RE: [PATCH v4 2/7] iommu: Lock group->mutex in iommu_deferred_attach()

Tian, Kevin
2025-09-12T09:34:16Z

> From: Nicolin Chen <nicolinc@nvidia.com>
> Sent: Monday, September 1, 2025 7:32 AM
>
> The iommu_deferred_attach() function invokes __iommu_attach_device()
> while
> not holding the group->mutex, like other __iommu_attach_device() callers.
>
> Though there is no pratical bug being triggered so far, it would be better
> to apply the same locking to this __iommu_attach_device(), since the
> IOMMU
> drivers nowaday are more aware of the group->mutex -- some of them use
> the
> iommu_group_mutex_assert() function that could be potentially in the path
> of an attach_dev callback function invoked by the __iommu_attach_device().
>
> The iommu_deferred_attach() will soon need to verify a new flag stored in
> the struct group_device. To iterate the gdev list, the group->mutex should
> be held for this matter too.
>
> So, grab the mutex to guard __iommu_attach_device() like other callers.
>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>