After the upgrade to OpenSuse 15.5 my laptop did not boot completely when using Xen. It just hangs after during the load of the i915 driver from the initrd and just displays a black screen.

The laptop boots normally if NOT using Xen (just booting directly to the Linux kernel) and it boots normally IF using Xen when using the Linux kernel command line parameter "nomodeset" (but of course, with bad graphics performance).

After a long debugging session using my own printk() statements and netconsole for logging I found out that the actual problem is that the kernel routine pat_enabled() incorrectly returns false in a Xen Dom0 and the i915 driver fails if it receives this value, which finally leads to a kernel oops during the cleanup (!) of the i915 driver.

With that knowledge I found out that the problem is a known one which was already discussed in the Linux kernel mailing list, see https://lore.kernel.org/lkml/bc13c66d-a885-e405-7b53-8cd7afdbecff@suse.com/t/ , but it seems that the included patch from that discussion is not contained in OpenSuse 15.5.

Changing the wrong value of pat_enabled() solves my problem and the system boots normally. So the patch from the LKML or a similiar one should be applied to the OpenSuse 15.5 kernel.