0)
                return;
        if (!prev_desc && !desc->more)
                set_page_private(page,(unsigned long)desc->shadow_ptes[0]);
        else
                if (prev_desc)
                        prev_desc->more = desc->more;
                else
                        set_page_private(page,(unsigned long)desc->more | 1);
        mmu_free_rmap_desc(vcpu, desc);
}

static void rmap_remove(struct kvm_vcpu *vcpu, u64 *spte)
{
        struct page *page;
        struct kvm_rmap_desc *desc;
        struct kvm_rmap_desc *prev_desc;
        int i;

        if (!is_rmap_pte(*spte))
                return;
        page = pfn_to_page((*spte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT);
        if (!page_private(page)) {
                printk(KERN_ERR "rmap_remove: %p %llx 0->BUG\n", spte, *spte);
                BUG();
        } else if (!(page_private(page) & 1)) {
                rmap_printk("rmap_remove:  %p %llx 1->0\n", spte, *spte);
                if ((u64 *)page_private(page) != spte) {
                        printk(KERN_ERR "rmap_remove:  %p %llx 1->BUG\n",
                               spte, *spte);
                        BUG();
                }
                set_page_private(page,0);
        } else {
                rmap_printk("rmap_remove:  %p %llx many->many\n", spte, *spte);
                desc = (struct kvm_rmap_desc *)(page_private(page) & ~1ul);
                prev_desc = NULL;
                while (desc) {
                        for (i = 0; i < RMAP_EXT && desc->shadow_ptes[i]; ++i)
                                if (desc->shadow_ptes[i] == spte) {
                                        rmap_desc_remove_entry(vcpu, page,
                                                               desc, i,
                                                               prev_desc);
                                        return;
                                }
                        prev_desc = desc;
                        desc = desc->more;
                }
                BUG();
        }
}

static void rmap_write_protect(struct kvm_vcpu *vcpu, u64 gfn)
{
        struct kvm *kvm = vcpu->kvm;
        struct page *page;
        struct kvm_rmap_desc *desc;
        u64 *spte;

        page = gfn_to_page(kvm, gfn);
        BUG_ON(!page);

        while (page_private(page)) {
                if (!(page_private(page) & 1))
                        spte = (u64 *)page_private(page);
                else {
                        desc = (struct kvm_rmap_desc *)(page_private(page) & ~1ul);
                        spte = desc->shadow_ptes[0];
                }
                BUG_ON(!spte);
                BUG_ON((*spte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT
                       != page_to_pfn(page));
                BUG_ON(!(*spte & PT_PRESENT_MASK));
                BUG_ON(!(*spte & PT_WRITABLE_MASK));
                rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
                rmap_remove(vcpu, spte);
                kvm_arch_ops->tlb_flush(vcpu);
                *spte &= ~(u64)PT_WRITABLE_MASK;
        }
}

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

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

static void kvm_mmu_free_page(struct kvm_vcpu *vcpu,
                              struct kvm_mmu_page *page_head)
{
        ASSERT(is_empty_shadow_page(page_head->page_hpa));
        list_move(&page_head->link, &vcpu->free_pages);
        ++vcpu->kvm->n_free_mmu_pages;
}

static unsigned kvm_page_table_hashfn(gfn_t gfn)
{
        return gfn;
}

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

        if (list_empty(&vcpu->free_pages))
                return NULL;

        page = list_entry(vcpu->free_pages.next, struct kvm_mmu_page, link);
        list_move(&page->link, &vcpu->kvm->active_mmu_pages);
        ASSERT(is_empty_shadow_page(page->page_hpa));
        page->slot_bitmap = 0;
        page->multimapped = 0;
        page->parent_pte = parent_pte;
        --vcpu->kvm->n_free_mmu_pages;
        return page;
}

