[Intel-gfx] [PATCH 4/4] i915: fix remap_io_sg to verify the pgprot

[Thomas Hellström]

On 5/18/21 3:24 PM, Christoph Hellwig wrote:
> On Tue, May 18, 2021 at 08:46:44AM +0200, Thomas Hellström wrote:
>> And worse, if we prefault a user-space buffer object map using
>> remap_io_sg() and then zap some ptes using madvise(), the next time those
>> ptes are accessed, we'd trigger a new call to remap_io_sg() which would now
>> find already populated ptes. While the old code looks to just silently
>> overwrite those, it looks like the new code would BUG in remap_pte_range()?
> How can you zap the PTEs using madvise?

Hmm, that's not possible with VM_PFNMAP. My bad. Should be OK then.

/Thomas