Bug 217222

I have (3) el8 servers that are failing to boot the latest elrepo kernel-lt (5.4.237-1.el8.elrepo.x86_64). These systems were and continue to boot fine with the previous kernel-lt (5.4.236-1.el8.elrepo.x86_64). All systems are exhibiting the same behavior - the system starts to boot, but at the point where the resolution normally changes, the system instead displays a black screen and locks up. At this point the system does not respond to the keyboard, nor acpi shutdown via the power button and must hard reset.

Two of these servers are IvyBridge CPUs and one is Haswell. All use Intel i915 graphics. I found by passing nomodeset or i915.modeset=0 as a kernel parameter allows the system to boot with the new kernel. I also found that if I pass vga=1440x900x16 as a kernel parameter, the system will still hang up, however it does so not at a black screen, but immediately after the output "fb0: switching to inteldrmfb from simple".

I reported this via the elrepo bug tracker and the elrepo kernel-lt devs noted a kernel patch had been applied to this kernel with comment "drm/i915: Dont use BAR mappings for ring buffers with LLC" and provided updated packages that reverted this patch. I tested these packages and verified my systems now boot normally. I was then advised to notify upstream at this bugzilla. Please let me know if I can provide any further information.

Elrepo bug report:
https://elrepo.org/bugs/view.php?id=1334