If the default DMA domain of a group doesn't fit a device, it
will still sit in the group but use a private identity domain.
When map/unmap/iova_to_phys come through iommu API, the driver
should still serve them, otherwise, other devices in the same
group will be impacted. Since identity domain has been mapped
with the whole available memory space and RMRRs, we don't need
to worry about the impact on it.

Link: https://www.spinics.net/lists/iommu/msg40416.html
Cc: Jerry Snitselaar <jsnitsel@redhat.com>
Reported-by: NJerry Snitselaar <jsnitsel@redhat.com>
Fixes: 942067f1 ("iommu/vt-d: Identify default domains replaced with private")
Cc: stable@vger.kernel.org # v5.3+
Signed-off-by: NLu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: NJerry Snitselaar <jsnitsel@redhat.com>
Tested-by: NJerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>