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