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

[Jason Gunthorpe]

On Wed, Feb 16, 2022 at 11:56:51AM -0500, Felix Kuehling wrote:

> In the case of DEVICE_COHERENT memory, the pfns correspond to real physical
> memory addresses. I don't think they have those PFN_DEV|PFN_MAP bits set.

So do DAX pages. The PTE flag does several things. As this would be
the first time ZONE_DEVICE pages do not set devmap it needs a full
audit.

eg the gup_fast bug Alistair pointed at needs fixing at least.

Jason