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

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

                if (!old) {
                        page->parent_pte = parent_pte;
                        return;
                }
                page->multimapped = 1;
                pte_chain = mmu_alloc_pte_chain(vcpu);
                INIT_HLIST_HEAD(&page->parent_ptes);
                hlist_add_head(&pte_chain->link, &page->parent_ptes);
                pte_chain->parent_ptes[0] = old;
        }
        hlist_for_each_entry(pte_chain, node, &page->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, &page->parent_ptes);
        pte_chain->parent_ptes[0] = parent_pte;
}

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

        if (!page->multimapped) {
                BUG_ON(page->parent_pte != parent_pte);
                page->parent_pte = NULL;
                return;
        }
        hlist_for_each_entry(pte_chain, node, &page->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(vcpu, pte_chain);
                                if (hlist_empty(&page->parent_ptes)) {
                                        page->multimapped = 0;
                                        page->parent_pte = NULL;
                                }
                        }
                        return;
                }
        BUG();
}

static struct kvm_mmu_page *kvm_mmu_lookup_page(struct kvm_vcpu *vcpu,
                                                gfn_t gfn)
{
        unsigned index;
        struct hlist_head *bucket;
        struct kvm_mmu_page *page;
        struct hlist_node *node;

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

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

        role.word = 0;
        role.glevels = vcpu->mmu.root_level;
        role.level = level;
        role.metaphysical = metaphysical;
        role.hugepage_access = hugepage_access;
        if (vcpu->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;
        }
        pgprintk("%s: looking gfn %lx role %x\n", __FUNCTION__,
                 gfn, role.word);
        index = kvm_page_table_hashfn(gfn) % KVM_NUM_MMU_PAGES;
        bucket = &vcpu->kvm->mmu_page_hash[index];
        hlist_for_each_entry(page, node, bucket, hash_link)
                if (page->gfn == gfn && page->role.word == role.word) {
                        mmu_page_add_parent_pte(vcpu, page, parent_pte);
                        pgprintk("%s: found\n", __FUNCTION__);
                        return page;
                }
        page = kvm_mmu_alloc_page(vcpu, parent_pte);
        if (!page)
                return page;
        pgprintk("%s: adding gfn %lx role %x\n", __FUNCTION__, gfn, role.word);
        page->gfn = gfn;
        page->role = role;
        hlist_add_head(&page->hash_link, bucket);
        if (!metaphysical)
                rmap_write_protect(vcpu, gfn);
        return page;
}

static void kvm_mmu_page_unlink_children(struct kvm_vcpu *vcpu,
                                         struct kvm_mmu_page *page)
{
        unsigned i;
        u64 *pt;
        u64 ent;

        pt = __va(page->page_hpa);

        if (page->role.level == PT_PAGE_TABLE_LEVEL) {
                for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
                        if (pt[i] & PT_PRESENT_MASK)
                                rmap_remove(vcpu, &pt[i]);
                        pt[i] = 0;
                }
                kvm_arch_ops->tlb_flush(vcpu);
                return;
        }

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

                pt[i] = 0;
                if (!(ent & PT_PRESENT_MASK))
                        continue;
                ent &= PT64_BASE_ADDR_MASK;
                mmu_page_remove_parent_pte(vcpu, page_header(ent), &pt[i]);
        }
}

static void kvm_mmu_put_page(struct kvm_vcpu *vcpu,
                             struct kvm_mmu_page *page,
                             u64 *parent_pte)
{
        mmu_page_remove_parent_pte(vcpu, page, parent_pte);
}

static void kvm_mmu_zap_page(struct kvm_vcpu *vcpu,
                             struct kvm_mmu_page *page)
{
        u64 *parent_pte;

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

                        chain = container_of(page->parent_ptes.first,
                                             struct kvm_pte_chain, link);
                        parent_pte = chain->parent_ptes[0];
                }
                BUG_ON(!parent_pte);
                kvm_mmu_put_page(vcpu, page, parent_pte);
                *parent_pte = 0;
        }
        kvm_mmu_page_unlink_children(vcpu, page);
        if (!page->root_count) {
                hlist_del(&page->hash_link);
                kvm_mmu_free_page(vcpu, page);
        } else
                list_move(&page->link, &vcpu->kvm->active_mmu_pages);
}

