[PATCH] iommu/io-pgtable-arm: Remove split on unmap behavior

[Jason Gunthorpe]

On Mon, Oct 21, 2024 at 12:32:21PM +0100, Steven Price wrote:

> > that, we can always do it in two steps (unmap the 2M region and remap
> > the borders). At some point it'd be good to have some kind of atomic
> > page table updates, so we don't have this short period of time during
> > which nothing is mapped (between the unmap and the remap), but that's a
> > different story.
> 
> The GPU hardware provides that. The only possible missing piece is that
> the driver needs to know ahead of time that the unmap would unmap the 2M
> region so it can do the correct lock before the entries are removed.

It looks like we need atomic update for some confidential compute
scenarios, so I am working toward that with the coming generic pt
stuff.

> >> If DRM does use this, I'd respin this to make it into a quirk and iommu won't
> >> set it.
> 
> You should be safe as far as Panfrost and Panthor are concerned.

Great, thanks!

Jason