https://bugs.freedesktop.org/show_bug.cgi?id=69670
--- Comment #5 from Eugene omegatype@gmail.com --- I am not sure how to confirm it. I tried launching:
LIBGL_ALWAYS_SOFTWARE=1 kwin --replace > kwin_stdout_LIBGL_ALWAYS_SOFTWARE.txt 2> kwin_stderr_LIBGL_ALWAYS_SOFTWARE.txt
and it disabled desktop effects; then I tried to switch to OpenGL 3.1 + Raster and Kwin crashed displaying 'report bug assignment' window and then was restarted automatically without effects. I could not enable effect anyhow.
kwin_stdout_LIBGL_ALWAYS_SOFTWARE.txt was empty.