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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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; 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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 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