From: Dexuan Cui <decui@microsoft.com>
To: Thomas Gleixner <tglx@linutronix.de>,
"dwmw@amazon.co.uk" <dwmw@amazon.co.uk>,
"x86@kernel.org" <x86@kernel.org>,
Michael Kelley <mikelley@microsoft.com>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Tianyu Lan <Tianyu.Lan@microsoft.com>,
vkuznets <vkuznets@redhat.com>, KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
"wei.liu@kernel.org" <wei.liu@kernel.org>
Subject: RE: [PATCH] iommu/hyper-v: Fix panic on a host without the 15-bit APIC ID support
Date: Wed, 2 Dec 2020 19:53:03 +0000 [thread overview]
Message-ID: <MWHPR21MB0863B35957EE6D2869B379ACBFF31@MWHPR21MB0863.namprd21.prod.outlook.com> (raw)
In-Reply-To: <87wny0edko.fsf@nanos.tec.linutronix.de>
> From: Thomas Gleixner <tglx@linutronix.de>
> Sent: Wednesday, December 2, 2020 1:56 AM
>
> On Tue, Dec 01 2020 at 16:45, Dexuan Cui wrote:
> > The commit f36a74b9345a itself is good, but it causes a panic in a
> > Linux VM that runs on a Hyper-V host that doesn't have the 15-bit
> > Extended APIC ID support:
> > kernel BUG at arch/x86/kernel/apic/io_apic.c:2408!
>
> This has nothing to do with the 15bit APIC ID support, really.
>
> The point is that the select() function only matches when I/O APIC ID is
> 0, which is not guaranteed. That's independent of the 15bit extended
> APIC ID feature. But the I/O-APIC ID is irrelevant on hyperv because
> there is only one.
>
> > This happens because the Hyper-V ioapic_ir_domain (which is defined in
> > drivers/iommu/hyperv-iommu.c) can not be found. Fix the panic by
> > properly claiming the only I/O APIC emulated by Hyper-V.
>
> We don't fix a panic. We fix a bug in the code :)
>
> I'll amend the changelog.
>
> Thanks,
>
> tglx
Thank you for reworking the commit log, tglx!
Dexuan
next prev parent reply other threads:[~2020-12-02 19:54 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 0:45 [PATCH] iommu/hyper-v: Fix panic on a host without the 15-bit APIC ID support Dexuan Cui
2020-12-02 1:28 ` Woodhouse, David
2020-12-02 9:56 ` Thomas Gleixner
2020-12-02 19:53 ` Dexuan Cui [this message]
2020-12-02 10:28 ` [tip: x86/apic] iommu/hyper-v: Remove I/O-APIC ID check from hyperv_irq_remapping_select() tip-bot2 for Dexuan Cui
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