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[linux-block.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.
 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
 *
 * 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 "irq.h"
#include "mmu.h"
#include "x86.h"
#include "kvm_cache_regs.h"
#include "cpuid.h"

#include <linux/kvm_host.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/moduleparam.h>
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/hugetlb.h>
#include <linux/compiler.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <linux/hash.h>
#include <linux/kern_levels.h>

#include <asm/page.h>
#include <asm/pat.h>
#include <asm/cmpxchg.h>
#include <asm/io.h>
#include <asm/vmx.h>
#include <asm/kvm_page_track.h>
#include "trace.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;

enum {
        AUDIT_PRE_PAGE_FAULT,
        AUDIT_POST_PAGE_FAULT,
        AUDIT_PRE_PTE_WRITE,
        AUDIT_POST_PTE_WRITE,
        AUDIT_PRE_SYNC,
        AUDIT_POST_SYNC
};

#undef MMU_DEBUG

#ifdef MMU_DEBUG
static bool dbg = 0;
module_param(dbg, bool, 0644);

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

#define PTE_PREFETCH_NUM                8

#define PT_FIRST_AVAIL_BITS_SHIFT 10
#define PT64_SECOND_AVAIL_BITS_SHIFT 52

#define PT64_LEVEL_BITS 9

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

#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_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 __sme_clr((((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 | shadow_user_mask \
                        | shadow_x_mask | shadow_nx_mask | shadow_me_mask)

#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)

/* The mask for the R/X bits in EPT PTEs */
#define PT64_EPT_READABLE_MASK                  0x1ull
#define PT64_EPT_EXECUTABLE_MASK                0x4ull

#include <trace/events/kvm.h>

#define CREATE_TRACE_POINTS
#include "mmutrace.h"

#define SPTE_HOST_WRITEABLE     (1ULL << PT_FIRST_AVAIL_BITS_SHIFT)
#define SPTE_MMU_WRITEABLE      (1ULL << (PT_FIRST_AVAIL_BITS_SHIFT + 1))

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

/* make pte_list_desc fit well in cache line */
#define PTE_LIST_EXT 3

/*
 * Return values of handle_mmio_page_fault and mmu.page_fault:
 * RET_PF_RETRY: let CPU fault again on the address.
 * RET_PF_EMULATE: mmio page fault, emulate the instruction directly.
 *
 * For handle_mmio_page_fault only:
 * RET_PF_INVALID: the spte is invalid, let the real page fault path update it.
 */
enum {
        RET_PF_RETRY = 0,
        RET_PF_EMULATE = 1,
        RET_PF_INVALID = 2,
};

struct pte_list_desc {
        u64 *sptes[PTE_LIST_EXT];
        struct pte_list_desc *more;
};

struct kvm_shadow_walk_iterator {
        u64 addr;
        hpa_t shadow_addr;
        u64 *sptep;
        int level;
        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)))

#define for_each_shadow_entry_lockless(_vcpu, _addr, _walker, spte)     \
        for (shadow_walk_init(&(_walker), _vcpu, _addr);                \
             shadow_walk_okay(&(_walker)) &&                            \
                ({ spte = mmu_spte_get_lockless(_walker.sptep); 1; });  \
             __shadow_walk_next(&(_walker), spte))

static struct kmem_cache *pte_list_desc_cache;
static struct kmem_cache *mmu_page_header_cache;
static struct percpu_counter kvm_total_used_mmu_pages;

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 u64 __read_mostly shadow_mmio_mask;
static u64 __read_mostly shadow_mmio_value;
static u64 __read_mostly shadow_present_mask;
static u64 __read_mostly shadow_me_mask;

/*
 * SPTEs used by MMUs without A/D bits are marked with shadow_acc_track_value.
 * Non-present SPTEs with shadow_acc_track_value set are in place for access
 * tracking.
 */
static u64 __read_mostly shadow_acc_track_mask;
static const u64 shadow_acc_track_value = SPTE_SPECIAL_MASK;

/*
 * The mask/shift to use for saving the original R/X bits when marking the PTE
 * as not-present for access tracking purposes. We do not save the W bit as the
 * PTEs being access tracked also need to be dirty tracked, so the W bit will be
 * restored only when a write is attempted to the page.
 */
static const u64 shadow_acc_track_saved_bits_mask = PT64_EPT_READABLE_MASK |
                                                    PT64_EPT_EXECUTABLE_MASK;
static const u64 shadow_acc_track_saved_bits_shift = PT64_SECOND_AVAIL_BITS_SHIFT;

static void mmu_spte_set(u64 *sptep, u64 spte);
static void mmu_free_roots(struct kvm_vcpu *vcpu);

void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask, u64 mmio_value)
{
        BUG_ON((mmio_mask & mmio_value) != mmio_value);
        shadow_mmio_value = mmio_value | SPTE_SPECIAL_MASK;
        shadow_mmio_mask = mmio_mask | SPTE_SPECIAL_MASK;
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask);

static inline bool sp_ad_disabled(struct kvm_mmu_page *sp)
{
        return sp->role.ad_disabled;
}

static inline bool spte_ad_enabled(u64 spte)
{
        MMU_WARN_ON((spte & shadow_mmio_mask) == shadow_mmio_value);
        return !(spte & shadow_acc_track_value);
}

static inline u64 spte_shadow_accessed_mask(u64 spte)
{
        MMU_WARN_ON((spte & shadow_mmio_mask) == shadow_mmio_value);
        return spte_ad_enabled(spte) ? shadow_accessed_mask : 0;
}

static inline u64 spte_shadow_dirty_mask(u64 spte)
{
        MMU_WARN_ON((spte & shadow_mmio_mask) == shadow_mmio_value);
        return spte_ad_enabled(spte) ? shadow_dirty_mask : 0;
}

static inline bool is_access_track_spte(u64 spte)
{
        return !spte_ad_enabled(spte) && (spte & shadow_acc_track_mask) == 0;
}

/*
 * the low bit of the generation number is always presumed to be zero.
 * This disables mmio caching during memslot updates.  The concept is
 * similar to a seqcount but instead of retrying the access we just punt
 * and ignore the cache.
 *
 * spte bits 3-11 are used as bits 1-9 of the generation number,
 * the bits 52-61 are used as bits 10-19 of the generation number.
 */
#define MMIO_SPTE_GEN_LOW_SHIFT         2
#define MMIO_SPTE_GEN_HIGH_SHIFT        52

#define MMIO_GEN_SHIFT                  20
#define MMIO_GEN_LOW_SHIFT              10
#define MMIO_GEN_LOW_MASK               ((1 << MMIO_GEN_LOW_SHIFT) - 2)
#define MMIO_GEN_MASK                   ((1 << MMIO_GEN_SHIFT) - 1)

static u64 generation_mmio_spte_mask(unsigned int gen)
{
        u64 mask;

        WARN_ON(gen & ~MMIO_GEN_MASK);

        mask = (gen & MMIO_GEN_LOW_MASK) << MMIO_SPTE_GEN_LOW_SHIFT;
        mask |= ((u64)gen >> MMIO_GEN_LOW_SHIFT) << MMIO_SPTE_GEN_HIGH_SHIFT;
        return mask;
}

static unsigned int get_mmio_spte_generation(u64 spte)
{
        unsigned int gen;

        spte &= ~shadow_mmio_mask;

        gen = (spte >> MMIO_SPTE_GEN_LOW_SHIFT) & MMIO_GEN_LOW_MASK;
        gen |= (spte >> MMIO_SPTE_GEN_HIGH_SHIFT) << MMIO_GEN_LOW_SHIFT;
        return gen;
}

static unsigned int kvm_current_mmio_generation(struct kvm_vcpu *vcpu)
{
        return kvm_vcpu_memslots(vcpu)->generation & MMIO_GEN_MASK;
}

static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn,
                           unsigned access)
{
        unsigned int gen = kvm_current_mmio_generation(vcpu);
        u64 mask = generation_mmio_spte_mask(gen);

        access &= ACC_WRITE_MASK | ACC_USER_MASK;
        mask |= shadow_mmio_value | access | gfn << PAGE_SHIFT;

        trace_mark_mmio_spte(sptep, gfn, access, gen);
        mmu_spte_set(sptep, mask);
}

static bool is_mmio_spte(u64 spte)
{
        return (spte & shadow_mmio_mask) == shadow_mmio_value;
}

static gfn_t get_mmio_spte_gfn(u64 spte)
{
        u64 mask = generation_mmio_spte_mask(MMIO_GEN_MASK) | shadow_mmio_mask;
        return (spte & ~mask) >> PAGE_SHIFT;
}

static unsigned get_mmio_spte_access(u64 spte)
{
        u64 mask = generation_mmio_spte_mask(MMIO_GEN_MASK) | shadow_mmio_mask;
        return (spte & ~mask) & ~PAGE_MASK;
}

static bool set_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn,
                          kvm_pfn_t pfn, unsigned access)
{
        if (unlikely(is_noslot_pfn(pfn))) {
                mark_mmio_spte(vcpu, sptep, gfn, access);
                return true;
        }

        return false;
}

static bool check_mmio_spte(struct kvm_vcpu *vcpu, u64 spte)
{
        unsigned int kvm_gen, spte_gen;

        kvm_gen = kvm_current_mmio_generation(vcpu);
        spte_gen = get_mmio_spte_generation(spte);

        trace_check_mmio_spte(spte, kvm_gen, spte_gen);
        return likely(kvm_gen == spte_gen);
}

/*
 * Sets the shadow PTE masks used by the MMU.
 *
 * Assumptions:
 *  - Setting either @accessed_mask or @dirty_mask requires setting both
 *  - At least one of @accessed_mask or @acc_track_mask must be set
 */
void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
                u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask,
                u64 acc_track_mask, u64 me_mask)
{
        BUG_ON(!dirty_mask != !accessed_mask);
        BUG_ON(!accessed_mask && !acc_track_mask);
        BUG_ON(acc_track_mask & shadow_acc_track_value);

        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;
        shadow_present_mask = p_mask;
        shadow_acc_track_mask = acc_track_mask;
        shadow_me_mask = me_mask;
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes);

static void kvm_mmu_clear_all_pte_masks(void)
{
        shadow_user_mask = 0;
        shadow_accessed_mask = 0;
        shadow_dirty_mask = 0;
        shadow_nx_mask = 0;
        shadow_x_mask = 0;
        shadow_mmio_mask = 0;
        shadow_present_mask = 0;
        shadow_acc_track_mask = 0;
}

static int is_cpuid_PSE36(void)
{
        return 1;
}

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

static int is_shadow_present_pte(u64 pte)
{
        return (pte != 0) && !is_mmio_spte(pte);
}

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

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 bool is_executable_pte(u64 spte)
{
        return (spte & (shadow_x_mask | shadow_nx_mask)) == shadow_x_mask;
}

static kvm_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;
}

#ifdef CONFIG_X86_64
static void __set_spte(u64 *sptep, u64 spte)
{
        WRITE_ONCE(*sptep, spte);
}

static void __update_clear_spte_fast(u64 *sptep, u64 spte)
{
        WRITE_ONCE(*sptep, spte);
}

static u64 __update_clear_spte_slow(u64 *sptep, u64 spte)
{
        return xchg(sptep, spte);
}

static u64 __get_spte_lockless(u64 *sptep)
{
        return READ_ONCE(*sptep);
}
#else
union split_spte {
        struct {
                u32 spte_low;
                u32 spte_high;
        };
        u64 spte;
};

static void count_spte_clear(u64 *sptep, u64 spte)
{
        struct kvm_mmu_page *sp =  page_header(__pa(sptep));

        if (is_shadow_present_pte(spte))
                return;

        /* Ensure the spte is completely set before we increase the count */
        smp_wmb();
        sp->clear_spte_count++;
}

static void __set_spte(u64 *sptep, u64 spte)
{
        union split_spte *ssptep, sspte;

        ssptep = (union split_spte *)sptep;
        sspte = (union split_spte)spte;

        ssptep->spte_high = sspte.spte_high;

        /*
         * If we map the spte from nonpresent to present, We should store
         * the high bits firstly, then set present bit, so cpu can not
         * fetch this spte while we are setting the spte.
         */
        smp_wmb();

        WRITE_ONCE(ssptep->spte_low, sspte.spte_low);
}

static void __update_clear_spte_fast(u64 *sptep, u64 spte)
{
        union split_spte *ssptep, sspte;

        ssptep = (union split_spte *)sptep;
        sspte = (union split_spte)spte;

        WRITE_ONCE(ssptep->spte_low, sspte.spte_low);

        /*
         * If we map the spte from present to nonpresent, we should clear
         * present bit firstly to avoid vcpu fetch the old high bits.
         */
        smp_wmb();

        ssptep->spte_high = sspte.spte_high;
        count_spte_clear(sptep, spte);
}

static u64 __update_clear_spte_slow(u64 *sptep, u64 spte)
{
        union split_spte *ssptep, sspte, orig;

        ssptep = (union split_spte *)sptep;
        sspte = (union split_spte)spte;

        /* xchg acts as a barrier before the setting of the high bits */
        orig.spte_low = xchg(&ssptep->spte_low, sspte.spte_low);
        orig.spte_high = ssptep->spte_high;
        ssptep->spte_high = sspte.spte_high;
        count_spte_clear(sptep, spte);

        return orig.spte;
}

/*
 * The idea using the light way get the spte on x86_32 guest is from
 * gup_get_pte(arch/x86/mm/gup.c).
 *
 * An spte tlb flush may be pending, because kvm_set_pte_rmapp
 * coalesces them and we are running out of the MMU lock.  Therefore
 * we need to protect against in-progress updates of the spte.
 *
 * Reading the spte while an update is in progress may get the old value
 * for the high part of the spte.  The race is fine for a present->non-present
 * change (because the high part of the spte is ignored for non-present spte),
 * but for a present->present change we must reread the spte.
 *
 * All such changes are done in two steps (present->non-present and
 * non-present->present), hence it is enough to count the number of
 * present->non-present updates: if it changed while reading the spte,
 * we might have hit the race.  This is done using clear_spte_count.
 */
static u64 __get_spte_lockless(u64 *sptep)
{
        struct kvm_mmu_page *sp =  page_header(__pa(sptep));
        union split_spte spte, *orig = (union split_spte *)sptep;
        int count;

retry:
        count = sp->clear_spte_count;
        smp_rmb();

        spte.spte_low = orig->spte_low;
        smp_rmb();

        spte.spte_high = orig->spte_high;
        smp_rmb();

        if (unlikely(spte.spte_low != orig->spte_low ||
              count != sp->clear_spte_count))
                goto retry;

        return spte.spte;
}
#endif

static bool spte_can_locklessly_be_made_writable(u64 spte)
{
        return (spte & (SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE)) ==
                (SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE);
}

static bool spte_has_volatile_bits(u64 spte)
{
        if (!is_shadow_present_pte(spte))
                return false;

        /*
         * Always atomically update spte if it can be updated
         * out of mmu-lock, it can ensure dirty bit is not lost,
         * also, it can help us to get a stable is_writable_pte()
         * to ensure tlb flush is not missed.
         */
        if (spte_can_locklessly_be_made_writable(spte) ||
            is_access_track_spte(spte))
                return true;

        if (spte_ad_enabled(spte)) {
                if ((spte & shadow_accessed_mask) == 0 ||
                    (is_writable_pte(spte) && (spte & shadow_dirty_mask) == 0))
                        return true;
        }

        return false;
}

static bool is_accessed_spte(u64 spte)
{
        u64 accessed_mask = spte_shadow_accessed_mask(spte);

        return accessed_mask ? spte & accessed_mask
                             : !is_access_track_spte(spte);
}

static bool is_dirty_spte(u64 spte)
{
        u64 dirty_mask = spte_shadow_dirty_mask(spte);

        return dirty_mask ? spte & dirty_mask : spte & PT_WRITABLE_MASK;
}

/* Rules for using mmu_spte_set:
 * Set the sptep from nonpresent to present.
 * Note: the sptep being assigned *must* be either not present
 * or in a state where the hardware will not attempt to update
 * the spte.
 */
static void mmu_spte_set(u64 *sptep, u64 new_spte)
{
        WARN_ON(is_shadow_present_pte(*sptep));
        __set_spte(sptep, new_spte);
}

/*
 * Update the SPTE (excluding the PFN), but do not track changes in its
 * accessed/dirty status.
 */
static u64 mmu_spte_update_no_track(u64 *sptep, u64 new_spte)
{
        u64 old_spte = *sptep;

        WARN_ON(!is_shadow_present_pte(new_spte));

        if (!is_shadow_present_pte(old_spte)) {
                mmu_spte_set(sptep, new_spte);
                return old_spte;
        }

        if (!spte_has_volatile_bits(old_spte))
                __update_clear_spte_fast(sptep, new_spte);
        else
                old_spte = __update_clear_spte_slow(sptep, new_spte);

        WARN_ON(spte_to_pfn(old_spte) != spte_to_pfn(new_spte));

        return old_spte;
}

/* Rules for using mmu_spte_update:
 * Update the state bits, it means the mapped pfn is not changed.
 *
 * Whenever we overwrite a writable spte with a read-only one we
 * should flush remote TLBs. Otherwise rmap_write_protect
 * will find a read-only spte, even though the writable spte
 * might be cached on a CPU's TLB, the return value indicates this
 * case.
 *
 * Returns true if the TLB needs to be flushed
 */
static bool mmu_spte_update(u64 *sptep, u64 new_spte)
{
        bool flush = false;
        u64 old_spte = mmu_spte_update_no_track(sptep, new_spte);

        if (!is_shadow_present_pte(old_spte))
                return false;

        /*
         * For the spte updated out of mmu-lock is safe, since
         * we always atomically update it, see the comments in
         * spte_has_volatile_bits().
         */
        if (spte_can_locklessly_be_made_writable(old_spte) &&
              !is_writable_pte(new_spte))
                flush = true;

        /*
         * Flush TLB when accessed/dirty states are changed in the page tables,
         * to guarantee consistency between TLB and page tables.
         */

        if (is_accessed_spte(old_spte) && !is_accessed_spte(new_spte)) {
                flush = true;
                kvm_set_pfn_accessed(spte_to_pfn(old_spte));
        }

        if (is_dirty_spte(old_spte) && !is_dirty_spte(new_spte)) {
                flush = true;
                kvm_set_pfn_dirty(spte_to_pfn(old_spte));
        }

        return flush;
}

/*
 * Rules for using mmu_spte_clear_track_bits:
 * It sets the sptep from present to nonpresent, and track the
 * state bits, it is used to clear the last level sptep.
 * Returns non-zero if the PTE was previously valid.
 */
static int mmu_spte_clear_track_bits(u64 *sptep)
{
        kvm_pfn_t pfn;
        u64 old_spte = *sptep;

        if (!spte_has_volatile_bits(old_spte))
                __update_clear_spte_fast(sptep, 0ull);
        else
                old_spte = __update_clear_spte_slow(sptep, 0ull);

        if (!is_shadow_present_pte(old_spte))
                return 0;

        pfn = spte_to_pfn(old_spte);

        /*
         * KVM does not hold the refcount of the page used by
         * kvm mmu, before reclaiming the page, we should
         * unmap it from mmu first.
         */
        WARN_ON(!kvm_is_reserved_pfn(pfn) && !page_count(pfn_to_page(pfn)));

        if (is_accessed_spte(old_spte))
                kvm_set_pfn_accessed(pfn);

        if (is_dirty_spte(old_spte))
                kvm_set_pfn_dirty(pfn);

        return 1;
}

/*
 * Rules for using mmu_spte_clear_no_track:
 * Directly clear spte without caring the state bits of sptep,
 * it is used to set the upper level spte.
 */
static void mmu_spte_clear_no_track(u64 *sptep)
{
        __update_clear_spte_fast(sptep, 0ull);
}

static u64 mmu_spte_get_lockless(u64 *sptep)
{
        return __get_spte_lockless(sptep);
}

static u64 mark_spte_for_access_track(u64 spte)
{
        if (spte_ad_enabled(spte))
                return spte & ~shadow_accessed_mask;

        if (is_access_track_spte(spte))
                return spte;

