From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967941AbcHBQfz (ORCPT ); Tue, 2 Aug 2016 12:35:55 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:56699 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935281AbcHBQfo (ORCPT ); Tue, 2 Aug 2016 12:35:44 -0400 X-IBM-Helo: d06dlp03.portsmouth.uk.ibm.com X-IBM-MailFrom: cornelia.huck@de.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Tue, 2 Aug 2016 18:35:02 +0200 From: Cornelia Huck To: Vegard Nossum Cc: Eric Van Hensbergen , "Michael S. Tsirkin" , "Aneesh Kumar K.V" , v9fs-developer@lists.sourceforge.net, LKML Subject: Re: Hang in 9p/virtio In-Reply-To: <57A0A1A6.3000504@oracle.com> References: <579D1F3A.7020806@oracle.com> <20160802110321.1fc7369f.cornelia.huck@de.ibm.com> <57A06420.3070508@oracle.com> <57A0A1A6.3000504@oracle.com> Organization: IBM Deutschland Research & Development GmbH Vorsitzende des Aufsichtsrats: Martina Koederitz =?UTF-8?B?R2VzY2jDpGZ0c2bDvGhydW5nOg==?= Dirk Wittkopp Sitz der Gesellschaft: =?UTF-8?B?QsO2Ymxpbmdlbg==?= Registergericht: Amtsgericht Stuttgart, HRB 243294 X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16080216-0012-0000-0000-0000043E787C X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16080216-0013-0000-0000-000014E49AB1 Message-Id: <20160802183502.5716e415.cornelia.huck@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-08-02_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1608020167 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2 Aug 2016 15:35:34 +0200 Vegard Nossum wrote: > On 08/02/2016 11:13 AM, Vegard Nossum wrote: > > On 08/02/2016 11:03 AM, Cornelia Huck wrote: > >> On Sat, 30 Jul 2016 23:42:18 +0200 > >> Vegard Nossum 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, > > I still seem to get it: > > $ qemu-system-x86_64 --version > QEMU emulator version 2.6.91 (v2.7.0-rc1-2-gcc0100f-dirty), Copyright > (c) 2003-2008 Fabrice Bellard :( Sorry, no good immediate idea. One thing would be to check whether you get notified by qemu after the request was queued (i.e., whether vring_interrupt() ever gets called with 9p's req_done() after the alloc failure was injected). This would help to suggest whether to continue debugging here or in qemu. I still think the root of this error is some failure of the virtio 9p code to deal with non-indirect buffers, either in the driver or in qemu.