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    Subject[PATCH v3 01/15] KVM: MMU: properly check last spte in fast_page_fault()
    Date
    Using sp->role.level instead of @level since @level is not got from the
    page table hierarchy

    There is no issue in current code since the fast page fault currently only
    fixes the fault caused by dirty-log that is always on the last level
    (level = 1)

    This patch makes the code more readable and avoids potential issue in the
    further development

    Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
    ---
    arch/x86/kvm/mmu.c | 10 ++++++----
    1 file changed, 6 insertions(+), 4 deletions(-)

    diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    index 40772ef..d2aacc2 100644
    --- a/arch/x86/kvm/mmu.c
    +++ b/arch/x86/kvm/mmu.c
    @@ -2798,9 +2798,9 @@ static bool page_fault_can_be_fast(u32 error_code)
    }

    static bool
    -fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 spte)
    +fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
    + u64 *sptep, u64 spte)
    {
    - struct kvm_mmu_page *sp = page_header(__pa(sptep));
    gfn_t gfn;

    WARN_ON(!sp->role.direct);
    @@ -2826,6 +2826,7 @@ 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 ret = false;
    u64 spte = 0ull;

    @@ -2846,7 +2847,8 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level,
    goto exit;
    }

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

    /*
    @@ -2872,7 +2874,7 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level,
    * the gfn is not stable for indirect shadow page.
    * See Documentation/virtual/kvm/locking.txt to get more detail.
    */
    - ret = fast_pf_fix_direct_spte(vcpu, iterator.sptep, spte);
    + ret = fast_pf_fix_direct_spte(vcpu, sp, iterator.sptep, spte);
    exit:
    trace_fast_page_fault(vcpu, gva, error_code, iterator.sptep,
    spte, ret);
    --
    1.8.1.4


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