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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Jun 2025 07:07:19.3523 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 70f7521e-e1c4-4343-dad3-08dda7ed70a5 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: BN2PEPF00004FBF.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB5870 On Tue, Jun 10, 2025 at 12:26:07PM +0800, Baolu Lu wrote: > On 6/10/25 02:45, Nicolin Chen wrote: > > + ops = dev_iommu_ops(dev); > > Should this be protected by group->mutext? Not seemingly, but should require the iommu_probe_device_lock I think. > > + /* > > + * group->mutex starts > > + * > > + * This has to hold the group mutex until the reset is done, to prevent > > + * any RID or PASID domain attachment/replacement, which otherwise might > > + * re-enable the ATS during the reset cycle. > > + */ > > + mutex_lock(&group->mutex); > > Is it possible that group has been freed when it reaches here? It doesn't look very obvious to me which lock we need here. But, it's a good point that dev->iommu_group is unsafe here. Will dig a bit later. > > +void iommu_dev_reset_done(struct device *dev) > > +{ > > + struct iommu_group *group = dev->iommu_group; > > + const struct iommu_ops *ops; > > + unsigned long pasid; > > + void *entry; > > + > > + /* Previously unlocked */ > > + if (!dev_has_iommu(dev)) > > + return; > > + ops = dev_iommu_ops(dev); > > + if (!ops->blocked_domain) > > + return; > > Should it be a WARN_ON()? As proposed, reset_prepare and reset_done must > be paired. So if reset_prepare returns failure, reset_done should not be > called. Or not? Yea, I agree. Should work like that. > > + /* group->mutex held in iommu_dev_reset_prepare() continues from here */ > > + WARN_ON(!lockdep_is_held(&group->mutex)); > > Probably iommu_group_mutex_assert() and move it up? Yes and not sure (will take another look). > How about combining these two helpers? Something like, > > int iommu_dev_block_dma_and_action(struct device *dev, > int (*action)(struct pci_dev *dev)) > { > prepare(); > action(); > done(); > } That's an interesting idea! So, we wouldn't need to worry about the pairing. Thanks! Nicolin