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Date: Sun, 10 Jul 2022 19:07:23 +0300 From: Maxim Levitsky <mlevitsk@...hat.com> To: "Shukla, Santosh" <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 Fri, 2022-06-17 at 20:35 +0530, Shukla, Santosh wrote: > > On 6/7/2022 6:44 PM, Maxim Levitsky wrote: > > 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. > > > Yes, in v2. > > > 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. > > > > V_NMI_MASK should be saved as 1 in the save area and > hypervisor will resume the NMI handler after handling the SMI. Answering my own question, because I did some homework in this area while working on that SMI int shadow bug: Actually what will happen (now I checked) is that we have a special KVM host state flag (called X86EMUL_SMM_MASK, and HF_SMM_INSIDE_NMI_MASK), and what we do is that if we receive SMI while in NMI handler, we don't mask the NMI again, on RSM we don't unmask NMI. Also, as I found out the hard way recently, the NMI is not blocked by the interrupt shadow. I don't think that anything is saved to the SMRAM in this case. Best regards, Maxim Levitsky > > Thanks, > Santosh > > > 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)
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