iommufd: Iterate the cache invalidation array in the core

The vIOMMU cache_invalidate() and the nested-HWPT cache_invalidate_user() ops are each handed the full user invalidation array and must report, via array->entry_num, how many of its entries they handled. That makes every driver open-code the same array walk, with real downsides:

- each driver carries its own loop and sub-array bookkeeping;
- the ARM SMMUv3 driver allocates a buffer sized to the whole array just to iterate over it;
- hand-rolling the loop left the ARM SMMUv3 driver with two long-standing bugs:
1) on a conversion failure it counts commands that it converted but never issued, so user space skips invalidations that never reached the cmdq;
2) it rejects a zero-length array, which the uAPI documents as a valid request that only probes the data type.

The walk is identical for every driver, so move it into the iommufd core.

The core now drives the iteration:

- it invokes the op on a sub-array starting at the first not-yet-handled entry;
- the op handles one chunk from the front of that sub-array and reports the count via array->entry_num;
- the core advances and re-invokes until the whole array is consumed or the op returns an error.

A driver then only has to handle one bounded chunk per call, e.g. the ARM SMMUv3 op copies a single cmdq batch into a fixed on-stack buffer and drops its whole-array allocation. An op still handling the entire array in one call keeps working, so each driver converts independently.

All the bugs fixed here are long-standing ones rather than regressions in this cycle, so the series targets for-next, not for-rc. The stable tag on the second patch takes care of the backport.

This is on Github:
https://github.com/nicolinc/iommufd/commits/iommufd_invalidation_loop-v6

Changelog
v6
* Rebase on top of v7.3-rc1
* Drop the merged IDR5.DS patch
v5
https://lore.kernel.org/all/[email protected]/
* Rebase on top of arm/smmu/updates branch
* Add "Reviewed-by" from Jason and Pranjal
* Patch-1: Drop the Fixes and Cc stable tags
* Patch-2: Reject an unsupported opcode in the validation helper
* Patch-2: Add an explicit NSNH_ALL case to the allowlist switch
v4
https://lore.kernel.org/all/[email protected]/
* Add "Reviewed-by" from Baolu and Pranjal
* Split the DS support out of the reject patch into a new patch-1, also listing DS in the iommu_hw_info_arm_smmuv3 kdoc
* Patch-2: Add "!!" to the bool range assignment
* Patch-2: Factor the allowlist into arm_vsmmu_validate_user_cmd()
v3
https://lore.kernel.org/all/[email protected]/
* Patch-1: Add a minimal FEAT_DS detection and allow the two DS-only range encodings on a DS-capable SMMU
* Patch-1: Mask the host's scale value to keep its 5-bit truncation
v2
https://lore.kernel.org/all/[email protected]/
* Add "Reviewed-by" from Kevin to patches 2-5
* Patch-1: Allow the ATC_INV Global bit gated on ssid_bits, correcting the wrong every-device claim: per the spec it only broadens a single device's invalidation across its PASIDs
* Patch-1: Move the FEAT_ATS check into the allowlist switch
* Patch-1: Gate the TTL range field on FEAT_RANGE_INV too
* Patch-1: Accept only asid_bits of the ASID field
* Patch-1: Reject Reserved range field value combinations
* Patch-1: Reject an ATC_INV Size above 52
* Patch-1: Add local smmu and data variables to simplify the long lines
* Patch-1: Document the valid-command contract in the uAPI header
* Patch-1: Note that unchecked out-of-range values are UNPREDICTABLE
* Patch-1: Note that SSID/Global are IGNORED, not RES0, when SSV == 0
* Patch-2: Consolidate the two invalidation loops into one
* Patch-2: Multiply by the size_t entry_len to avoid a u32 overflow
* Patch-3/5: Return 0 directly on a zero-length array
* Patch-4: Use a processed counter and an out label like the mock driver
v1
https://lore.kernel.org/all/[email protected]/

Nicolin Chen (5):
iommu/arm-smmu-v3-iommufd: Reject unsupported bits in invalidation
commands
iommufd: Iterate the cache invalidation array in the core iommufd/selftest: Convert cache invalidation mocks to the core array
loop
iommu/arm-smmu-v3-iommufd: Convert cache invalidation to the core
array loop
iommu/vt-d: Convert nested cache invalidation to the core array loop

 include/linux/iommu.h                         |   6 +-
 include/linux/iommufd.h                       |   2 +
 include/uapi/linux/iommufd.h                  |   4 +-
 .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     | 197 ++++++++++++++----
 drivers/iommu/intel/nested.c                  |  54 ++---
 drivers/iommu/iommufd/hw_pagetable.c          |  25 ++-
 drivers/iommu/iommufd/selftest.c              | 147 +++++++------
 7 files changed, 282 insertions(+), 153 deletions(-)

base-commit: cee9395acd8043be0644b25c34bfa86623f2b935

2.43.0