On 23.04.2010, at 16:22, Joerg Roedel wrote: > On Fri, Apr 23, 2010 at 04:19:40PM +0200, Alexander Graf wrote: >> >> On 23.04.2010, at 16:13, Joerg Roedel wrote: >> >>> 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 <[email protected]> >>>>> --- >>>>> 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. >> >> So where did the code go that does the #vmexit in case the nested >> hypervisor does intercept it? It used to be nested_svm_nmi(), right? > > No, nested_svm_nmi runs in atomic context where we can't emulate a > vmexit. We set exit_required and emulate the vmexit later.
So we modify the L2 rflags and then trigger a #vmexit, leaving the l2 state broken? Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
