Re: [RFT 3/5] drm/msm: Extract out map/unmap helpers

[Rob Clark]

On Tue, Oct 6, 2026 at 10:19 PM Karl Mehltretter <kmehltretter@xxxxxxxxx> wrote:
>
> > Does this error path miss an IOTLB flush?
>
> Yes. msm_iommu_pagetable_unmap() called iommu_flush_iotlb_all() after
> rollback. __do_map() now calls __do_unmap() directly and loses that
> flush.
>
> An arm64 QEMU/SMMUv3 test:
>
> - mapped one 4 KiB page,
> - hit -EEXIST on the second page, and
> - verified that rollback removed the first PTE.
>
> No stale translation was observed because the device had not accessed
> the mapping. This tested the low-level IOMMU sequence, not the MSM driver
> or Qualcomm hardware.
>
> Restoring iommu_flush_iotlb_all() on this error path preserves the old
> behavior.

I have a fixup, but haven't sent a v2 yet.. current series is still
enough to verify whether there is more work needed on older
pre-arm-smmu hw or not

BR,
-R