[PATCH v16 0/4] RDMA: Add dma-buf support

[Jason Gunthorpe]

On Fri, Feb 05, 2021 at 04:39:47PM +0100, Daniel Vetter wrote:

> > And again, for slightly older hardware, without pinning to VRAM there is
> > no way to use this solution here for peer-to-peer. So I'm glad to see that
> > so far you're not ruling out the pinning option.
> 
> Since HMM and ZONE_DEVICE came up, I'm kinda tempted to make ZONE_DEVICE
> ZONE_MOVEABLE (at least if you don't have a pinned vram contigent in your
> cgroups) or something like that, so we could benefit from the work to make
> sure pin_user_pages and all these never end up in there?

ZONE_DEVICE should already not be returned from GUP.

I've understood in the hmm casse the idea was a CPU touch of some
ZONE_DEVICE pages would trigger a migration to CPU memory, GUP would
want to follow the same logic, presumably it comes for free with the
fault handler somehow

Jason