From: Stefano Garzarella <sgarzare@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
"Carlos López" <clopez@suse.de>, "Chris Oo" <cho@microsoft.com>
Subject: Re: [PATCH] KVM: SVM: Sync CR8 to the local APIC after marking the VMCB clean
Date: Sun, 15 Nov 2026 09:10:14 +0100 [thread overview]
Message-ID: <avlowrJCV-dgtAD3@sgarzare-redhat> (raw)
In-Reply-To: <20261113162556.461390-1-seanjc@google.com>
On Fri, Nov 13, 2026 at 08:25:56AM -0800, Sean Christopherson wrote:
>From: Chris Oo <cho@microsoft.com>
>
>Sync CR8 from the VMCB to the TPR *after* marking all VMCB fields as clean,
>as syncing CR8 can toggle the CR8 write intercept and thus mark INTERCEPTS
>as dirty. Clobbering the dirty bit can result in KVM failing to detect CR8
>writes if the underlying "hardware" uses the clean bits to optimize VMRUN,
>e.g. when KVM is running on Hyper-V.
>
>Failure to intercept CR8 usually manifests as hangs when running Windows as
>L2, as KVM's view of vTPR stays high and so KVM never injects pending IRQs.
>
>Fixes: bb365a506b1e ("KVM: x86: Unconditionally recompute CR8 intercept on PPR update")
>Cc: stable@vger.kernel.org
>Cc: Carlos López <clopez@suse.de>
>Cc: Stefano Garzarella <sgarzare@redhat.com>
>Not-signed-off-by: Chris Oo <cho@microsoft.com>
>[sean: rewrite changelog, massage comment]
>Signed-off-by: Sean Christopherson <seanjc@google.com>
>---
LGTM!
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
prev parent reply other threads:[~2026-11-15 8:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-13 16:25 Sean Christopherson
2026-11-13 16:36 ` [EXTERNAL] " Chris Oo
2026-11-13 16:59 ` Yosry Ahmed
2026-11-15 8:10 ` Stefano Garzarella [this message]
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