Messages in this thread | | | Date | Thu, 25 Aug 2022 16:16:10 +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 16:05, Shukla, Santosh wrote: > On 8/25/2022 6:15 PM, Maciej S. 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 <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. >> > > 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.
Perhaps there was a misunderstanding here - the case here isn't the code under discussion running as L1, but as L0 where L1 not using vNMI - L1 here can be an old version of KVM, or Hyper-V, or any other hypervisor.
In this case L0 is re-injecting an EVENTINJ NMI into L2 on the behalf of L1. That's when "nmi_l1_to_l2" is true.
Since the code is physically running on L0 (which makes use of vNMI) it has the "vnmi" param set.
So is_vnmi_enabled() will return true and vNMI will be used for the re-injection instead of the required EVENTINJ.
> 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
Thanks, Maciej
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