        /*
         * Making an Access Tracking PTE will result in removal of write access
         * from the PTE. So, verify that we will be able to restore the write
         * access in the fast page fault path later on.
         */
        WARN_ONCE((spte & PT_WRITABLE_MASK) &&
                  !spte_can_locklessly_be_made_writable(spte),
                  "kvm: Writable SPTE is not locklessly dirty-trackable\n");

        WARN_ONCE(spte & (shadow_acc_track_saved_bits_mask <<
                          shadow_acc_track_saved_bits_shift),
                  "kvm: Access Tracking saved bit locations are not zero\n");

        spte |= (spte & shadow_acc_track_saved_bits_mask) <<
                shadow_acc_track_saved_bits_shift;
        spte &= ~shadow_acc_track_mask;

        return spte;
}

/* Restore an acc-track PTE back to a regular PTE */
static u64 restore_acc_track_spte(u64 spte)
{
        u64 new_spte = spte;
        u64 saved_bits = (spte >> shadow_acc_track_saved_bits_shift)
                         & shadow_acc_track_saved_bits_mask;

        WARN_ON_ONCE(spte_ad_enabled(spte));
        WARN_ON_ONCE(!is_access_track_spte(spte));

        new_spte &= ~shadow_acc_track_mask;
        new_spte &= ~(shadow_acc_track_saved_bits_mask <<
                      shadow_acc_track_saved_bits_shift);
        new_spte |= saved_bits;

        return new_spte;
}

/* Returns the Accessed status of the PTE and resets it at the same time. */
static bool mmu_spte_age(u64 *sptep)
{
        u64 spte = mmu_spte_get_lockless(sptep);

        if (!is_accessed_spte(spte))
                return false;

        if (spte_ad_enabled(spte)) {
                clear_bit((ffs(shadow_accessed_mask) - 1),
                          (unsigned long *)sptep);
        } else {
                /*
                 * Capture the dirty status of the page, so that it doesn't get
                 * lost when the SPTE is marked for access tracking.
                 */
                if (is_writable_pte(spte))
                        kvm_set_pfn_dirty(spte_to_pfn(spte));

                spte = mark_spte_for_access_track(spte);
                mmu_spte_update_no_track(sptep, spte);
        }

        return true;
}

static void walk_shadow_page_lockless_begin(struct kvm_vcpu *vcpu)
{
        /*
         * Prevent page table teardown by making any free-er wait during
         * kvm_flush_remote_tlbs() IPI to all active vcpus.
         */
        local_irq_disable();

        /*
         * Make sure a following spte read is not reordered ahead of the write
         * to vcpu->mode.
         */
        smp_store_mb(vcpu->mode, READING_SHADOW_PAGE_TABLES);
}

static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu)
{
        /*
         * Make sure the write to vcpu->mode is not reordered in front of
         * reads to sptes.  If it does, kvm_commit_zap_page() can see us
         * OUTSIDE_GUEST_MODE and proceed to free the shadow page table.
         */
        smp_store_release(&vcpu->mode, OUTSIDE_GUEST_MODE);
        local_irq_enable();
}

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 int mmu_memory_cache_free_objects(struct kvm_mmu_memory_cache *cache)
{
        return cache->nobjs;
}

static void mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc,
                                  struct kmem_cache *cache)
{
        while (mc->nobjs)
                kmem_cache_free(cache, mc->objects[--mc->nobjs]);
}

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

        if (cache->nobjs >= min)
                return 0;
        while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
                page = (void *)__get_free_page(GFP_KERNEL);
                if (!page)
                        return -ENOMEM;
                cache->objects[cache->nobjs++] = 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_list_desc_cache,
                                   pte_list_desc_cache, 8 + PTE_PREFETCH_NUM);
        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_list_desc_cache,
                                pte_list_desc_cache);
        mmu_free_memory_cache_page(&vcpu->arch.mmu_page_cache);
        mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache,
                                mmu_page_header_cache);
}

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

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

static struct pte_list_desc *mmu_alloc_pte_list_desc(struct kvm_vcpu *vcpu)
{
        return mmu_memory_cache_alloc(&vcpu->arch.mmu_pte_list_desc_cache);
}

static void mmu_free_pte_list_desc(struct pte_list_desc *pte_list_desc)
{
        kmem_cache_free(pte_list_desc_cache, pte_list_desc);
}

static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index)
{
        if (!sp->role.direct)
                return sp->gfns[index];

        return sp->gfn + (index << ((sp->role.level - 1) * PT64_LEVEL_BITS));
}

static void kvm_mmu_page_set_gfn(struct kvm_mmu_page *sp, int index, gfn_t gfn)
{
        if (sp->role.direct)
                BUG_ON(gfn != kvm_mmu_page_get_gfn(sp, index));
        else
                sp->gfns[index] = gfn;
}

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

        idx = gfn_to_index(gfn, slot->base_gfn, level);
        return &slot->arch.lpage_info[level - 2][idx];
}

static void update_gfn_disallow_lpage_count(struct kvm_memory_slot *slot,
                                            gfn_t gfn, int count)
{
        struct kvm_lpage_info *linfo;
        int i;

        for (i = PT_DIRECTORY_LEVEL; i <= PT_MAX_HUGEPAGE_LEVEL; ++i) {
                linfo = lpage_info_slot(gfn, slot, i);
                linfo->disallow_lpage += count;
                WARN_ON(linfo->disallow_lpage < 0);
        }
}

void kvm_mmu_gfn_disallow_lpage(struct kvm_memory_slot *slot, gfn_t gfn)
{
        update_gfn_disallow_lpage_count(slot, gfn, 1);
}

void kvm_mmu_gfn_allow_lpage(struct kvm_memory_slot *slot, gfn_t gfn)
{
        update_gfn_disallow_lpage_count(slot, gfn, -1);
}

static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *slot;
        gfn_t gfn;

        kvm->arch.indirect_shadow_pages++;
        gfn = sp->gfn;
        slots = kvm_memslots_for_spte_role(kvm, sp->role);
        slot = __gfn_to_memslot(slots, gfn);

        /* the non-leaf shadow pages are keeping readonly. */
        if (sp->role.level > PT_PAGE_TABLE_LEVEL)
                return kvm_slot_page_track_add_page(kvm, slot, gfn,
                                                    KVM_PAGE_TRACK_WRITE);

        kvm_mmu_gfn_disallow_lpage(slot, gfn);
}

static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *slot;
        gfn_t gfn;

        kvm->arch.indirect_shadow_pages--;
        gfn = sp->gfn;
        slots = kvm_memslots_for_spte_role(kvm, sp->role);
        slot = __gfn_to_memslot(slots, gfn);
        if (sp->role.level > PT_PAGE_TABLE_LEVEL)
                return kvm_slot_page_track_remove_page(kvm, slot, gfn,
                                                       KVM_PAGE_TRACK_WRITE);

        kvm_mmu_gfn_allow_lpage(slot, gfn);
}

static bool __mmu_gfn_lpage_is_disallowed(gfn_t gfn, int level,
                                          struct kvm_memory_slot *slot)
{
        struct kvm_lpage_info *linfo;

        if (slot) {
                linfo = lpage_info_slot(gfn, slot, level);
                return !!linfo->disallow_lpage;
        }

        return true;
}

static bool mmu_gfn_lpage_is_disallowed(struct kvm_vcpu *vcpu, gfn_t gfn,
                                        int level)
{
        struct kvm_memory_slot *slot;

        slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        return __mmu_gfn_lpage_is_disallowed(gfn, level, slot);
}

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

        page_size = kvm_host_page_size(kvm, gfn);

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

        return ret;
}

static inline bool memslot_valid_for_gpte(struct kvm_memory_slot *slot,
                                          bool no_dirty_log)
{
        if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
                return false;
        if (no_dirty_log && slot->dirty_bitmap)
                return false;

        return true;
}

static struct kvm_memory_slot *
gfn_to_memslot_dirty_bitmap(struct kvm_vcpu *vcpu, gfn_t gfn,
                            bool no_dirty_log)
{
        struct kvm_memory_slot *slot;

        slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        if (!memslot_valid_for_gpte(slot, no_dirty_log))
                slot = NULL;

        return slot;
}

static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn,
                         bool *force_pt_level)
{
        int host_level, level, max_level;
        struct kvm_memory_slot *slot;

        if (unlikely(*force_pt_level))
                return PT_PAGE_TABLE_LEVEL;

        slot = kvm_vcpu_gfn_to_memslot(vcpu, large_gfn);
        *force_pt_level = !memslot_valid_for_gpte(slot, true);
        if (unlikely(*force_pt_level))
                return PT_PAGE_TABLE_LEVEL;

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

        if (host_level == PT_PAGE_TABLE_LEVEL)
                return host_level;

        max_level = min(kvm_x86_ops->get_lpage_level(), host_level);

        for (level = PT_DIRECTORY_LEVEL; level <= max_level; ++level)
                if (__mmu_gfn_lpage_is_disallowed(large_gfn, level, slot))
                        break;

        return level - 1;
}

/*
 * About rmap_head encoding:
 *
 * If the bit zero of rmap_head->val is clear, then it points to the only spte
 * in this rmap chain. Otherwise, (rmap_head->val & ~1) points to a struct
 * pte_list_desc containing more mappings.
 */

/*
 * Returns the number of pointers in the rmap chain, not counting the new one.
 */
static int pte_list_add(struct kvm_vcpu *vcpu, u64 *spte,
                        struct kvm_rmap_head *rmap_head)
{
        struct pte_list_desc *desc;
        int i, count = 0;

        if (!rmap_head->val) {
                rmap_printk("pte_list_add: %p %llx 0->1\n", spte, *spte);
                rmap_head->val = (unsigned long)spte;
        } else if (!(rmap_head->val & 1)) {
                rmap_printk("pte_list_add: %p %llx 1->many\n", spte, *spte);
                desc = mmu_alloc_pte_list_desc(vcpu);
                desc->sptes[0] = (u64 *)rmap_head->val;
                desc->sptes[1] = spte;
                rmap_head->val = (unsigned long)desc | 1;
                ++count;
        } else {
                rmap_printk("pte_list_add: %p %llx many->many\n", spte, *spte);
                desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
                while (desc->sptes[PTE_LIST_EXT-1] && desc->more) {
                        desc = desc->more;
                        count += PTE_LIST_EXT;
                }
                if (desc->sptes[PTE_LIST_EXT-1]) {
                        desc->more = mmu_alloc_pte_list_desc(vcpu);
                        desc = desc->more;
                }
                for (i = 0; desc->sptes[i]; ++i)
                        ++count;
                desc->sptes[i] = spte;
        }
        return count;
}

static void
pte_list_desc_remove_entry(struct kvm_rmap_head *rmap_head,
                           struct pte_list_desc *desc, int i,
                           struct pte_list_desc *prev_desc)
{
        int j;

        for (j = PTE_LIST_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)
                rmap_head->val = (unsigned long)desc->sptes[0];
        else
                if (prev_desc)
                        prev_desc->more = desc->more;
                else
                        rmap_head->val = (unsigned long)desc->more | 1;
        mmu_free_pte_list_desc(desc);
}

static void pte_list_remove(u64 *spte, struct kvm_rmap_head *rmap_head)
{
        struct pte_list_desc *desc;
        struct pte_list_desc *prev_desc;
        int i;

        if (!rmap_head->val) {
                printk(KERN_ERR "pte_list_remove: %p 0->BUG\n", spte);
                BUG();
        } else if (!(rmap_head->val & 1)) {
                rmap_printk("pte_list_remove:  %p 1->0\n", spte);
                if ((u64 *)rmap_head->val != spte) {
                        printk(KERN_ERR "pte_list_remove:  %p 1->BUG\n", spte);
                        BUG();
                }
                rmap_head->val = 0;
        } else {
                rmap_printk("pte_list_remove:  %p many->many\n", spte);
                desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
                prev_desc = NULL;
                while (desc) {
                        for (i = 0; i < PTE_LIST_EXT && desc->sptes[i]; ++i) {
                                if (desc->sptes[i] == spte) {
                                        pte_list_desc_remove_entry(rmap_head,
                                                        desc, i, prev_desc);
                                        return;
                                }
                        }
                        prev_desc = desc;
                        desc = desc->more;
                }
                pr_err("pte_list_remove: %p many->many\n", spte);
                BUG();
        }
}

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

        idx = gfn_to_index(gfn, slot->base_gfn, level);
        return &slot->arch.rmap[level - PT_PAGE_TABLE_LEVEL][idx];
}

static struct kvm_rmap_head *gfn_to_rmap(struct kvm *kvm, gfn_t gfn,
                                         struct kvm_mmu_page *sp)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *slot;

        slots = kvm_memslots_for_spte_role(kvm, sp->role);
        slot = __gfn_to_memslot(slots, gfn);
        return __gfn_to_rmap(gfn, sp->role.level, slot);
}

static bool rmap_can_add(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_memory_cache *cache;

        cache = &vcpu->arch.mmu_pte_list_desc_cache;
        return mmu_memory_cache_free_objects(cache);
}

static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
{
        struct kvm_mmu_page *sp;
        struct kvm_rmap_head *rmap_head;

        sp = page_header(__pa(spte));
        kvm_mmu_page_set_gfn(sp, spte - sp->spt, gfn);
        rmap_head = gfn_to_rmap(vcpu->kvm, gfn, sp);
        return pte_list_add(vcpu, spte, rmap_head);
}

static void rmap_remove(struct kvm *kvm, u64 *spte)
{
        struct kvm_mmu_page *sp;
        gfn_t gfn;
        struct kvm_rmap_head *rmap_head;

        sp = page_header(__pa(spte));
        gfn = kvm_mmu_page_get_gfn(sp, spte - sp->spt);
        rmap_head = gfn_to_rmap(kvm, gfn, sp);
        pte_list_remove(spte, rmap_head);
}

/*
 * Used by the following functions to iterate through the sptes linked by a
 * rmap.  All fields are private and not assumed to be used outside.
 */
struct rmap_iterator {
        /* private fields */
        struct pte_list_desc *desc;     /* holds the sptep if not NULL */
        int pos;                        /* index of the sptep */
};

/*
 * Iteration must be started by this function.  This should also be used after
 * removing/dropping sptes from the rmap link because in such cases the
 * information in the itererator may not be valid.
 *
 * Returns sptep if found, NULL otherwise.
 */
static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head,
                           struct rmap_iterator *iter)
{
        u64 *sptep;

        if (!rmap_head->val)
                return NULL;

        if (!(rmap_head->val & 1)) {
                iter->desc = NULL;
                sptep = (u64 *)rmap_head->val;
                goto out;
        }

        iter->desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
        iter->pos = 0;
        sptep = iter->desc->sptes[iter->pos];
out:
        BUG_ON(!is_shadow_present_pte(*sptep));
        return sptep;
}

/*
 * Must be used with a valid iterator: e.g. after rmap_get_first().
 *
 * Returns sptep if found, NULL otherwise.
 */
static u64 *rmap_get_next(struct rmap_iterator *iter)
{
        u64 *sptep;

        if (iter->desc) {
                if (iter->pos < PTE_LIST_EXT - 1) {
                        ++iter->pos;
                        sptep = iter->desc->sptes[iter->pos];
                        if (sptep)
                                goto out;
                }

                iter->desc = iter->desc->more;

                if (iter->desc) {
                        iter->pos = 0;
                        /* desc->sptes[0] cannot be NULL */
                        sptep = iter->desc->sptes[iter->pos];
                        goto out;
                }
        }

        return NULL;
out:
        BUG_ON(!is_shadow_present_pte(*sptep));
        return sptep;
}

#define for_each_rmap_spte(_rmap_head_, _iter_, _spte_)                 \
        for (_spte_ = rmap_get_first(_rmap_head_, _iter_);              \
             _spte_; _spte_ = rmap_get_next(_iter_))

static void drop_spte(struct kvm *kvm, u64 *sptep)
{
        if (mmu_spte_clear_track_bits(sptep))
                rmap_remove(kvm, sptep);
}


static bool __drop_large_spte(struct kvm *kvm, u64 *sptep)
{
        if (is_large_pte(*sptep)) {
                WARN_ON(page_header(__pa(sptep))->role.level ==
                        PT_PAGE_TABLE_LEVEL);
                drop_spte(kvm, sptep);
                --kvm->stat.lpages;
                return true;
        }

        return false;
}

static void drop_large_spte(struct kvm_vcpu *vcpu, u64 *sptep)
{
        if (__drop_large_spte(vcpu->kvm, sptep))
                kvm_flush_remote_tlbs(vcpu->kvm);
}

/*
 * Write-protect on the specified @sptep, @pt_protect indicates whether
 * spte write-protection is caused by protecting shadow page table.
 *
 * Note: write protection is difference between dirty logging and spte
 * protection:
 * - for dirty logging, the spte can be set to writable at anytime if
 *   its dirty bitmap is properly set.
 * - for spte protection, the spte can be writable only after unsync-ing
 *   shadow page.
 *
 * Return true if tlb need be flushed.
 */
static bool spte_write_protect(u64 *sptep, bool pt_protect)
{
        u64 spte = *sptep;

        if (!is_writable_pte(spte) &&
              !(pt_protect && spte_can_locklessly_be_made_writable(spte)))
                return false;

        rmap_printk("rmap_write_protect: spte %p %llx\n", sptep, *sptep);

        if (pt_protect)
                spte &= ~SPTE_MMU_WRITEABLE;
        spte = spte & ~PT_WRITABLE_MASK;

        return mmu_spte_update(sptep, spte);
}

static bool __rmap_write_protect(struct kvm *kvm,
                                 struct kvm_rmap_head *rmap_head,
                                 bool pt_protect)
{
        u64 *sptep;
        struct rmap_iterator iter;
        bool flush = false;

        for_each_rmap_spte(rmap_head, &iter, sptep)
                flush |= spte_write_protect(sptep, pt_protect);

        return flush;
}

static bool spte_clear_dirty(u64 *sptep)
{
        u64 spte = *sptep;

        rmap_printk("rmap_clear_dirty: spte %p %llx\n", sptep, *sptep);

        spte &= ~shadow_dirty_mask;

        return mmu_spte_update(sptep, spte);
}

static bool wrprot_ad_disabled_spte(u64 *sptep)
{
        bool was_writable = test_and_clear_bit(PT_WRITABLE_SHIFT,
                                               (unsigned long *)sptep);
        if (was_writable)
                kvm_set_pfn_dirty(spte_to_pfn(*sptep));

        return was_writable;
}

/*
 * Gets the GFN ready for another round of dirty logging by clearing the
 *      - D bit on ad-enabled SPTEs, and
 *      - W bit on ad-disabled SPTEs.
 * Returns true iff any D or W bits were cleared.
 */
static bool __rmap_clear_dirty(struct kvm *kvm, struct kvm_rmap_head *rmap_head)
{
        u64 *sptep;
        struct rmap_iterator iter;
        bool flush = false;

        for_each_rmap_spte(rmap_head, &iter, sptep)
                if (spte_ad_enabled(*sptep))
                        flush |= spte_clear_dirty(sptep);
                else
                        flush |= wrprot_ad_disabled_spte(sptep);

        return flush;
}

static bool spte_set_dirty(u64 *sptep)
{
        u64 spte = *sptep;

        rmap_printk("rmap_set_dirty: spte %p %llx\n", sptep, *sptep);

        spte |= shadow_dirty_mask;

        return mmu_spte_update(sptep, spte);
}

static bool __rmap_set_dirty(struct kvm *kvm, struct kvm_rmap_head *rmap_head)
{
        u64 *sptep;
        struct rmap_iterator iter;
        bool flush = false;

        for_each_rmap_spte(rmap_head, &iter, sptep)
                if (spte_ad_enabled(*sptep))
                        flush |= spte_set_dirty(sptep);

        return flush;
}

/**
 * kvm_mmu_write_protect_pt_masked - write protect selected PT level pages
 * @kvm: kvm instance
 * @slot: slot to protect
 * @gfn_offset: start of the BITS_PER_LONG pages we care about
 * @mask: indicates which pages we should protect
 *
 * Used when we do not need to care about huge page mappings: e.g. during dirty
 * logging we do not have any such mappings.
 */
static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
                                     struct kvm_memory_slot *slot,
                                     gfn_t gfn_offset, unsigned long mask)
{
        struct kvm_rmap_head *rmap_head;

        while (mask) {
                rmap_head = __gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask),
                                          PT_PAGE_TABLE_LEVEL, slot);
                __rmap_write_protect(kvm, rmap_head, false);

