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[54.240.197.238]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5dc7240487csm9012982a12.34.2025.02.04.01.31.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Feb 2025 01:31:17 -0800 (PST) From: Paul Durrant X-Google-Original-From: Paul Durrant Message-ID: <8038e5c0-d0dc-4582-b076-3d514656af1e@xen.org> Date: Tue, 4 Feb 2025 09:31:16 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: paul@xen.org Subject: Re: [PATCH v2 07/11] KVM: x86: Set PVCLOCK_GUEST_STOPPED only for kvmclock, not for Xen PV clock To: Sean Christopherson , Paolo Bonzini , David Woodhouse Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+352e553a86e0d75f5120@syzkaller.appspotmail.com, Paul Durrant , David Woodhouse , Vitaly Kuznetsov References: <20250201013827.680235-1-seanjc@google.com> <20250201013827.680235-8-seanjc@google.com> Content-Language: en-US Organization: Xen Project In-Reply-To: <20250201013827.680235-8-seanjc@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 01/02/2025 01:38, Sean Christopherson wrote: > Handle "guest stopped" propagation only for kvmclock, as the flag is set > if and only if kvmclock is "active", i.e. can only be set for Xen PV clock > if kvmclock *and* Xen PV clock are in-use by the guest, which creates very > bizarre behavior for the guest. > > Simply restrict the flag to kvmclock, e.g. instead of trying to handle > Xen PV clock, as propagation of PVCLOCK_GUEST_STOPPED was unintentionally > added during a refactoring, and while Xen proper defines > XEN_PVCLOCK_GUEST_STOPPED, there's no evidence that Xen guests actually > support the flag. > > Check and clear pvclock_set_guest_stopped_request if and only if kvmclock > is active to preserve the original behavior, i.e. keep the flag pending > if kvmclock happens to be disabled when KVM processes the initial request. > > Fixes: aa096aa0a05f ("KVM: x86/xen: setup pvclock updates") > Cc: Paul Durrant > Cc: David Woodhouse > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/x86.c | 19 ++++++++++--------- > 1 file changed, 10 insertions(+), 9 deletions(-) > Reviewed-by: Paul Durrant