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Wysocki" , Len Brown , Pranjal Shrivastava , Mostafa Saleh , Lu Baolu , Kevin Tian , linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org, vsethi@nvidia.com, Shuai Xue Subject: Re: [PATCH v4 17/24] iommu/arm-smmu-v3: Add master in arm_smmu_inv for ATS entries Message-ID: <20260519120152.GA3477375@nvidia.com> References: <2ea9edeaf0b23840670c62a57e71e7cf73f41ad6.1779161849.git.nicolinc@nvidia.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2ea9edeaf0b23840670c62a57e71e7cf73f41ad6.1779161849.git.nicolinc@nvidia.com> X-ClientProxiedBy: YT4PR01CA0473.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:d6::6) To LV8PR12MB9620.namprd12.prod.outlook.com (2603:10b6:408:2a1::19) Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV8PR12MB9620:EE_|DM4PR12MB6040:EE_ X-MS-Office365-Filtering-Correlation-Id: 3c8216fd-349d-4690-9410-08deb59e6b89 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014|11063799006|18002099003|22082099003|56012099003|4143699003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?sp8+lmNPIAB+cTCzBusqNzcjzhg/tXs3c6fxJRS2MXdXiTpxbqgBRNbAID+d?= =?us-ascii?Q?wYTAxKJiQxB1RE+v89ZJVvtnRDtvM1n+lHxefHOd2CUri6m8wqh2zcU2AX9/?= =?us-ascii?Q?C49xshu8qTvUqBpAL/Ntba6BVFOdvBGFjSrAiOLDEo4g3jX2TsR174ZjC/Pd?= =?us-ascii?Q?Fy8+4LgkEqPhojBR7fC2ihsXUzb+H8t8XDyrXtRZCJYsi6FGksvaU8nQzI6Q?= =?us-ascii?Q?2neiTLIFC0TWBYIVX9K4iLyyJRDFDPmLV39vf+birtlTzF0IPcau3itPCpLn?= =?us-ascii?Q?/3Br5iaJwHgKvH6hjrl3v7peyyPv6nGxPR00pH4SUWWogfy6gyNnprFWRVhy?= =?us-ascii?Q?pbbxX6VNHJpTiy4v26QFqvYWfAJ9+ctoHGxO07fro03VJVj5uNaijPr38kV5?= =?us-ascii?Q?LRBkIt6ZDWl7S+c+dbOwr+5axb3DSU1irPvMHAuhpBZ5K+bCKJ0M1wRBHpFO?= =?us-ascii?Q?9LTprBGR2q8uD3zn4JGU2n45qn6nxwFdKh51Z6K3uj+IhhM2JrTb/mt6hMRW?= =?us-ascii?Q?Pwyb6HZ8PblnF2HJNueFyUP1BYyVVCJYlp4YHGiwLolZhioiqU5hAA+RIjvd?= =?us-ascii?Q?EXgLN6R8mFu6dpKfX7e7EVHrCYuTv2ckvgl32WROGP3xUU2q+gAUhdvYoAps?= =?us-ascii?Q?Etsd21+eyf0n/LK2Wcnemunrl2Hdq5WuSQj+WvxHPjoF1TND2TN3/Mpy5I/k?= =?us-ascii?Q?WXCA9zPzPfECkFrH1sR6KklWt42MT8Uu6ofj6bmvkpUDEsQbrjd7/PbVJ7+t?= =?us-ascii?Q?0XsV1LYhHNBtU7QkL44DEYkWGhbIvLk3OaJ2OFvxyYH/QGQgPE3bFVrLx3+l?= =?us-ascii?Q?i+yE8i533SxQbPG/GbUmODYcz2m4yL55Ggs9Vgka1wzlDmJSgB7ouDfW/RTW?= =?us-ascii?Q?94KBDHzWZnFgK1d09q0lcomFymCrjpuonP2rtd5n2LvEA2r70Q9WqdvmvE6O?= =?us-ascii?Q?gR1eAfBsfC4MaN2C/mwSBAdtG6duq2oJREWnTQP/5t89p1MI45Ia70DLncNP?= =?us-ascii?Q?CD8h5M/buQDQmbT7w9Zpfnc4HM+x2JRVrSCBHGExHz8AhpkZoqipbjIfrRnd?= =?us-ascii?Q?+RCn+l9gTbHdHGwoXmqlUOSN4ZjHp8JVNd6xLGUouajwEWSZQQgf/H1UgvlI?= =?us-ascii?Q?8qc4lr80a2EP4o7I8PrJngXKN4smKvgb4i8dPp4SW78gSVpkNEUltKzbSNec?= =?us-ascii?Q?6IojiQElTuqJV+nu28Vcp9mtdt4aExhz80++tWxzzCctuVvKGTsnX/BjgE9F?= =?us-ascii?Q?r5uX/NbhOSjW+WiKOCVC7Pr/q3F8TMlrLaE6Y1zHL86onT7nPI4iowyzBW8c?= =?us-ascii?Q?MzmqI9T1QQP/1Lu73AmxWNRHHwPEKZyONkA94986CKlnW1AwbtaJCD76bODQ?= =?us-ascii?Q?sKOweHg1QA56v/YfwEdZnkdhgdxg2dhpD66eP7k2LSbgydXAW+MoAng9NW24?= =?us-ascii?Q?PdtB6uv+3Q0lm8v2gd9JZPH5y2eC9FGETXgoGJCeSefbrbk1VN3BYBzMy5ge?= =?us-ascii?Q?UNT0TB7y3oMgon+23OuPgfixC2TzWK9KCav0IAym7gRi/P6J8azyCw7k1E20?= =?us-ascii?Q?EZ4nyqk8WiHWLRT6jmdLrcf1MxQZWgwU1JszrzF0rtiy8CUminxvZbjzXrUF?= =?us-ascii?Q?C0iNVwGFcqDx66D64+oBR0pKcecYXBOhXn1DN2oP9Lt9580yzwqJIHqUycWZ?= =?us-ascii?Q?pWvoX/aYHE5Ci8+/cijUzIeVCrfoUqKtLt9YU/igkNSaC3Sg?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3c8216fd-349d-4690-9410-08deb59e6b89 X-MS-Exchange-CrossTenant-AuthSource: LV8PR12MB9620.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 May 2026 12:01:55.0629 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: zwsHI67kUTFDsVanJBpDNEn5VqI6eRkGsy8ge9zuQRldB5tnisoDvQ7Pv4UOwtHQ X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6040 On Mon, May 18, 2026 at 08:39:00PM -0700, Nicolin Chen wrote: > Storing the master pointer allows backtracking it from an ATS invalidation > entry, which will be useful when handling ATC invalidation timeouts. > > Don't simply swap the "smmu" pointer for the "master": a non-ATS entry may > be shared across multiple devices (masters). An ATS entry is okay since it > is tied to a unique SID. > > Master must outlive any concurrent RCU reader iterating the domain->invs, > because inv->master is dereferenced inside the read-side critical section. > > Add a synchronize_rcu() in arm_smmu_release_device() before freeing master. > > Signed-off-by: Nicolin Chen > --- > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 + > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 14 +++++++++++--- > 2 files changed, 12 insertions(+), 3 deletions(-) > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h > index 604f7edf54158..df6e539f75274 100644 > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h > @@ -738,6 +738,7 @@ enum arm_smmu_inv_type { > > struct arm_smmu_inv { > struct arm_smmu_device *smmu; > + struct arm_smmu_master *master; /* INV_TYPE_ATS* */ I don't like this and the locking for just a slow error case.. You should use the SID for this and have a spinlocked ATS master list to search for the SID. Jason