                /* clear the first set bit */
                mask &= mask - 1;
        }
}

/**
 * kvm_mmu_clear_dirty_pt_masked - clear MMU D-bit for PT level pages, or write
 * protect the page if the D-bit isn't supported.
 * @kvm: kvm instance
 * @slot: slot to clear D-bit
 * @gfn_offset: start of the BITS_PER_LONG pages we care about
 * @mask: indicates which pages we should clear D-bit
 *
 * Used for PML to re-log the dirty GPAs after userspace querying dirty_bitmap.
 */
void kvm_mmu_clear_dirty_pt_masked(struct kvm *kvm,
                                     struct kvm_memory_slot *slot,
                                     gfn_t gfn_offset, unsigned long mask)
{
        struct kvm_rmap_head *rmap_head;

        while (mask) {
                rmap_head = __gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask),
                                          PT_PAGE_TABLE_LEVEL, slot);
                __rmap_clear_dirty(kvm, rmap_head);

                /* clear the first set bit */
                mask &= mask - 1;
        }
}
EXPORT_SYMBOL_GPL(kvm_mmu_clear_dirty_pt_masked);

/**
 * kvm_arch_mmu_enable_log_dirty_pt_masked - enable dirty logging for selected
 * PT level pages.
 *
 * It calls kvm_mmu_write_protect_pt_masked to write protect selected pages to
 * enable dirty logging for them.
 *
 * Used when we do not need to care about huge page mappings: e.g. during dirty
 * logging we do not have any such mappings.
 */
void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
                                struct kvm_memory_slot *slot,
                                gfn_t gfn_offset, unsigned long mask)
{
        if (kvm_x86_ops->enable_log_dirty_pt_masked)
                kvm_x86_ops->enable_log_dirty_pt_masked(kvm, slot, gfn_offset,
                                mask);
        else
                kvm_mmu_write_protect_pt_masked(kvm, slot, gfn_offset, mask);
}

/**
 * kvm_arch_write_log_dirty - emulate dirty page logging
 * @vcpu: Guest mode vcpu
 *
 * Emulate arch specific page modification logging for the
 * nested hypervisor
 */
int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu)
{
        if (kvm_x86_ops->write_log_dirty)
                return kvm_x86_ops->write_log_dirty(vcpu);

        return 0;
}

bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
                                    struct kvm_memory_slot *slot, u64 gfn)
{
        struct kvm_rmap_head *rmap_head;
        int i;
        bool write_protected = false;

        for (i = PT_PAGE_TABLE_LEVEL; i <= PT_MAX_HUGEPAGE_LEVEL; ++i) {
                rmap_head = __gfn_to_rmap(gfn, i, slot);
                write_protected |= __rmap_write_protect(kvm, rmap_head, true);
        }

        return write_protected;
}

static bool rmap_write_protect(struct kvm_vcpu *vcpu, u64 gfn)
{
        struct kvm_memory_slot *slot;

        slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        return kvm_mmu_slot_gfn_write_protect(vcpu->kvm, slot, gfn);
}

static bool kvm_zap_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head)
{
        u64 *sptep;
        struct rmap_iterator iter;
        bool flush = false;

        while ((sptep = rmap_get_first(rmap_head, &iter))) {
                rmap_printk("%s: spte %p %llx.\n", __func__, sptep, *sptep);

                drop_spte(kvm, sptep);
                flush = true;
        }

        return flush;
}

static int kvm_unmap_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                           struct kvm_memory_slot *slot, gfn_t gfn, int level,
                           unsigned long data)
{
        return kvm_zap_rmapp(kvm, rmap_head);
}

static int kvm_set_pte_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                             struct kvm_memory_slot *slot, gfn_t gfn, int level,
                             unsigned long data)
{
        u64 *sptep;
        struct rmap_iterator iter;
        int need_flush = 0;
        u64 new_spte;
        pte_t *ptep = (pte_t *)data;
        kvm_pfn_t new_pfn;

        WARN_ON(pte_huge(*ptep));
        new_pfn = pte_pfn(*ptep);

restart:
        for_each_rmap_spte(rmap_head, &iter, sptep) {
                rmap_printk("kvm_set_pte_rmapp: spte %p %llx gfn %llx (%d)\n",
                            sptep, *sptep, gfn, level);

                need_flush = 1;

                if (pte_write(*ptep)) {
                        drop_spte(kvm, sptep);
                        goto restart;
                } else {
                        new_spte = *sptep & ~PT64_BASE_ADDR_MASK;
                        new_spte |= (u64)new_pfn << PAGE_SHIFT;

                        new_spte &= ~PT_WRITABLE_MASK;
                        new_spte &= ~SPTE_HOST_WRITEABLE;

                        new_spte = mark_spte_for_access_track(new_spte);

                        mmu_spte_clear_track_bits(sptep);
                        mmu_spte_set(sptep, new_spte);
                }
        }

        if (need_flush)
                kvm_flush_remote_tlbs(kvm);

        return 0;
}

struct slot_rmap_walk_iterator {
        /* input fields. */
        struct kvm_memory_slot *slot;
        gfn_t start_gfn;
        gfn_t end_gfn;
        int start_level;
        int end_level;

        /* output fields. */
        gfn_t gfn;
        struct kvm_rmap_head *rmap;
        int level;

        /* private field. */
        struct kvm_rmap_head *end_rmap;
};

static void
rmap_walk_init_level(struct slot_rmap_walk_iterator *iterator, int level)
{
        iterator->level = level;
        iterator->gfn = iterator->start_gfn;
        iterator->rmap = __gfn_to_rmap(iterator->gfn, level, iterator->slot);
        iterator->end_rmap = __gfn_to_rmap(iterator->end_gfn, level,
                                           iterator->slot);
}

static void
slot_rmap_walk_init(struct slot_rmap_walk_iterator *iterator,
                    struct kvm_memory_slot *slot, int start_level,
                    int end_level, gfn_t start_gfn, gfn_t end_gfn)
{
        iterator->slot = slot;
        iterator->start_level = start_level;
        iterator->end_level = end_level;
        iterator->start_gfn = start_gfn;
        iterator->end_gfn = end_gfn;

        rmap_walk_init_level(iterator, iterator->start_level);
}

static bool slot_rmap_walk_okay(struct slot_rmap_walk_iterator *iterator)
{
        return !!iterator->rmap;
}

static void slot_rmap_walk_next(struct slot_rmap_walk_iterator *iterator)
{
        if (++iterator->rmap <= iterator->end_rmap) {
                iterator->gfn += (1UL << KVM_HPAGE_GFN_SHIFT(iterator->level));
                return;
        }

        if (++iterator->level > iterator->end_level) {
                iterator->rmap = NULL;
                return;
        }

        rmap_walk_init_level(iterator, iterator->level);
}

#define for_each_slot_rmap_range(_slot_, _start_level_, _end_level_,    \
           _start_gfn, _end_gfn, _iter_)                                \
        for (slot_rmap_walk_init(_iter_, _slot_, _start_level_,         \
                                 _end_level_, _start_gfn, _end_gfn);    \
             slot_rmap_walk_okay(_iter_);                               \
             slot_rmap_walk_next(_iter_))

static int kvm_handle_hva_range(struct kvm *kvm,
                                unsigned long start,
                                unsigned long end,
                                unsigned long data,
                                int (*handler)(struct kvm *kvm,
                                               struct kvm_rmap_head *rmap_head,
                                               struct kvm_memory_slot *slot,
                                               gfn_t gfn,
                                               int level,
                                               unsigned long data))
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;
        struct slot_rmap_walk_iterator iterator;
        int ret = 0;
        int i;

        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                slots = __kvm_memslots(kvm, i);
                kvm_for_each_memslot(memslot, slots) {
                        unsigned long hva_start, hva_end;
                        gfn_t gfn_start, gfn_end;

                        hva_start = max(start, memslot->userspace_addr);
                        hva_end = min(end, memslot->userspace_addr +
                                      (memslot->npages << PAGE_SHIFT));
                        if (hva_start >= hva_end)
                                continue;
                        /*
                         * {gfn(page) | page intersects with [hva_start, hva_end)} =
                         * {gfn_start, gfn_start+1, ..., gfn_end-1}.
                         */
                        gfn_start = hva_to_gfn_memslot(hva_start, memslot);
                        gfn_end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, memslot);

                        for_each_slot_rmap_range(memslot, PT_PAGE_TABLE_LEVEL,
                                                 PT_MAX_HUGEPAGE_LEVEL,
                                                 gfn_start, gfn_end - 1,
                                                 &iterator)
                                ret |= handler(kvm, iterator.rmap, memslot,
                                               iterator.gfn, iterator.level, data);
                }
        }

        return ret;
}

static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
                          unsigned long data,
                          int (*handler)(struct kvm *kvm,
                                         struct kvm_rmap_head *rmap_head,
                                         struct kvm_memory_slot *slot,
                                         gfn_t gfn, int level,
                                         unsigned long data))
{
        return kvm_handle_hva_range(kvm, hva, hva + 1, data, handler);
}

int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
{
        return kvm_handle_hva(kvm, hva, 0, kvm_unmap_rmapp);
}

int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end)
{
        return kvm_handle_hva_range(kvm, start, end, 0, kvm_unmap_rmapp);
}

void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
{
        kvm_handle_hva(kvm, hva, (unsigned long)&pte, kvm_set_pte_rmapp);
}

static int kvm_age_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                         struct kvm_memory_slot *slot, gfn_t gfn, int level,
                         unsigned long data)
{
        u64 *sptep;
        struct rmap_iterator uninitialized_var(iter);
        int young = 0;

        for_each_rmap_spte(rmap_head, &iter, sptep)
                young |= mmu_spte_age(sptep);

        trace_kvm_age_page(gfn, level, slot, young);
        return young;
}

static int kvm_test_age_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                              struct kvm_memory_slot *slot, gfn_t gfn,
                              int level, unsigned long data)
{
        u64 *sptep;
        struct rmap_iterator iter;

        for_each_rmap_spte(rmap_head, &iter, sptep)
                if (is_accessed_spte(*sptep))
                        return 1;
        return 0;
}

#define RMAP_RECYCLE_THRESHOLD 1000

static void rmap_recycle(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
{
        struct kvm_rmap_head *rmap_head;
        struct kvm_mmu_page *sp;

        sp = page_header(__pa(spte));

        rmap_head = gfn_to_rmap(vcpu->kvm, gfn, sp);

        kvm_unmap_rmapp(vcpu->kvm, rmap_head, NULL, gfn, sp->role.level, 0);
        kvm_flush_remote_tlbs(vcpu->kvm);
}

int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end)
{
        return kvm_handle_hva_range(kvm, start, end, 0, kvm_age_rmapp);
}

int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
{
        return kvm_handle_hva(kvm, hva, 0, kvm_test_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

/*
 * This value is the sum of all of the kvm instances's
 * kvm->arch.n_used_mmu_pages values.  We need a global,
 * aggregate version in order to make the slab shrinker
 * faster
 */
static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, int nr)
{
        kvm->arch.n_used_mmu_pages += nr;
        percpu_counter_add(&kvm_total_used_mmu_pages, nr);
}

static void kvm_mmu_free_page(struct kvm_mmu_page *sp)
{
        MMU_WARN_ON(!is_empty_shadow_page(sp->spt));
        hlist_del(&sp->hash_link);
        list_del(&sp->link);
        free_page((unsigned long)sp->spt);
        if (!sp->role.direct)
                free_page((unsigned long)sp->gfns);
        kmem_cache_free(mmu_page_header_cache, sp);
}

static unsigned kvm_page_table_hashfn(gfn_t gfn)
{
        return hash_64(gfn, KVM_MMU_HASH_SHIFT);
}

static void mmu_page_add_parent_pte(struct kvm_vcpu *vcpu,
                                    struct kvm_mmu_page *sp, u64 *parent_pte)
{
        if (!parent_pte)
                return;

        pte_list_add(vcpu, parent_pte, &sp->parent_ptes);
}

static void mmu_page_remove_parent_pte(struct kvm_mmu_page *sp,
                                       u64 *parent_pte)
{
        pte_list_remove(parent_pte, &sp->parent_ptes);
}

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

static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu, int direct)
{
        struct kvm_mmu_page *sp;

        sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
        sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
        if (!direct)
                sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
        set_page_private(virt_to_page(sp->spt), (unsigned long)sp);

        /*
         * The active_mmu_pages list is the FIFO list, do not move the
         * page until it is zapped. kvm_zap_obsolete_pages depends on
         * this feature. See the comments in kvm_zap_obsolete_pages().
         */
        list_add(&sp->link, &vcpu->kvm->arch.active_mmu_pages);
        kvm_mod_used_mmu_pages(vcpu->kvm, +1);
        return sp;
}

static void mark_unsync(u64 *spte);
static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp)
{
        u64 *sptep;
        struct rmap_iterator iter;

        for_each_rmap_spte(&sp->parent_ptes, &iter, sptep) {
                mark_unsync(sptep);
        }
}

static void mark_unsync(u64 *spte)
{
        struct kvm_mmu_page *sp;
        unsigned int index;

        sp = page_header(__pa(spte));
        index = spte - sp->spt;
        if (__test_and_set_bit(index, sp->unsync_child_bitmap))
                return;
        if (sp->unsync_children++)
                return;
        kvm_mmu_mark_parents_unsync(sp);
}

static int nonpaging_sync_page(struct kvm_vcpu *vcpu,
                               struct kvm_mmu_page *sp)
{
        return 0;
}

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

static void nonpaging_update_pte(struct kvm_vcpu *vcpu,
                                 struct kvm_mmu_page *sp, u64 *spte,
                                 const void *pte)
{
        WARN_ON(1);
}

#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;
};

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 inline void clear_unsync_child_bit(struct kvm_mmu_page *sp, int idx)
{
        --sp->unsync_children;
        WARN_ON((int)sp->unsync_children < 0);
        __clear_bit(idx, sp->unsync_child_bitmap);
}

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

        for_each_set_bit(i, sp->unsync_child_bitmap, 512) {
                struct kvm_mmu_page *child;
                u64 ent = sp->spt[i];

                if (!is_shadow_present_pte(ent) || is_large_pte(ent)) {
                        clear_unsync_child_bit(sp, i);
                        continue;
                }

                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_unsync_child_bit(sp, i);
                                continue;
                        } else if (ret > 0) {
                                nr_unsync_leaf += ret;
                        } else
                                return ret;
                } else if (child->unsync) {
                        nr_unsync_leaf++;
                        if (mmu_pages_add(pvec, child, i))
                                return -ENOSPC;
                } else
                        clear_unsync_child_bit(sp, i);
        }

        return nr_unsync_leaf;
}

#define INVALID_INDEX (-1)

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

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

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

static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
                                    struct list_head *invalid_list);
static void kvm_mmu_commit_zap_page(struct kvm *kvm,
                                    struct list_head *invalid_list);

/*
 * NOTE: we should pay more attention on the zapped-obsolete page
 * (is_obsolete_sp(sp) && sp->role.invalid) when you do hash list walk
 * since it has been deleted from active_mmu_pages but still can be found
 * at hast list.
 *
 * for_each_valid_sp() has skipped that kind of pages.
 */
#define for_each_valid_sp(_kvm, _sp, _gfn)                              \
        hlist_for_each_entry(_sp,                                       \
          &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)], hash_link) \
                if (is_obsolete_sp((_kvm), (_sp)) || (_sp)->role.invalid) {    \
                } else

#define for_each_gfn_indirect_valid_sp(_kvm, _sp, _gfn)                 \
        for_each_valid_sp(_kvm, _sp, _gfn)                              \
                if ((_sp)->gfn != (_gfn) || (_sp)->role.direct) {} else

/* @sp->gfn should be write-protected at the call site */
static bool __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
                            struct list_head *invalid_list)
{
        if (sp->role.cr4_pae != !!is_pae(vcpu)) {
                kvm_mmu_prepare_zap_page(vcpu->kvm, sp, invalid_list);
                return false;
        }

        if (vcpu->arch.mmu.sync_page(vcpu, sp) == 0) {
                kvm_mmu_prepare_zap_page(vcpu->kvm, sp, invalid_list);
                return false;
        }

        return true;
}

static void kvm_mmu_flush_or_zap(struct kvm_vcpu *vcpu,
                                 struct list_head *invalid_list,
                                 bool remote_flush, bool local_flush)
{
        if (!list_empty(invalid_list)) {
                kvm_mmu_commit_zap_page(vcpu->kvm, invalid_list);
                return;
        }

        if (remote_flush)
                kvm_flush_remote_tlbs(vcpu->kvm);
        else if (local_flush)
                kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
}

#ifdef CONFIG_KVM_MMU_AUDIT
#include "mmu_audit.c"
#else
static void kvm_mmu_audit(struct kvm_vcpu *vcpu, int point) { }
static void mmu_audit_disable(void) { }
#endif

static bool is_obsolete_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        return unlikely(sp->mmu_valid_gen != kvm->arch.mmu_valid_gen);
}

static bool kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
                         struct list_head *invalid_list)
{
        kvm_unlink_unsync_page(vcpu->kvm, sp);
        return __kvm_sync_page(vcpu, sp, invalid_list);
}

/* @gfn should be write-protected at the call site */
static bool kvm_sync_pages(struct kvm_vcpu *vcpu, gfn_t gfn,
                           struct list_head *invalid_list)
{
        struct kvm_mmu_page *s;
        bool ret = false;

        for_each_gfn_indirect_valid_sp(vcpu->kvm, s, gfn) {
                if (!s->unsync)
                        continue;

                WARN_ON(s->role.level != PT_PAGE_TABLE_LEVEL);
                ret |= kvm_sync_page(vcpu, s, invalid_list);
        }

        return ret;
}

struct mmu_page_path {
        struct kvm_mmu_page *parent[PT64_ROOT_MAX_LEVEL];
        unsigned int idx[PT64_ROOT_MAX_LEVEL];
};

#define for_each_sp(pvec, sp, parents, i)                       \
                for (i = mmu_pages_first(&pvec, &parents);      \
                        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;
                unsigned idx = pvec->page[n].idx;
                int level = sp->role.level;

                parents->idx[level-1] = idx;
                if (level == PT_PAGE_TABLE_LEVEL)
                        break;

                parents->parent[level-2] = sp;
        }

        return n;
}

static int mmu_pages_first(struct kvm_mmu_pages *pvec,
                           struct mmu_page_path *parents)
{
        struct kvm_mmu_page *sp;
        int level;

        if (pvec->nr == 0)
                return 0;

