Earlier this week Debian unstable and Ubuntu Yakkety switched to load the ‘modesetting’ X video driver by default on Intel graphics gen4 and newer. This roughly maps to GPU’s made since 2007 (965GM->). The main reason for this was to get rid of chasing after upstream git, because there hasn’t been a stable release in nearly three years and even the latest devel snapshot is over a year and a half old. It also means sharing the glamor 2D acceleration backend with radeon/amdgpu, which is a nice change knowing that the intel SNA backend was constantly slightly broken for some GPU generation(s).
Xserver 1.18.4 was released this week with a number of backported fixes to glamor and modesetting driver from master, so the time was right to make the switch now while both Stretch and Yakkety are still on the development phase. So I wrote a small patch for the xserver to load intel driver only on gen2 & gen3 which can’t do glamor efficiently. Newer Intel GPU’s will fall back to modesetting. This approach is good since it can be easily overridden by dropping a conffile to /etc/X11 that uses something else.
I’ve seen only one bug filed that was caused by this change so far, and it turned out to be a kernel bug fixed in 4.6 (Yak will ship with 4.8). If you see something strange like corrupt widgets or whatnot after upgrading to current Yakkety, verify it doesn’t happen with intel (‘cp /usr/share/doc/xserver-xorg-video-intel/xorg.conf /etc/X11’ followed by login manager restart or reboot) and file a bug against xserver-xorg-core (verify xdiagnose is installed, then run ‘ubuntu-bug xserver-xorg-core)’. We’ll take it from there.