Re: [PATCH v5 05/15] mm/frame-vector: Use FOLL_LONGTERM

Jason Gunthorpe
2020-11-05T12:49:56Z

On Thu, Nov 05, 2020 at 10:25:24AM +0100, Daniel Vetter wrote:
> > /*
> > * If we can't determine whether or not a pte is special, then fail immediately
> > * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
> > * to be special.
> > *
> > * For a futex to be placed on a THP tail page, get_futex_key requires a
> > * get_user_pages_fast_only implementation that can pin pages. Thus it's still
> > * useful to have gup_huge_pmd even if we can't operate on ptes.
> > */
>
> We support hugepage faults in gpu drivers since recently, and I'm not
> seeing a pud_mkhugespecial anywhere. So not sure this works, but probably
> just me missing something again.

It means ioremap can't create an IO page PUD, it has to be broken up.

Does ioremap even create anything larger than PTEs?

Jason