i915 drm GPU hang, GUI freeze with flickering

[Tomas Zemek]

GUI suddenly freezes and starts flickering, dmesg:

Aug 8 22:18:11 kernel: [37254.612789] i915 0000:00:02.0: [drm] GPU HANG: ecode 7:0:00000000
Aug 8 22:18:11 kernel: [37254.612858] i915 0000:00:02.0: [drm] Resetting chip for stopped heartbeat on rcs0
Aug 8 22:18:11 kernel: [37254.714421] i915 0000:00:02.0: [drm] VMSVGA FIFO[8731] context reset due to GPU hang
Aug 8 22:18:14 kernel: [37257.670342] i915 0000:00:02.0: [drm] GPU HANG: ecode 7:0:00000000
Aug 8 22:18:14 kernel: [37257.670382] i915 0000:00:02.0: [drm] Resetting chip for stopped heartbeat on rcs0
Aug 8 22:18:14 kernel: [37257.773493] i915 0000:00:02.0: [drm] kwin_x11[7538] context reset due to GPU hang

Few months ago the same symptoms started to occur as well after upgrade to kernel 5.8.0-49 (https://bugs.launchpad.net/ubuntu/+source/linux-meta-hwe-5.8/+bug/1924624) but they seemed to be fixed with 5.8.0-52.
Now after upgrade to 5.11.0-25, the problem seems to be back.

System is Ivy Bridge i7-3770 with iGPU HD4000.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.11.0-25-generic 5.11.0-25.27~20.04.1
ProcVersionSignature: Ubuntu 5.11.0-25.27~20.04.1-generic 5.11.22
Uname: Linux 5.11.0-25-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.18
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Mon Aug 9 13:56:52 2021
SourcePackage: linux-signed-hwe-5.11
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

Please attach the full system log containing the error. If you experience a hang and have to reboot then you can run this command to collect the log of the previous boot:

  journalctl -b-1 > prevboot.txt

[Launchpad Janitor (janitor)]

[Expired for linux-signed-hwe-5.11 (Ubuntu) because there has been no activity for 60 days.]