        WARN_ON(pvec->page[0].idx != INVALID_INDEX);

        sp = pvec->page[0].sp;
        level = sp->role.level;
        WARN_ON(level == PT_PAGE_TABLE_LEVEL);

        parents->parent[level-2] = sp;

        /* Also set up a sentinel.  Further entries in pvec are all
         * children of sp, so this element is never overwritten.
         */
        parents->parent[level-1] = NULL;
        return mmu_pages_next(pvec, parents, 0);
}

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;

                WARN_ON(idx == INVALID_INDEX);
                clear_unsync_child_bit(sp, idx);
                level++;
        } while (!sp->unsync_children);
}

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;
        LIST_HEAD(invalid_list);
        bool flush = false;

        while (mmu_unsync_walk(parent, &pages)) {
                bool protected = false;

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

                if (protected) {
                        kvm_flush_remote_tlbs(vcpu->kvm);
                        flush = false;
                }

                for_each_sp(pages, sp, parents, i) {
                        flush |= kvm_sync_page(vcpu, sp, &invalid_list);
                        mmu_pages_clear_parents(&parents);
                }
                if (need_resched() || spin_needbreak(&vcpu->kvm->mmu_lock)) {
                        kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush);
                        cond_resched_lock(&vcpu->kvm->mmu_lock);
                        flush = false;
                }
        }

        kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush);
}

static void __clear_sp_write_flooding_count(struct kvm_mmu_page *sp)
{
        atomic_set(&sp->write_flooding_count,  0);
}

static void clear_sp_write_flooding_count(u64 *spte)
{
        struct kvm_mmu_page *sp =  page_header(__pa(spte));

        __clear_sp_write_flooding_count(sp);
}

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)
{
        union kvm_mmu_page_role role;
        unsigned quadrant;
        struct kvm_mmu_page *sp;
        bool need_sync = false;
        bool flush = false;
        int collisions = 0;
        LIST_HEAD(invalid_list);

        role = vcpu->arch.mmu.base_role;
        role.level = level;
        role.direct = direct;
        if (role.direct)
                role.cr4_pae = 0;
        role.access = access;
        if (!vcpu->arch.mmu.direct_map
            && 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;
        }
        for_each_valid_sp(vcpu->kvm, sp, gfn) {
                if (sp->gfn != gfn) {
                        collisions++;
                        continue;
                }

                if (!need_sync && sp->unsync)
                        need_sync = true;

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

                if (sp->unsync) {
                        /* The page is good, but __kvm_sync_page might still end
                         * up zapping it.  If so, break in order to rebuild it.
                         */
                        if (!__kvm_sync_page(vcpu, sp, &invalid_list))
                                break;

                        WARN_ON(!list_empty(&invalid_list));
                        kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
                }

                if (sp->unsync_children)
                        kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);

                __clear_sp_write_flooding_count(sp);
                trace_kvm_mmu_get_page(sp, false);
                goto out;
        }

        ++vcpu->kvm->stat.mmu_cache_miss;

        sp = kvm_mmu_alloc_page(vcpu, direct);

        sp->gfn = gfn;
        sp->role = role;
        hlist_add_head(&sp->hash_link,
                &vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)]);
        if (!direct) {
                /*
                 * we should do write protection before syncing pages
                 * otherwise the content of the synced shadow page may
                 * be inconsistent with guest page table.
                 */
                account_shadowed(vcpu->kvm, sp);
                if (level == PT_PAGE_TABLE_LEVEL &&
                      rmap_write_protect(vcpu, gfn))
                        kvm_flush_remote_tlbs(vcpu->kvm);

                if (level > PT_PAGE_TABLE_LEVEL && need_sync)
                        flush |= kvm_sync_pages(vcpu, gfn, &invalid_list);
        }
        sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
        clear_page(sp->spt);
        trace_kvm_mmu_get_page(sp, true);

        kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush);
out:
        if (collisions > vcpu->kvm->stat.max_mmu_page_hash_collisions)
                vcpu->kvm->stat.max_mmu_page_hash_collisions = collisions;
        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 == PT64_ROOT_4LEVEL &&
            vcpu->arch.mmu.root_level < PT64_ROOT_4LEVEL &&
            !vcpu->arch.mmu.direct_map)
                --iterator->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;

        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,
                               u64 spte)
{
        if (is_last_spte(spte, iterator->level)) {
                iterator->level = 0;
                return;
        }

        iterator->shadow_addr = spte & PT64_BASE_ADDR_MASK;
        --iterator->level;
}

static void shadow_walk_next(struct kvm_shadow_walk_iterator *iterator)
{
        __shadow_walk_next(iterator, *iterator->sptep);
}

static void link_shadow_page(struct kvm_vcpu *vcpu, u64 *sptep,
                             struct kvm_mmu_page *sp)
{
        u64 spte;

        BUILD_BUG_ON(VMX_EPT_WRITABLE_MASK != PT_WRITABLE_MASK);

        spte = __pa(sp->spt) | shadow_present_mask | PT_WRITABLE_MASK |
               shadow_user_mask | shadow_x_mask | shadow_me_mask;

        if (sp_ad_disabled(sp))
                spte |= shadow_acc_track_value;
        else
                spte |= shadow_accessed_mask;

        mmu_spte_set(sptep, spte);

        mmu_page_add_parent_pte(vcpu, sp, sptep);

        if (sp->unsync_children || sp->unsync)
                mark_unsync(sptep);
}

static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                                   unsigned direct_access)
{
        if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
                struct kvm_mmu_page *child;

                /*
                 * For the direct sp, if the guest pte's dirty bit
                 * changed form clean to dirty, it will corrupt the
                 * sp's access: allow writable in the read-only sp,
                 * so we should update the spte at this point to get
                 * a new sp with the correct access.
                 */
                child = page_header(*sptep & PT64_BASE_ADDR_MASK);
                if (child->role.access == direct_access)
                        return;

                drop_parent_pte(child, sptep);
                kvm_flush_remote_tlbs(vcpu->kvm);
        }
}

static bool mmu_page_zap_pte(struct kvm *kvm, 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)) {
                        drop_spte(kvm, spte);
                        if (is_large_pte(pte))
                                --kvm->stat.lpages;
                } else {
                        child = page_header(pte & PT64_BASE_ADDR_MASK);
                        drop_parent_pte(child, spte);
                }
                return true;
        }

        if (is_mmio_spte(pte))
                mmu_spte_clear_no_track(spte);

        return false;
}

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

        for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
                mmu_page_zap_pte(kvm, sp, sp->spt + i);
}

static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        u64 *sptep;
        struct rmap_iterator iter;

        while ((sptep = rmap_get_first(&sp->parent_ptes, &iter)))
                drop_parent_pte(sp, sptep);
}

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

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

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

                for_each_sp(pages, sp, parents, i) {
                        kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
                        mmu_pages_clear_parents(&parents);
                        zapped++;
                }
        }

        return zapped;
}

static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
                                    struct list_head *invalid_list)
{
        int ret;

        trace_kvm_mmu_prepare_zap_page(sp);
        ++kvm->stat.mmu_shadow_zapped;
        ret = mmu_zap_unsync_children(kvm, sp, invalid_list);
        kvm_mmu_page_unlink_children(kvm, sp);
        kvm_mmu_unlink_parents(kvm, sp);

        if (!sp->role.invalid && !sp->role.direct)
                unaccount_shadowed(kvm, sp);

        if (sp->unsync)
                kvm_unlink_unsync_page(kvm, sp);
        if (!sp->root_count) {
                /* Count self */
                ret++;
                list_move(&sp->link, invalid_list);
                kvm_mod_used_mmu_pages(kvm, -1);
        } else {
                list_move(&sp->link, &kvm->arch.active_mmu_pages);

                /*
                 * The obsolete pages can not be used on any vcpus.
                 * See the comments in kvm_mmu_invalidate_zap_all_pages().
                 */
                if (!sp->role.invalid && !is_obsolete_sp(kvm, sp))
                        kvm_reload_remote_mmus(kvm);
        }

        sp->role.invalid = 1;
        return ret;
}

static void kvm_mmu_commit_zap_page(struct kvm *kvm,
                                    struct list_head *invalid_list)
{
        struct kvm_mmu_page *sp, *nsp;

        if (list_empty(invalid_list))
                return;

        /*
         * We need to make sure everyone sees our modifications to
         * the page tables and see changes to vcpu->mode here. The barrier
         * in the kvm_flush_remote_tlbs() achieves this. This pairs
         * with vcpu_enter_guest and walk_shadow_page_lockless_begin/end.
         *
         * In addition, kvm_flush_remote_tlbs waits for all vcpus to exit
         * guest mode and/or lockless shadow page table walks.
         */
        kvm_flush_remote_tlbs(kvm);

        list_for_each_entry_safe(sp, nsp, invalid_list, link) {
                WARN_ON(!sp->role.invalid || sp->root_count);
                kvm_mmu_free_page(sp);
        }
}

static bool prepare_zap_oldest_mmu_page(struct kvm *kvm,
                                        struct list_head *invalid_list)
{
        struct kvm_mmu_page *sp;

        if (list_empty(&kvm->arch.active_mmu_pages))
                return false;

        sp = list_last_entry(&kvm->arch.active_mmu_pages,
                             struct kvm_mmu_page, link);
        return kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
}

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

        spin_lock(&kvm->mmu_lock);

        if (kvm->arch.n_used_mmu_pages > goal_nr_mmu_pages) {
                /* Need to free some mmu pages to achieve the goal. */
                while (kvm->arch.n_used_mmu_pages > goal_nr_mmu_pages)
                        if (!prepare_zap_oldest_mmu_page(kvm, &invalid_list))
                                break;

                kvm_mmu_commit_zap_page(kvm, &invalid_list);
                goal_nr_mmu_pages = kvm->arch.n_used_mmu_pages;
        }

        kvm->arch.n_max_mmu_pages = goal_nr_mmu_pages;

        spin_unlock(&kvm->mmu_lock);
}

int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn)
{
        struct kvm_mmu_page *sp;
        LIST_HEAD(invalid_list);
        int r;

        pgprintk("%s: looking for gfn %llx\n", __func__, gfn);
        r = 0;
        spin_lock(&kvm->mmu_lock);
        for_each_gfn_indirect_valid_sp(kvm, sp, gfn) {
                pgprintk("%s: gfn %llx role %x\n", __func__, gfn,
                         sp->role.word);
                r = 1;
                kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
        }
        kvm_mmu_commit_zap_page(kvm, &invalid_list);
        spin_unlock(&kvm->mmu_lock);

        return r;
}
EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page);

static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
        trace_kvm_mmu_unsync_page(sp);
        ++vcpu->kvm->stat.mmu_unsync;
        sp->unsync = 1;

        kvm_mmu_mark_parents_unsync(sp);
}

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

        if (kvm_page_track_is_active(vcpu, gfn, KVM_PAGE_TRACK_WRITE))
                return true;

        for_each_gfn_indirect_valid_sp(vcpu->kvm, sp, gfn) {
                if (!can_unsync)
                        return true;

                if (sp->unsync)
                        continue;

                WARN_ON(sp->role.level != PT_PAGE_TABLE_LEVEL);
                kvm_unsync_page(vcpu, sp);
        }

        return false;
}

static bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
{
        if (pfn_valid(pfn))
                return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)) &&
                        /*
                         * Some reserved pages, such as those from NVDIMM
                         * DAX devices, are not for MMIO, and can be mapped
                         * with cached memory type for better performance.
                         * However, the above check misconceives those pages
                         * as MMIO, and results in KVM mapping them with UC
                         * memory type, which would hurt the performance.
                         * Therefore, we check the host memory type in addition
                         * and only treat UC/UC-/WC pages as MMIO.
                         */
                        (!pat_enabled() || pat_pfn_immune_to_uc_mtrr(pfn));

        return true;
}

static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                    unsigned pte_access, int level,
                    gfn_t gfn, kvm_pfn_t pfn, bool speculative,
                    bool can_unsync, bool host_writable)
{
        u64 spte = 0;
        int ret = 0;
        struct kvm_mmu_page *sp;

        if (set_mmio_spte(vcpu, sptep, gfn, pfn, pte_access))
                return 0;

        sp = page_header(__pa(sptep));
        if (sp_ad_disabled(sp))
                spte |= shadow_acc_track_value;

        /*
         * For the EPT case, shadow_present_mask is 0 if hardware
         * supports exec-only page table entries.  In that case,
         * ACC_USER_MASK and shadow_user_mask are used to represent
         * read access.  See FNAME(gpte_access) in paging_tmpl.h.
         */
        spte |= shadow_present_mask;
        if (!speculative)
                spte |= spte_shadow_accessed_mask(spte);

        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));

        if (host_writable)
                spte |= SPTE_HOST_WRITEABLE;
        else
                pte_access &= ~ACC_WRITE_MASK;

        if (!kvm_is_mmio_pfn(pfn))
                spte |= shadow_me_mask;

        spte |= (u64)pfn << PAGE_SHIFT;

        if (pte_access & ACC_WRITE_MASK) {

                /*
                 * Other vcpu creates new sp in the window between
                 * mapping_level() and acquiring mmu-lock. We can
                 * allow guest to retry the access, the mapping can
                 * be fixed if guest refault.
                 */
                if (level > PT_PAGE_TABLE_LEVEL &&
                    mmu_gfn_lpage_is_disallowed(vcpu, gfn, level))
                        goto done;

                spte |= PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE;

                /*
                 * 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_writable_pte(*sptep))
                        goto set_pte;

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

        if (pte_access & ACC_WRITE_MASK) {
                kvm_vcpu_mark_page_dirty(vcpu, gfn);
                spte |= spte_shadow_dirty_mask(spte);
        }

        if (speculative)
                spte = mark_spte_for_access_track(spte);

set_pte:
        if (mmu_spte_update(sptep, spte))
                kvm_flush_remote_tlbs(vcpu->kvm);
done:
        return ret;
}

static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access,
                        int write_fault, int level, gfn_t gfn, kvm_pfn_t pfn,
                        bool speculative, bool host_writable)
{
        int was_rmapped = 0;
        int rmap_count;
        int ret = RET_PF_RETRY;

        pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__,
                 *sptep, write_fault, gfn);

        if (is_shadow_present_pte(*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);
                        drop_parent_pte(child, sptep);
                        kvm_flush_remote_tlbs(vcpu->kvm);
                } else if (pfn != spte_to_pfn(*sptep)) {
                        pgprintk("hfn old %llx new %llx\n",
                                 spte_to_pfn(*sptep), pfn);
                        drop_spte(vcpu->kvm, sptep);
                        kvm_flush_remote_tlbs(vcpu->kvm);
                } else
                        was_rmapped = 1;
        }

        if (set_spte(vcpu, sptep, pte_access, level, gfn, pfn, speculative,
              true, host_writable)) {
                if (write_fault)
                        ret = RET_PF_EMULATE;
                kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
        }

        if (unlikely(is_mmio_spte(*sptep)))
                ret = RET_PF_EMULATE;

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

        if (is_shadow_present_pte(*sptep)) {
                if (!was_rmapped) {
                        rmap_count = rmap_add(vcpu, sptep, gfn);
                        if (rmap_count > RMAP_RECYCLE_THRESHOLD)
                                rmap_recycle(vcpu, sptep, gfn);
                }
        }

        kvm_release_pfn_clean(pfn);

        return ret;
}

static kvm_pfn_t pte_prefetch_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn,
                                     bool no_dirty_log)
{
        struct kvm_memory_slot *slot;

        slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, no_dirty_log);
        if (!slot)
                return KVM_PFN_ERR_FAULT;

        return gfn_to_pfn_memslot_atomic(slot, gfn);
}

static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
                                    struct kvm_mmu_page *sp,
                                    u64 *start, u64 *end)
{
        struct page *pages[PTE_PREFETCH_NUM];
        struct kvm_memory_slot *slot;
        unsigned access = sp->role.access;
        int i, ret;
        gfn_t gfn;

        gfn = kvm_mmu_page_get_gfn(sp, start - sp->spt);
        slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, access & ACC_WRITE_MASK);
        if (!slot)
                return -1;

        ret = gfn_to_page_many_atomic(slot, gfn, pages, end - start);
        if (ret <= 0)
                return -1;

        for (i = 0; i < ret; i++, gfn++, start++)
                mmu_set_spte(vcpu, start, access, 0, sp->role.level, gfn,
                             page_to_pfn(pages[i]), true, true);

        return 0;
}

static void __direct_pte_prefetch(struct kvm_vcpu *vcpu,
                                  struct kvm_mmu_page *sp, u64 *sptep)
{
        u64 *spte, *start = NULL;
        int i;

        WARN_ON(!sp->role.direct);

        i = (sptep - sp->spt) & ~(PTE_PREFETCH_NUM - 1);
        spte = sp->spt + i;

        for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
                if (is_shadow_present_pte(*spte) || spte == sptep) {
                        if (!start)
                                continue;
                        if (direct_pte_prefetch_many(vcpu, sp, start, spte) < 0)
                                break;
                        start = NULL;
                } else if (!start)
                        start = spte;
        }
}

static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
{
        struct kvm_mmu_page *sp;

        sp = page_header(__pa(sptep));

        /*
         * Without accessed bits, there's no way to distinguish between
         * actually accessed translations and prefetched, so disable pte
         * prefetch if accessed bits aren't available.
         */
        if (sp_ad_disabled(sp))
                return;

        if (sp->role.level > PT_PAGE_TABLE_LEVEL)
                return;

        __direct_pte_prefetch(vcpu, sp, sptep);
}

static int __direct_map(struct kvm_vcpu *vcpu, int write, int map_writable,
                        int level, gfn_t gfn, kvm_pfn_t pfn, bool prefault)
{
        struct kvm_shadow_walk_iterator iterator;
        struct kvm_mmu_page *sp;
        int emulate = 0;
        gfn_t pseudo_gfn;

        if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
                return 0;

        for_each_shadow_entry(vcpu, (u64)gfn << PAGE_SHIFT, iterator) {
                if (iterator.level == level) {
                        emulate = mmu_set_spte(vcpu, iterator.sptep, ACC_ALL,
                                               write, level, gfn, pfn, prefault,
                                               map_writable);
                        direct_pte_prefetch(vcpu, iterator.sptep);
                        ++vcpu->stat.pf_fixed;
                        break;
                }

                drop_large_spte(vcpu, iterator.sptep);
                if (!is_shadow_present_pte(*iterator.sptep)) {
                        u64 base_addr = iterator.addr;

                        base_addr &= PT64_LVL_ADDR_MASK(iterator.level);
                        pseudo_gfn = base_addr >> PAGE_SHIFT;
                        sp = kvm_mmu_get_page(vcpu, pseudo_gfn, iterator.addr,
                                              iterator.level - 1, 1, ACC_ALL);

                        link_shadow_page(vcpu, iterator.sptep, sp);
                }
        }
        return emulate;
}

static void kvm_send_hwpoison_signal(unsigned long address, struct task_struct *tsk)
{
        siginfo_t info;

        info.si_signo   = SIGBUS;
        info.si_errno   = 0;
        info.si_code    = BUS_MCEERR_AR;
        info.si_addr    = (void __user *)address;
        info.si_addr_lsb = PAGE_SHIFT;

        send_sig_info(SIGBUS, &info, tsk);
}

static int kvm_handle_bad_page(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn)
{
        /*
         * Do not cache the mmio info caused by writing the readonly gfn
         * into the spte otherwise read access on readonly gfn also can
         * caused mmio page fault and treat it as mmio access.
         */
        if (pfn == KVM_PFN_ERR_RO_FAULT)
                return RET_PF_EMULATE;

        if (pfn == KVM_PFN_ERR_HWPOISON) {
                kvm_send_hwpoison_signal(kvm_vcpu_gfn_to_hva(vcpu, gfn), current);
                return RET_PF_RETRY;
        }

        return RET_PF_EMULATE;
}

static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu,
                                        gfn_t *gfnp, kvm_pfn_t *pfnp,
                                        int *levelp)
{
        kvm_pfn_t pfn = *pfnp;
        gfn_t gfn = *gfnp;
        int level = *levelp;

