From: Sean Christopherson <seanjc@google.com>
To: Naveen N Rao <naveen@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Jim Mattson <jmattson@google.com>,
"Maciej S . Szmigiero" <maciej.szmigiero@oracle.com>
Subject: Re: [PATCH 2/2] KVM: SVM: Set/clear CR8 write interception when AVIC is (de)activated
Date: Fri, 6 Feb 2026 09:55:02 -0800 [thread overview]
Message-ID: <aYYq9u7bZWsmJNMr@google.com> (raw)
In-Reply-To: <aYYgShD2-47P51ZM@blrnaveerao1>
On Fri, Feb 06, 2026, Naveen N Rao wrote:
> On Tue, Feb 03, 2026 at 11:07:10AM -0800, Sean Christopherson wrote:
> > Explicitly set/clear CR8 write interception when AVIC is (de)activated to
> > fix a bug where KVM leaves the interception enabled after AVIC is
> > activated. E.g. if KVM emulates INIT=>WFS while AVIC is deactivated, CR8
> > will remain intercepted in perpetuity.
>
> Looking at svm_update_cr8_intercept(), I suppose this could also more
> commonly happen whenever AVIC is inhibited (IRQ Windows, as an example)?
Maybe? I don't think it's actually common in practice. Because the bug requires
the source of the inhibition to be removed while the vCPU still has a pending IRQ
that is below PPR. Which is definitely possible, but that seems overall unlikely,
and it'd also be self-healing to some extent. E.g. if a workload is triggering
ExtINT, then odds are good it's going to _keep_ generating ExtINT, keep toggling
the inhibit, and thus reconcile CR8 interception every time AVIC is inhibited.
next prev parent reply other threads:[~2026-02-06 17:55 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-03 19:07 [PATCH 0/2] KVM: SVM: Fix CR8 intercpetion woes with AVIC Sean Christopherson
2026-02-03 19:07 ` [PATCH 1/2] KVM: SVM: Initialize AVIC VMCB fields if AVIC is enabled with in-kernel APIC Sean Christopherson
2026-02-05 4:21 ` Jim Mattson
2026-02-06 14:00 ` Naveen N Rao
2026-02-06 18:17 ` Sean Christopherson
2026-02-09 10:23 ` Naveen N Rao
2026-02-09 21:36 ` Sean Christopherson
2026-02-03 19:07 ` [PATCH 2/2] KVM: SVM: Set/clear CR8 write interception when AVIC is (de)activated Sean Christopherson
2026-02-05 4:22 ` Jim Mattson
2026-02-06 17:11 ` Naveen N Rao
2026-02-06 17:55 ` Sean Christopherson [this message]
2026-03-10 15:41 ` Aithal, Srikanth
2026-03-10 17:17 ` Sean Christopherson
2026-03-10 17:36 ` Tom Lendacky
2026-03-10 17:48 ` Naveen N Rao
2026-03-10 18:00 ` Naveen N Rao
2026-03-10 18:12 ` Tom Lendacky
2026-03-10 18:35 ` Sean Christopherson
2026-03-10 21:41 ` Tom Lendacky
2026-03-10 21:58 ` Sean Christopherson
2026-03-10 22:33 ` Tom Lendacky
2026-03-10 22:40 ` Sean Christopherson
2026-03-11 13:43 ` Tom Lendacky
2026-03-11 17:39 ` Paolo Bonzini
2026-03-05 17:07 ` [PATCH 0/2] KVM: SVM: Fix CR8 intercpetion woes with AVIC Sean Christopherson
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