From: Maxim Levitsky <mlevitsk@redhat.com>
To: "Shukla, Santosh" <santosh.shukla@amd.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Tom Lendacky <thomas.lendacky@amd.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/7] KVM: SVM: Add VNMI support in inject_nmi
Date: Sun, 10 Jul 2022 19:07:23 +0300 [thread overview]
Message-ID: <670ce789f6139143f781bdd5ebfead79d5a4fadb.camel@redhat.com> (raw)
In-Reply-To: <0981fd1c-b4b4-84ad-27e9-babcfa2524db@amd.com>
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@amd.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)
next prev parent reply other threads:[~2022-07-10 16:07 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-02 14:26 [PATCH 0/7] Virtual NMI feature Santosh Shukla
2022-06-02 14:26 ` [PATCH 1/7] x86/cpu: Add CPUID feature bit for VNMI Santosh Shukla
2022-06-07 12:32 ` Maxim Levitsky
2022-06-02 14:26 ` [PATCH 2/7] KVM: SVM: Add VNMI bit definition Santosh Shukla
2022-06-07 12:55 ` Maxim Levitsky
2022-06-17 14:42 ` Shukla, Santosh
2022-06-02 14:26 ` [PATCH 3/7] KVM: SVM: Add VNMI support in get/set_nmi_mask Santosh Shukla
2022-06-07 13:07 ` Maxim Levitsky
2022-06-17 14:45 ` Shukla, Santosh
2022-06-17 14:48 ` Shukla, Santosh
2022-07-10 16:09 ` Maxim Levitsky
2022-07-21 9:25 ` Shukla, Santosh
2022-07-10 18:39 ` Maxim Levitsky
2022-06-02 14:26 ` [PATCH 4/7] KVM: SVM: Report NMI not allowed when Guest busy handling VNMI Santosh Shukla
2022-06-07 13:10 ` Maxim Levitsky
2022-06-07 13:12 ` Maxim Levitsky
2022-06-17 14:59 ` Shukla, Santosh
2022-07-10 16:08 ` Maxim Levitsky
2022-07-21 9:31 ` Shukla, Santosh
2022-07-21 11:56 ` Maxim Levitsky
2022-06-02 14:26 ` [PATCH 5/7] KVM: SVM: Add VNMI support in inject_nmi Santosh Shukla
2022-06-07 13:14 ` Maxim Levitsky
2022-06-17 15:05 ` Shukla, Santosh
2022-07-10 16:07 ` Maxim Levitsky [this message]
2022-06-02 14:26 ` [PATCH 6/7] KVM: nSVM: implement nested VNMI Santosh Shukla
2022-06-07 13:22 ` Maxim Levitsky
2022-06-17 15:08 ` Shukla, Santosh
2022-06-02 14:26 ` [PATCH 7/7] KVM: SVM: Enable VNMI feature Santosh Shukla
2022-06-06 23:01 ` [PATCH 0/7] Virtual NMI feature Jim Mattson
2022-06-08 8:23 ` Shukla, Santosh
2022-09-05 19:45 ` Jim Mattson
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