From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C77FBC41517 for ; Wed, 24 Jul 2019 11:01:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A9EFB22387 for ; Wed, 24 Jul 2019 11:01:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727327AbfGXLBe (ORCPT ); Wed, 24 Jul 2019 07:01:34 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:12264 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726300AbfGXLBe (ORCPT ); Wed, 24 Jul 2019 07:01:34 -0400 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x6OAvSC9126834 for ; Wed, 24 Jul 2019 07:01:33 -0400 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 2txnkus8u1-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 24 Jul 2019 07:01:32 -0400 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 24 Jul 2019 12:01:27 +0100 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x6OB1PAf47448152 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 24 Jul 2019 11:01:25 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 934A652059; Wed, 24 Jul 2019 11:01:25 +0000 (GMT) Received: from oc2783563651 (unknown [9.152.224.141]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 53D9A52052; Wed, 24 Jul 2019 11:01:25 +0000 (GMT) Date: Wed, 24 Jul 2019 13:01:24 +0200 From: Halil Pasic To: Christian Borntraeger Cc: Cornelia Huck , kvm@vger.kernel.org, linux-s390@vger.kernel.org, Janosch Frank , Marc Hartmayer , virtualization@lists.linux-foundation.org, stable@vger.kernel.org Subject: Re: [PATCH 1/1] virtio/s390: fix race on airq_areas[] In-Reply-To: <74087255-fdae-01a1-7152-f6fac8e13019@de.ibm.com> References: <20190723225817.12800-1-pasic@linux.ibm.com> <74087255-fdae-01a1-7152-f6fac8e13019@de.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19072411-0028-0000-0000-000003875644 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19072411-0029-0000-0000-00002447919D Message-Id: <20190724130124.0dcfc5c0.pasic@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-24_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1907240124 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, 24 Jul 2019 08:44:19 +0200 Christian Borntraeger wrote: > > > On 24.07.19 00:58, Halil Pasic wrote: > > The access to airq_areas was racy ever since the adapter interrupts got > > introduced to virtio-ccw, but since commit 39c7dcb15892 ("virtio/s390: > > make airq summary indicators DMA") this became an issue in practice as > > well. Namely before that commit the airq_info that got overwritten was > > still functional. After that commit however the two infos share a > > summary_indicator, which aggravates the situation. Which means > > auto-online mechanism occasionally hangs the boot with virtio_blk. > > > > Signed-off-by: Halil Pasic > > Reported-by: Marc Hartmayer > > Fixes: 96b14536d935 ("virtio-ccw: virtio-ccw adapter interrupt support.") > > --- > > * We need definitely this fixed for 5.3. For older stable kernels it is > > to be discussed. @Connie what do you think: do we need a cc stable? > > Unless you can prove that the problem could never happen on old version > we absolutely do need cc stable. No I would not like to make an attempt at proving that. I prefer code race free anyway. CC-ing stable. > > > > > * I have a variant that does not need the extra mutex but uses cmpxchg(). > > Decided to post this one because that one is more complex. But if there > > is interest we can have a look at it as well. > > This is slow path (startup) and never called in hot path. Correct? Mutex should be > fine. Right, this is only relevant during device initialization, which is an infrequent operation. Thanks, Halil > > --- > > drivers/s390/virtio/virtio_ccw.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c > > index 1a55e5942d36..d97742662755 100644 > > --- a/drivers/s390/virtio/virtio_ccw.c > > +++ b/drivers/s390/virtio/virtio_ccw.c > > @@ -145,6 +145,8 @@ struct airq_info { > > struct airq_iv *aiv; > > }; > > static struct airq_info *airq_areas[MAX_AIRQ_AREAS]; > > +DEFINE_MUTEX(airq_areas_lock); > > + > > static u8 *summary_indicators; > > > > static inline u8 *get_summary_indicator(struct airq_info *info) > > @@ -265,9 +267,11 @@ static unsigned long get_airq_indicator(struct virtqueue *vqs[], int nvqs, > > unsigned long bit, flags; > > > > for (i = 0; i < MAX_AIRQ_AREAS && !indicator_addr; i++) { > > + mutex_lock(&airq_areas_lock); > > if (!airq_areas[i]) > > airq_areas[i] = new_airq_info(i); > > info = airq_areas[i]; > > + mutex_unlock(&airq_areas_lock); > > if (!info) > > return 0; > > write_lock_irqsave(&info->lock, flags); > > >