[PATCH] iommu/io-pgtable-arm: Remove split on unmap behavior
Jason Gunthorpe
jgg at nvidia.com
Mon Oct 21 12:17:24 UTC 2024
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
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