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

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

static void page_header_update_slot(struct kvm *kvm, void *pte, gpa_t gpa)
{
        int slot = memslot_id(kvm, gfn_to_memslot(kvm, gpa >> PAGE_SHIFT));
        struct kvm_mmu_page *page_head = page_header(__pa(pte));

        __set_bit(slot, &page_head->slot_bitmap);
}

hpa_t safe_gpa_to_hpa(struct kvm_vcpu *vcpu, gpa_t gpa)
{
        hpa_t hpa = gpa_to_hpa(vcpu, gpa);

        return is_error_hpa(hpa) ? bad_page_address | (gpa & ~PAGE_MASK): hpa;
}

hpa_t gpa_to_hpa(struct kvm_vcpu *vcpu, gpa_t gpa)
{
        struct page *page;

        ASSERT((gpa & HPA_ERR_MASK) == 0);
        page = gfn_to_page(vcpu->kvm, gpa >> PAGE_SHIFT);
        if (!page)
                return gpa | HPA_ERR_MASK;
        return ((hpa_t)page_to_pfn(page) << PAGE_SHIFT)
                | (gpa & (PAGE_SIZE-1));
}

hpa_t gva_to_hpa(struct kvm_vcpu *vcpu, gva_t gva)
{
        gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, gva);

        if (gpa == UNMAPPED_GVA)
                return UNMAPPED_GVA;
        return gpa_to_hpa(vcpu, gpa);
}

struct page *gva_to_page(struct kvm_vcpu *vcpu, gva_t gva)
{
        gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, gva);

        if (gpa == UNMAPPED_GVA)
                return NULL;
        return pfn_to_page(gpa_to_hpa(vcpu, gpa) >> PAGE_SHIFT);
}

static void nonpaging_new_cr3(struct kvm_vcpu *vcpu)
{
}

static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, hpa_t p)
{
        int level = PT32E_ROOT_LEVEL;
        hpa_t table_addr = vcpu->mmu.root_hpa;

        for (; ; level--) {
                u32 index = PT64_INDEX(v, level);
                u64 *table;
                u64 pte;

                ASSERT(VALID_PAGE(table_addr));
                table = __va(table_addr);

                if (level == 1) {
                        pte = table[index];
                        if (is_present_pte(pte) && is_writeble_pte(pte))
                                return 0;
                        mark_page_dirty(vcpu->kvm, v >> PAGE_SHIFT);
                        page_header_update_slot(vcpu->kvm, table, v);
                        table[index] = p | PT_PRESENT_MASK | PT_WRITABLE_MASK |
                                                                PT_USER_MASK;
                        rmap_add(vcpu, &table[index]);
                        return 0;
                }

                if (table[index] == 0) {
                        struct kvm_mmu_page *new_table;
                        gfn_t pseudo_gfn;

                        pseudo_gfn = (v & PT64_DIR_BASE_ADDR_MASK)
                                >> PAGE_SHIFT;
                        new_table = kvm_mmu_get_page(vcpu, pseudo_gfn,
                                                     v, level - 1,
                                                     1, 0, &table[index]);
                        if (!new_table) {
                                pgprintk("nonpaging_map: ENOMEM\n");
                                return -ENOMEM;
                        }

                        table[index] = new_table->page_hpa | PT_PRESENT_MASK
                                | PT_WRITABLE_MASK | PT_USER_MASK;
                }
                table_addr = table[index] & PT64_BASE_ADDR_MASK;
        }
}

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

#ifdef CONFIG_X86_64
        if (vcpu->mmu.shadow_root_level == PT64_ROOT_LEVEL) {
                hpa_t root = vcpu->mmu.root_hpa;

