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

[Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>]

Hi

On 11/26/2025 9:46 PM, Nicolin Chen wrote:
> 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@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 :)
> 

Sure.

Thanks
Dheeraj

> 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@amd.com> (✓ DKIM/amd.com)
>    ✗ [PATCH v7 2/5] iommu: Tidy domain for iommu_setup_dma_ops()
>      + Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> (✗ DKIM/Nvidia.com)
>    ✗ [PATCH v7 3/5] iommu: Add iommu_driver_get_domain_for_dev() helper
>      + Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> (✗ DKIM/Nvidia.com)
>    ✗ [PATCH v7 4/5] iommu: Introduce pci_dev_reset_iommu_prepare/done()
>      + Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> (✗ DKIM/Nvidia.com)
>    ✗ [PATCH v7 5/5] PCI: Suspend iommu function prior to resetting a device
>      + Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> (✗ DKIM/Nvidia.com)
> 
> Thank you
> Nicolin