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[82.81.161.50]) by smtp.gmail.com with ESMTPSA id z22-20020ac87116000000b00304f7449e17sm1439142qto.93.2022.06.07.06.12.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jun 2022 06:12:10 -0700 (PDT) Message-ID: <45e9ccafcdb48c7521b697b41e849dab98a7a76c.camel@redhat.com> Subject: Re: [PATCH 4/7] KVM: SVM: Report NMI not allowed when Guest busy handling VNMI From: Maxim Levitsky To: Santosh Shukla , Paolo Bonzini Cc: Sean Christopherson , Vitaly Kuznetsov , Jim Mattson , Joerg Roedel , Tom Lendacky , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 07 Jun 2022 16:12:07 +0300 In-Reply-To: References: <20220602142620.3196-1-santosh.shukla@amd.com> <20220602142620.3196-5-santosh.shukla@amd.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.40.4 (3.40.4-2.fc34) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2022-06-07 at 16:10 +0300, Maxim Levitsky wrote: > On Thu, 2022-06-02 at 19:56 +0530, Santosh Shukla wrote: > > In the VNMI case, Report NMI is not allowed when the processor set the > > V_NMI_MASK to 1 which means the Guest is busy handling VNMI. > > > > Signed-off-by: Santosh Shukla > > --- > >  arch/x86/kvm/svm/svm.c | 6 ++++++ > >  1 file changed, 6 insertions(+) > > > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > > index d67a54517d95..a405e414cae4 100644 > > --- a/arch/x86/kvm/svm/svm.c > > +++ b/arch/x86/kvm/svm/svm.c > > @@ -3483,6 +3483,9 @@ bool svm_nmi_blocked(struct kvm_vcpu *vcpu) > >         struct vmcb *vmcb = svm->vmcb; > >         bool ret; > >   > > +       if (is_vnmi_enabled(vmcb) && is_vnmi_mask_set(vmcb)) > > +               return true; > > How does this interact with GIF? if the guest does clgi, will the > CPU update the V_NMI_MASK on its own If vGIF is enabled? > > What happens if vGIF is disabled and vNMI is enabled? KVM then intercepts > the stgi/clgi, and it should then update the V_NMI_MASK? > > > > > > + > >         if (!gif_set(svm)) > >                 return true; > >   > > @@ -3618,6 +3621,9 @@ static void svm_enable_nmi_window(struct kvm_vcpu *vcpu) > >  { > >         struct vcpu_svm *svm = to_svm(vcpu); > >   > > +       if (is_vnmi_enabled(svm->vmcb) && is_vnmi_mask_set(svm->vmcb)) > > +               return; > > This might have hidden assumption that we will only enable NMI window when vNMI is masked. Also what if vNMI is already pending? Best regards, Maxim Levitsky > > > > > + > >         if ((vcpu->arch.hflags & (HF_NMI_MASK | HF_IRET_MASK)) == HF_NMI_MASK) > >                 return; /* IRET will cause a vm exit */ > >   > > > Best regards, >         Maxim Levitsky