Nouveau - Jul 2025 - [PATCH] drm/nouveau: check ioctl command codes better

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

On Mon, Jul 21, 2025, at 14:22, 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.
Thanks for the report!  Can you run the failing command with
'strace -f -o logfile.txt -e trace=ioctl ...' to see which command
it tries?

Either I made a stupid mistake in my patch and don't catch the
intended command any more, or the command that gets sent is actually
different from the one that the kernel expects.

      Arnd

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

On Tue, Jul 22, 2025, at 12:29, Chris Bainbridge wrote:
> 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"
>
> 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 won't have time to work on fixing my patch before the merge window,
let's just revert it.

      Arnd