Making drm_gpuvm work across gpu devices

[Daniel Vetter]

On Wed, Jan 31, 2024 at 09:12:39AM +1000, David Airlie wrote:
> On Wed, Jan 31, 2024 at 8:29 AM Zeng, Oak <oak.zeng at intel.com> wrote:
> >
> > Hi Christian,
> >
> >
> >
> > Nvidia Nouveau driver uses exactly the same concept of SVM with HMM, GPU address in the same process is exactly the same with CPU virtual address. It is already in upstream Linux kernel. We Intel just follow the same direction for our customers. Why we are not allowed?
> 
> 
> Oak, this isn't how upstream works, you don't get to appeal to
> customer or internal design. nouveau isn't "NVIDIA"'s and it certainly
> isn't something NVIDIA would ever suggest for their customers. We also
> likely wouldn't just accept NVIDIA's current solution upstream without
> some serious discussions. The implementation in nouveau was more of a
> sample HMM use case rather than a serious implementation. I suspect if
> we do get down the road of making nouveau an actual compute driver for
> SVM etc then it would have to severely change.

Yeah on the nouveau hmm code specifically my gut feeling impression is
that we didn't really make friends with that among core kernel
maintainers. It's a bit too much just a tech demo to be able to merge the
hmm core apis for nvidia's out-of-tree driver.

Also, a few years of learning and experience gaining happened meanwhile -
you always have to look at an api design in the context of when it was
designed, and that context changes all the time.

Cheers, Sima
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch