[RFC] GTT added to preferred domain (?)

[Malte Dronskowski]

Hello,

I want to prepend that I've never done kernel programming and am not familiar 
with the amdgpu driver. That said, I read through the issues on Mesa regarding 
its behavior when RADV runs out of VRAM [1] and the related information.

Thereby I stumbled upon Christian König mentioning that it would be buggy 
behavior if the preferred domain included GTT when the initial domain was 
updated [2]. I read some of the related code in the kernel driver, trying to 
understand it, and got the impression that this is actually the case. When 
amdgpu_gem_object_create() fails in amdgpu_gem_create_ioctl(), 
"AMDGPU_GEM_DOMAIN_GTT" is added to "initial_domain" which during the retry 
gets written into both, "domain" and "preferred_domain" in 
amdgpu_gem_object_create(). Is this intended or a bug?

I've attached a minimal proof-of-concept patch (applied to kernel 6.14-rc7) 
that runs fine for me. I don't know though if this has any real effect on the 
driver's memory management. So please excuse me if this is a dumb 
question/patch and I did steal your time. Any insight would still be 
appreciated.

Thanks and best regards
Malte

[1] https://gitlab.freedesktop.org/mesa/mesa/-/issues/8763
[2] https://lists.freedesktop.org/archives/amd-gfx/2024-April/107401.html
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