[PATCH v6 01/10] mm: add zone device coherent type memory support

[David Hildenbrand]

On 11.02.22 17:45, Jason Gunthorpe wrote:
> On Fri, Feb 11, 2022 at 05:15:25PM +0100, David Hildenbrand wrote:
> 
>> ... I'm pretty sure we cannot FOLL_PIN DEVICE_PRIVATE pages
> 
> Currently the only way to get a DEVICE_PRIVATE page out of the page
> tables is via hmm_range_fault() and that doesn't manipulate any ref
> counts.

Thanks for clarifying Jason! ... and AFAIU, device exclusive entries are
essentially just pointers at ordinary PageAnon() pages. So with DEVICE
COHERENT we'll have the first PageAnon() ZONE_DEVICE pages mapped as
present in the page tables where GUP could FOLL_PIN them.


-- 
Thanks,

David / dhildenb