RE: [PATCH v2 06/11] vfio-iommufd: Allow iommufd to be used in place of a container fd

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Tuesday, November 8, 2022 8:53 AM
> 
> This makes VFIO_GROUP_SET_CONTAINER accept both a vfio container FD
> and an
> iommufd.
> 
> In iommufd mode an IOAS will exist after the SET_CONTAINER, but it will
> not be attached to any groups.
> 
> For VFIO this means that the VFIO_GROUP_GET_STATUS and
> VFIO_GROUP_FLAGS_VIABLE works subtly differently. With the container FD
> the iommu_group_claim_dma_owner() is done during SET_CONTAINER but
> for
> IOMMUFD this is done during VFIO_GROUP_GET_DEVICE_FD. Meaning that
> VFIO_GROUP_FLAGS_VIABLE could be set but GET_DEVICE_FD will fail due to
> viability.
> 
> As GET_DEVICE_FD can fail for many reasons already this is not expected to
> be a meaningful difference.
> 
> Reorganize the tests for if the group has an assigned container or iommu
> into a vfio_group_has_iommu() function and consolidate all the duplicated
> WARN_ON's etc related to this.
> 
> Call container functions only if a container is actually present on the
> group.
> 
> Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

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