                ASSERT(VALID_PAGE(root));
                page = page_header(root);
                --page->root_count;
                vcpu->mmu.root_hpa = INVALID_PAGE;
                return;
        }
#endif
        for (i = 0; i < 4; ++i) {
                hpa_t root = vcpu->mmu.pae_root[i];

                if (root) {
                        ASSERT(VALID_PAGE(root));
                        root &= PT64_BASE_ADDR_MASK;
                        page = page_header(root);
                        --page->root_count;
                }
                vcpu->mmu.pae_root[i] = INVALID_PAGE;
        }
        vcpu->mmu.root_hpa = INVALID_PAGE;
}

static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
{
        int i;
        gfn_t root_gfn;
        struct kvm_mmu_page *page;

        root_gfn = vcpu->cr3 >> PAGE_SHIFT;

#ifdef CONFIG_X86_64
        if (vcpu->mmu.shadow_root_level == PT64_ROOT_LEVEL) {
                hpa_t root = vcpu->mmu.root_hpa;

                ASSERT(!VALID_PAGE(root));
                page = kvm_mmu_get_page(vcpu, root_gfn, 0,
                                        PT64_ROOT_LEVEL, 0, 0, NULL);
                root = page->page_hpa;
                ++page->root_count;
                vcpu->mmu.root_hpa = root;
                return;
        }
#endif
        for (i = 0; i < 4; ++i) {
                hpa_t root = vcpu->mmu.pae_root[i];

                ASSERT(!VALID_PAGE(root));
                if (vcpu->mmu.root_level == PT32E_ROOT_LEVEL) {
                        if (!is_present_pte(vcpu->pdptrs[i])) {
                                vcpu->mmu.pae_root[i] = 0;
                                continue;
                        }
                        root_gfn = vcpu->pdptrs[i] >> PAGE_SHIFT;
                } else if (vcpu->mmu.root_level == 0)
                        root_gfn = 0;
                page = kvm_mmu_get_page(vcpu, root_gfn, i << 30,
                                        PT32_ROOT_LEVEL, !is_paging(vcpu),
                                        0, NULL);
                root = page->page_hpa;
                ++page->root_count;
                vcpu->mmu.pae_root[i] = root | PT_PRESENT_MASK;
        }
        vcpu->mmu.root_hpa = __pa(vcpu->mmu.pae_root);
}

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)
{
        gpa_t addr = gva;
        hpa_t paddr;
        int r;

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

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


        paddr = gpa_to_hpa(vcpu , addr & PT64_BASE_ADDR_MASK);

        if (is_error_hpa(paddr))
                return 1;

        return nonpaging_map(vcpu, addr & PAGE_MASK, paddr);
}

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->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->root_level = 0;
        context->shadow_root_level = PT32E_ROOT_LEVEL;
        mmu_alloc_roots(vcpu);
        ASSERT(VALID_PAGE(context->root_hpa));
        kvm_arch_ops->set_cr3(vcpu, context->root_hpa);
        return 0;
}

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

static void paging_new_cr3(struct kvm_vcpu *vcpu)
{
        pgprintk("%s: cr3 %lx\n", __FUNCTION__, vcpu->cr3);
        mmu_free_roots(vcpu);
        if (unlikely(vcpu->kvm->n_free_mmu_pages < KVM_MIN_FREE_MMU_PAGES))
                kvm_mmu_free_some_pages(vcpu);
        mmu_alloc_roots(vcpu);
        kvm_mmu_flush_tlb(vcpu);
        kvm_arch_ops->set_cr3(vcpu, vcpu->mmu.root_hpa);
}

static inline void set_pte_common(struct kvm_vcpu *vcpu,
                             u64 *shadow_pte,
                             gpa_t gaddr,
                             int dirty,
                             u64 access_bits,
                             gfn_t gfn)
{
        hpa_t paddr;

