** Description changed: - Currently it's impossible to install from xenial-desktop-amd64.iso on a - wide range of hardware with Nvidia GPUs. + [Description updated to reflect state of 16.04 release ISO] - The problem is invalid opcode(s) when using llvmpipe (the software - opengl fallback, used when using Unity with the Nouveau driver). The - result is that compiz crashes over and over; Upstart will continue to - restart compiz till it gives up. To confirm whether this bug is - happening, switch to a VT and check dmesg, in which you'll see something - like: + == In summary == + + If you have an Intel Skylake (6th gen) CPU and an NVIDIA GPU (or + possibly other GPUs that likewise require use of the llvmpipe opengl + software fallback), a work-around is needed to install Ubuntu 16.04 + desktop. + + To work-around this, you'll need to: + + 1) Choose "Install Ubuntu" in the pre-boot menu (rather than "Try Ubuntu + without installing") + + 2) Check "Download updates while installing Ubuntu" + + ** Note the above work-around wont work till + llvm-toolchain-3.8 1:3.8-2ubuntu3 lands in xenial-updates (it's currently only in xenial-proposed). FIXME: update description once this happens. + + == In detail == + + The Ubuntu 16.04 desktop ISOs includes libllvm3.8 1:3.8-2ubuntu1, which + has a bug that results in invalid JIT code generation when using the + mesa llvmpipe opengl software fallback on Skylake CPUs. + + When you encounter this bug, Unity/Compiz will fail to start, and you'll + see something like this in dmesg: [ 2092.557913] traps: compiz[10155] trap invalid opcode ip:7efc940030d4 sp:7ffccd914ea0 error:0 - A workable solution seems to be to re-build mesa against llvm-3.6-dev, - libclang-3.6-dev (rather that 3.8). This would get us a working Xenial - ISO for the effected hardware. Post 16.04 release, this could be - revisited, and mesa in Xenial could possibly switch back to llvm 3.8 - once this issue is resolved. - - I have mesa test packages built against llvm 3.6 here: - - https://launchpad.net/~jderose/+archive/ubuntu/mesa/+packages - - I couldn't test the installation without a re-spun ISO, but I did - confirm that after updating to the mesa packages in my PPA, I could - again use Unity. So I'm pretty sure this will fix installing from the - ISO as well. - - My hunch is that llvm 3.8 is generating invalid code during its JIT - compilation for llvmpipe, but it could also be the result of memory - corruption. Either way, building mesa against llvm 3.6 seems to be quick - the fix. - - Note this is a regression from 14.04.4 and 15.10, both of which install - fine on the hardware effected by this bug. - - For concrete examples of System76 hardware effected by this: - - 1) All Skylake laptops with 970m, 980m, and 980gtx GPUs - - 2) All Skylake and Haswell-E desktops with 970gtx and 980gtx GPUs - (although strangely, things seem to work with when you connect to a - monitor over HDMI, but always fails when connecting to a monitor over - DisplayPort) - - Note that none of the above failed tested scenarios are using Optimus: - all are using discrete GPU configurations. - - In my testing thus far on the effected hardware, the install always - fails if you choose "Try Ubuntu without installing". The install usually - seems to work when you choose "Install Ubuntu", but even this 2nd - scenario sometimes fails (and when it does, you'll see the same "trap - invalid opcode" bits in dmesg). - - Also note that so far I've only tested amd64, haven't tested i386. - - I suspect there is some deeper weirdness here, but at this point - System76 is just trying to make sure we have a Xenial ISO from which - customers can re-install Ubuntu. - - Old description - =============== - 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 definitely effects hardware we've tested with NVIDIA 970m and 980m - GPUs (when using the nouveau driver), and probably effects others as - well. - - Although strangely, with some NVIDIA 900 series hardware we're not - seeing this bug when using the nouveau driver. This will be investigated - further. - - In the current state, it's not possible to install Xenial on effected - 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). + libllvm3.8 1:3.8-2ubuntu3 fixes this issue, but the fix did not make it + onto the 16.04 release ISO. It will be included on the 16.04.1 ISO.
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to mesa in Ubuntu. https://bugs.launchpad.net/bugs/1564156 Title: xenial: invalid opcode when using llvmpipe Status in OEM Priority Project: New Status in System76: Fix Committed Status in llvm-toolchain-3.8 package in Ubuntu: Fix Committed Status in mesa package in Ubuntu: New Status in llvm-toolchain-3.8 source package in Xenial: Fix Committed Status in mesa source package in Xenial: New Bug description: [Description updated to reflect state of 16.04 release ISO] == In summary == If you have an Intel Skylake (6th gen) CPU and an NVIDIA GPU (or possibly other GPUs that likewise require use of the llvmpipe opengl software fallback), a work-around is needed to install Ubuntu 16.04 desktop. To work-around this, you'll need to: 1) Choose "Install Ubuntu" in the pre-boot menu (rather than "Try Ubuntu without installing") 2) Check "Download updates while installing Ubuntu" ** Note the above work-around wont work till llvm-toolchain-3.8 1:3.8-2ubuntu3 lands in xenial-updates (it's currently only in xenial-proposed). FIXME: update description once this happens. == In detail == The Ubuntu 16.04 desktop ISOs includes libllvm3.8 1:3.8-2ubuntu1, which has a bug that results in invalid JIT code generation when using the mesa llvmpipe opengl software fallback on Skylake CPUs. When you encounter this bug, Unity/Compiz will fail to start, and you'll see something like this in dmesg: [ 2092.557913] traps: compiz[10155] trap invalid opcode ip:7efc940030d4 sp:7ffccd914ea0 error:0 libllvm3.8 1:3.8-2ubuntu3 fixes this issue, but the fix did not make it onto the 16.04 release ISO. It will be included on the 16.04.1 ISO. To manage notifications about this bug go to: https://bugs.launchpad.net/oem-priority/+bug/1564156/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
