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    SubjectRe: [PATCH] KVM: nVMX: fix AD condition when handling EPT violation
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    On 14/04/2017 00:39, Radim Krčmář wrote:
    > I have introduced this bug when applying and simplifying Paolo's patch
    > as we agreed on the list. The original was "x &= ~y; if (z) x |= y;".
    >
    > Here is the story of a bad workflow:
    >
    > A maintainer was already testing with the intended change, but it was
    > applied only to a testing repo on a different machine. When the time
    > to push tested patches to kvm/next came, he realized that this change
    > was missing and quickly added it to the maintenance repo, didn't test
    > again (because the change is trivial, right), and pushed the world to
    > fire.
    >
    > Fixes: ae1e2d1082ae ("kvm: nVMX: support EPT accessed/dirty bits")
    > Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
    > ---
    > arch/x86/kvm/vmx.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
    > index cfdb0d9389d1..837f6dd1ae9c 100644
    > --- a/arch/x86/kvm/vmx.c
    > +++ b/arch/x86/kvm/vmx.c
    > @@ -6221,7 +6221,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
    > * page table accesses are reads or writes.
    > */
    > u64 eptp = nested_ept_get_cr3(vcpu);
    > - if (eptp & VMX_EPT_AD_ENABLE_BIT)
    > + if (!(eptp & VMX_EPT_AD_ENABLE_BIT))
    > exit_qualification &= ~EPT_VIOLATION_ACC_WRITE;
    > }
    >
    >

    I have done this as well, so you're forgiven. :)

    More important: did kvm-unit-test catch the bug?

    Paolo

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