On 11/5/20 4:49 AM, Jason Gunthorpe wrote:

On Thu, Nov 05, 2020 at 10:25:24AM +0100, Daniel Vetter wrote:

quoted

quoted

/*
  * 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?

 From my reading, yes. See ioremap_try_huge_pmd().

thanks,
-- 
John Hubbard
NVIDIA

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