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    SubjectRe: [PATCH v3] KVM: MMU: Fix guest stuck during boot due to read/write emulation against GVA
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    On 11.08.2017 08:46, Wanpeng Li wrote:
    > From: Wanpeng Li <wanpeng.li@hotmail.com>
    >
    > Commit c016004494b0 (KVM: x86: Avoid guest page table walk when gpa_available
    > is set) avoids the page table walk when cr2 has already contained a valid GPA.
    > However, that is not the truth if ept == 0 and shadow page table is used. In
    > this scenario cr2 can just contains a valid GVA. The commit results in guest
    > stuck during boot due to read/write emulation against GVA instead of GPA of
    > the guest.
    >
    > This patch fixes it by setting the gpa_available flag under direct mode.
    >
    > Cc: Paolo Bonzini <pbonzini@redhat.com>
    > Cc: Radim Krčmář <rkrcmar@redhat.com>
    > Cc: Brijesh Singh <brijesh.singh@amd.com>
    > Cc: David Hildenbrand <david@redhat.com>
    > Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
    > ---
    > arch/x86/kvm/mmu.c | 7 +++++--
    > 1 file changed, 5 insertions(+), 2 deletions(-)
    >
    > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
    > index 849312d..4780348 100644
    > --- a/arch/x86/kvm/mmu.c
    > +++ b/arch/x86/kvm/mmu.c
    > @@ -3791,8 +3791,11 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
    >
    > if (need_unprotect && kvm_event_needs_reinjection(vcpu))
    > kvm_mmu_unprotect_page_virt(vcpu, fault_address);
    > - vcpu->arch.gpa_available = true;
    > - vcpu->arch.gpa_val = fault_address;
    > + /* With shadow page tables, cr2 could contain a GVA, not a GPA */
    > + if (vcpu->arch.mmu.direct_map) {
    > + vcpu->arch.gpa_available = true;
    > + vcpu->arch.gpa_val = fault_address;
    > + }
    > r = kvm_mmu_page_fault(vcpu, fault_address, error_code, insn,
    > insn_len);
    > break;
    >

    Reviewed-by: David Hildenbrand <david@redhat.com>

    --

    Thanks,

    David

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