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Mon, 7 Oct 2024 12:56:42 -0700 Date: Mon, 7 Oct 2024 12:56:40 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v2 10/19] iommufd/viommu: Add vdev_id helpers for IOMMU drivers Message-ID: References: <20240905161415.GS1358970@nvidia.com> <20240911231103.GR58321@nvidia.com> <20241007153837.GT1365916@nvidia.com> <20241007171119.GY1365916@nvidia.com> <20241007182816.GD1365916@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20241007182816.GD1365916@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY4PEPF0000EE3E:EE_|PH7PR12MB5733:EE_ X-MS-Office365-Filtering-Correlation-Id: fdbd344f-c9b5-4053-3bfb-08dce70a3489 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|82310400026|36860700013|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?W3ZjSCyKDfhztkL1rrAppoyHSHWyBJesl3f4VDi3hYz1a1P/NuFi+6WujcMw?= =?us-ascii?Q?W7Jtn6Le7Qf8z94ieGqJwBqfdDvevZ5aSchLY7Nf9OdWtrCMYD7CMu5c1aGe?= =?us-ascii?Q?ltyp7uy/JbyHruWXVmH4hk2xG7AWex57DCjcJVQ+gNsMrpxScOw9ttPhoo2s?= =?us-ascii?Q?CGzfLsy4BC6eQcLP4XXMkHKbgU5UVgV3wXYnjj6G+PJ4HNnvtjfUvJeK8eek?= =?us-ascii?Q?tRFH2KNuX693K2TMKzOj5d1SVdQ0x6MCwwkWJnOxm5d3hatjqB74ChIWwyFD?= =?us-ascii?Q?w1Zfhc2np7pbYllJc/ePrCdI6qZLVQGjbB68GdfQNymIv1q1D/QwI3HspVoX?= =?us-ascii?Q?bRxNHPoAM3RjGiKqgxjHxXdfmN6X9dRo9t+K+EO742jX7mbptwL85I/8cgE3?= =?us-ascii?Q?5i3yuajb8eOzXH9MbuaoIqevX6hk5pqM0qfJ9WpfEef0DLtry9Ys15ZWJKvs?= =?us-ascii?Q?nxTw8SDgLExPPjkWzQxURLORXzqiuUFVFm65mD+QFP2fR/JV3XiLQjMZkjJI?= =?us-ascii?Q?koclDS6CAO0cs2biCQyrjHOJfqnSK1at+9kFb5hDBmKuMQpQnMXvwRmzO+Yp?= =?us-ascii?Q?m5/TFAPVMOg04bpHDRaxF5jVPuK7vYqu8QMld8d7MfnTngR0Prit9cuNS8z2?= =?us-ascii?Q?uXaqHbUg66ipxOSl0p4v+pzYgnPfJgyXENNLiLk4PXwE7Kf1wXJJef8YNcjS?= =?us-ascii?Q?94xjIfPhf6Jfg+3ein90uAoebMeVjn95BQjbXUNadKtj8Ol+WDUILLaS/VYc?= =?us-ascii?Q?hvmj4saSgLlGAsAPjDi6zHPtq2K/csEi9cgh+f0/zLFNeyAWrqPNxIG8qnNn?= =?us-ascii?Q?Q+wfv+SQy6NGFZhwL80AQOGSoOprLkMO4jbcq2TtHyxVF1dX/z2gVgVZ0xyq?= =?us-ascii?Q?MUFXchw/22RQBiFf2t/o+ipocYZiHGVyOCdEJOynTA7g4wGsHd2ey+tM/HHS?= =?us-ascii?Q?LJKyKMk80u8zaaUht1fqfLp7DX4IunSfhWjLJQ987mpA5QIkjdiX5yF/JEF6?= =?us-ascii?Q?HxvSJp0cyqFGu5TWov2Z+Bo10CJMr+T+UIW8mgFintFkFaQMqEwY+yDQHFt9?= =?us-ascii?Q?1wBzuyDFbrrG7MGQFwDCG0r0JU3MqfFVk7lzGozqdPY26DvnrqCSqSnb+IPN?= =?us-ascii?Q?hjD9bPdigxBtEa79VN7QbWuJjtFWIBvMZV41x24+3SwefubOHQwwG9zztYM4?= =?us-ascii?Q?3jO0LckEajbniKzLCzVyx5buEe+e8uFw6974O949NXB74DvU/AqaMctiNMUa?= =?us-ascii?Q?2O5SFUrTrVqkBGaRlZ8raCespVnrPPwQqk9zlpj3aI1aaG39uYCri6aoX4jF?= =?us-ascii?Q?PJw0v6+Sg5dRMM2NMFgsMjCVCDYN6zgffgjn3JqaB51NSS6YMtYU5U3k+KgS?= =?us-ascii?Q?2ODziWsjZioEjD9vneys3i9UscX2?= 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)(1800799024)(376014)(82310400026)(36860700013)(7416014);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Oct 2024 19:56:59.5772 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fdbd344f-c9b5-4053-3bfb-08dce70a3489 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: CY4PEPF0000EE3E.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB5733 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241007_125706_057828_805B69E5 X-CRM114-Status: GOOD ( 13.73 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Oct 07, 2024 at 03:28:16PM -0300, Jason Gunthorpe wrote: > On Mon, Oct 07, 2024 at 10:25:01AM -0700, Nicolin Chen wrote: > > > This is for vdev/dev v.s. hwpt. We need the lock for viommu's > > vdev xarray. > > > > Yet, giving a 2nd thought, I feel the lock would be useless if > > a driver tries to refer the returned vdev (with this helper) > > after the vdev object is destroyed.. > > > > We could only note something similar that caller must be aware > > of the life cycle of vdev itself.. > > Yes, I imagined you'd use the xa_lock for this an it solves both > problems at once. Ah! We don't even need a rwsem then.. Thanks! Nicolin