Created attachment 121859 [details]
Full dmesg output
I've been encountering this bug since I've bought this laptop in Nov, 2015. When I launch an application that uses hw acceleration (e.g. any video game, firefox (with hw accel enabled), video in vlc/mplayer, etc). This *bug* may include screen blinking and/or graphical anomalies and/or system hang for a while (or forever). I also noticed the *bug* behavior is changing a little over mesa/libdrm/kernel module/kernel upgrades I usually make. I decided to mark it with major priority since it doesn't allow me to use hardware acceleration at all (please change it if necessary).
Please also refer to dmesg output and error log (from /sys/class/drm/card0/error) provided. My uname -a is "Linux ThinkPad 4.4.2-gentoo #1 SMP Sat Feb 20 13:17:36 MSK 2016 x86_64 Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz GenuineIntel GNU/Linux". My laptop model is "ThinkPad E550". I use libdrm-2.4.67, mesa-11.1.2, xf86-video-intel-2.99.917_p20160218 (driver). Please ask for any additional information needed.
Created attachment 121860 [details]
Error log from /sys/class/drm/card0/error
Looks like the DMAR hang, please try booting with intel_iommu=igfx_off
*** This bug has been marked as a duplicate of bug 89360 ***