Re: [PATCH] drm/nouveau: check ioctl command codes better

[Chris Bainbridge <chris.bainbridge@gmail.com>]

On Mon, Jul 21, 2025 at 08:22:48AM -0400, Satadru Pramanik wrote:
> Hello all,
> 
> I suspect this commit in 6.16-rc7 has broken acceleration with Mesa's
> nouveau drivers on my machine.
> 
> glxinfo -B reports that I'm using llvmpipe.
> 
> Reverting this in 6.16-rc7 restores nouveau acceleration, and glxinfo
> then reports: "OpenGL renderer string: NVE7"
> 
> inxi -G
> Graphics:
>   Device-1: NVIDIA GK107M [GeForce GT 750M Mac Edition] driver: nouveau
>     v: kernel
>   Display: wayland server: X.Org v: 24.1.8 with: Xwayland v: 24.1.8
>     compositor: gnome-shell v: 48.0 driver: X: loaded: modesetting
>     unloaded: fbdev,vesa dri: nouveau gpu: nouveau resolution: 2880x1800~60Hz
>   API: EGL v: 1.5 drivers: nouveau,swrast
>     platforms: gbm,wayland,x11,surfaceless,device
>   API: OpenGL v: 4.5 compat-v: 4.3 vendor: mesa
>     v: 25.2.0~rc1+git2507191056.03f67b52319~p~mesarc0 renderer: NVE7
>   API: Vulkan v: 1.4.304 drivers: N/A surfaces: xcb,xlib,wayland
>   Info: Tools: api: eglinfo, glxinfo, vulkaninfo x11: xdriinfo, xdpyinfo,
>     xprop, xrandr
> 
> Best,
> Satadru Pramanik

I also bisected an issue to this commit. On my laptop, this commit
results in an intermittent desktop crash (Xorg segfault) when changing
display scale, which can be more reliably reproduced with:

for x in {1..100}; do
  xrandr --output eDP-1 --mode 2560x1600 --scale 0.5 --filter nearest
  xrandr --output eDP-1 --mode 2560x1600 --scale 1 --filter nearest
done

I also see the same glxinfo llvmpipe change that Satadru reported.
Reverting the commit fixes my scale test case, and also the glxinfo
renderer.

#regzbot introduced: e5478166dffb51fa64e76cdbb5c24421f22f2d43 ^
#regzbot title: nouveau hardware acceleration broken