Comment 0 for bug 1564156

Jason Gerard DeRose (jderose) wrote :

Currently Unity on Xenial is unusable when the llvmpipe software fallback is used, at least on certain hardware.

For example, from dmesg:

[ 2092.557913] traps: compiz[10155] trap invalid opcode ip:7efc940030d4 sp:7ffccd914ea0 error:0
[ 2093.109485] traps: compiz[10192] trap invalid opcode ip:7f38ac01a0d4 sp:7ffe5ed737e0 error:0
[ 2093.718863] traps: compiz[10212] trap invalid opcode ip:7fe6900010d4 sp:7ffd55804020 error:0

This certainly effects hardware with NVIDIA 970m and 980m GPUs, and possibly others.

In the current state, it's not possible to install Xenial on such hardware using recent daily desktop amd64 ISOs.

Note this problem exists both when run against mesa 11.1.2-1ubuntu2 in Xenial proper, and when run against mesa 11.2.0~rc4-1ubuntu0.1 from ppa:canonical-x/x-staging. (The later test was done with the System76 imaging system using an image with ppa:canonical-x/x-staging and nvidia-361 pre-installed, then removing nvidia-361 and rebooting).

I'm kinda shooting in the dark here, but I did my best to rule out the kernel as a variable:

(1) I built and installed the 4.4.0-16 kernel on 15.10, rebooted, and had no problems.

(2) On Xenial I tried the 4.5 and 4.6rc1 mainline builds, but they don't fix the problem.

I'm not sure the underling bug is in compiz, but I'm filing it against compiz anyway because that's where the dmesg output is pointing me.

Other likely culprits include nux, mesa, maybe even llvm, and probably others I'm not thinking of :)

Also, I'm positive llvmpipe is being used when this invalid opcode is trapped because I added this to /etc/X11/Xsession.d/50_check_unity_support:

/usr/lib/nux/unity_support_test -p > /tmp/compiz-debug.log

That way I could figure out what renderer was being used from a VT (as the X session is darn near unusable in this state).