linux-kernel - Re: [PATCH] iommu/hyper-v: Fix panic on a host without the 15-bit APIC ID support

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Message-ID: <eba320d980578ff37685967f8cafa5cf3ecb48e2.camel@amazon.co.uk>
Date:   Wed, 2 Dec 2020 01:28:20 +0000
From:   "Woodhouse, David" <dwmw@...zon.co.uk>
To:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "decui@...rosoft.com" <decui@...rosoft.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "mikelley@...rosoft.com" <mikelley@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
CC:     "sthemmin@...rosoft.com" <sthemmin@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Tianyu.Lan@...rosoft.com" <Tianyu.Lan@...rosoft.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "kys@...rosoft.com" <kys@...rosoft.com>,
        "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>
Subject: Re: [PATCH] iommu/hyper-v: Fix panic on a host without the 15-bit APIC ID
 support

On Tue, 2020-12-01 at 16:45 -0800, 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 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.
> 
> Cc: David Woodhouse <dwmw@...zon.co.uk>
> Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
> Fixes: f36a74b9345a ("x86/ioapic: Use I/O-APIC ID for finding irqdomain, not index")
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>

Oops, apologies for missing that.

Reviewed-by: David Woodhouse <dwmw@...zon.co.uk>



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