Messages in this thread | | | Date | Fri, 23 Apr 2010 16:13:56 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH 1/8] KVM: SVM: Fix nested nmi handling |
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On Fri, Apr 23, 2010 at 03:46:07PM +0200, Alexander Graf wrote: > > 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?
Why not? We can't inject an NMI directly into L2 if the nested hypervisor intercepts it.
Joerg
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