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Szmigiero wrote: > 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 >>>>>> --- >>>>>> 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. > Yes, I meant is_vnmi_enabled() will return false if vnmi param is unset. > 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 > No. In L1 case (vnmi disabled) - vnmi param will be false. In L0 case (vnmi enabled) - vnmi param will be true. So in L1 case, is_vnmi_enabled() will return false and in L0 case will return true. Thanks, Santosh >> >>     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