hrm... UEFI allows you to mark part of memory to not clear on reboot... i wonder if there's any downsides to maybe preserving the last bit of kernel messages

in case of say a panic and thing didn't get saved for some reason... could potentially still have the last few bits that could be saved after reboot

(AFAICT we don't do this today)

though ISTR that maybe on sparc it did?

(vaguely recall)

Yes I believe that is a thing SPARC did