linux-kernel - Re: [PATCH] virtio-pci: Remove affinity hint before freeing the interrupt

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Message-ID: <87o9xbyifi.fsf@on-the-bus.cambridge.arm.com>
Date:   Wed, 08 Mar 2017 14:03:29 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] virtio-pci: Remove affinity hint before freeing the interrupt

On Wed, Mar 08 2017 at  1:28:13 pm GMT, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> On Wed, Mar 08, 2017 at 08:09:27AM +0000, Marc Zyngier wrote:
>> virtio-pci registers a per-vq affinity hint when using MSIX,
>> but fails to remove it when freeing the interrupt, resulting
>> in this type of splat:
>> 
>> [   31.111202] WARNING: CPU: 0 PID: 2823 at kernel/irq/manage.c:1503 __free_irq+0x2c4/0x2c8
>> [   31.114689] Modules linked in:
>> [   31.116101] CPU: 0 PID: 2823 Comm: kexec Not tainted 4.10.0+ #6941
>> [   31.118911] Hardware name: Generic DT based system
>> [   31.121319] [<c022fb78>] (unwind_backtrace) from [<c0229d8c>] (show_stack+0x18/0x1c)
>> [   31.125017] [<c0229d8c>] (show_stack) from [<c05192f4>] (dump_stack+0x84/0x98)
>> [   31.128427] [<c05192f4>] (dump_stack) from [<c023d940>] (__warn+0xf4/0x10c)
>> [   31.131910] [<c023d940>] (__warn) from [<c023da20>] (warn_slowpath_null+0x28/0x30)
>> [   31.135543] [<c023da20>] (warn_slowpath_null) from [<c0290238>] (__free_irq+0x2c4/0x2c8)
>> [   31.139355] [<c0290238>] (__free_irq) from [<c02902d0>] (free_irq+0x44/0x78)
>> [   31.142909] [<c02902d0>] (free_irq) from [<c059d3a8>] (vp_del_vqs+0x68/0x1c0)
>> [   31.146299] [<c059d3a8>] (vp_del_vqs) from [<c056ca4c>] (pci_device_shutdown+0x3c/0x78)
>> 
>> The obvious fix is to drop the affinity hint before freeing the
>> interrupt.
>> 
>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>
> Is this introduced by the changes in latest rc?

No, this was there already in 4.10, just in a different function (I had
to rebase the fix, as I originally fixed vp_del_vqs). -rc1 just moved
the bug to a new function.

Thanks,

	M.
-- 
Jazz is not dead, it just smell funny.