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Tue, 31 Mar 2026 05:23:26 -0700 Date: Tue, 31 Mar 2026 05:23:25 -0700 From: Nicolin Chen To: "Tian, Kevin" CC: Shuai Xue , "joro@8bytes.org" , "will@kernel.org" , "robin.murphy@arm.com" , "baolu.lu@linux.intel.com" , "jgg@nvidia.com" , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH rc v2] iommu: Fix nested pci_dev_reset_iommu_prepare/done() Message-ID: References: <20260319043135.1153534-1-nicolinc@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: X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY4PEPF0000FCC4:EE_|BY5PR12MB4145:EE_ X-MS-Office365-Filtering-Correlation-Id: 4b3c9a96-dcd9-489b-3511-08de8f205d20 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|376014|36860700016|18002099003|22082099003|56012099003; X-Microsoft-Antispam-Message-Info: pDq/iZyivh0/bzzCs3r2N0QnqB6CMCA5fI8c7sW3z7WQeIy1nIKkUc61ZUiZsAzvOx6wKhjC6syN+wPzn8guWyZY3vHxWKm6T7yIfOb5SsgAz2eTkf9RkSTHM5dqj3L9vX5mmepvAnlgssh4+IcRxaHFv0G2CpkC7FMXTxGU9E6FqvJ1RiCpGtZfS3O5n99xL/sr6HX24XVf+YqrCvDXkev6ZhTi3N75MOrbGw171xhaJAu7JoACZFNIW7C469f+ImLFoVCzLRKS6//+UOz4+k5FBiLEXzljyXEWSr3nGlWHY4kZzdl2xUCzUBMsRi1up9RoojF1Tb+Gfayqgf1qm7BMAw5fd3LAJ+pISl8rRRI1LEXEnjQ5z9ck2II3Kx3W1XoB2vHdG4mbL7PF1scM0nB+kG3PYDQtSfbr+bf+ugEeDMF4dw2/8GFOPW73F748UhY8kmQsTnhE1PtnJkIiVXhY0gHjdeJuAcis8HQFCOb5ZEwLY5sSJcbDjhFm06/TmpGkF4IQj5xiTQANNcBl2rrRKY1sfcWEqMAe0k4NV9hMiK/SH3pKWmBfnbx5gsbwtfBEDehlSFAIiT+WkDyn53eXaCnvWY18WT1IWoKqJfXQEtZf4V3DI+D4mAKtxkZqugAiAADZIkbfTNd0s2r6nH3bT4D8Ted3VKbesUeiJSoDajWMl4nfw1xL1gO6giwSfZje7uAUxIOHowQBnVcdk10rpfVfloncABy9a5iBpPgLc5FU7cHQ75lfOODZaT2m6+B3McD4zzyonB5Ia92FOA== 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)(82310400026)(376014)(36860700016)(18002099003)(22082099003)(56012099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: qHof5ytoBq+0R9Xh02PreJGa66s84e0gdOYhFuQM8edUpvrX4oEmP8MTFFO3KKiYX69tMECwVU8gFTgaNHpNJTHXcWz9W1pJ4woPLl2zzwBRl5noFP3Ug1FvPIHdD47p8P8RU1+I0uh6erE30HIQxr7bcAEAb0l8f1t2I4Lcu3+oDsUuCTpPxZ88bzj93USEs6E20US0YXa/mFHLdsl9r96ppZ5vQ8v7Dg6DItxU6aEByb+eWnTeL8XwvQAAv5s2vew0pXwzJNzeelxujYG6fIGnrZJAKtCV/t80/7jD5qnpRcdHY93fhPbqt1dvyrZAc09VCOjVW1Gg2LhcFjES3LT5G3VVm3nmbmuXLbudkVXmRIx8CMBDrhkE/V9lgCpRQqTLuJ1LtlUX3qS8OSzOdnkQu8/JXK1v57yWbLNZcefD/27QbH4mOYJDfqpTMX0M X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 31 Mar 2026 12:23:49.6200 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4b3c9a96-dcd9-489b-3511-08de8f205d20 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: CY4PEPF0000FCC4.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR12MB4145 On Tue, Mar 31, 2026 at 07:12:19AM +0000, Tian, Kevin wrote: > > > > > - prepare() only detaches the specific pdev, leaving other > > > > > devices in the group still attached to the original domain > > > > > > no, attach is per-group. all devices are changed together. > > > > I think prepare() should use the per-device ops: > > ops->attach_dev (via __iommu_attach_device) > > ops->set_dev_pasid > > right? > > it's per-device op but the condition of calling it is per-group: > > if (group->domain != group->blocking_domain) { > ret = __iommu_attach_device(group->blocking_domain, &pdev->dev, > group->domain); > if (ret) > return ret; > } If the group->domain is not blocking_domain, this device will move away from group->domain to blocking_domain, while other device (in the same group) are staying in group->domain. No? > > And it is intended to limit to the resetting device only. Other > > devices in the group can still stay in the attached domain, but > > they cannot do new attachment (-EBUSY) because that's per-group. > > how could other devices stay in the attached domain? We call __iommu_attach_device only on one gdev, not looping the entire group, right? > > Since prepare() is per-device, the per-group reset_cnt wouldn't > > be sufficient if one device is resetting while the other isn't. > > > > iommu_driver_get_domain_for_dev() for example would return the > > blocking_domain for both devices, but physically only the first > > device is attached to blocking_domain. > > what do you mean by 'physically'? I mean SMMU driver will program STE to ask SMMU HW to reflect the change "physically". But it won't program the other STEs. Nicolin