The HW supports this, use the S1DSS bits to configure the behavior
of SSID=0 which is the RID's translation.

If SSID's are currently being used in the CD table then just update the
S1DSS bits in the STE, remove the master_domain and leave ATS alone.

For iommufd the driver design has a small problem that all the unused CD
table entries are set with V=0 which will generate an event if VFIO
userspace tries to use the CD entry. This patch extends this problem to
include the RID as well if PASID is being used.

For BLOCKED with used PASIDs the
F_STREAM_DISABLED (STRTAB_STE_1_S1DSS_TERMINATE) event is generated on
untagged traffic and a substream CD table entry with V=0 (removed pasid)
will generate C_BAD_CD. Arguably there is no advantage to using S1DSS over
the CD entry 0 with V=0.

As we don't yet support PASID in iommufd this is a problem to resolve
later, possibly by using EPD0 for unused CD table entries instead of V=0,
and not using S1DSS for BLOCKED.
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/11-v9-5cd718286059+79186-smmuv3_newapi_p2b_jgg@nvidia.comSigned-off-by: Will Deacon <will@kernel.org>