        /*
         * Check if it's a transparent hugepage. If this would be an
         * hugetlbfs page, level wouldn't be set to
         * PT_PAGE_TABLE_LEVEL and there would be no adjustment done
         * here.
         */
        if (!is_error_noslot_pfn(pfn) && !kvm_is_reserved_pfn(pfn) &&
            level == PT_PAGE_TABLE_LEVEL &&
            PageTransCompoundMap(pfn_to_page(pfn)) &&
            !mmu_gfn_lpage_is_disallowed(vcpu, gfn, PT_DIRECTORY_LEVEL)) {
                unsigned long mask;
                /*
                 * mmu_notifier_retry was successful and we hold the
                 * mmu_lock here, so the pmd can't become splitting
                 * from under us, and in turn
                 * __split_huge_page_refcount() can't run from under
                 * us and we can safely transfer the refcount from
                 * PG_tail to PG_head as we switch the pfn to tail to
                 * head.
                 */
                *levelp = level = PT_DIRECTORY_LEVEL;
                mask = KVM_PAGES_PER_HPAGE(level) - 1;
                VM_BUG_ON((gfn & mask) != (pfn & mask));
                if (pfn & mask) {
                        gfn &= ~mask;
                        *gfnp = gfn;
                        kvm_release_pfn_clean(pfn);
                        pfn &= ~mask;
                        kvm_get_pfn(pfn);
                        *pfnp = pfn;
                }
        }
}

static bool handle_abnormal_pfn(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
                                kvm_pfn_t pfn, unsigned access, int *ret_val)
{
        /* The pfn is invalid, report the error! */
        if (unlikely(is_error_pfn(pfn))) {
                *ret_val = kvm_handle_bad_page(vcpu, gfn, pfn);
                return true;
        }

        if (unlikely(is_noslot_pfn(pfn)))
                vcpu_cache_mmio_info(vcpu, gva, gfn, access);

        return false;
}

static bool page_fault_can_be_fast(u32 error_code)
{
        /*
         * Do not fix the mmio spte with invalid generation number which
         * need to be updated by slow page fault path.
         */
        if (unlikely(error_code & PFERR_RSVD_MASK))
                return false;

        /* See if the page fault is due to an NX violation */
        if (unlikely(((error_code & (PFERR_FETCH_MASK | PFERR_PRESENT_MASK))
                      == (PFERR_FETCH_MASK | PFERR_PRESENT_MASK))))
                return false;

        /*
         * #PF can be fast if:
         * 1. The shadow page table entry is not present, which could mean that
         *    the fault is potentially caused by access tracking (if enabled).
         * 2. The shadow page table entry is present and the fault
         *    is caused by write-protect, that means we just need change the W
         *    bit of the spte which can be done out of mmu-lock.
         *
         * However, if access tracking is disabled we know that a non-present
         * page must be a genuine page fault where we have to create a new SPTE.
         * So, if access tracking is disabled, we return true only for write
         * accesses to a present page.
         */

        return shadow_acc_track_mask != 0 ||
               ((error_code & (PFERR_WRITE_MASK | PFERR_PRESENT_MASK))
                == (PFERR_WRITE_MASK | PFERR_PRESENT_MASK));
}

/*
 * Returns true if the SPTE was fixed successfully. Otherwise,
 * someone else modified the SPTE from its original value.
 */
static bool
fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
                        u64 *sptep, u64 old_spte, u64 new_spte)
{
        gfn_t gfn;

        WARN_ON(!sp->role.direct);

        /*
         * Theoretically we could also set dirty bit (and flush TLB) here in
         * order to eliminate unnecessary PML logging. See comments in
         * set_spte. But fast_page_fault is very unlikely to happen with PML
         * enabled, so we do not do this. This might result in the same GPA
         * to be logged in PML buffer again when the write really happens, and
         * eventually to be called by mark_page_dirty twice. But it's also no
         * harm. This also avoids the TLB flush needed after setting dirty bit
         * so non-PML cases won't be impacted.
         *
         * Compare with set_spte where instead shadow_dirty_mask is set.
         */
        if (cmpxchg64(sptep, old_spte, new_spte) != old_spte)
                return false;

        if (is_writable_pte(new_spte) && !is_writable_pte(old_spte)) {
                /*
                 * The gfn of direct spte is stable since it is
                 * calculated by sp->gfn.
                 */
                gfn = kvm_mmu_page_get_gfn(sp, sptep - sp->spt);
                kvm_vcpu_mark_page_dirty(vcpu, gfn);
        }

        return true;
}

static bool is_access_allowed(u32 fault_err_code, u64 spte)
{
        if (fault_err_code & PFERR_FETCH_MASK)
                return is_executable_pte(spte);

        if (fault_err_code & PFERR_WRITE_MASK)
                return is_writable_pte(spte);

        /* Fault was on Read access */
        return spte & PT_PRESENT_MASK;
}

/*
 * Return value:
 * - true: let the vcpu to access on the same address again.
 * - false: let the real page fault path to fix it.
 */
static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level,
                            u32 error_code)
{
        struct kvm_shadow_walk_iterator iterator;
        struct kvm_mmu_page *sp;
        bool fault_handled = false;
        u64 spte = 0ull;
        uint retry_count = 0;

        if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
                return false;

        if (!page_fault_can_be_fast(error_code))
                return false;

        walk_shadow_page_lockless_begin(vcpu);

        do {
                u64 new_spte;

                for_each_shadow_entry_lockless(vcpu, gva, iterator, spte)
                        if (!is_shadow_present_pte(spte) ||
                            iterator.level < level)
                                break;

                sp = page_header(__pa(iterator.sptep));
                if (!is_last_spte(spte, sp->role.level))
                        break;

                /*
                 * Check whether the memory access that caused the fault would
                 * still cause it if it were to be performed right now. If not,
                 * then this is a spurious fault caused by TLB lazily flushed,
                 * or some other CPU has already fixed the PTE after the
                 * current CPU took the fault.
                 *
                 * Need not check the access of upper level table entries since
                 * they are always ACC_ALL.
                 */
                if (is_access_allowed(error_code, spte)) {
                        fault_handled = true;
                        break;
                }

                new_spte = spte;

                if (is_access_track_spte(spte))
                        new_spte = restore_acc_track_spte(new_spte);

                /*
                 * Currently, to simplify the code, write-protection can
                 * be removed in the fast path only if the SPTE was
                 * write-protected for dirty-logging or access tracking.
                 */
                if ((error_code & PFERR_WRITE_MASK) &&
                    spte_can_locklessly_be_made_writable(spte))
                {
                        new_spte |= PT_WRITABLE_MASK;

                        /*
                         * Do not fix write-permission on the large spte.  Since
                         * we only dirty the first page into the dirty-bitmap in
                         * fast_pf_fix_direct_spte(), other pages are missed
                         * if its slot has dirty logging enabled.
                         *
                         * Instead, we let the slow page fault path create a
                         * normal spte to fix the access.
                         *
                         * See the comments in kvm_arch_commit_memory_region().
                         */
                        if (sp->role.level > PT_PAGE_TABLE_LEVEL)
                                break;
                }

                /* Verify that the fault can be handled in the fast path */
                if (new_spte == spte ||
                    !is_access_allowed(error_code, new_spte))
                        break;

                /*
                 * Currently, fast page fault only works for direct mapping
                 * since the gfn is not stable for indirect shadow page. See
                 * Documentation/virtual/kvm/locking.txt to get more detail.
                 */
                fault_handled = fast_pf_fix_direct_spte(vcpu, sp,
                                                        iterator.sptep, spte,
                                                        new_spte);
                if (fault_handled)
                        break;

                if (++retry_count > 4) {
                        printk_once(KERN_WARNING
                                "kvm: Fast #PF retrying more than 4 times.\n");
                        break;
                }

        } while (true);

        trace_fast_page_fault(vcpu, gva, error_code, iterator.sptep,
                              spte, fault_handled);
        walk_shadow_page_lockless_end(vcpu);

        return fault_handled;
}

static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
                         gva_t gva, kvm_pfn_t *pfn, bool write, bool *writable);
static int make_mmu_pages_available(struct kvm_vcpu *vcpu);

static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, u32 error_code,
                         gfn_t gfn, bool prefault)
{
        int r;
        int level;
        bool force_pt_level = false;
        kvm_pfn_t pfn;
        unsigned long mmu_seq;
        bool map_writable, write = error_code & PFERR_WRITE_MASK;

        level = mapping_level(vcpu, gfn, &force_pt_level);
        if (likely(!force_pt_level)) {
                /*
                 * 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);
        }

        if (fast_page_fault(vcpu, v, level, error_code))
                return RET_PF_RETRY;

        mmu_seq = vcpu->kvm->mmu_notifier_seq;
        smp_rmb();

        if (try_async_pf(vcpu, prefault, gfn, v, &pfn, write, &map_writable))
                return RET_PF_RETRY;

        if (handle_abnormal_pfn(vcpu, v, gfn, pfn, ACC_ALL, &r))
                return r;

        spin_lock(&vcpu->kvm->mmu_lock);
        if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
                goto out_unlock;
        if (make_mmu_pages_available(vcpu) < 0)
                goto out_unlock;
        if (likely(!force_pt_level))
                transparent_hugepage_adjust(vcpu, &gfn, &pfn, &level);
        r = __direct_map(vcpu, write, map_writable, level, gfn, pfn, prefault);
        spin_unlock(&vcpu->kvm->mmu_lock);

        return r;

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


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

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

        if (vcpu->arch.mmu.shadow_root_level >= PT64_ROOT_4LEVEL &&
            (vcpu->arch.mmu.root_level >= PT64_ROOT_4LEVEL ||
             vcpu->arch.mmu.direct_map)) {
                hpa_t root = vcpu->arch.mmu.root_hpa;

                spin_lock(&vcpu->kvm->mmu_lock);
                sp = page_header(root);
                --sp->root_count;
                if (!sp->root_count && sp->role.invalid) {
                        kvm_mmu_prepare_zap_page(vcpu->kvm, sp, &invalid_list);
                        kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list);
                }
                spin_unlock(&vcpu->kvm->mmu_lock);
                vcpu->arch.mmu.root_hpa = INVALID_PAGE;
                return;
        }

        spin_lock(&vcpu->kvm->mmu_lock);
        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_prepare_zap_page(vcpu->kvm, sp,
                                                         &invalid_list);
                }
                vcpu->arch.mmu.pae_root[i] = INVALID_PAGE;
        }
        kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list);
        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)) {
                kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
                ret = 1;
        }

        return ret;
}

static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_page *sp;
        unsigned i;

        if (vcpu->arch.mmu.shadow_root_level >= PT64_ROOT_4LEVEL) {
                spin_lock(&vcpu->kvm->mmu_lock);
                if(make_mmu_pages_available(vcpu) < 0) {
                        spin_unlock(&vcpu->kvm->mmu_lock);
                        return -ENOSPC;
                }
                sp = kvm_mmu_get_page(vcpu, 0, 0,
                                vcpu->arch.mmu.shadow_root_level, 1, ACC_ALL);
                ++sp->root_count;
                spin_unlock(&vcpu->kvm->mmu_lock);
                vcpu->arch.mmu.root_hpa = __pa(sp->spt);
        } else if (vcpu->arch.mmu.shadow_root_level == PT32E_ROOT_LEVEL) {
                for (i = 0; i < 4; ++i) {
                        hpa_t root = vcpu->arch.mmu.pae_root[i];

                        MMU_WARN_ON(VALID_PAGE(root));
                        spin_lock(&vcpu->kvm->mmu_lock);
                        if (make_mmu_pages_available(vcpu) < 0) {
                                spin_unlock(&vcpu->kvm->mmu_lock);
                                return -ENOSPC;
                        }
                        sp = kvm_mmu_get_page(vcpu, i << (30 - PAGE_SHIFT),
                                        i << 30, PT32_ROOT_LEVEL, 1, ACC_ALL);
                        root = __pa(sp->spt);
                        ++sp->root_count;
                        spin_unlock(&vcpu->kvm->mmu_lock);
                        vcpu->arch.mmu.pae_root[i] = root | PT_PRESENT_MASK;
                }
                vcpu->arch.mmu.root_hpa = __pa(vcpu->arch.mmu.pae_root);
        } else
                BUG();

        return 0;
}

static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_page *sp;
        u64 pdptr, pm_mask;
        gfn_t root_gfn;
        int i;

        root_gfn = vcpu->arch.mmu.get_cr3(vcpu) >> PAGE_SHIFT;

        if (mmu_check_root(vcpu, root_gfn))
                return 1;

        /*
         * Do we shadow a long mode page table? If so we need to
         * write-protect the guests page table root.
         */
        if (vcpu->arch.mmu.root_level >= PT64_ROOT_4LEVEL) {
                hpa_t root = vcpu->arch.mmu.root_hpa;

                MMU_WARN_ON(VALID_PAGE(root));

                spin_lock(&vcpu->kvm->mmu_lock);
                if (make_mmu_pages_available(vcpu) < 0) {
                        spin_unlock(&vcpu->kvm->mmu_lock);
                        return -ENOSPC;
                }
                sp = kvm_mmu_get_page(vcpu, root_gfn, 0,
                                vcpu->arch.mmu.shadow_root_level, 0, ACC_ALL);
                root = __pa(sp->spt);
                ++sp->root_count;
                spin_unlock(&vcpu->kvm->mmu_lock);
                vcpu->arch.mmu.root_hpa = root;
                return 0;
        }

        /*
         * We shadow a 32 bit page table. This may be a legacy 2-level
         * or a PAE 3-level page table. In either case we need to be aware that
         * the shadow page table may be a PAE or a long mode page table.
         */
        pm_mask = PT_PRESENT_MASK;
        if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_4LEVEL)
                pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK;

        for (i = 0; i < 4; ++i) {
                hpa_t root = vcpu->arch.mmu.pae_root[i];

                MMU_WARN_ON(VALID_PAGE(root));
                if (vcpu->arch.mmu.root_level == PT32E_ROOT_LEVEL) {
                        pdptr = vcpu->arch.mmu.get_pdptr(vcpu, i);
                        if (!(pdptr & PT_PRESENT_MASK)) {
                                vcpu->arch.mmu.pae_root[i] = 0;
                                continue;
                        }
                        root_gfn = pdptr >> PAGE_SHIFT;
                        if (mmu_check_root(vcpu, root_gfn))
                                return 1;
                }
                spin_lock(&vcpu->kvm->mmu_lock);
                if (make_mmu_pages_available(vcpu) < 0) {
                        spin_unlock(&vcpu->kvm->mmu_lock);
                        return -ENOSPC;
                }
                sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30, PT32_ROOT_LEVEL,
                                      0, ACC_ALL);
                root = __pa(sp->spt);
                ++sp->root_count;
                spin_unlock(&vcpu->kvm->mmu_lock);

                vcpu->arch.mmu.pae_root[i] = root | pm_mask;
        }
        vcpu->arch.mmu.root_hpa = __pa(vcpu->arch.mmu.pae_root);

        /*
         * If we shadow a 32 bit page table with a long mode page
         * table we enter this path.
         */
        if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_4LEVEL) {
                if (vcpu->arch.mmu.lm_root == NULL) {
                        /*
                         * The additional page necessary for this is only
                         * allocated on demand.
                         */

                        u64 *lm_root;

                        lm_root = (void*)get_zeroed_page(GFP_KERNEL);
                        if (lm_root == NULL)
                                return 1;

                        lm_root[0] = __pa(vcpu->arch.mmu.pae_root) | pm_mask;

                        vcpu->arch.mmu.lm_root = lm_root;
                }

                vcpu->arch.mmu.root_hpa = __pa(vcpu->arch.mmu.lm_root);
        }

        return 0;
}

static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
{
        if (vcpu->arch.mmu.direct_map)
                return mmu_alloc_direct_roots(vcpu);
        else
                return mmu_alloc_shadow_roots(vcpu);
}

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

        if (vcpu->arch.mmu.direct_map)
                return;

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

        vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);
        kvm_mmu_audit(vcpu, AUDIT_PRE_SYNC);
        if (vcpu->arch.mmu.root_level >= PT64_ROOT_4LEVEL) {
                hpa_t root = vcpu->arch.mmu.root_hpa;
                sp = page_header(root);
                mmu_sync_children(vcpu, sp);
                kvm_mmu_audit(vcpu, AUDIT_POST_SYNC);
                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);
                }
        }
        kvm_mmu_audit(vcpu, AUDIT_POST_SYNC);
}

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);
}
EXPORT_SYMBOL_GPL(kvm_mmu_sync_roots);

static gpa_t nonpaging_gva_to_gpa(struct kvm_vcpu *vcpu, gva_t vaddr,
                                  u32 access, struct x86_exception *exception)
{
        if (exception)
                exception->error_code = 0;
        return vaddr;
}

static gpa_t nonpaging_gva_to_gpa_nested(struct kvm_vcpu *vcpu, gva_t vaddr,
                                         u32 access,
                                         struct x86_exception *exception)
{
        if (exception)
                exception->error_code = 0;
        return vcpu->arch.nested_mmu.translate_gpa(vcpu, vaddr, access, exception);
}

static bool
__is_rsvd_bits_set(struct rsvd_bits_validate *rsvd_check, u64 pte, int level)
{
        int bit7 = (pte >> 7) & 1, low6 = pte & 0x3f;

        return (pte & rsvd_check->rsvd_bits_mask[bit7][level-1]) |
                ((rsvd_check->bad_mt_xwr & (1ull << low6)) != 0);
}

static bool is_rsvd_bits_set(struct kvm_mmu *mmu, u64 gpte, int level)
{
        return __is_rsvd_bits_set(&mmu->guest_rsvd_check, gpte, level);
}

static bool is_shadow_zero_bits_set(struct kvm_mmu *mmu, u64 spte, int level)
{
        return __is_rsvd_bits_set(&mmu->shadow_zero_check, spte, level);
}

static bool mmio_info_in_cache(struct kvm_vcpu *vcpu, u64 addr, bool direct)
{
        /*
         * A nested guest cannot use the MMIO cache if it is using nested
         * page tables, because cr2 is a nGPA while the cache stores GPAs.
         */
        if (mmu_is_nested(vcpu))
                return false;

        if (direct)
                return vcpu_match_mmio_gpa(vcpu, addr);

        return vcpu_match_mmio_gva(vcpu, addr);
}

/* return true if reserved bit is detected on spte. */
static bool
walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
{
        struct kvm_shadow_walk_iterator iterator;
        u64 sptes[PT64_ROOT_MAX_LEVEL], spte = 0ull;
        int root, leaf;
        bool reserved = false;

        if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
                goto exit;

        walk_shadow_page_lockless_begin(vcpu);

        for (shadow_walk_init(&iterator, vcpu, addr),
                 leaf = root = iterator.level;
             shadow_walk_okay(&iterator);
             __shadow_walk_next(&iterator, spte)) {
                spte = mmu_spte_get_lockless(iterator.sptep);

                sptes[leaf - 1] = spte;
                leaf--;

                if (!is_shadow_present_pte(spte))
                        break;

                reserved |= is_shadow_zero_bits_set(&vcpu->arch.mmu, spte,
                                                    iterator.level);
        }

        walk_shadow_page_lockless_end(vcpu);

        if (reserved) {
                pr_err("%s: detect reserved bits on spte, addr 0x%llx, dump hierarchy:\n",
                       __func__, addr);
                while (root > leaf) {
                        pr_err("------ spte 0x%llx level %d.\n",
                               sptes[root - 1], root);
                        root--;
                }
        }
exit:
        *sptep = spte;
        return reserved;
}

static int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct)
{
        u64 spte;
        bool reserved;

        if (mmio_info_in_cache(vcpu, addr, direct))
                return RET_PF_EMULATE;

        reserved = walk_shadow_page_get_mmio_spte(vcpu, addr, &spte);
        if (WARN_ON(reserved))
                return -EINVAL;

        if (is_mmio_spte(spte)) {
                gfn_t gfn = get_mmio_spte_gfn(spte);
                unsigned access = get_mmio_spte_access(spte);

                if (!check_mmio_spte(vcpu, spte))
                        return RET_PF_INVALID;

                if (direct)
                        addr = 0;

                trace_handle_mmio_page_fault(addr, gfn, access);
                vcpu_cache_mmio_info(vcpu, addr, gfn, access);
                return RET_PF_EMULATE;
        }

