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Tue, 18 Nov 2025 16:52:24 -0800 From: Nicolin Chen To: , , , , , , CC: , , , , , , , , , , , , , Subject: [PATCH v6 1/5] iommu: Lock group->mutex in iommu_deferred_attach() Date: Tue, 18 Nov 2025 16:52:07 -0800 Message-ID: X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF0002636E:EE_|LV3PR12MB9266:EE_ X-MS-Office365-Filtering-Correlation-Id: a7f236d8-e029-4ffa-bb6a-08de2705f483 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|7416014|36860700013|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?zANtdOEQOoaoCYcgF/VIBLoMMYm+vCkK5rFq/pWAxF4+kt6twvwobcaI6h3I?= =?us-ascii?Q?QqC875t1ofMAorlF7gDQ1wCdBcqkmN9ai2jFWcREGmY8PH2F1thj3xamTSxV?= =?us-ascii?Q?HgwPpXjyYnQBrP3svzMjAwl3vHFfNi2cEQUcLid2Su77jwSw9v719yL3R5fB?= =?us-ascii?Q?yK/qRkqeAEhr6ToNTWfdi6N6uPm6IubwxYSMtyEL2Ga++KiM0Y5PU7KNpvaj?= =?us-ascii?Q?tWGwKuu/jPGL16PXzCL8Kcn1axqm6PJIosZfiSxYhhOrsr5w1Lr4n9zbWGkN?= =?us-ascii?Q?ETvGuUufgbzHYSpt5VVgjJZK6wPkdGM7nmRbVxfPGeuZZN604juEahdwzbIv?= =?us-ascii?Q?Jl7kI6AyBVSlcu7FNqE/7jQCmKumpleHpG2eBot3NZ2204HxK28sT8BmPQlB?= =?us-ascii?Q?zGGlHaeqUc+dILi6BJeOyOHH9S1U5Cq2w1+JW9d9uqxsIafvTaJ9JGQKc9/N?= =?us-ascii?Q?gGstc8qgD9/zLwAIn9SM2z/zCpArLOyAhvYVFqvwTI6B1X77zQxJ52qPyuM8?= =?us-ascii?Q?ThroZosjl5hsY2eKelrCutiZZsLOcPXdXp5uM0FE+toZtDbqBH6O0orMO8Wr?= =?us-ascii?Q?KZWd7RhoyyxkjLsSTAPkaCRKyotq0n7gXqXwsDl4wQORrZCgRXUPNUywdu+2?= =?us-ascii?Q?8A2zwf+oNOvJfugtJdTuTpJF/p4ROS2GUF4mE8fIaut4+kSOiqJyo9iwHN/S?= =?us-ascii?Q?0tZAMo7zq0Ty5xEDPtWrLoG+q1zVMwvUV9fNrybhaVutdxt4vbRyxLNfydXb?= =?us-ascii?Q?u+MFTBcBMG0XGSt/PSMrYJYYMhdeIzNYFECK+Zvwh1WIeg/IxB3xyjcll9qN?= =?us-ascii?Q?ivpzQSW5gBk/AWqRYFPyOQ7JEBft1NYXwn5UGByIEjxI7C2mPiBWGyryR63V?= =?us-ascii?Q?l3X4pLIEZYdS8/VJ1ZMfSWuBCN6BQdCFotPI+xEtgldMahEBn9uwfQGhvArF?= =?us-ascii?Q?R+0BuLpYliWbCHnhIOYUc8nlgOV16EhP5w8GIAHYJWGG4DW12m5pIbjxQjvz?= =?us-ascii?Q?CcgPxOEcHLJcOW6IZdmuh2n7Z0CJh4+eFrsrzPdSRXhk+P+XzsvT0o7QzM8L?= =?us-ascii?Q?BWhJKQOE42o+CR+s7eDjMUzTtAw6Kl3wZOl/h1Onq8GtsOSAOF7nbKgLOecl?= =?us-ascii?Q?Ubeuxu6zDeq2bZvel2rl3jMUj/sbyVm5u8NTRPyOkJTpLYrhSdcVs/1Rmj6u?= =?us-ascii?Q?X4SI96/3x3cEVelw6TsU8b9yOicoNTY3Fcjh9/Vp3TE260S17TFodWxyA7gb?= =?us-ascii?Q?mY8LNe/xx4AuAQ2uw/TYdbsAqmJ5td762Vk4QuhrYRTmW0ohuVftd9bhgImU?= =?us-ascii?Q?qtCaafs8hErI6FAcorJgP5j6WdlhyEbjz8UL2jmpk+e+0u92XupXZ+D0QUPP?= =?us-ascii?Q?v1QHYNC4IOg3h/1QUIF9j8ZKPy/29zfJ1C7s0Up1+qq65X+MFRqoD2eTrkZ6?= =?us-ascii?Q?MBK3rgYuogvZFax1rqzijUKYZZeoSxJh8NnxELT3cJ0ONfpdRpJXAaYAoazA?= =?us-ascii?Q?AKOLTmcXofGpQFvVFAC9JSLh79I4axb18ZwkxfAw6pbBYOS8HeDFCNPAMExJ?= =?us-ascii?Q?8IzGEp2nVo7edwnw8Pw=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(1800799024)(7416014)(36860700013)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Nov 2025 00:52:46.2392 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a7f236d8-e029-4ffa-bb6a-08de2705f483 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF0002636E.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV3PR12MB9266 Content-Type: text/plain; charset="utf-8" The iommu_deferred_attach() function invokes __iommu_attach_device(), but doesn't hold the group->mutex like other __iommu_attach_device() callers. Though there is no pratical bug being triggered so far, it would be better to apply the same locking to this __iommu_attach_device(), since the IOMMU drivers nowaday are more aware of the group->mutex -- some of them use the iommu_group_mutex_assert() function that could be potentially in the path of an attach_dev callback function invoked by the __iommu_attach_device(). Worth mentioning that the iommu_deferred_attach() will soon need to check group->resetting_domain that must be locked also. Thus, grab the mutex to guard __iommu_attach_device() like other callers. Reviewed-by: Jason Gunthorpe Reviewed-by: Kevin Tian Reviewed-by: Lu Baolu Signed-off-by: Nicolin Chen --- drivers/iommu/iommu.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 2ca990dfbb884..170e522b5bda4 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -2185,10 +2185,17 @@ EXPORT_SYMBOL_GPL(iommu_attach_device); =20 int iommu_deferred_attach(struct device *dev, struct iommu_domain *domain) { - if (dev->iommu && dev->iommu->attach_deferred) - return __iommu_attach_device(domain, dev, NULL); + /* + * This is called on the dma mapping fast path so avoid locking. This is + * racy, but we have an expectation that the driver will setup its DMAs + * inside probe while being single threaded to avoid racing. + */ + if (!dev->iommu || !dev->iommu->attach_deferred) + return 0; =20 - return 0; + guard(mutex)(&dev->iommu_group->mutex); + + return __iommu_attach_device(domain, dev, NULL); } =20 void iommu_detach_device(struct iommu_domain *domain, struct device *dev) --=20 2.43.0