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    Subject[PATCH v4 3/3] KVM: MMU: retry #PF for softmmu
    Retry #PF for softmmu only when the current vcpu has the same cr3 as the time
    when #PF occurs

    Changelog:
    Just compare cr3 value since It's harmless to instantiate an spte for an
    unused translation from Marcelo's comment

    Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
    arch/x86/include/asm/kvm_host.h | 1 +
    arch/x86/kvm/mmu.c | 2 ++
    arch/x86/kvm/paging_tmpl.h | 34 +++++++++++++++++++++++-----------
    arch/x86/kvm/x86.c | 6 +++++-
    4 files changed, 31 insertions(+), 12 deletions(-)

    diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    index a0c066e..1e876e5 100644
    --- a/arch/x86/include/asm/kvm_host.h
    +++ b/arch/x86/include/asm/kvm_host.h
    @@ -602,6 +602,7 @@ struct kvm_x86_ops {
    struct kvm_arch_async_pf {
    u32 token;
    gfn_t gfn;
    + unsigned long cr3;
    bool direct_map;
    };

    diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    index c6bb449..3f0d9a0 100644
    --- a/arch/x86/kvm/mmu.c
    +++ b/arch/x86/kvm/mmu.c
    @@ -2607,9 +2607,11 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
    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, gfn, &arch);
    }
    diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
    index 23275d0..437e11a 100644
    --- a/arch/x86/kvm/paging_tmpl.h
    +++ b/arch/x86/kvm/paging_tmpl.h
    @@ -116,7 +116,7 @@ static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte)
    */
    static int FNAME(walk_addr_generic)(struct guest_walker *walker,
    struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
    - gva_t addr, u32 access)
    + gva_t addr, u32 access, bool prefault)
    {
    pt_element_t pte;
    gfn_t table_gfn;
    @@ -194,6 +194,13 @@ walk:
    #endif

    if (!eperm && !rsvd_fault && !(pte & PT_ACCESSED_MASK)) {
    + /*
    + * Don't set gpte accessed bit if it's on
    + * speculative path.
    + */
    + if (prefault)
    + goto error;
    +
    trace_kvm_mmu_set_accessed_bit(table_gfn, index,
    sizeof(pte));
    if (FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn,
    @@ -287,10 +294,11 @@ error:
    }

    static int FNAME(walk_addr)(struct guest_walker *walker,
    - struct kvm_vcpu *vcpu, gva_t addr, u32 access)
    + struct kvm_vcpu *vcpu, gva_t addr,
    + u32 access, bool prefault)
    {
    return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.mmu, addr,
    - access);
    + access, prefault);
    }

    static int FNAME(walk_addr_nested)(struct guest_walker *walker,
    @@ -298,7 +306,7 @@ static int FNAME(walk_addr_nested)(struct guest_walker *walker,
    u32 access)
    {
    return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.nested_mmu,
    - addr, access);
    + addr, access, false);
    }

    static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu,
    @@ -438,7 +446,8 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,
    static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
    struct guest_walker *gw,
    int user_fault, int write_fault, int hlevel,
    - int *ptwrite, pfn_t pfn, bool map_writable)
    + int *ptwrite, pfn_t pfn, bool map_writable,
    + bool prefault)
    {
    unsigned access = gw->pt_access;
    struct kvm_mmu_page *sp = NULL;
    @@ -512,7 +521,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,

    mmu_set_spte(vcpu, it.sptep, access, gw->pte_access & access,
    user_fault, write_fault, dirty, ptwrite, it.level,
    - gw->gfn, pfn, false, map_writable);
    + gw->gfn, pfn, prefault, map_writable);
    FNAME(pte_prefetch)(vcpu, gw, it.sptep);

    return it.sptep;
    @@ -561,15 +570,18 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
    /*
    * Look up the guest pte for the faulting address.
    */
    - r = FNAME(walk_addr)(&walker, vcpu, addr, error_code);
    + r = FNAME(walk_addr)(&walker, vcpu, addr, error_code, prefault);

    /*
    * The page is not mapped by the guest. Let the guest handle it.
    */
    if (!r) {
    pgprintk("%s: guest page fault\n", __func__);
    - inject_page_fault(vcpu);
    - vcpu->arch.last_pt_write_count = 0; /* reset fork detector */
    + if (!prefault) {
    + inject_page_fault(vcpu);
    + /* reset fork detector */
    + vcpu->arch.last_pt_write_count = 0;
    + }
    return 0;
    }

    @@ -599,7 +611,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
    trace_kvm_mmu_audit(vcpu, AUDIT_PRE_PAGE_FAULT);
    kvm_mmu_free_some_pages(vcpu);
    sptep = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
    - level, &write_pt, pfn, map_writable);
    + level, &write_pt, pfn, map_writable, prefault);
    (void)sptep;
    pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __func__,
    sptep, *sptep, write_pt);
    @@ -685,7 +697,7 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access,
    gpa_t gpa = UNMAPPED_GVA;
    int r;

    - r = FNAME(walk_addr)(&walker, vcpu, vaddr, access);
    + r = FNAME(walk_addr)(&walker, vcpu, vaddr, access, false);

    if (r) {
    gpa = gfn_to_gpa(walker.gfn);
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index bfd2878..de5e57b 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -6183,7 +6183,7 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
    {
    int r;

    - if (!vcpu->arch.mmu.direct_map || !work->arch.direct_map ||
    + if ((vcpu->arch.mmu.direct_map != work->arch.direct_map) ||
    is_error_page(work->page))
    return;

    @@ -6191,6 +6191,10 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
    if (unlikely(r))
    return;

    + if (!vcpu->arch.mmu.direct_map &&
    + work->arch.cr3 != vcpu->arch.mmu.get_cr3(vcpu))
    + return;
    +
    vcpu->arch.mmu.page_fault(vcpu, work->gva, 0, true);
    }

    --
    1.7.0.4


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