        /*
         * If the page table is zapped by other cpus, let CPU fault again on
         * the address.
         */
        return RET_PF_RETRY;
}
EXPORT_SYMBOL_GPL(handle_mmio_page_fault);

static bool page_fault_handle_page_track(struct kvm_vcpu *vcpu,
                                         u32 error_code, gfn_t gfn)
{
        if (unlikely(error_code & PFERR_RSVD_MASK))
                return false;

        if (!(error_code & PFERR_PRESENT_MASK) ||
              !(error_code & PFERR_WRITE_MASK))
                return false;

        /*
         * guest is writing the page which is write tracked which can
         * not be fixed by page fault handler.
         */
        if (kvm_page_track_is_active(vcpu, gfn, KVM_PAGE_TRACK_WRITE))
                return true;

        return false;
}

static void shadow_page_table_clear_flood(struct kvm_vcpu *vcpu, gva_t addr)
{
        struct kvm_shadow_walk_iterator iterator;
        u64 spte;

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

        walk_shadow_page_lockless_begin(vcpu);
        for_each_shadow_entry_lockless(vcpu, addr, iterator, spte) {
                clear_sp_write_flooding_count(iterator.sptep);
                if (!is_shadow_present_pte(spte))
                        break;
        }
        walk_shadow_page_lockless_end(vcpu);
}

static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
                                u32 error_code, bool prefault)
{
        gfn_t gfn = gva >> PAGE_SHIFT;
        int r;

        pgprintk("%s: gva %lx error %x\n", __func__, gva, error_code);

        if (page_fault_handle_page_track(vcpu, error_code, gfn))
                return RET_PF_EMULATE;

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

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


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

static int kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn)
{
        struct kvm_arch_async_pf arch;

        arch.token = (vcpu->arch.apf.id++ << 12) | vcpu->vcpu_id;
        arch.gfn = gfn;
        arch.direct_map = vcpu->arch.mmu.direct_map;
        arch.cr3 = vcpu->arch.mmu.get_cr3(vcpu);

        return kvm_setup_async_pf(vcpu, gva, kvm_vcpu_gfn_to_hva(vcpu, gfn), &arch);
}

bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu)
{
        if (unlikely(!lapic_in_kernel(vcpu) ||
                     kvm_event_needs_reinjection(vcpu) ||
                     vcpu->arch.exception.pending))
                return false;

        if (!vcpu->arch.apf.delivery_as_pf_vmexit && is_guest_mode(vcpu))
                return false;

        return kvm_x86_ops->interrupt_allowed(vcpu);
}

static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
                         gva_t gva, kvm_pfn_t *pfn, bool write, bool *writable)
{
        struct kvm_memory_slot *slot;
        bool async;

        slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        async = false;
        *pfn = __gfn_to_pfn_memslot(slot, gfn, false, &async, write, writable);
        if (!async)
                return false; /* *pfn has correct page already */

        if (!prefault && kvm_can_do_async_pf(vcpu)) {
                trace_kvm_try_async_get_page(gva, gfn);
                if (kvm_find_async_pf_gfn(vcpu, gfn)) {
                        trace_kvm_async_pf_doublefault(gva, gfn);
                        kvm_make_request(KVM_REQ_APF_HALT, vcpu);
                        return true;
                } else if (kvm_arch_setup_async_pf(vcpu, gva, gfn))
                        return true;
        }

        *pfn = __gfn_to_pfn_memslot(slot, gfn, false, NULL, write, writable);
        return false;
}

int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
                                u64 fault_address, char *insn, int insn_len)
{
        int r = 1;

        switch (vcpu->arch.apf.host_apf_reason) {
        default:
                trace_kvm_page_fault(fault_address, error_code);

                if (kvm_event_needs_reinjection(vcpu))
                        kvm_mmu_unprotect_page_virt(vcpu, fault_address);
                r = kvm_mmu_page_fault(vcpu, fault_address, error_code, insn,
                                insn_len);
                break;
        case KVM_PV_REASON_PAGE_NOT_PRESENT:
                vcpu->arch.apf.host_apf_reason = 0;
                local_irq_disable();
                kvm_async_pf_task_wait(fault_address, 0);
                local_irq_enable();
                break;
        case KVM_PV_REASON_PAGE_READY:
                vcpu->arch.apf.host_apf_reason = 0;
                local_irq_disable();
                kvm_async_pf_task_wake(fault_address);
                local_irq_enable();
                break;
        }
        return r;
}
EXPORT_SYMBOL_GPL(kvm_handle_page_fault);

static bool
check_hugepage_cache_consistency(struct kvm_vcpu *vcpu, gfn_t gfn, int level)
{
        int page_num = KVM_PAGES_PER_HPAGE(level);

        gfn &= ~(page_num - 1);

        return kvm_mtrr_check_gfn_range_consistency(vcpu, gfn, page_num);
}

static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
                          bool prefault)
{
        kvm_pfn_t pfn;
        int r;
        int level;
        bool force_pt_level;
        gfn_t gfn = gpa >> PAGE_SHIFT;
        unsigned long mmu_seq;
        int write = error_code & PFERR_WRITE_MASK;
        bool map_writable;

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

        if (page_fault_handle_page_track(vcpu, error_code, gfn))
                return RET_PF_EMULATE;

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

        force_pt_level = !check_hugepage_cache_consistency(vcpu, gfn,
                                                           PT_DIRECTORY_LEVEL);
        level = mapping_level(vcpu, gfn, &force_pt_level);
        if (likely(!force_pt_level)) {
                if (level > PT_DIRECTORY_LEVEL &&
                    !check_hugepage_cache_consistency(vcpu, gfn, level))
                        level = PT_DIRECTORY_LEVEL;
                gfn &= ~(KVM_PAGES_PER_HPAGE(level) - 1);
        }

        if (fast_page_fault(vcpu, gpa, level, error_code))
                return RET_PF_RETRY;

        mmu_seq = vcpu->kvm->mmu_notifier_seq;
        smp_rmb();

        if (try_async_pf(vcpu, prefault, gfn, gpa, &pfn, write, &map_writable))
                return RET_PF_RETRY;

        if (handle_abnormal_pfn(vcpu, 0, gfn, pfn, ACC_ALL, &r))
                return r;

        spin_lock(&vcpu->kvm->mmu_lock);
        if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
                goto out_unlock;
        if (make_mmu_pages_available(vcpu) < 0)
                goto out_unlock;
        if (likely(!force_pt_level))
                transparent_hugepage_adjust(vcpu, &gfn, &pfn, &level);
        r = __direct_map(vcpu, write, map_writable, level, gfn, pfn, prefault);
        spin_unlock(&vcpu->kvm->mmu_lock);

        return r;

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

static void nonpaging_init_context(struct kvm_vcpu *vcpu,
                                   struct kvm_mmu *context)
{
        context->page_fault = nonpaging_page_fault;
        context->gva_to_gpa = nonpaging_gva_to_gpa;
        context->sync_page = nonpaging_sync_page;
        context->invlpg = nonpaging_invlpg;
        context->update_pte = nonpaging_update_pte;
        context->root_level = 0;
        context->shadow_root_level = PT32E_ROOT_LEVEL;
        context->root_hpa = INVALID_PAGE;
        context->direct_map = true;
        context->nx = false;
}

void kvm_mmu_new_cr3(struct kvm_vcpu *vcpu)
{
        mmu_free_roots(vcpu);
}

static unsigned long get_cr3(struct kvm_vcpu *vcpu)
{
        return kvm_read_cr3(vcpu);
}

static void inject_page_fault(struct kvm_vcpu *vcpu,
                              struct x86_exception *fault)
{
        vcpu->arch.mmu.inject_page_fault(vcpu, fault);
}

static bool sync_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn,
                           unsigned access, int *nr_present)
{
        if (unlikely(is_mmio_spte(*sptep))) {
                if (gfn != get_mmio_spte_gfn(*sptep)) {
                        mmu_spte_clear_no_track(sptep);
                        return true;
                }

                (*nr_present)++;
                mark_mmio_spte(vcpu, sptep, gfn, access);
                return true;
        }

        return false;
}

static inline bool is_last_gpte(struct kvm_mmu *mmu,
                                unsigned level, unsigned gpte)
{
        /*
         * The RHS has bit 7 set iff level < mmu->last_nonleaf_level.
         * If it is clear, there are no large pages at this level, so clear
         * PT_PAGE_SIZE_MASK in gpte if that is the case.
         */
        gpte &= level - mmu->last_nonleaf_level;

        /*
         * PT_PAGE_TABLE_LEVEL always terminates.  The RHS has bit 7 set
         * iff level <= PT_PAGE_TABLE_LEVEL, which for our purpose means
         * level == PT_PAGE_TABLE_LEVEL; set PT_PAGE_SIZE_MASK in gpte then.
         */
        gpte |= level - PT_PAGE_TABLE_LEVEL - 1;

        return gpte & PT_PAGE_SIZE_MASK;
}

#define PTTYPE_EPT 18 /* arbitrary */
#define PTTYPE PTTYPE_EPT
#include "paging_tmpl.h"
#undef PTTYPE

#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,
                        struct rsvd_bits_validate *rsvd_check,
                        int maxphyaddr, int level, bool nx, bool gbpages,
                        bool pse, bool amd)
{
        u64 exb_bit_rsvd = 0;
        u64 gbpages_bit_rsvd = 0;
        u64 nonleaf_bit8_rsvd = 0;

        rsvd_check->bad_mt_xwr = 0;

        if (!nx)
                exb_bit_rsvd = rsvd_bits(63, 63);
        if (!gbpages)
                gbpages_bit_rsvd = rsvd_bits(7, 7);

        /*
         * Non-leaf PML4Es and PDPEs reserve bit 8 (which would be the G bit for
         * leaf entries) on AMD CPUs only.
         */
        if (amd)
                nonleaf_bit8_rsvd = rsvd_bits(8, 8);

        switch (level) {
        case PT32_ROOT_LEVEL:
                /* no rsvd bits for 2 level 4K page table entries */
                rsvd_check->rsvd_bits_mask[0][1] = 0;
                rsvd_check->rsvd_bits_mask[0][0] = 0;
                rsvd_check->rsvd_bits_mask[1][0] =
                        rsvd_check->rsvd_bits_mask[0][0];

                if (!pse) {
                        rsvd_check->rsvd_bits_mask[1][1] = 0;
                        break;
                }

                if (is_cpuid_PSE36())
                        /* 36bits PSE 4MB page */
                        rsvd_check->rsvd_bits_mask[1][1] = rsvd_bits(17, 21);
                else
                        /* 32 bits PSE 4MB page */
                        rsvd_check->rsvd_bits_mask[1][1] = rsvd_bits(13, 21);
                break;
        case PT32E_ROOT_LEVEL:
                rsvd_check->rsvd_bits_mask[0][2] =
                        rsvd_bits(maxphyaddr, 63) |
                        rsvd_bits(5, 8) | rsvd_bits(1, 2);      /* PDPTE */
                rsvd_check->rsvd_bits_mask[0][1] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 62);      /* PDE */
                rsvd_check->rsvd_bits_mask[0][0] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 62);      /* PTE */
                rsvd_check->rsvd_bits_mask[1][1] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 62) |
                        rsvd_bits(13, 20);              /* large page */
                rsvd_check->rsvd_bits_mask[1][0] =
                        rsvd_check->rsvd_bits_mask[0][0];
                break;
        case PT64_ROOT_5LEVEL:
                rsvd_check->rsvd_bits_mask[0][4] = exb_bit_rsvd |
                        nonleaf_bit8_rsvd | rsvd_bits(7, 7) |
                        rsvd_bits(maxphyaddr, 51);
                rsvd_check->rsvd_bits_mask[1][4] =
                        rsvd_check->rsvd_bits_mask[0][4];
        case PT64_ROOT_4LEVEL:
                rsvd_check->rsvd_bits_mask[0][3] = exb_bit_rsvd |
                        nonleaf_bit8_rsvd | rsvd_bits(7, 7) |
                        rsvd_bits(maxphyaddr, 51);
                rsvd_check->rsvd_bits_mask[0][2] = exb_bit_rsvd |
                        nonleaf_bit8_rsvd | gbpages_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51);
                rsvd_check->rsvd_bits_mask[0][1] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51);
                rsvd_check->rsvd_bits_mask[0][0] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51);
                rsvd_check->rsvd_bits_mask[1][3] =
                        rsvd_check->rsvd_bits_mask[0][3];
                rsvd_check->rsvd_bits_mask[1][2] = exb_bit_rsvd |
                        gbpages_bit_rsvd | rsvd_bits(maxphyaddr, 51) |
                        rsvd_bits(13, 29);
                rsvd_check->rsvd_bits_mask[1][1] = exb_bit_rsvd |
                        rsvd_bits(maxphyaddr, 51) |
                        rsvd_bits(13, 20);              /* large page */
                rsvd_check->rsvd_bits_mask[1][0] =
                        rsvd_check->rsvd_bits_mask[0][0];
                break;
        }
}

static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
                                  struct kvm_mmu *context)
{
        __reset_rsvds_bits_mask(vcpu, &context->guest_rsvd_check,
                                cpuid_maxphyaddr(vcpu), context->root_level,
                                context->nx,
                                guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES),
                                is_pse(vcpu), guest_cpuid_is_amd(vcpu));
}

static void
__reset_rsvds_bits_mask_ept(struct rsvd_bits_validate *rsvd_check,
                            int maxphyaddr, bool execonly)
{
        u64 bad_mt_xwr;

        rsvd_check->rsvd_bits_mask[0][4] =
                rsvd_bits(maxphyaddr, 51) | rsvd_bits(3, 7);
        rsvd_check->rsvd_bits_mask[0][3] =
                rsvd_bits(maxphyaddr, 51) | rsvd_bits(3, 7);
        rsvd_check->rsvd_bits_mask[0][2] =
                rsvd_bits(maxphyaddr, 51) | rsvd_bits(3, 6);
        rsvd_check->rsvd_bits_mask[0][1] =
                rsvd_bits(maxphyaddr, 51) | rsvd_bits(3, 6);
        rsvd_check->rsvd_bits_mask[0][0] = rsvd_bits(maxphyaddr, 51);

        /* large page */
        rsvd_check->rsvd_bits_mask[1][4] = rsvd_check->rsvd_bits_mask[0][4];
        rsvd_check->rsvd_bits_mask[1][3] = rsvd_check->rsvd_bits_mask[0][3];
        rsvd_check->rsvd_bits_mask[1][2] =
                rsvd_bits(maxphyaddr, 51) | rsvd_bits(12, 29);
        rsvd_check->rsvd_bits_mask[1][1] =
                rsvd_bits(maxphyaddr, 51) | rsvd_bits(12, 20);
        rsvd_check->rsvd_bits_mask[1][0] = rsvd_check->rsvd_bits_mask[0][0];

        bad_mt_xwr = 0xFFull << (2 * 8);        /* bits 3..5 must not be 2 */
        bad_mt_xwr |= 0xFFull << (3 * 8);       /* bits 3..5 must not be 3 */
        bad_mt_xwr |= 0xFFull << (7 * 8);       /* bits 3..5 must not be 7 */
        bad_mt_xwr |= REPEAT_BYTE(1ull << 2);   /* bits 0..2 must not be 010 */
        bad_mt_xwr |= REPEAT_BYTE(1ull << 6);   /* bits 0..2 must not be 110 */
        if (!execonly) {
                /* bits 0..2 must not be 100 unless VMX capabilities allow it */
                bad_mt_xwr |= REPEAT_BYTE(1ull << 4);
        }
        rsvd_check->bad_mt_xwr = bad_mt_xwr;
}

static void reset_rsvds_bits_mask_ept(struct kvm_vcpu *vcpu,
                struct kvm_mmu *context, bool execonly)
{
        __reset_rsvds_bits_mask_ept(&context->guest_rsvd_check,
                                    cpuid_maxphyaddr(vcpu), execonly);
}

/*
 * the page table on host is the shadow page table for the page
 * table in guest or amd nested guest, its mmu features completely
 * follow the features in guest.
 */
void
reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context)
{
        bool uses_nx = context->nx || context->base_role.smep_andnot_wp;
        struct rsvd_bits_validate *shadow_zero_check;
        int i;

        /*
         * Passing "true" to the last argument is okay; it adds a check
         * on bit 8 of the SPTEs which KVM doesn't use anyway.
         */
        shadow_zero_check = &context->shadow_zero_check;
        __reset_rsvds_bits_mask(vcpu, shadow_zero_check,
                                boot_cpu_data.x86_phys_bits,
                                context->shadow_root_level, uses_nx,
                                guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES),
                                is_pse(vcpu), true);

        if (!shadow_me_mask)
                return;

        for (i = context->shadow_root_level; --i >= 0;) {
                shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_mask;
                shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_mask;
        }

}
EXPORT_SYMBOL_GPL(reset_shadow_zero_bits_mask);

static inline bool boot_cpu_is_amd(void)
{
        WARN_ON_ONCE(!tdp_enabled);
        return shadow_x_mask == 0;
}

/*
 * the direct page table on host, use as much mmu features as
 * possible, however, kvm currently does not do execution-protection.
 */
static void
reset_tdp_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
                                struct kvm_mmu *context)
{
        struct rsvd_bits_validate *shadow_zero_check;
        int i;

        shadow_zero_check = &context->shadow_zero_check;

        if (boot_cpu_is_amd())
                __reset_rsvds_bits_mask(vcpu, shadow_zero_check,
                                        boot_cpu_data.x86_phys_bits,
                                        context->shadow_root_level, false,
                                        boot_cpu_has(X86_FEATURE_GBPAGES),
                                        true, true);
        else
                __reset_rsvds_bits_mask_ept(shadow_zero_check,
                                            boot_cpu_data.x86_phys_bits,
                                            false);

        if (!shadow_me_mask)
                return;

        for (i = context->shadow_root_level; --i >= 0;) {
                shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_mask;
                shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_mask;
        }
}

/*
 * as the comments in reset_shadow_zero_bits_mask() except it
 * is the shadow page table for intel nested guest.
 */
static void
reset_ept_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
                                struct kvm_mmu *context, bool execonly)
{
        __reset_rsvds_bits_mask_ept(&context->shadow_zero_check,
                                    boot_cpu_data.x86_phys_bits, execonly);
}

#define BYTE_MASK(access) \
        ((1 & (access) ? 2 : 0) | \
         (2 & (access) ? 4 : 0) | \
         (3 & (access) ? 8 : 0) | \
         (4 & (access) ? 16 : 0) | \
         (5 & (access) ? 32 : 0) | \
         (6 & (access) ? 64 : 0) | \
         (7 & (access) ? 128 : 0))


static void update_permission_bitmask(struct kvm_vcpu *vcpu,
                                      struct kvm_mmu *mmu, bool ept)
{
        unsigned byte;

        const u8 x = BYTE_MASK(ACC_EXEC_MASK);
        const u8 w = BYTE_MASK(ACC_WRITE_MASK);
        const u8 u = BYTE_MASK(ACC_USER_MASK);

        bool cr4_smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP) != 0;
        bool cr4_smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP) != 0;
        bool cr0_wp = is_write_protection(vcpu);

        for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) {
                unsigned pfec = byte << 1;

