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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Nov 2025 17:41:42.3195 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 31930bd6-cc2b-41af-5c5b-08de2212bded X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SA2PEPF00003AEB.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB7261 Hi Baolu, On Wed, Nov 12, 2025 at 01:58:51PM +0800, Baolu Lu wrote: > On 11/11/25 13:12, Nicolin Chen wrote: > > +/** > > + * iommu_get_domain_for_dev() - Return the DMA API domain pointer > > + * @dev - Device to query > > + * > > + * This function can be called within a driver bound to dev. The returned > > + * pointer is valid for the lifetime of the bound driver. > > + * > > + * It should not be called by drivers with driver_managed_dma = true. > > "driver_managed_dma != true" means the driver will use the default > domain allocated by the iommu core during iommu probe. Hmm, I am not very sure. Jason's remarks pointed out that There is an exception in host1x_client_iommu_detach(): https://lore.kernel.org/all/20250924191055.GJ2617119@nvidia.com/ Where the group->domain could be NULL, i.e. not attached to the default domain? > The iommu core > ensures that this domain stored at group->domain will not be changed > during the driver's whole lifecycle. That's reasonable. > > How about making some code to enforce this requirement? Something like > below ... > > > + */ > > struct iommu_domain *iommu_get_domain_for_dev(struct device *dev) > > { > > /* Caller must be a probed driver on dev */ > > @@ -2225,10 +2234,29 @@ struct iommu_domain *iommu_get_domain_for_dev(struct device *dev) > > if (!group) > > return NULL; > > + lockdep_assert_not_held(&group->mutex); > > ... > if (WARN_ON(!dev->driver || !group->owner_cnt || group->owner)) > return NULL; With that, could host1x_client_iommu_detach() trigger WARN_ON? Thanks! Nicolin