linux-kernel - Re: Hang in 9p/virtio

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Date:	Tue, 2 Aug 2016 11:13:04 +0200
From:	Vegard Nossum <vegard.nossum@...cle.com>
To:	Cornelia Huck <cornelia.huck@...ibm.com>
Cc:	Eric Van Hensbergen <ericvh@...il.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	v9fs-developer@...ts.sourceforge.net,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Hang in 9p/virtio

On 08/02/2016 11:03 AM, Cornelia Huck wrote:
> On Sat, 30 Jul 2016 23:42:18 +0200
> Vegard Nossum <vegard.nossum@...cle.com> wrote:
>
>> Hi,
>>
>> With fault injection triggering an allocation failure for the
>> alloc_indirect() call in virtqueue_add() I'm seeing a hang in
>> p9_virtio_zc_request() -- it seems to be waiting here indefinitely
>> (i.e. at least 120 seconds):
>>
[...]

> What happens is that the code falls back to direct virtio addressing
> (after indirect addressing failed) - and this should work.
>
> I'm more inclined to suspect a qemu instead of a kernel bug, as your
> qemu version is quite old and there have been fixes in the virtio
> buffer handling and virtio-9p in the meantime. (I'm suspecting
> "virtio-9p: fix any_layout".)
>
> Could you retry with a more recent qemu (at least version 2.4)?

I think maybe the version number in the stack trace is a bit misleading,
this is the full/actual version:

$ kvm --version
QEMU emulator version 2.5.0 (Debian 1:2.5+dfsg-5ubuntu10.1), Copyright 
(c) 2003-2008 Fabrice Bellard

I'll still try to get qemu from git and see if it makes a difference.
Thanks,


Vegard