OpenGL faulty rendering after Arch linux update

Question

I am working on a Dell Optioplex 7010 with intel Core i5 vPro running Arch linux. I did a regular OS update to version 5.11.9-arch1-1 recently (April 2021) and noticed that anything that uses OpenGL shows incomplete filling of surfaces such that you get multiple 'see through' triangles and rectangles. This picture illustrates the problem: X-screen saver geodesic gears showing the OpenGL problem Any ideas how to diagnose and fix this problem?

Here is what i have tried so far:

• Looking at different software to see if it was an issue with a particular package. Result: This is not limited to the X-Screen saver or any particular software package - the same corruption occurs in Cura, FreeCAD, etc. anything that uses openGL.
• Manually overriding the mesa loader driver using 'export MESA_LOADER_DRIVER_OVERRIDE' but none of the available drivers made a difference to the problem.
• Check my graphics card status. Result:

$ sudo lspci -vnn | grep VGA -A 12

 00:02.0 VGA compatible controller [0300]: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor Graphics Controller [8086:0152] (rev 09) (prog-if 00 [VGA controller])


    DeviceName:  Onboard IGD
     Subsystem: Dell Device [1028:0577]
     Flags: bus master, fast devsel, latency 0, IRQ 30
     Memory at f7800000 (64-bit, non-prefetchable) [size=4M]
     Memory at e0000000 (64-bit, prefetchable) [size=256M]
     I/O ports at f000 [size=64]
     Expansion ROM at 000c0000 [virtual] [disabled] [size=128K]
     Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
     Capabilities: [d0] Power Management version 2
     Capabilities: [a4] PCI Advanced Features
     Kernel driver in use: i915
     Kernel modules: i915

• Check my OpenGL status. Result:

$ sudo glxinfo | grep OpenGL
OpenGL vendor string: Intel Open Source Technology Center
OpenGL renderer string: Mesa DRI Intel(R) HD Graphics 2500 (IVB GT1)
OpenGL core profile version string: 4.2 (Core Profile) Mesa 20.3.4
OpenGL core profile shading language version string: 4.20
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 3.0 Mesa 20.3.4
OpenGL shading language version string: 1.30
OpenGL context flags: (none)
OpenGL extensions:
OpenGL ES profile version string:
OpenGL ES 3.0 Mesa 20.3.4
OpenGL ES profile shading language version string:
OpenGL ES GLSL ES 3.00
OpenGL ES profile extensions:

Everything was working fine before the OS update. I can't see an error or anything to fix in the above. Any help appreciated.

[EDIT - in response to comments]

I also checked the pacman log to see what packages were changed or added in the last -Syyu update. I found the following which I thought might have something to do with the OpenGL graphics rendering:

• installed box2d (2.4.1-1)
• installed gts (0.7.6.121130-2)
• upgraded intel-media-driver (20.4.5-1 -> 21.1.2-1)
• upgraded glslang (11.1.0-1 -> 11.2.0-3)
• upgraded gegl (0.4.26-1 -> 0.4.28-2)
• upgraded gd (2.3.0-1 -> 2.3.2-2)
• upgraded mesa (20.3.3-1 -> 20.3.4-3)

So I downgraded the packages that were upgraded (one-by-one, rebooting after each) and uninstalled the newly installed packages with pacman -Rsc. Unfortunately none of this fixed the issue.

Answer 1

I also sought help for this from the Arch forum. Thanks to a post there I found the answer. It turns out that I needed to set a kernel parameter for the i915 module. Specifically: i915.mitigations=off (in my setup is was set to 'auto' previously). When I appended this kernel parameter to my /boot/loader/entries/arch.conf file and rebooted, The problem no longer existed. No idea why this suddenly became necessary when it was working fine before.