linux-kernel - Re: [PATCHv2 5/7] KVM: SVM: Add VNMI support in inject

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Date:   Wed, 20 Jul 2022 23:04:56 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     Santosh Shukla <santosh.shukla@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 5/7] KVM: SVM: Add VNMI support in inject_nmi

On Wed, Jul 20, 2022, Jim Mattson wrote:
> On Wed, Jul 20, 2022 at 2:41 PM Sean Christopherson <seanjc@...gle.com> wrote:
> >
> > On Sat, Jul 09, 2022, 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>
> > > ---
> > > 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 | 10 +++++++++-
> > >  1 file changed, 9 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > > index 44c1f2317b45..c73a1809a7c7 100644
> > > --- a/arch/x86/kvm/svm/svm.c
> > > +++ b/arch/x86/kvm/svm/svm.c
> > > @@ -3375,12 +3375,20 @@ 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;
> > > +
> > > +     ++vcpu->stat.nmi_injections;
> > > +     if (is_vnmi_enabled(svm)) {
> > > +             vmcb = get_vnmi_vmcb(svm);
> > > +             WARN_ON(vmcb->control.int_ctl & V_NMI_PENDING);
> >
> > Haven't read the spec, but based on the changelog I assume the flag doesn't get
> > cleared until the NMI is fully delivered.
> 
> Ooh! Is there a spec to read now?!?

Apparently not.  I just assumed there's a spec, but I haven't found one.