                /*
                 * Each "*f" variable has a 1 bit for each UWX value
                 * that causes a fault with the given PFEC.
                 */

                /* Faults from writes to non-writable pages */
                u8 wf = (pfec & PFERR_WRITE_MASK) ? ~w : 0;
                /* Faults from user mode accesses to supervisor pages */
                u8 uf = (pfec & PFERR_USER_MASK) ? ~u : 0;
                /* Faults from fetches of non-executable pages*/
                u8 ff = (pfec & PFERR_FETCH_MASK) ? ~x : 0;
                /* Faults from kernel mode fetches of user pages */
                u8 smepf = 0;
                /* Faults from kernel mode accesses of user pages */
                u8 smapf = 0;

                if (!ept) {
                        /* Faults from kernel mode accesses to user pages */
                        u8 kf = (pfec & PFERR_USER_MASK) ? 0 : u;

                        /* Not really needed: !nx will cause pte.nx to fault */
                        if (!mmu->nx)
                                ff = 0;

                        /* Allow supervisor writes if !cr0.wp */
                        if (!cr0_wp)
                                wf = (pfec & PFERR_USER_MASK) ? wf : 0;

                        /* Disallow supervisor fetches of user code if cr4.smep */
                        if (cr4_smep)
                                smepf = (pfec & PFERR_FETCH_MASK) ? kf : 0;

                        /*
                         * SMAP:kernel-mode data accesses from user-mode
                         * mappings should fault. A fault is considered
                         * as a SMAP violation if all of the following
                         * conditions are ture:
                         *   - X86_CR4_SMAP is set in CR4
                         *   - A user page is accessed
                         *   - The access is not a fetch
                         *   - Page fault in kernel mode
                         *   - if CPL = 3 or X86_EFLAGS_AC is clear
                         *
                         * Here, we cover the first three conditions.
                         * The fourth is computed dynamically in permission_fault();
                         * PFERR_RSVD_MASK bit will be set in PFEC if the access is
                         * *not* subject to SMAP restrictions.
                         */
                        if (cr4_smap)
                                smapf = (pfec & (PFERR_RSVD_MASK|PFERR_FETCH_MASK)) ? 0 : kf;
                }

                mmu->permissions[byte] = ff | uf | wf | smepf | smapf;
        }
}

/*
* PKU is an additional mechanism by which the paging controls access to
* user-mode addresses based on the value in the PKRU register.  Protection
* key violations are reported through a bit in the page fault error code.
* Unlike other bits of the error code, the PK bit is not known at the
* call site of e.g. gva_to_gpa; it must be computed directly in
* permission_fault based on two bits of PKRU, on some machine state (CR4,
* CR0, EFER, CPL), and on other bits of the error code and the page tables.
*
* In particular the following conditions come from the error code, the
* page tables and the machine state:
* - PK is always zero unless CR4.PKE=1 and EFER.LMA=1
* - PK is always zero if RSVD=1 (reserved bit set) or F=1 (instruction fetch)
* - PK is always zero if U=0 in the page tables
* - PKRU.WD is ignored if CR0.WP=0 and the access is a supervisor access.
*
* The PKRU bitmask caches the result of these four conditions.  The error
* code (minus the P bit) and the page table's U bit form an index into the
* PKRU bitmask.  Two bits of the PKRU bitmask are then extracted and ANDed
* with the two bits of the PKRU register corresponding to the protection key.
* For the first three conditions above the bits will be 00, thus masking
* away both AD and WD.  For all reads or if the last condition holds, WD
* only will be masked away.
*/
static void update_pkru_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
                                bool ept)
{
        unsigned bit;
        bool wp;

        if (ept) {
                mmu->pkru_mask = 0;
                return;
        }

        /* PKEY is enabled only if CR4.PKE and EFER.LMA are both set. */
        if (!kvm_read_cr4_bits(vcpu, X86_CR4_PKE) || !is_long_mode(vcpu)) {
                mmu->pkru_mask = 0;
                return;
        }

        wp = is_write_protection(vcpu);

        for (bit = 0; bit < ARRAY_SIZE(mmu->permissions); ++bit) {
                unsigned pfec, pkey_bits;
                bool check_pkey, check_write, ff, uf, wf, pte_user;

                pfec = bit << 1;
                ff = pfec & PFERR_FETCH_MASK;
                uf = pfec & PFERR_USER_MASK;
                wf = pfec & PFERR_WRITE_MASK;

                /* PFEC.RSVD is replaced by ACC_USER_MASK. */
                pte_user = pfec & PFERR_RSVD_MASK;

                /*
                 * Only need to check the access which is not an
                 * instruction fetch and is to a user page.
                 */
                check_pkey = (!ff && pte_user);
                /*
                 * write access is controlled by PKRU if it is a
                 * user access or CR0.WP = 1.
                 */
                check_write = check_pkey && wf && (uf || wp);

                /* PKRU.AD stops both read and write access. */
                pkey_bits = !!check_pkey;
                /* PKRU.WD stops write access. */
                pkey_bits |= (!!check_write) << 1;

                mmu->pkru_mask |= (pkey_bits & 3) << pfec;
        }
}

static void update_last_nonleaf_level(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
{
        unsigned root_level = mmu->root_level;

        mmu->last_nonleaf_level = root_level;
        if (root_level == PT32_ROOT_LEVEL && is_pse(vcpu))
                mmu->last_nonleaf_level++;
}

static void paging64_init_context_common(struct kvm_vcpu *vcpu,
                                         struct kvm_mmu *context,
                                         int level)
{
        context->nx = is_nx(vcpu);
        context->root_level = level;

        reset_rsvds_bits_mask(vcpu, context);
        update_permission_bitmask(vcpu, context, false);
        update_pkru_bitmask(vcpu, context, false);
        update_last_nonleaf_level(vcpu, context);

        MMU_WARN_ON(!is_pae(vcpu));
        context->page_fault = paging64_page_fault;
        context->gva_to_gpa = paging64_gva_to_gpa;
        context->sync_page = paging64_sync_page;
        context->invlpg = paging64_invlpg;
        context->update_pte = paging64_update_pte;
        context->shadow_root_level = level;
        context->root_hpa = INVALID_PAGE;
        context->direct_map = false;
}

static void paging64_init_context(struct kvm_vcpu *vcpu,
                                  struct kvm_mmu *context)
{
        int root_level = is_la57_mode(vcpu) ?
                         PT64_ROOT_5LEVEL : PT64_ROOT_4LEVEL;

        paging64_init_context_common(vcpu, context, root_level);
}

static void paging32_init_context(struct kvm_vcpu *vcpu,
                                  struct kvm_mmu *context)
{
        context->nx = false;
        context->root_level = PT32_ROOT_LEVEL;

        reset_rsvds_bits_mask(vcpu, context);
        update_permission_bitmask(vcpu, context, false);
        update_pkru_bitmask(vcpu, context, false);
        update_last_nonleaf_level(vcpu, context);

        context->page_fault = paging32_page_fault;
        context->gva_to_gpa = paging32_gva_to_gpa;
        context->sync_page = paging32_sync_page;
        context->invlpg = paging32_invlpg;
        context->update_pte = paging32_update_pte;
        context->shadow_root_level = PT32E_ROOT_LEVEL;
        context->root_hpa = INVALID_PAGE;
        context->direct_map = false;
}

static void paging32E_init_context(struct kvm_vcpu *vcpu,
                                   struct kvm_mmu *context)
{
        paging64_init_context_common(vcpu, context, PT32E_ROOT_LEVEL);
}

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

        context->base_role.word = 0;
        context->base_role.smm = is_smm(vcpu);
        context->base_role.ad_disabled = (shadow_accessed_mask == 0);
        context->page_fault = tdp_page_fault;
        context->sync_page = nonpaging_sync_page;
        context->invlpg = nonpaging_invlpg;
        context->update_pte = nonpaging_update_pte;
        context->shadow_root_level = kvm_x86_ops->get_tdp_level(vcpu);
        context->root_hpa = INVALID_PAGE;
        context->direct_map = true;
        context->set_cr3 = kvm_x86_ops->set_tdp_cr3;
        context->get_cr3 = get_cr3;
        context->get_pdptr = kvm_pdptr_read;
        context->inject_page_fault = kvm_inject_page_fault;

        if (!is_paging(vcpu)) {
                context->nx = false;
                context->gva_to_gpa = nonpaging_gva_to_gpa;
                context->root_level = 0;
        } else if (is_long_mode(vcpu)) {
                context->nx = is_nx(vcpu);
                context->root_level = is_la57_mode(vcpu) ?
                                PT64_ROOT_5LEVEL : PT64_ROOT_4LEVEL;
                reset_rsvds_bits_mask(vcpu, context);
                context->gva_to_gpa = paging64_gva_to_gpa;
        } else if (is_pae(vcpu)) {
                context->nx = is_nx(vcpu);
                context->root_level = PT32E_ROOT_LEVEL;
                reset_rsvds_bits_mask(vcpu, context);
                context->gva_to_gpa = paging64_gva_to_gpa;
        } else {
                context->nx = false;
                context->root_level = PT32_ROOT_LEVEL;
                reset_rsvds_bits_mask(vcpu, context);
                context->gva_to_gpa = paging32_gva_to_gpa;
        }

        update_permission_bitmask(vcpu, context, false);
        update_pkru_bitmask(vcpu, context, false);
        update_last_nonleaf_level(vcpu, context);
        reset_tdp_shadow_zero_bits_mask(vcpu, context);
}

void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
{
        bool smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP);
        bool smap = kvm_read_cr4_bits(vcpu, X86_CR4_SMAP);
        struct kvm_mmu *context = &vcpu->arch.mmu;

        MMU_WARN_ON(VALID_PAGE(context->root_hpa));

        if (!is_paging(vcpu))
                nonpaging_init_context(vcpu, context);
        else if (is_long_mode(vcpu))
                paging64_init_context(vcpu, context);
        else if (is_pae(vcpu))
                paging32E_init_context(vcpu, context);
        else
                paging32_init_context(vcpu, context);

        context->base_role.nxe = is_nx(vcpu);
        context->base_role.cr4_pae = !!is_pae(vcpu);
        context->base_role.cr0_wp  = is_write_protection(vcpu);
        context->base_role.smep_andnot_wp
                = smep && !is_write_protection(vcpu);
        context->base_role.smap_andnot_wp
                = smap && !is_write_protection(vcpu);
        context->base_role.smm = is_smm(vcpu);
        reset_shadow_zero_bits_mask(vcpu, context);
}
EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);

void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
                             bool accessed_dirty)
{
        struct kvm_mmu *context = &vcpu->arch.mmu;

        MMU_WARN_ON(VALID_PAGE(context->root_hpa));

        context->shadow_root_level = PT64_ROOT_4LEVEL;

        context->nx = true;
        context->ept_ad = accessed_dirty;
        context->page_fault = ept_page_fault;
        context->gva_to_gpa = ept_gva_to_gpa;
        context->sync_page = ept_sync_page;
        context->invlpg = ept_invlpg;
        context->update_pte = ept_update_pte;
        context->root_level = PT64_ROOT_4LEVEL;
        context->root_hpa = INVALID_PAGE;
        context->direct_map = false;
        context->base_role.ad_disabled = !accessed_dirty;

        update_permission_bitmask(vcpu, context, true);
        update_pkru_bitmask(vcpu, context, true);
        update_last_nonleaf_level(vcpu, context);
        reset_rsvds_bits_mask_ept(vcpu, context, execonly);
        reset_ept_shadow_zero_bits_mask(vcpu, context, execonly);
}
EXPORT_SYMBOL_GPL(kvm_init_shadow_ept_mmu);

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

        kvm_init_shadow_mmu(vcpu);
        context->set_cr3           = kvm_x86_ops->set_cr3;
        context->get_cr3           = get_cr3;
        context->get_pdptr         = kvm_pdptr_read;
        context->inject_page_fault = kvm_inject_page_fault;
}

static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu *g_context = &vcpu->arch.nested_mmu;

        g_context->get_cr3           = get_cr3;
        g_context->get_pdptr         = kvm_pdptr_read;
        g_context->inject_page_fault = kvm_inject_page_fault;

        /*
         * Note that arch.mmu.gva_to_gpa translates l2_gpa to l1_gpa using
         * L1's nested page tables (e.g. EPT12). The nested translation
         * of l2_gva to l1_gpa is done by arch.nested_mmu.gva_to_gpa using
         * L2's page tables as the first level of translation and L1's
         * nested page tables as the second level of translation. Basically
         * the gva_to_gpa functions between mmu and nested_mmu are swapped.
         */
        if (!is_paging(vcpu)) {
                g_context->nx = false;
                g_context->root_level = 0;
                g_context->gva_to_gpa = nonpaging_gva_to_gpa_nested;
        } else if (is_long_mode(vcpu)) {
                g_context->nx = is_nx(vcpu);
                g_context->root_level = is_la57_mode(vcpu) ?
                                        PT64_ROOT_5LEVEL : PT64_ROOT_4LEVEL;
                reset_rsvds_bits_mask(vcpu, g_context);
                g_context->gva_to_gpa = paging64_gva_to_gpa_nested;
        } else if (is_pae(vcpu)) {
                g_context->nx = is_nx(vcpu);
                g_context->root_level = PT32E_ROOT_LEVEL;
                reset_rsvds_bits_mask(vcpu, g_context);
                g_context->gva_to_gpa = paging64_gva_to_gpa_nested;
        } else {
                g_context->nx = false;
                g_context->root_level = PT32_ROOT_LEVEL;
                reset_rsvds_bits_mask(vcpu, g_context);
                g_context->gva_to_gpa = paging32_gva_to_gpa_nested;
        }

        update_permission_bitmask(vcpu, g_context, false);
        update_pkru_bitmask(vcpu, g_context, false);
        update_last_nonleaf_level(vcpu, g_context);
}

static void init_kvm_mmu(struct kvm_vcpu *vcpu)
{
        if (mmu_is_nested(vcpu))
                init_kvm_nested_mmu(vcpu);
        else if (tdp_enabled)
                init_kvm_tdp_mmu(vcpu);
        else
                init_kvm_softmmu(vcpu);
}

void kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
{
        kvm_mmu_unload(vcpu);
        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;
        r = mmu_alloc_roots(vcpu);
        kvm_mmu_sync_roots(vcpu);
        if (r)
                goto out;
        /* set_cr3() should ensure TLB has been flushed */
        vcpu->arch.mmu.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);
        WARN_ON(VALID_PAGE(vcpu->arch.mmu.root_hpa));
}
EXPORT_SYMBOL_GPL(kvm_mmu_unload);

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;
        vcpu->arch.mmu.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 ^= shadow_nx_mask;
        new ^= shadow_nx_mask;
        return (old & ~new & PT64_PERM_MASK) != 0;
}

static u64 mmu_pte_write_fetch_gpte(struct kvm_vcpu *vcpu, gpa_t *gpa,
                                    const u8 *new, int *bytes)
{
        u64 gentry;
        int r;

        /*
         * Assume that the pte write on a page table of the same type
         * as the current vcpu paging mode since we update the sptes only
         * when they have the same mode.
         */
        if (is_pae(vcpu) && *bytes == 4) {
                /* Handle a 32-bit guest writing two halves of a 64-bit gpte */
                *gpa &= ~(gpa_t)7;
                *bytes = 8;
                r = kvm_vcpu_read_guest(vcpu, *gpa, &gentry, 8);
                if (r)
                        gentry = 0;
                new = (const u8 *)&gentry;
        }

        switch (*bytes) {
        case 4:
                gentry = *(const u32 *)new;
                break;
        case 8:
                gentry = *(const u64 *)new;
                break;
        default:
                gentry = 0;
                break;
        }

        return gentry;
}

/*
 * 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.
 */
static bool detect_write_flooding(struct kvm_mmu_page *sp)
{
        /*
         * Skip write-flooding detected for the sp whose level is 1, because
         * it can become unsync, then the guest page is not write-protected.
         */
        if (sp->role.level == PT_PAGE_TABLE_LEVEL)
                return false;

        atomic_inc(&sp->write_flooding_count);
        return atomic_read(&sp->write_flooding_count) >= 3;
}

/*
 * Misaligned accesses are too much trouble to fix up; also, they usually
 * indicate a page is not used as a page table.
 */
static bool detect_write_misaligned(struct kvm_mmu_page *sp, gpa_t gpa,
                                    int bytes)
{
        unsigned offset, pte_size, misaligned;

        pgprintk("misaligned: gpa %llx bytes %d role %x\n",
                 gpa, bytes, sp->role.word);

        offset = offset_in_page(gpa);
        pte_size = sp->role.cr4_pae ? 8 : 4;

        /*
         * Sometimes, the OS only writes the last one bytes to update status
         * bits, for example, in linux, andb instruction is used in clear_bit().
         */
        if (!(offset & (pte_size - 1)) && bytes == 1)
                return false;

        misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1);
        misaligned |= bytes < 4;

        return misaligned;
}

static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte)
{
        unsigned page_offset, quadrant;
        u64 *spte;
        int level;

        page_offset = offset_in_page(gpa);
        level = sp->role.level;
        *nspte = 1;
        if (!sp->role.cr4_pae) {
                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;
                        *nspte = 2;
                }
                quadrant = page_offset >> PAGE_SHIFT;
                page_offset &= ~PAGE_MASK;
                if (quadrant != sp->role.quadrant)
                        return NULL;
        }

        spte = &sp->spt[page_offset / sizeof(*spte)];
        return spte;
}

static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
                              const u8 *new, int bytes,
                              struct kvm_page_track_notifier_node *node)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        struct kvm_mmu_page *sp;
        LIST_HEAD(invalid_list);
        u64 entry, gentry, *spte;
        int npte;
        bool remote_flush, local_flush;
        union kvm_mmu_page_role mask = { };

        mask.cr0_wp = 1;
        mask.cr4_pae = 1;
        mask.nxe = 1;
        mask.smep_andnot_wp = 1;
        mask.smap_andnot_wp = 1;
        mask.smm = 1;
        mask.ad_disabled = 1;

        /*
         * If we don't have indirect shadow pages, it means no page is
         * write-protected, so we can exit simply.
         */
        if (!READ_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
                return;

        remote_flush = local_flush = false;

        pgprintk("%s: gpa %llx bytes %d\n", __func__, gpa, bytes);

        gentry = mmu_pte_write_fetch_gpte(vcpu, &gpa, new, &bytes);

        /*
         * No need to care whether allocation memory is successful
         * or not since pte prefetch is skiped if it does not have
         * enough objects in the cache.
         */
        mmu_topup_memory_caches(vcpu);

        spin_lock(&vcpu->kvm->mmu_lock);
        ++vcpu->kvm->stat.mmu_pte_write;
        kvm_mmu_audit(vcpu, AUDIT_PRE_PTE_WRITE);

        for_each_gfn_indirect_valid_sp(vcpu->kvm, sp, gfn) {
                if (detect_write_misaligned(sp, gpa, bytes) ||
                      detect_write_flooding(sp)) {
                        kvm_mmu_prepare_zap_page(vcpu->kvm, sp, &invalid_list);
                        ++vcpu->kvm->stat.mmu_flooded;
                        continue;
                }

                spte = get_written_sptes(sp, gpa, &npte);
                if (!spte)
                        continue;

                local_flush = true;
                while (npte--) {
                        entry = *spte;
                        mmu_page_zap_pte(vcpu->kvm, sp, spte);
                        if (gentry &&
                              !((sp->role.word ^ vcpu->arch.mmu.base_role.word)
                              & mask.word) && rmap_can_add(vcpu))
                                mmu_pte_write_new_pte(vcpu, sp, spte, &gentry);
                        if (need_remote_flush(entry, *spte))
                                remote_flush = true;
                        ++spte;
                }
        }
        kvm_mmu_flush_or_zap(vcpu, &invalid_list, remote_flush, local_flush);
        kvm_mmu_audit(vcpu, AUDIT_POST_PTE_WRITE);
        spin_unlock(&vcpu->kvm->mmu_lock);
}

