Re: [PATCHv3 5/8] KVM: SVM: Add VNMI support in inject_nmi

[Maciej S. Szmigiero]

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@xxxxxxx>
> ---
> 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.

As you said in the cover letter, this field has different semantics
than vNMI - specifically, it should allow injecting even if L2 is in
NMI blocking state (it's then up to L1 to keep track of NMI injectability
for its L2 guest - so L0 should be transparently injecting it when L1
wants so).

> +		vmcb = get_vnmi_vmcb(svm);
> +		vmcb->control.int_ctl |= V_NMI_PENDING;
> +		++vcpu->stat.nmi_injections;
> +		return;
> +	}
>   	svm->vmcb->control.event_inj = SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_NMI;
>   
>   	if (svm->nmi_l1_to_l2)

Thanks,
Maciej