[PATCH v4 4/7] iommu: Pass in old domain to attach_dev callback functions

[Tian, Kevin]

> From: Nicolin Chen <nicolinc at nvidia.com>
> Sent: Monday, September 1, 2025 7:32 AM
> 
> The IOMMU core attaches each device to a default domain on probe(). Then,
> every new "attach" operation has a fundamental meaning of two-fold:
>  - detach from its currently attached (old) domain
>  - attach to a given new domain
> 
> Modern IOMMU drivers following this pattern usually want to clean up the
> things related to the old domain, so they call iommu_get_domain_for_dev()
> to fetch the old domain.
> 
> Pass in the old domain pointer from the core to drivers, aligning with the
> set_dev_pasid op that passes in already.
> 
> Ensure all low-level attach fcuntions in the core can forward the correct
> old domain pointer. Thus, rework those functions as well.
> 
> Suggested-by: Jason Gunthorpe <jgg at nvidia.com>
> Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>

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