Comment 3 for bug 1302270

Confirmed. Here's what I just reported in a duplicate:

After updating today Unity only starts in software rendering mode. I can tell because:
  1. There's no dash blur.
  2. Graphics performance is slow.
  3. .xsession-errors says:
       libGL error: failed to open drm device: Permission denied
       libGL error: failed to load driver: i965
  4. compiz is linked to the software driver:

$ pmap `pidof compiz` | grep dri
00007f9a1e386000 3256K r-x-- swrast_dri.so
00007f9a1e6b4000 2048K ----- swrast_dri.so
00007f9a1e8b4000 60K r---- swrast_dri.so
00007f9a1e8c3000 32K rw--- swrast_dri.so