[Question] Are "device exclusive non-swap entries" / "SVM atomics in Nouveau" still getting used in practice?

[David Hildenbrand]

Hi,

I keep finding issues in our implementation of "device exclusive 
non-swap entries", and the way it messes with mapcounts is disgusting.

As a reminder, what we do here is to replace a PTE pointing to an 
anonymous page by a "device exclusive non-swap entry".

As long as the original PTE is in place, the only CPU can access it, as 
soon as the "device exclusive non-swap entry" is in place, only the 
device can access it. Conversion back and forth is triggered by CPU / 
device faults.

I have fixes/reworks/simplifications for most things, but as there is 
only a "real" single user in-tree of make_device_exclusive():

	drivers/gpu/drm/nouveau/nouveau_svm.c

to "support SVM atomics in Nouveau [1]"

naturally I am wondering: is this still a thing on actual hardware, or 
is it already stale on recent hardware and not really required anymore?


[1] https://lore.kernel.org/linux-kernel//6621654.gmDyfcmpjF@nvdebian/T/

-- 
Cheers,

David / dhildenb