[PATCH v7 1/5] iommu: Lock group->mutex in iommu_deferred_attach()

[Nicolin Chen]

On Wed, Nov 26, 2025 at 06:25:34PM +0530, Srivastava, Dheeraj Kumar wrote:
> On 11/22/2025 7:27 AM, Nicolin Chen wrote:
> > The iommu_deferred_attach() function invokes __iommu_attach_device(), but
> > doesn't hold 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().
> > 
> > Worth mentioning that the iommu_deferred_attach() will soon need to check
> > group->resetting_domain that must be locked also.
> > 
> > Thus, grab the mutex to guard __iommu_attach_device() like other callers.
> > 
> 
> Tested the series with PCI reset on PFs and VFs, including device
> pass-through to a Linux guest. All scenarios worked as expected.
> 
> Tested-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava at amd.com>

Thanks for testing!

Yet, this is replying to PATCH-1. So, you might want to reply with
your "Tested-by" tag to PATCH-0 :)

Otherwise, default B4 command might miss your tag in other patches:

  ✗ [PATCH v7 1/5] iommu: Lock group->mutex in iommu_deferred_attach()
    + Tested-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava at amd.com> (✓ DKIM/amd.com)
  ✗ [PATCH v7 2/5] iommu: Tidy domain for iommu_setup_dma_ops()
    + Reviewed-by: Jason Gunthorpe <jgg at nvidia.com> (✗ DKIM/Nvidia.com)
  ✗ [PATCH v7 3/5] iommu: Add iommu_driver_get_domain_for_dev() helper
    + Reviewed-by: Jason Gunthorpe <jgg at nvidia.com> (✗ DKIM/Nvidia.com)
  ✗ [PATCH v7 4/5] iommu: Introduce pci_dev_reset_iommu_prepare/done()
    + Reviewed-by: Jason Gunthorpe <jgg at nvidia.com> (✗ DKIM/Nvidia.com)
  ✗ [PATCH v7 5/5] PCI: Suspend iommu function prior to resetting a device
    + Reviewed-by: Jason Gunthorpe <jgg at nvidia.com> (✗ DKIM/Nvidia.com)

Thank you
Nicolin