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    Subject[PATCH v4 07/11] KVM: MMU: fast prefetch spte on invlpg path
    Fast prefetch spte for the unsync shadow page on invlpg path

    Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
    ---
    arch/x86/include/asm/kvm_host.h | 4 +---
    arch/x86/kvm/mmu.c | 38 +++++++++++++++-----------------------
    arch/x86/kvm/paging_tmpl.h | 30 ++++++++++++++++++------------
    arch/x86/kvm/x86.c | 4 ++--
    4 files changed, 36 insertions(+), 40 deletions(-)

    diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    index 58ea3a7..927ba73 100644
    --- a/arch/x86/include/asm/kvm_host.h
    +++ b/arch/x86/include/asm/kvm_host.h
    @@ -460,7 +460,6 @@ struct kvm_arch {
    unsigned int n_requested_mmu_pages;
    unsigned int n_max_mmu_pages;
    unsigned int indirect_shadow_pages;
    - atomic_t invlpg_counter;
    struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
    /*
    * Hash table of struct kvm_mmu_page.
    @@ -754,8 +753,7 @@ int fx_init(struct kvm_vcpu *vcpu);

    void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu);
    void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
    - const u8 *new, int bytes,
    - bool guest_initiated);
    + const u8 *new, int bytes);
    int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn);
    int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);
    void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
    diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    index 805a9d5..4128aba 100644
    --- a/arch/x86/kvm/mmu.c
    +++ b/arch/x86/kvm/mmu.c
    @@ -3530,8 +3530,7 @@ static bool last_updated_pte_accessed(struct kvm_vcpu *vcpu)
    }

    void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
    - const u8 *new, int bytes,
    - bool guest_initiated)
    + const u8 *new, int bytes)
    {
    gfn_t gfn = gpa >> PAGE_SHIFT;
    union kvm_mmu_page_role mask = { .word = 0 };
    @@ -3540,7 +3539,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
    LIST_HEAD(invalid_list);
    u64 entry, gentry, *spte;
    unsigned pte_size, page_offset, misaligned, quadrant, offset;
    - int level, npte, invlpg_counter, r, flooded = 0;
    + int level, npte, r, flooded = 0;
    bool remote_flush, local_flush, zap_page;

    /*
    @@ -3555,19 +3554,16 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,

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

    - invlpg_counter = atomic_read(&vcpu->kvm->arch.invlpg_counter);
    -
    /*
    * 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) || !new) {
    + if (is_pae(vcpu) && bytes == 4) {
    /* Handle a 32-bit guest writing two halves of a 64-bit gpte */
    - if (is_pae(vcpu)) {
    - gpa &= ~(gpa_t)7;
    - bytes = 8;
    - }
    + gpa &= ~(gpa_t)7;
    + bytes = 8;
    +
    r = kvm_read_guest(vcpu->kvm, gpa, &gentry, min(bytes, 8));
    if (r)
    gentry = 0;
    @@ -3593,22 +3589,18 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
    */
    mmu_topup_memory_caches(vcpu);
    spin_lock(&vcpu->kvm->mmu_lock);
    - if (atomic_read(&vcpu->kvm->arch.invlpg_counter) != invlpg_counter)
    - gentry = 0;
    kvm_mmu_free_some_pages(vcpu);
    ++vcpu->kvm->stat.mmu_pte_write;
    trace_kvm_mmu_audit(vcpu, AUDIT_PRE_PTE_WRITE);
    - if (guest_initiated) {
    - if (gfn == vcpu->arch.last_pt_write_gfn
    - && !last_updated_pte_accessed(vcpu)) {
    - ++vcpu->arch.last_pt_write_count;
    - if (vcpu->arch.last_pt_write_count >= 3)
    - flooded = 1;
    - } else {
    - vcpu->arch.last_pt_write_gfn = gfn;
    - vcpu->arch.last_pt_write_count = 1;
    - vcpu->arch.last_pte_updated = NULL;
    - }
    + if (gfn == vcpu->arch.last_pt_write_gfn
    + && !last_updated_pte_accessed(vcpu)) {
    + ++vcpu->arch.last_pt_write_count;
    + if (vcpu->arch.last_pt_write_count >= 3)
    + flooded = 1;
    + } else {
    + vcpu->arch.last_pt_write_gfn = gfn;
    + vcpu->arch.last_pt_write_count = 1;
    + vcpu->arch.last_pte_updated = NULL;
    }

    mask.cr0_wp = mask.cr4_pae = mask.nxe = 1;
    diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
    index d8d3906..9efb860 100644
    --- a/arch/x86/kvm/paging_tmpl.h
    +++ b/arch/x86/kvm/paging_tmpl.h
    @@ -672,20 +672,27 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
    {
    struct kvm_shadow_walk_iterator iterator;
    struct kvm_mmu_page *sp;
    - gpa_t pte_gpa = -1;
    int level;
    u64 *sptep;

    vcpu_clear_mmio_info(vcpu, gva);

    - spin_lock(&vcpu->kvm->mmu_lock);
    + /*
    + * No need to check return value here, rmap_can_add() can
    + * help us to skip pte prefetch later.
    + */
    + mmu_topup_memory_caches(vcpu);

    + spin_lock(&vcpu->kvm->mmu_lock);
    for_each_shadow_entry(vcpu, gva, iterator) {
    level = iterator.level;
    sptep = iterator.sptep;

    sp = page_header(__pa(sptep));
    if (is_last_spte(*sptep, level)) {
    + pt_element_t gpte;
    + gpa_t pte_gpa;
    +
    if (!sp->unsync)
    break;

    @@ -694,22 +701,21 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)

    if (mmu_page_zap_pte(vcpu->kvm, sp, sptep))
    kvm_flush_remote_tlbs(vcpu->kvm);
    +
    + if (!rmap_can_add(vcpu))
    + break;
    +
    + if (kvm_read_guest_atomic(vcpu->kvm, pte_gpa, &gpte,
    + sizeof(pt_element_t)))
    + break;
    +
    + FNAME(update_pte)(vcpu, sp, sptep, &gpte);
    }

    if (!is_shadow_present_pte(*sptep) || !sp->unsync_children)
    break;
    }
    -
    - atomic_inc(&vcpu->kvm->arch.invlpg_counter);
    -
    spin_unlock(&vcpu->kvm->mmu_lock);
    -
    - if (pte_gpa == -1)
    - return;
    -
    - if (mmu_topup_memory_caches(vcpu))
    - return;
    - kvm_mmu_pte_write(vcpu, pte_gpa, NULL, sizeof(pt_element_t), 0);
    }

    static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access,
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index a69a3e5..9206e39 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -4065,7 +4065,7 @@ int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
    ret = kvm_write_guest(vcpu->kvm, gpa, val, bytes);
    if (ret < 0)
    return 0;
    - kvm_mmu_pte_write(vcpu, gpa, val, bytes, 1);
    + kvm_mmu_pte_write(vcpu, gpa, val, bytes);
    return 1;
    }

    @@ -4302,7 +4302,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
    if (!exchanged)
    return X86EMUL_CMPXCHG_FAILED;

    - kvm_mmu_pte_write(vcpu, gpa, new, bytes, 1);
    + kvm_mmu_pte_write(vcpu, gpa, new, bytes);

    return X86EMUL_CONTINUE;

    --
    1.7.5.4


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