Re: [PATCH] iommu/io-pgtable-arm: Add support for contiguous hint bit

[Jason Gunthorpe]

On Wed, Jul 15, 2026 at 01:14:18PM +0100, Robin Murphy wrote:

> Conversely though, I really wouldn't want to have to maintain arm-smmu
> supporting two completely different pagetable APIs simultaneously either :/

Does arm-smmu era HW even support CONT?

AFAICR the biggest issue with arm-smmu was it using IO_PGTABLE_ARMV7S
as well. I think it would be fine to implement all the unique LPAE
features it needs in iommupt, I did most of them already.

I do have an ARMV7S implementation for iommupt, but I did not solve
the sub page problem. So while it is functionally working it is not
usable since it wastes so much memory. That's a tricky problem to
solve since the algorithms depend on the gather->freelist.

I didn't spend any time trying to do anything about this as I was not
intending to touch arm-smmu

Jason