Comment 12 for bug 1942684

I also can't boot the mainline 5.14-4 or 5.14-5 kernels on a Lenovo S7 (AMD 5800H and NVIDIA GPU) - it goes to a blank screen when trying to boot graphics and freezes - I can't open a tty and have to hard reset the system.

It looks like I have the laptop in the same mode as the other posters, ie hybrid/dynamic graphics mode using the amdgpu driver for the laptop screen.

I can't see any relevant errors in the output "journalctl -b -1" for the failed boot - I think the hang occurs before it has a chance to log them.

However, when booting the stock Ubuntu 21.10 5.13.0-16 kernel I do see some nvidia_drm RIP errors in the log in nv_drm_master_set(). Presumably these errors in combination with CONFIG_UBSAN_TRAP are causing the hang? The documentation says that in order to save around 5% of the kernel size, CONFIG_UBSAN_TRAP "reduces the kernel size overhead but turns all warnings (including potentially harmless conditions) into full exceptions that abort the running kernel code (regardless of context, locks held, etc), which may destabilize the system." It seems like a pretty aggressive config option to set!