Re: [PATCH 6/7] iommu/arm-smmu-v3: Use the generic iommu page table

[Mostafa Saleh <smostafa@google.com>]

On Mon, Jul 06, 2026 at 01:29:12PM -0300, Jason Gunthorpe wrote:
> Switch to use the iommupt provided page table. This is fairly
> straightforward now since the page table construction and hwinfo are very
> similar to io-pgtable-arm.
> 
> The struct pt_iommu_armv8_hw_info is a direct replacement for 'tcr' and I
> have a kunit compare test validating that the fields have identical values
> for identical configurations.
> 
> Quirks are replaced by features
>  IO_PGTABLE_QUIRK_ARM_HD -> PT_FEAT_ARMV8_DBM
>  IO_PGTABLE_QUIRK_ARM_S2FWB -> PT_FEAT_ARMV8_S2FWB
> 
> SMMU features are mapped to iommupt features:
>  ARM_SMMU_FEAT_COHERENCY -> PT_FEAT_DMA_INCOHERENT
>  ARM_SMMU_FEAT_VAX -> PT_FEAT_ARMV8_LVA
>  ARM_SMMU_FEAT_S2FWB -> PT_FEAT_ARMV8_S2FWB
> 
> Remove the iommu_flush_ops entirely, iommupt only uses gathers for
> invalidation. Wire the tlbi directly to the gather.
> 
> Remove the trampoline for map/unmap/iova/read_and_clear_dirt. iommupt
> directly provides the domain ops. Domain initialization is largely moved
> into iommupt common code.
> 
> Change the kunit to fully create a page table to generate the tcr bits for
> testing.
> 
> Compared to io-pgtable-arm iommupt has a number of key differences:
>  - CONT support, including always using RIL to avoid errata 3673557
>  - Unmap yields a single gather which generates a single tlbi operation
>     * free_list is always used to free after invalidate
>     * walk cache and leaf invalidation are combined for non-RIL cases
>       instead of being duplicated
>     * non-RIL cut over to all-invalidate covers walk invalidation now too,
>       umap -> single gather -> single all invalidate.
>     * RIL flushes the walk cache and leafs together with a good TTL hint.
>     * RIL always generates one command from any gather.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/iommu/arm/Kconfig                     |   4 +-
>  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-test.c  |  45 +--
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 256 ++++++------------
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  11 +-
>  4 files changed, 110 insertions(+), 206 deletions(-)
> 

[...]

> -
>  static bool arm_smmu_dbm_capable(struct arm_smmu_device *smmu)
>  {
>  	u32 features = (ARM_SMMU_FEAT_HD | ARM_SMMU_FEAT_COHERENCY);
> @@ -2831,7 +2785,6 @@ static bool arm_smmu_capable(struct device *dev, enum iommu_cap cap)
>  	case IOMMU_CAP_ENFORCE_CACHE_COHERENCY:
>  		return arm_smmu_master_canwbs(master);
>  	case IOMMU_CAP_NOEXEC:
> -	case IOMMU_CAP_DEFERRED_FLUSH:

Why this is removed? That would drop support for FQ domains.

Thanks,
Mostafa

>  		return true;
>  	case IOMMU_CAP_DIRTY_TRACKING:
>  		return arm_smmu_dbm_capable(master->smmu);