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    SubjectRe: [PATCH 1/8] KVM: SVM: Fix nested nmi handling
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    On 22.04.2010, at 12:33, Joerg Roedel wrote:

    > The patch introducing nested nmi handling had a bug. The
    > check does not belong to enable_nmi_window but must be in
    > nmi_allowed. This patch fixes this.
    >
    > Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
    > ---
    > arch/x86/kvm/svm.c | 16 +++++++++-------
    > 1 files changed, 9 insertions(+), 7 deletions(-)
    >
    > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
    > index ab78eb8..ec20584 100644
    > --- a/arch/x86/kvm/svm.c
    > +++ b/arch/x86/kvm/svm.c
    > @@ -2771,8 +2771,12 @@ static int svm_nmi_allowed(struct kvm_vcpu *vcpu)
    > {
    > struct vcpu_svm *svm = to_svm(vcpu);
    > struct vmcb *vmcb = svm->vmcb;
    > - return !(vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK) &&
    > - !(svm->vcpu.arch.hflags & HF_NMI_MASK);
    > + int ret;
    > + ret = !(vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK) &&
    > + !(svm->vcpu.arch.hflags & HF_NMI_MASK);
    > + ret = ret && gif_set(svm) && nested_svm_nmi(svm);
    > +
    > + return ret;
    > }
    >
    > static bool svm_get_nmi_mask(struct kvm_vcpu *vcpu)
    > @@ -2841,11 +2845,9 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
    > * Something prevents NMI from been injected. Single step over possible
    > * problem (IRET or exception injection or interrupt shadow)
    > */
    > - if (gif_set(svm) && nested_svm_nmi(svm)) {
    > - svm->nmi_singlestep = true;
    > - svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
    > - update_db_intercept(vcpu);
    > - }
    > + svm->nmi_singlestep = true;
    > + svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
    > + update_db_intercept(vcpu);

    So we're always messing with the nested guest state when the host wants to inject an nmi into the l1 guest? Is that safe?


    Alex



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