With v1 page table, the AMD IOMMU spec states that the hardware must use
the domain ID to tag its internal translation caches. I/O devices with
different v1 page tables must be given different domain IDs. I/O devices
that share the same v1 page table __may__ be given the same domain ID.
This domain ID management policy is currently implemented by the AMD
IOMMU driver. In this case, only the domain ID is needed when issuing the
INVALIDATE_IOMMU_PAGES command to invalidate the IOMMU translation cache
(TLB).

With v2 page table, the hardware uses domain ID and PASID as parameters
to tag and issue the INVALIDATE_IOMMU_PAGES command. Since the GCR3 table
is setup per-device, and there is no guarantee for PASID to be unique
across multiple devices. The same PASID for different devices could
have different v2 page tables. In such case, if multiple devices share the
same domain ID, IOMMU translation cache for these devices would be polluted
due to TLB aliasing.

Hence, avoid the TLB aliasing issue with v2 page table by allocating unique
domain ID for each device even when multiple devices are sharing the same v1
page table. Please note that this fix would result in multiple
INVALIDATE_IOMMU_PAGES commands (one per domain id) when unmapping a
translation.

Domain ID can be shared until device starts using PASID. We will enhance this
code later where we will allocate per device domain ID only when its needed.
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240205115615.6053-18-vasant.hegde@amd.comSigned-off-by: Joerg Roedel <jroedel@suse.de>