        *shadow_pte |= access_bits << PT_SHADOW_BITS_OFFSET;
        if (!dirty)
                access_bits &= ~PT_WRITABLE_MASK;

        paddr = gpa_to_hpa(vcpu, gaddr & PT64_BASE_ADDR_MASK);

        *shadow_pte |= access_bits;

        if (is_error_hpa(paddr)) {
                *shadow_pte |= gaddr;
                *shadow_pte |= PT_SHADOW_IO_MARK;
                *shadow_pte &= ~PT_PRESENT_MASK;
                return;
        }

        *shadow_pte |= paddr;

        if (access_bits & PT_WRITABLE_MASK) {
                struct kvm_mmu_page *shadow;

                shadow = kvm_mmu_lookup_page(vcpu, gfn);
                if (shadow) {
                        pgprintk("%s: found shadow page for %lx, marking ro\n",
                                 __FUNCTION__, gfn);
                        access_bits &= ~PT_WRITABLE_MASK;
                        if (is_writeble_pte(*shadow_pte)) {
                                    *shadow_pte &= ~PT_WRITABLE_MASK;
                                    kvm_arch_ops->tlb_flush(vcpu);
                        }
                }
        }

        if (access_bits & PT_WRITABLE_MASK)
                mark_page_dirty(vcpu->kvm, gaddr >> PAGE_SHIFT);

        page_header_update_slot(vcpu->kvm, shadow_pte, gaddr);
        rmap_add(vcpu, shadow_pte);
}

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

static inline int fix_read_pf(u64 *shadow_ent)
{
        if ((*shadow_ent & PT_SHADOW_USER_MASK) &&
            !(*shadow_ent & PT_USER_MASK)) {
                /*
                 * If supervisor write protect is disabled, we shadow kernel
                 * pages as user pages so we can trap the write access.
                 */
                *shadow_ent |= PT_USER_MASK;
                *shadow_ent &= ~PT_WRITABLE_MASK;

                return 1;

        }
        return 0;
}

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

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

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

static int paging64_init_context_common(struct kvm_vcpu *vcpu, int level)
{
        struct kvm_mmu *context = &vcpu->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->free = paging_free;
        context->root_level = level;
        context->shadow_root_level = level;
        mmu_alloc_roots(vcpu);
        ASSERT(VALID_PAGE(context->root_hpa));
        kvm_arch_ops->set_cr3(vcpu, context->root_hpa |
                    (vcpu->cr3 & (CR3_PCD_MASK | CR3_WPT_MASK)));
        return 0;
}

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

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

        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->root_level = PT32_ROOT_LEVEL;
        context->shadow_root_level = PT32E_ROOT_LEVEL;
        mmu_alloc_roots(vcpu);
        ASSERT(VALID_PAGE(context->root_hpa));
        kvm_arch_ops->set_cr3(vcpu, context->root_hpa |
                    (vcpu->cr3 & (CR3_PCD_MASK | CR3_WPT_MASK)));
        return 0;
}

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

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

        if (!is_paging(vcpu))
                return nonpaging_init_context(vcpu);
        else if (is_long_mode(vcpu))
                return paging64_init_context(vcpu);
        else if (is_pae(vcpu))
                return paging32E_init_context(vcpu);
        else
                return paging32_init_context(vcpu);
}

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

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

        destroy_kvm_mmu(vcpu);
        r = init_kvm_mmu(vcpu);
        if (r < 0)
                goto out;
        r = mmu_topup_memory_caches(vcpu);
out:
        return r;
}

