From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:7880 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731201AbfGWW6l (ORCPT ); Tue, 23 Jul 2019 18:58:41 -0400 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x6NMuuL7040282 for ; Tue, 23 Jul 2019 18:58:39 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0b-001b2d01.pphosted.com with ESMTP id 2tx927585v-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 23 Jul 2019 18:58:39 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 23 Jul 2019 23:58:37 +0100 From: Halil Pasic Subject: [PATCH 1/1] virtio/s390: fix race on airq_areas[] Date: Wed, 24 Jul 2019 00:58:17 +0200 Message-Id: <20190723225817.12800-1-pasic@linux.ibm.com> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Cornelia Huck , kvm@vger.kernel.org, linux-s390@vger.kernel.org Cc: Halil Pasic , Christian Borntraeger , Janosch Frank , Marc Hartmayer , virtualization@lists.linux-foundation.org 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? * 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. --- 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); -- 2.17.1