linux-kernel - Re: [PATCH v3 2/2] KVM: x86/xen: Stop Xen timer before changing IRQ

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Message-ID: <YvGrkII3Sgw/qTeo@google.com>
Date:   Tue, 9 Aug 2022 00:34:24 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Coleman Dietsch <dietschc@....edu>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org, Pavel Skripkin <paskripkin@...il.com>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        stable@...r.kernel.org,
        syzbot+e54f930ed78eb0f85281@...kaller.appspotmail.com
Subject: Re: [PATCH v3 2/2] KVM: x86/xen: Stop Xen timer before changing IRQ

On Mon, Aug 08, 2022, Coleman Dietsch wrote:
> Stop Xen timer (if it's running) prior to changing the IRQ vector and
> potentially (re)starting the timer. Changing the IRQ vector while the
> timer is still running can result in KVM injecting a garbage event, e.g.
> vm_xen_inject_timer_irqs() could see a non-zero xen.timer_pending from
> a previous timer but inject the new xen.timer_virq.
> 
> Fixes: 536395260582 ("KVM: x86/xen: handle PV timers oneshot mode")
> Cc: stable@...r.kernel.org
> Link: https://syzkaller.appspot.com/bug?id=8234a9dfd3aafbf092cc5a7cd9842e3ebc45fc42
> Reported-by: syzbot+e54f930ed78eb0f85281@...kaller.appspotmail.com
> Signed-off-by: Coleman Dietsch <dietschc@....edu>
> ---

Reviewed-by: Sean Christopherson <seanjc@...gle.com>