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

        pte = *spte;
        if (is_present_pte(pte)) {
                if (page->role.level == PT_PAGE_TABLE_LEVEL)
                        rmap_remove(vcpu, spte);
                else {
                        child = page_header(pte & PT64_BASE_ADDR_MASK);
                        mmu_page_remove_parent_pte(vcpu, child, spte);
                }
        }
        *spte = 0;
}

static void mmu_pte_write_new_pte(struct kvm_vcpu *vcpu,
                                  struct kvm_mmu_page *page,
                                  u64 *spte,
                                  const void *new, int bytes)
{
        if (page->role.level != PT_PAGE_TABLE_LEVEL)
                return;

        if (page->role.glevels == PT32_ROOT_LEVEL)
                paging32_update_pte(vcpu, page, spte, new, bytes);
        else
                paging64_update_pte(vcpu, page, spte, new, bytes);
}

void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
                       const u8 *old, const u8 *new, int bytes)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        struct kvm_mmu_page *page;
        struct hlist_node *node, *n;
        struct hlist_head *bucket;
        unsigned index;
        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;

        pgprintk("%s: gpa %llx bytes %d\n", __FUNCTION__, gpa, bytes);
        if (gfn == vcpu->last_pt_write_gfn) {
                ++vcpu->last_pt_write_count;
                if (vcpu->last_pt_write_count >= 3)
                        flooded = 1;
        } else {
                vcpu->last_pt_write_gfn = gfn;
                vcpu->last_pt_write_count = 1;
        }
        index = kvm_page_table_hashfn(gfn) % KVM_NUM_MMU_PAGES;
        bucket = &vcpu->kvm->mmu_page_hash[index];
        hlist_for_each_entry_safe(page, node, n, bucket, hash_link) {
                if (page->gfn != gfn || page->role.metaphysical)
                        continue;
                pte_size = page->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, page->role.word);
                        kvm_mmu_zap_page(vcpu, page);
                        continue;
                }
                page_offset = offset;
                level = page->role.level;
                npte = 1;
                if (page->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 != page->role.quadrant)
                                continue;
                }
                spte = __va(page->page_hpa);
                spte += page_offset / sizeof(*spte);
                while (npte--) {
                        mmu_pte_write_zap_pte(vcpu, page, spte);
                        mmu_pte_write_new_pte(vcpu, page, spte, new, bytes);
                        ++spte;
                }
        }
}

int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
{
        gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, gva);

        return kvm_mmu_unprotect_page(vcpu, gpa >> PAGE_SHIFT);
}

void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
{
        while (vcpu->kvm->n_free_mmu_pages < KVM_REFILL_PAGES) {
                struct kvm_mmu_page *page;

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

static void free_mmu_pages(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_page *page;

        while (!list_empty(&vcpu->kvm->active_mmu_pages)) {
                page = container_of(vcpu->kvm->active_mmu_pages.next,
                                    struct kvm_mmu_page, link);
                kvm_mmu_zap_page(vcpu, page);
        }
        while (!list_empty(&vcpu->free_pages)) {
                page = list_entry(vcpu->free_pages.next,
                                  struct kvm_mmu_page, link);
                list_del(&page->link);
                __free_page(pfn_to_page(page->page_hpa >> PAGE_SHIFT));
                page->page_hpa = INVALID_PAGE;
        }
        free_page((unsigned long)vcpu->mmu.pae_root);
}

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

        ASSERT(vcpu);

        for (i = 0; i < KVM_NUM_MMU_PAGES; i++) {
                struct kvm_mmu_page *page_header = &vcpu->page_header_buf[i];

                INIT_LIST_HEAD(&page_header->link);
                if ((page = alloc_page(GFP_KERNEL)) == NULL)
                        goto error_1;
                set_page_private(page, (unsigned long)page_header);
                page_header->page_hpa = (hpa_t)page_to_pfn(page) << PAGE_SHIFT;
                memset(__va(page_header->page_hpa), 0, PAGE_SIZE);
                list_add(&page_header->link, &vcpu->free_pages);
                ++vcpu->kvm->n_free_mmu_pages;
        }

