[PATCH v4 08/23] iommufd/selftest: Add covearge for viommu data

[Tian, Kevin]

> From: Nicolin Chen <nicolinc at nvidia.com>
> Sent: Friday, May 9, 2025 11:02 AM
> 
> Extend the existing test_cmd/err_viommu_alloc helpers to accept optional
> user data. And add a TEST_F for a loopback test.
> 
> Reviewed-by: Pranjal Shrivastava <praan at google.com>
> Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>

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