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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 67561ECAAD3 for ; Thu, 1 Sep 2022 07:56:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232007AbiIAH4m (ORCPT ); Thu, 1 Sep 2022 03:56:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233301AbiIAH4i (ORCPT ); Thu, 1 Sep 2022 03:56:38 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03AC8C9E8D; Thu, 1 Sep 2022 00:56:33 -0700 (PDT) Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 2817q8UV009562; Thu, 1 Sep 2022 07:56:16 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : mime-version : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=VWJ0iF7Jqd3Q1V4eJazCtQU9rpjJz6u+8TnZDmEJ39s=; b=jgV94N6NED0GjOVcnrETcQrYaRq21r0e3WGYNzW0H0grghtGskaxOOgVywjHrGsL86UV HGnd5fIUOONfVq+OFeSyyLI+YYLLg4miSwvNE512HYVuAezFCyprI/IEWJf+9SZ6OJBE RRCUlpG3OAO3wnZDMPam79EIf5g/Z0/gKzdG9AcI1etrY/vo+cL4eMMOyEXth0eoUMvM cZTHzIgUdiRgPjGlWHFLnrI5K+55ZpNpFSEwKzJHFpA7eU2w1T9Xi9OYndvKkrzHQ4tA 1Hnp7QTS7fR8+/Q+9vcBE4gRu34TweWZta49fjMQMAAwI3MQuzuLED3svvIu24DRRUyp RQ== Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3jarqrg240-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 01 Sep 2022 07:56:15 +0000 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 2817tuW8029348; Thu, 1 Sep 2022 07:56:14 GMT Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by ppma06ams.nl.ibm.com with ESMTP id 3j7ahj6dq4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 01 Sep 2022 07:56:14 +0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 2817uArh37552432 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 1 Sep 2022 07:56:10 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CDCD9A4054; Thu, 1 Sep 2022 07:56:10 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2054EA405F; Thu, 1 Sep 2022 07:56:10 +0000 (GMT) Received: from [9.171.52.69] (unknown [9.171.52.69]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 1 Sep 2022 07:56:10 +0000 (GMT) Message-ID: <9887e2f4-3f3d-137d-dad7-59dab5f98aab@linux.ibm.com> Date: Thu, 1 Sep 2022 09:56:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH v4 1/2] iommu/s390: Fix race with release_device ops Content-Language: en-US To: Matthew Rosato , iommu@lists.linux.dev Cc: linux-s390@vger.kernel.org, schnelle@linux.ibm.com, borntraeger@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, jgg@nvidia.com, linux-kernel@vger.kernel.org References: <20220831201236.77595-1-mjrosato@linux.ibm.com> <20220831201236.77595-2-mjrosato@linux.ibm.com> From: Pierre Morel In-Reply-To: <20220831201236.77595-2-mjrosato@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 1tmo4lT0ADQ0FCDWTdxaB8P2OmHyGC7e X-Proofpoint-ORIG-GUID: 1tmo4lT0ADQ0FCDWTdxaB8P2OmHyGC7e X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-09-01_04,2022-08-31_03,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 impostorscore=0 priorityscore=1501 spamscore=0 mlxlogscore=999 suspectscore=0 malwarescore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 mlxscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2207270000 definitions=main-2209010033 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 8/31/22 22:12, Matthew Rosato wrote: > With commit fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev > calls") s390-iommu is supposed to handle dynamic switching between IOMMU > domains and the DMA API handling. However, this commit does not > sufficiently handle the case where the device is released via a call > to the release_device op as it may occur at the same time as an opposing > attach_dev or detach_dev since the group mutex is not held over > release_device. This was observed if the device is deconfigured during a > small window during vfio-pci initialization and can result in WARNs and > potential kernel panics. > > Handle this by tracking when the device is probed/released via > dev_iommu_priv_set/get(). Ensure that once the device is released only > release_device handles the re-init of the device DMA. > > Fixes: fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev calls") > Signed-off-by: Matthew Rosato > --- > arch/s390/include/asm/pci.h | 1 + > arch/s390/pci/pci.c | 1 + > drivers/iommu/s390-iommu.c | 39 ++++++++++++++++++++++++++++++++++--- > 3 files changed, 38 insertions(+), 3 