        /*
         * 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->mmu.pae_root = page_address(page);
        for (i = 0; i < 4; ++i)
                vcpu->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->mmu.root_hpa));
        ASSERT(list_empty(&vcpu->free_pages));

        return alloc_mmu_pages(vcpu);
}

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

        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_vcpu *vcpu, int slot)
{
        struct kvm *kvm = vcpu->kvm;
        struct kvm_mmu_page *page;

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

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

                pt = __va(page->page_hpa);
                for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
                        /* avoid RMW */
                        if (pt[i] & PT_WRITABLE_MASK) {
                                rmap_remove(vcpu, &pt[i]);
                                pt[i] &= ~PT_WRITABLE_MASK;
                        }
        }
}

void kvm_mmu_zap_all(struct kvm_vcpu *vcpu)
{
        destroy_kvm_mmu(vcpu);

        while (!list_empty(&vcpu->kvm->active_mmu_pages)) {
                struct kvm_mmu_page *page;

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

        mmu_free_memory_caches(vcpu);
        kvm_arch_ops->tlb_flush(vcpu);
        init_kvm_mmu(vcpu);
}

void kvm_mmu_module_exit(void)
{
        if (pte_chain_cache)
                kmem_cache_destroy(pte_chain_cache);
        if (rmap_desc_cache)
                kmem_cache_destroy(rmap_desc_cache);
}

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

        return 0;

nomem:
        kvm_mmu_module_exit();
        return -ENOMEM;
}

#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;
}

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 & PT_PRESENT_MASK))
                        continue;

                va = canonicalize(va);
                if (level > 1)
                        audit_mappings_page(vcpu, ent, va, level - 1);
                else {
                        gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, va);
                        hpa_t hpa = gpa_to_hpa(vcpu, gpa);

                        if ((ent & PT_PRESENT_MASK)
                            && (ent & PT64_BASE_ADDR_MASK) != hpa)
                                printk(KERN_ERR "audit error: (%s) levels %d"
                                       " gva %lx gpa %llx hpa %llx ent %llx\n",
                                       audit_msg, vcpu->mmu.root_level,
                                       va, gpa, hpa, ent);
                }
        }
}

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

        if (vcpu->mmu.root_level == 4)
                audit_mappings_page(vcpu, vcpu->mmu.root_hpa, 0, 4);
        else
                for (i = 0; i < 4; ++i)
                        if (vcpu->mmu.pae_root[i] & PT_PRESENT_MASK)
                                audit_mappings_page(vcpu,
                                                    vcpu->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) {
                        struct page *page = m->phys_mem[j];

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

static int count_writable_mappings(struct kvm_vcpu *vcpu)
{
        int nmaps = 0;
        struct kvm_mmu_page *page;
        int i;

        list_for_each_entry(page, &vcpu->kvm->active_mmu_pages, link) {
                u64 *pt = __va(page->page_hpa);

                if (page->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;
                        ++nmaps;
                }
        }
        return nmaps;
}

static void audit_rmap(struct kvm_vcpu *vcpu)
{
        int n_rmap = count_rmaps(vcpu);
        int n_actual = count_writable_mappings(vcpu);

        if (n_rmap != n_actual)
                printk(KERN_ERR "%s: (%s) rmap %d actual %d\n",
                       __FUNCTION__, audit_msg, n_rmap, n_actual);
}

static void audit_write_protection(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_page *page;

        list_for_each_entry(page, &vcpu->kvm->active_mmu_pages, link) {
                hfn_t hfn;
                struct page *pg;

                if (page->role.metaphysical)
                        continue;

                hfn = gpa_to_hpa(vcpu, (gpa_t)page->gfn << PAGE_SHIFT)
                        >> PAGE_SHIFT;
                pg = pfn_to_page(hfn);
                if (pg->private)
                        printk(KERN_ERR "%s: (%s) shadow page has writable"
                               " mappings: gfn %lx role %x\n",
                               __FUNCTION__, audit_msg, page->gfn,
                               page->role.word);
        }
}

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);
        audit_mappings(vcpu);
        dbg = olddbg;
}

#endif