linux-kernel - Re: [PATCH v2] KVM: SVM: Don't intercept IRET when injecting NMI and vNMI is enabled

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Date:   Thu, 30 Nov 2023 17:52:30 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Santosh Shukla <santosh.shukla@....com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: Re: [PATCH v2] KVM: SVM: Don't intercept IRET when injecting NMI and
 vNMI is enabled

On Wed, 18 Oct 2023 12:20:21 -0700, Sean Christopherson wrote:
> When vNMI is enabled, rely entirely on hardware to correctly handle NMI
> blocking, i.e. don't intercept IRET to detect when NMIs are no longer
> blocked.  KVM already correctly ignores svm->nmi_masked when vNMI is
> enabled, so the effect of the bug is essentially an unnecessary VM-Exit.
> 
> KVM intercepts IRET for two reasons:
>  - To track NMI masking to be able to know at any point of time if NMI
>    is masked.
>  - To track NMI windows (to inject another NMI after the guest executes
>    IRET, i.e. unblocks NMIs)
> 
> [...]

Applied to kvm-x86 svm, thanks!

[1/1] KVM: SVM: Don't intercept IRET when injecting NMI and vNMI is enabled
      https://github.com/kvm-x86/linux/commit/72046d0a077a

--
https://github.com/kvm-x86/linux/tree/next