iommu/arm-smmu-v3: Add unit tests for arm_smmu_write_entry

Add tests for some of the more common STE update operations that we expect
to see, as well as some artificial STE updates to test the edges of
arm_smmu_write_entry. These also serve as a record of which common
operation is expected to be hitless, and how many syncs they require.

arm_smmu_write_entry implements a generic algorithm that updates an STE/CD
to any other abritrary STE/CD configuration. The update requires a
sequence of write+sync operations with some invariants that must be held
true after each sync. arm_smmu_write_entry lends itself well to
unit-testing since the function's interaction with the STE/CD is already
abstracted by input callbacks that we can hook to introspect into the
sequence of operations. We can use these hooks to guarantee that
invariants are held throughout the entire update operation.

Link: https://lore.kernel.org/r/20240106083617.1173871-3-mshavit@google.com
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Michael Shavit <mshavit@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/9-v9-5040dc602008+177d7-smmuv3_newapi_p2_jgg@nvidia.com
Signed-off-by: Will Deacon <will@kernel.org>
6 files changed