Comment 44 for bug 1942684

Done

Point 1) above WORKS on zen3, haswell, and ivybridge.
That means disabled 'CONFIG_UBSAN_TRAP' in the kernel config prior to building.
Just nano or vim into the ".config" and put a '#' in front of the line to disable it. before running "$ make olddefconfig"

I built the kernel using LLVM-13 and LTO thin with O3 optimisation with -march=<cpuType>

Point 2) above FAILED on ivybridge. I didn't bother trying to build it for other march types.
It was built using the Ubuntu mainline config for 5.14.14 with the debian pems removed for a custom kernel build. "CONFIG_UBSAN_TRAP" is enabled by default in the Ubuntu kernel config.

I built the kernel using GCC-11.1 with O3 optimisation with -march=<cpuType>

I highly recommend that Ubuntu Mainline Kernel team DISABLE "CONFIG_UBSAN_TRAP" from their mainline kernel config as it can FAIL production kernels as that option forces what otherwise would have been a harmless warning into an error and possibly an abort or kernel panic of some sort.