(In reply to Javi Ballester Tomás from comment #3)
> Hi Emil.
> The upgrade that initiated the problem was (17.0~git1701100730.17eac3~gd~x,
> 17.1~git1702040730.106a51~gd~x), something happened between 170110 and
> 170204.
> 
Perfect - what you're looking for is "how to use git bisect". There's dozens of
sources out there - from `git help bisect' (in the command line) to the Wine
example [1]. In case you're wondering - Mesa source tree is located at [2]

Note that you will need to rebuild and test mesa ~10 times. Make sure to use
exact same build (configure) flags as your distro.

[1] https://wiki.winehq.org/Regression_Testing#Running_the_bisection
[2] https://cgit.freedesktop.org/mesa/mesa

(In reply to Javi Ballester Tomás from comment #4)
> "LIBGL_ALWAYS_SOFTWARE=1 blender" works. Blender runs without errors. Also
> Mpv, glmark2 and glxgears.

This is very good step - it tells us that the software rasteriser is working
fine.
I.e. the variable 'disables' the GPU driver and makes the CPU do all the heavy
lifting.