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

        if (vcpu->arch.mmu.direct_map)
                return 0;

        gpa = kvm_mmu_gva_to_gpa_read(vcpu, gva, NULL);

        r = kvm_mmu_unprotect_page(vcpu->kvm, gpa >> PAGE_SHIFT);

        return r;
}
EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page_virt);

static int make_mmu_pages_available(struct kvm_vcpu *vcpu)
{
        LIST_HEAD(invalid_list);

        if (likely(kvm_mmu_available_pages(vcpu->kvm) >= KVM_MIN_FREE_MMU_PAGES))
                return 0;

        while (kvm_mmu_available_pages(vcpu->kvm) < KVM_REFILL_PAGES) {
                if (!prepare_zap_oldest_mmu_page(vcpu->kvm, &invalid_list))
                        break;

                ++vcpu->kvm->stat.mmu_recycled;
        }
        kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list);

        if (!kvm_mmu_available_pages(vcpu->kvm))
                return -ENOSPC;
        return 0;
}

int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
                       void *insn, int insn_len)
{
        int r, emulation_type = EMULTYPE_RETRY;
        enum emulation_result er;
        bool direct = vcpu->arch.mmu.direct_map;

        /* With shadow page tables, fault_address contains a GVA or nGPA.  */
        if (vcpu->arch.mmu.direct_map) {
                vcpu->arch.gpa_available = true;
                vcpu->arch.gpa_val = cr2;
        }

        r = RET_PF_INVALID;
        if (unlikely(error_code & PFERR_RSVD_MASK)) {
                r = handle_mmio_page_fault(vcpu, cr2, direct);
                if (r == RET_PF_EMULATE) {
                        emulation_type = 0;
                        goto emulate;
                }
        }

        if (r == RET_PF_INVALID) {
                r = vcpu->arch.mmu.page_fault(vcpu, cr2, lower_32_bits(error_code),
                                              false);
                WARN_ON(r == RET_PF_INVALID);
        }

        if (r == RET_PF_RETRY)
                return 1;
        if (r < 0)
                return r;

        /*
         * Before emulating the instruction, check if the error code
         * was due to a RO violation while translating the guest page.
         * This can occur when using nested virtualization with nested
         * paging in both guests. If true, we simply unprotect the page
         * and resume the guest.
         */
        if (vcpu->arch.mmu.direct_map &&
            (error_code & PFERR_NESTED_GUEST_PAGE) == PFERR_NESTED_GUEST_PAGE) {
                kvm_mmu_unprotect_page(vcpu->kvm, gpa_to_gfn(cr2));
                return 1;
        }

        if (mmio_info_in_cache(vcpu, cr2, direct))
                emulation_type = 0;
emulate:
        /*
         * On AMD platforms, under certain conditions insn_len may be zero on #NPF.
         * This can happen if a guest gets a page-fault on data access but the HW
         * table walker is not able to read the instruction page (e.g instruction
         * page is not present in memory). In those cases we simply restart the
         * guest.
         */
        if (unlikely(insn && !insn_len))
                return 1;

        er = x86_emulate_instruction(vcpu, cr2, emulation_type, insn, insn_len);

        switch (er) {
        case EMULATE_DONE:
                return 1;
        case EMULATE_USER_EXIT:
                ++vcpu->stat.mmio_exits;
                /* fall through */
        case EMULATE_FAIL:
                return 0;
        default:
                BUG();
        }
}
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_make_request(KVM_REQ_TLB_FLUSH, 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);
        free_page((unsigned long)vcpu->arch.mmu.lm_root);
}

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

        /*
         * 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)
                return -ENOMEM;

        vcpu->arch.mmu.pae_root = page_address(page);
        for (i = 0; i < 4; ++i)
                vcpu->arch.mmu.pae_root[i] = INVALID_PAGE;

        return 0;
}

int kvm_mmu_create(struct kvm_vcpu *vcpu)
{
        vcpu->arch.walk_mmu = &vcpu->arch.mmu;
        vcpu->arch.mmu.root_hpa = INVALID_PAGE;
        vcpu->arch.mmu.translate_gpa = translate_gpa;
        vcpu->arch.nested_mmu.translate_gpa = translate_nested_gpa;

        return alloc_mmu_pages(vcpu);
}

void kvm_mmu_setup(struct kvm_vcpu *vcpu)
{
        MMU_WARN_ON(VALID_PAGE(vcpu->arch.mmu.root_hpa));

        init_kvm_mmu(vcpu);
}

static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
                        struct kvm_memory_slot *slot,
                        struct kvm_page_track_notifier_node *node)
{
        kvm_mmu_invalidate_zap_all_pages(kvm);
}

void kvm_mmu_init_vm(struct kvm *kvm)
{
        struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;

        node->track_write = kvm_mmu_pte_write;
        node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
        kvm_page_track_register_notifier(kvm, node);
}

void kvm_mmu_uninit_vm(struct kvm *kvm)
{
        struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;

        kvm_page_track_unregister_notifier(kvm, node);
}

/* The return value indicates if tlb flush on all vcpus is needed. */
typedef bool (*slot_level_handler) (struct kvm *kvm, struct kvm_rmap_head *rmap_head);

/* The caller should hold mmu-lock before calling this function. */
static __always_inline bool
slot_handle_level_range(struct kvm *kvm, struct kvm_memory_slot *memslot,
                        slot_level_handler fn, int start_level, int end_level,
                        gfn_t start_gfn, gfn_t end_gfn, bool lock_flush_tlb)
{
        struct slot_rmap_walk_iterator iterator;
        bool flush = false;

        for_each_slot_rmap_range(memslot, start_level, end_level, start_gfn,
                        end_gfn, &iterator) {
                if (iterator.rmap)
                        flush |= fn(kvm, iterator.rmap);

                if (need_resched() || spin_needbreak(&kvm->mmu_lock)) {
                        if (flush && lock_flush_tlb) {
                                kvm_flush_remote_tlbs(kvm);
                                flush = false;
                        }
                        cond_resched_lock(&kvm->mmu_lock);
                }
        }

        if (flush && lock_flush_tlb) {
                kvm_flush_remote_tlbs(kvm);
                flush = false;
        }

        return flush;
}

static __always_inline bool
slot_handle_level(struct kvm *kvm, struct kvm_memory_slot *memslot,
                  slot_level_handler fn, int start_level, int end_level,
                  bool lock_flush_tlb)
{
        return slot_handle_level_range(kvm, memslot, fn, start_level,
                        end_level, memslot->base_gfn,
                        memslot->base_gfn + memslot->npages - 1,
                        lock_flush_tlb);
}

static __always_inline bool
slot_handle_all_level(struct kvm *kvm, struct kvm_memory_slot *memslot,
                      slot_level_handler fn, bool lock_flush_tlb)
{
        return slot_handle_level(kvm, memslot, fn, PT_PAGE_TABLE_LEVEL,
                                 PT_MAX_HUGEPAGE_LEVEL, lock_flush_tlb);
}

static __always_inline bool
slot_handle_large_level(struct kvm *kvm, struct kvm_memory_slot *memslot,
                        slot_level_handler fn, bool lock_flush_tlb)
{
        return slot_handle_level(kvm, memslot, fn, PT_PAGE_TABLE_LEVEL + 1,
                                 PT_MAX_HUGEPAGE_LEVEL, lock_flush_tlb);
}

static __always_inline bool
slot_handle_leaf(struct kvm *kvm, struct kvm_memory_slot *memslot,
                 slot_level_handler fn, bool lock_flush_tlb)
{
        return slot_handle_level(kvm, memslot, fn, PT_PAGE_TABLE_LEVEL,
                                 PT_PAGE_TABLE_LEVEL, lock_flush_tlb);
}

void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *memslot;
        int i;

        spin_lock(&kvm->mmu_lock);
        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                slots = __kvm_memslots(kvm, i);
                kvm_for_each_memslot(memslot, slots) {
                        gfn_t start, end;

                        start = max(gfn_start, memslot->base_gfn);
                        end = min(gfn_end, memslot->base_gfn + memslot->npages);
                        if (start >= end)
                                continue;

                        slot_handle_level_range(kvm, memslot, kvm_zap_rmapp,
                                                PT_PAGE_TABLE_LEVEL, PT_MAX_HUGEPAGE_LEVEL,
                                                start, end - 1, true);
                }
        }

        spin_unlock(&kvm->mmu_lock);
}

static bool slot_rmap_write_protect(struct kvm *kvm,
                                    struct kvm_rmap_head *rmap_head)
{
        return __rmap_write_protect(kvm, rmap_head, false);
}

void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
                                      struct kvm_memory_slot *memslot)
{
        bool flush;

        spin_lock(&kvm->mmu_lock);
        flush = slot_handle_all_level(kvm, memslot, slot_rmap_write_protect,
                                      false);
        spin_unlock(&kvm->mmu_lock);

        /*
         * kvm_mmu_slot_remove_write_access() and kvm_vm_ioctl_get_dirty_log()
         * which do tlb flush out of mmu-lock should be serialized by
         * kvm->slots_lock otherwise tlb flush would be missed.
         */
        lockdep_assert_held(&kvm->slots_lock);

        /*
         * We can flush all the TLBs out of the mmu lock without TLB
         * corruption since we just change the spte from writable to
         * readonly so that we only need to care the case of changing
         * spte from present to present (changing the spte from present
         * to nonpresent will flush all the TLBs immediately), in other
         * words, the only case we care is mmu_spte_update() where we
         * haved checked SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE
         * instead of PT_WRITABLE_MASK, that means it does not depend
         * on PT_WRITABLE_MASK anymore.
         */
        if (flush)
                kvm_flush_remote_tlbs(kvm);
}

static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
                                         struct kvm_rmap_head *rmap_head)
{
        u64 *sptep;
        struct rmap_iterator iter;
        int need_tlb_flush = 0;
        kvm_pfn_t pfn;
        struct kvm_mmu_page *sp;

restart:
        for_each_rmap_spte(rmap_head, &iter, sptep) {
                sp = page_header(__pa(sptep));
                pfn = spte_to_pfn(*sptep);

                /*
                 * We cannot do huge page mapping for indirect shadow pages,
                 * which are found on the last rmap (level = 1) when not using
                 * tdp; such shadow pages are synced with the page table in
                 * the guest, and the guest page table is using 4K page size
                 * mapping if the indirect sp has level = 1.
                 */
                if (sp->role.direct &&
                        !kvm_is_reserved_pfn(pfn) &&
                        PageTransCompoundMap(pfn_to_page(pfn))) {
                        drop_spte(kvm, sptep);
                        need_tlb_flush = 1;
                        goto restart;
                }
        }

        return need_tlb_flush;
}

void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
                                   const struct kvm_memory_slot *memslot)
{
        /* FIXME: const-ify all uses of struct kvm_memory_slot.  */
        spin_lock(&kvm->mmu_lock);
        slot_handle_leaf(kvm, (struct kvm_memory_slot *)memslot,
                         kvm_mmu_zap_collapsible_spte, true);
        spin_unlock(&kvm->mmu_lock);
}

void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
                                   struct kvm_memory_slot *memslot)
{
        bool flush;

        spin_lock(&kvm->mmu_lock);
        flush = slot_handle_leaf(kvm, memslot, __rmap_clear_dirty, false);
        spin_unlock(&kvm->mmu_lock);

        lockdep_assert_held(&kvm->slots_lock);

        /*
         * It's also safe to flush TLBs out of mmu lock here as currently this
         * function is only used for dirty logging, in which case flushing TLB
         * out of mmu lock also guarantees no dirty pages will be lost in
         * dirty_bitmap.
         */
        if (flush)
                kvm_flush_remote_tlbs(kvm);
}
EXPORT_SYMBOL_GPL(kvm_mmu_slot_leaf_clear_dirty);

void kvm_mmu_slot_largepage_remove_write_access(struct kvm *kvm,
                                        struct kvm_memory_slot *memslot)
{
        bool flush;

        spin_lock(&kvm->mmu_lock);
        flush = slot_handle_large_level(kvm, memslot, slot_rmap_write_protect,
                                        false);
        spin_unlock(&kvm->mmu_lock);

        /* see kvm_mmu_slot_remove_write_access */
        lockdep_assert_held(&kvm->slots_lock);

        if (flush)
                kvm_flush_remote_tlbs(kvm);
}
EXPORT_SYMBOL_GPL(kvm_mmu_slot_largepage_remove_write_access);

void kvm_mmu_slot_set_dirty(struct kvm *kvm,
                            struct kvm_memory_slot *memslot)
{
        bool flush;

        spin_lock(&kvm->mmu_lock);
        flush = slot_handle_all_level(kvm, memslot, __rmap_set_dirty, false);
        spin_unlock(&kvm->mmu_lock);

        lockdep_assert_held(&kvm->slots_lock);

        /* see kvm_mmu_slot_leaf_clear_dirty */
        if (flush)
                kvm_flush_remote_tlbs(kvm);
}
EXPORT_SYMBOL_GPL(kvm_mmu_slot_set_dirty);

#define BATCH_ZAP_PAGES 10
static void kvm_zap_obsolete_pages(struct kvm *kvm)
{
        struct kvm_mmu_page *sp, *node;
        int batch = 0;

restart:
        list_for_each_entry_safe_reverse(sp, node,
              &kvm->arch.active_mmu_pages, link) {
                int ret;

                /*
                 * No obsolete page exists before new created page since
                 * active_mmu_pages is the FIFO list.
                 */
                if (!is_obsolete_sp(kvm, sp))
                        break;

                /*
                 * Since we are reversely walking the list and the invalid
                 * list will be moved to the head, skip the invalid page
                 * can help us to avoid the infinity list walking.
                 */
                if (sp->role.invalid)
                        continue;

                /*
                 * Need not flush tlb since we only zap the sp with invalid
                 * generation number.
                 */
                if (batch >= BATCH_ZAP_PAGES &&
                      cond_resched_lock(&kvm->mmu_lock)) {
                        batch = 0;
                        goto restart;
                }

                ret = kvm_mmu_prepare_zap_page(kvm, sp,
                                &kvm->arch.zapped_obsolete_pages);
                batch += ret;

                if (ret)
                        goto restart;
        }

        /*
         * Should flush tlb before free page tables since lockless-walking
         * may use the pages.
         */
        kvm_mmu_commit_zap_page(kvm, &kvm->arch.zapped_obsolete_pages);
}

/*
 * Fast invalidate all shadow pages and use lock-break technique
 * to zap obsolete pages.
 *
 * It's required when memslot is being deleted or VM is being
 * destroyed, in these cases, we should ensure that KVM MMU does
 * not use any resource of the being-deleted slot or all slots
 * after calling the function.
 */
void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm)
{
        spin_lock(&kvm->mmu_lock);
        trace_kvm_mmu_invalidate_zap_all_pages(kvm);
        kvm->arch.mmu_valid_gen++;

        /*
         * Notify all vcpus to reload its shadow page table
         * and flush TLB. Then all vcpus will switch to new
         * shadow page table with the new mmu_valid_gen.
         *
         * Note: we should do this under the protection of
         * mmu-lock, otherwise, vcpu would purge shadow page
         * but miss tlb flush.
         */
        kvm_reload_remote_mmus(kvm);

        kvm_zap_obsolete_pages(kvm);
        spin_unlock(&kvm->mmu_lock);
}

static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
{
        return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
}

void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, struct kvm_memslots *slots)
{
        /*
         * The very rare case: if the generation-number is round,
         * zap all shadow pages.
         */
        if (unlikely((slots->generation & MMIO_GEN_MASK) == 0)) {
                kvm_debug_ratelimited("kvm: zapping shadow pages for mmio generation wraparound\n");
                kvm_mmu_invalidate_zap_all_pages(kvm);
        }
}

static unsigned long
mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
{
        struct kvm *kvm;
        int nr_to_scan = sc->nr_to_scan;
        unsigned long freed = 0;

        spin_lock(&kvm_lock);

        list_for_each_entry(kvm, &vm_list, vm_list) {
                int idx;
                LIST_HEAD(invalid_list);

                /*
                 * Never scan more than sc->nr_to_scan VM instances.
                 * Will not hit this condition practically since we do not try
                 * to shrink more than one VM and it is very unlikely to see
                 * !n_used_mmu_pages so many times.
                 */
                if (!nr_to_scan--)
                        break;
                /*
                 * n_used_mmu_pages is accessed without holding kvm->mmu_lock
                 * here. We may skip a VM instance errorneosly, but we do not
                 * want to shrink a VM that only started to populate its MMU
                 * anyway.
                 */
                if (!kvm->arch.n_used_mmu_pages &&
                      !kvm_has_zapped_obsolete_pages(kvm))
                        continue;

                idx = srcu_read_lock(&kvm->srcu);
                spin_lock(&kvm->mmu_lock);

                if (kvm_has_zapped_obsolete_pages(kvm)) {
                        kvm_mmu_commit_zap_page(kvm,
                              &kvm->arch.zapped_obsolete_pages);
                        goto unlock;
                }

                if (prepare_zap_oldest_mmu_page(kvm, &invalid_list))
                        freed++;
                kvm_mmu_commit_zap_page(kvm, &invalid_list);

unlock:
                spin_unlock(&kvm->mmu_lock);
                srcu_read_unlock(&kvm->srcu, idx);

                /*
                 * unfair on small ones
                 * per-vm shrinkers cry out
                 * sadness comes quickly
                 */
                list_move_tail(&kvm->vm_list, &vm_list);
                break;
        }

        spin_unlock(&kvm_lock);
        return freed;
}

static unsigned long
mmu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
        return percpu_counter_read_positive(&kvm_total_used_mmu_pages);
}

static struct shrinker mmu_shrinker = {
        .count_objects = mmu_shrink_count,
        .scan_objects = mmu_shrink_scan,
        .seeks = DEFAULT_SEEKS * 10,
};

static void mmu_destroy_caches(void)
{
        kmem_cache_destroy(pte_list_desc_cache);
        kmem_cache_destroy(mmu_page_header_cache);
}

int kvm_mmu_module_init(void)
{
        int ret = -ENOMEM;

        kvm_mmu_clear_all_pte_masks();

        pte_list_desc_cache = kmem_cache_create("pte_list_desc",
                                            sizeof(struct pte_list_desc),
                                            0, SLAB_ACCOUNT, NULL);
        if (!pte_list_desc_cache)
                goto out;

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

        if (percpu_counter_init(&kvm_total_used_mmu_pages, 0, GFP_KERNEL))
                goto out;

        ret = register_shrinker(&mmu_shrinker);
        if (ret)
                goto out;

        return 0;

out:
        mmu_destroy_caches();
        return ret;
}

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

        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                slots = __kvm_memslots(kvm, i);

                kvm_for_each_memslot(memslot, slots)
                        nr_pages += memslot->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;
}

void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
{
        kvm_mmu_unload(vcpu);
        free_mmu_pages(vcpu);
        mmu_free_memory_caches(vcpu);
}

void kvm_mmu_module_exit(void)
{
        mmu_destroy_caches();
        percpu_counter_destroy(&kvm_total_used_mmu_pages);
        unregister_shrinker(&mmu_shrinker);
        mmu_audit_disable();
}