deletions(-) > > diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h > index 7b4cdadbc023..080251e7b275 100644 > --- a/arch/s390/include/asm/pci.h > +++ b/arch/s390/include/asm/pci.h > @@ -157,6 +157,7 @@ struct zpci_dev { > /* DMA stuff */ > unsigned long *dma_table; > spinlock_t dma_table_lock; > + struct mutex dma_domain_lock; /* protects s390_domain value */ > int tlb_refresh; > > spinlock_t iommu_bitmap_lock; > diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c > index 73cdc5539384..973edd32ecc9 100644 > --- a/arch/s390/pci/pci.c > +++ b/arch/s390/pci/pci.c > @@ -832,6 +832,7 @@ struct zpci_dev *zpci_create_device(u32 fid, u32 fh, enum zpci_state state) > kref_init(&zdev->kref); > mutex_init(&zdev->lock); > mutex_init(&zdev->kzdev_lock); > + mutex_init(&zdev->dma_domain_lock); > > rc = zpci_init_iommu(zdev); > if (rc) > diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c > index c898bcbbce11..1137d669e849 100644 > --- a/drivers/iommu/s390-iommu.c > +++ b/drivers/iommu/s390-iommu.c > @@ -99,6 +99,14 @@ static int s390_iommu_attach_device(struct iommu_domain *domain, > if (!domain_device) > return -ENOMEM; > > + /* Leave now if the device has already been released */ > + mutex_lock(&zdev->dma_domain_lock); > + if (!dev_iommu_priv_get(dev)) { > + mutex_unlock(&zdev->dma_domain_lock); > + kfree(domain_device); > + return 0; > + } > + > if (zdev->dma_table && !zdev->s390_domain) { > cc = zpci_dma_exit_device(zdev); > if (cc) { > @@ -132,9 +140,10 @@ static int s390_iommu_attach_device(struct iommu_domain *domain, > goto out_restore; > } > domain_device->zdev = zdev; > - zdev->s390_domain = s390_domain; > list_add(&domain_device->list, &s390_domain->devices); > spin_unlock_irqrestore(&s390_domain->list_lock, flags); > + zdev->s390_domain = s390_domain; > + mutex_unlock(&zdev->dma_domain_lock); > > return 0; > > @@ -147,6 +156,7 @@ static int s390_iommu_attach_device(struct iommu_domain *domain, > virt_to_phys(zdev->dma_table)); > } > out_free: > + mutex_unlock(&zdev->dma_domain_lock); > kfree(domain_device); > > return rc; > @@ -176,17 +186,22 @@ static void s390_iommu_detach_device(struct iommu_domain *domain, > } > spin_unlock_irqrestore(&s390_domain->list_lock, flags); > > - if (found && (zdev->s390_domain == s390_domain)) { > + mutex_lock(&zdev->dma_domain_lock); > + if (found && (zdev->s390_domain == s390_domain) && > + dev_iommu_priv_get(dev)) { > zdev->s390_domain = NULL; > zpci_unregister_ioat(zdev, 0); > zpci_dma_init_device(zdev); > } > + mutex_unlock(&zdev->dma_domain_lock); > } > > static struct iommu_device *s390_iommu_probe_device(struct device *dev) > { > struct zpci_dev *zdev = to_zpci_dev(dev); > > + dev_iommu_priv_set(dev, zdev); > + > return &zdev->iommu_dev; > } > > @@ -206,10 +221,28 @@ static void s390_iommu_release_device(struct device *dev) > * > * So let's call detach_dev from here if it hasn't been called before. > */ > - if (zdev && zdev->s390_domain) { > + if (zdev) { > + /* > + * Clear priv to block further attaches for this device, > + * ensure detaches don't init DMA. Hold the domain lock > + * to ensure that attach/detach get a consistent view of > + * whether or not the device is released. > + */ > + mutex_lock(&zdev->dma_domain_lock); > + dev_iommu_priv_set(dev, NULL); > + mutex_unlock(&zdev->dma_domain_lock); We release the lock here to later call s390_iommu_detach_device safely right? Couldn't we keep the lock and put the common code from s390_iommu_release_device and s390_iommu_detach_device inside a common function? > + /* Make sure this device is removed from the domain list */ > domain = iommu_get_domain_for_dev(dev); > if (domain) > s390_iommu_detach_device(domain, dev); > + /* Now ensure DMA is initialized from here */ > + mutex_lock(&zdev->dma_domain_lock); > + if (zdev->s390_domain) { > + zdev->s390_domain = NULL; > + zpci_unregister_ioat(zdev, 0); > + zpci_dma_init_device(zdev); Sorry if it is a stupid question, but two things looks strange to me: - having DMA initialized just after having unregistered the IOAT Is that really all we need to unregister before calling dma_init_device? - having DMA initialized inside the release_device callback: Why isn't it done in the device_probe ? > + } > + mutex_unlock(&zdev->dma_domain_lock); > } > } > > -- Pierre Morel IBM Lab Boeblingen