Messages in this thread | | | Date | Thu, 25 Aug 2022 14:45:53 +0200 | From | "Maciej S. Szmigiero" <> | Subject | Re: [PATCHv3 5/8] KVM: SVM: Add VNMI support in inject_nmi |
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On 25.08.2022 12:56, Shukla, Santosh wrote: > On 8/24/2022 6:26 PM, Maciej S. Szmigiero wrote: >> On 24.08.2022 14:13, Shukla, Santosh wrote: >>> Hi Maciej, >>> >>> On 8/11/2022 2:54 AM, Maciej S. Szmigiero wrote: >>>> On 10.08.2022 08:12, Santosh Shukla wrote: >>>>> Inject the NMI by setting V_NMI in the VMCB interrupt control. processor >>>>> will clear V_NMI to acknowledge processing has started and will keep the >>>>> V_NMI_MASK set until the processor is done with processing the NMI event. >>>>> >>>>> Signed-off-by: Santosh Shukla <santosh.shukla@amd.com> >>>>> --- >>>>> v3: >>>>> - Removed WARN_ON check. >>>>> >>>>> v2: >>>>> - Added WARN_ON check for vnmi pending. >>>>> - use `get_vnmi_vmcb` to get correct vmcb so to inject vnmi. >>>>> >>>>> arch/x86/kvm/svm/svm.c | 7 +++++++ >>>>> 1 file changed, 7 insertions(+) >>>>> >>>>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c >>>>> index e260e8cb0c81..8c4098b8a63e 100644 >>>>> --- a/arch/x86/kvm/svm/svm.c >>>>> +++ b/arch/x86/kvm/svm/svm.c >>>>> @@ -3479,7 +3479,14 @@ static void pre_svm_run(struct kvm_vcpu *vcpu) >>>>> static void svm_inject_nmi(struct kvm_vcpu *vcpu) >>>>> { >>>>> struct vcpu_svm *svm = to_svm(vcpu); >>>>> + struct vmcb *vmcb = NULL; >>>>> + if (is_vnmi_enabled(svm)) { >>>> >>>> I guess this should be "is_vnmi_enabled(svm) && !svm->nmi_l1_to_l2" >>>> since if nmi_l1_to_l2 is true then the NMI to be injected originally >>>> comes from L1's VMCB12 EVENTINJ field. >>>> >>> >>> Not sure if I understood the case fully.. so trying to sketch scenario here - >>> if nmi_l1_to_l2 is true then event is coming from EVTINJ. .which could >>> be one of following case - >>> 1) L0 (vnmi enabled) and L1 (vnmi disabled) >> >> As far as I can see in this case: >> is_vnmi_enabled() returns whether VMCB02's int_ctl has V_NMI_ENABLE bit set. >> > > For L1 with vnmi disabled case - is_vnmi_enabled()->get_vnmi_vmcb() will return false so the > execution path will opt EVTINJ model for re-injection.
I guess by "get_vnmi_vmcb() will return false" you mean it will return NULL, since this function returns a pointer, not a bool.
I can't see however, how this will happen: >static inline struct vmcb *get_vnmi_vmcb(struct vcpu_svm *svm) >{ > if (!vnmi) > return NULL; ^ "vnmi" variable controls whether L0 uses vNMI, so this variable is true in our case
> > if (is_guest_mode(&svm->vcpu)) > return svm->nested.vmcb02.ptr; ^ this should be always non-NULL.
So get_vnmi_vmcb() will return VMCB02 pointer in our case, not NULL...
> > Thanks, > Santosh > >> This field in VMCB02 comes from nested_vmcb02_prepare_control() which >> in the !nested_vnmi_enabled() case (L1 is not using vNMI) copies these bits >> from VMCB01: >>> int_ctl_vmcb01_bits |= (V_NMI_PENDING | V_NMI_ENABLE | V_NMI_MASK); >> >> So in this case (L0 uses vNMI) V_NMI_ENABLE will be set in VMCB01, right? >> >> This bit will then be copied to VMCB02
... and due to the above is_vnmi_enabled() will return true, so re-injection will attempt to use vNMI instead of EVTINJ (wrong).
>>> 2) L0 & L1 both vnmi disabled. >> >> This case is ok. >> >>> >>> In both cases the vnmi check will fail for L1 and execution path >>> will fall back to default - right? >>> >>> Thanks, >>> Santosh >>
Thanks, Maciej
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