iommu/arm-smmu-v3: Handle ARM erratum for CONT under invalidation with SVA

The erratum (MMU-700: #3777127, S3: #3673557) deals with under
invalidation of a CONT PTE grouping in the SMMU. The recommended work
around is to use a range invalidation that spans the entire CONT. The only
user of CONT in the kernel right now is through SVA sharing a CPU page
table that contains a CONT created by the mm.

Previously it was thought that this errata was dealt with because the
driver always uses range invalidation. However, there is a subtle detail
in the errata that the invalidation range must fully enclose the entire
CONT for it to work.

It seems that two sequential range invalidations, with a split point
falling inside a CONT grouping, will not prevent the errata.

The SMMU's range invalidation generation algorithm does not produce a
single invalidation for a single SVA invalidation request, nor does the mm
carefully align the SVA invalidation ranges to accommodate the splitting
of the invalidation into several ranges.

Thus, when processing a SVA invalidation, the range invalidation splitting
routine can generate a range invalidation that is split in the middle of
the CONT and risk under invalidation from this errata. This condition
could be triggered by a malicious userspace manipulating the TLB gathers
via mmap/mprotect/munmap.

Update the errata list to the include the S3 variation, detect the IOMMUs
that have it, and then have SVA invalidations use a simplified version of
the over invalidation algorithm from the tlbi rework series. This ensures
that a single range invalidation is issued for a single MMU notifier
callback and now the range invalidation is guarenteed to cover any posible
CONT.

Future work to add CONT to iommu_domain page tables should either use this
one-invalidate/one-range invalidation algorithm or disable CONT support in
the iommu_domain.

Cc: stable@vger.kernel.org
Cc: Vijayanand Jitta <vijayanand.jitta@oss.qualcomm.com>
Fixes: 3f1ce8e85ee0 ("iommu/arm-smmu-v3: Share process page tables")
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Pranjal Shrivastava <peaan@google.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Pranjal Shrivastava <praan@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Will Deacon <will@kernel.org>

0 files changed, 0 insertions, 0 deletions