linux-kernel - Re: [PATCH 5/7] KVM: SVM: Add VNMI support in inject

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Message-ID: <dfc2ce68a10181b1ac6c07ca3927d474e13ca973.camel@redhat.com>
Date:   Tue, 07 Jun 2022 16:14:25 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Santosh Shukla <santosh.shukla@....com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Tom Lendacky <thomas.lendacky@....com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] KVM: SVM: Add VNMI support in inject_nmi

On Thu, 2022-06-02 at 19:56 +0530, 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@....com>
> ---
>  arch/x86/kvm/svm/svm.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index a405e414cae4..200f979169e0 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3385,11 +3385,16 @@ static void svm_inject_nmi(struct kvm_vcpu *vcpu)
>  {
>         struct vcpu_svm *svm = to_svm(vcpu);
>  
> +       ++vcpu->stat.nmi_injections;
> +       if (is_vnmi_enabled(svm->vmcb)) {
> +               svm->vmcb->control.int_ctl |= V_NMI_PENDING;
> +               return;
> +       }
Here I would advice to have a warning to check if vNMI is already pending.

Also we need to check what happens if we make vNMI pending and get #SMI,
while in #NMI handler, or if #NMI is blocked due to interrupt window.

Best regards,
	Maxim Levitsky


> +
>         svm->vmcb->control.event_inj = SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_NMI;
>         vcpu->arch.hflags |= HF_NMI_MASK;
>         if (!sev_es_guest(vcpu->kvm))
>                 svm_set_intercept(svm, INTERCEPT_IRET);
> -       ++vcpu->stat.nmi_injections;
>  }
>  
>  static void svm_inject_irq(struct kvm_vcpu *vcpu)