Created attachment 200210 [details]
Picture of the video output of the KVM console (sorry no serial console on this KVM)
I was performing an upgrade from 11.2 to 12.0 using svn (releng/12.0 r342177) on my amd64 machine (Intel S1200BT with Xeon E3-1240). I'm using ZFS on root, had the booting environment set.
Booting to newly built kernel went ok. I had the 12.0 kernel with 11.2 world. After installworld and other expected tasks (mergemaster,...,reboot) I was not able to boot anymore. Attaching the picture of the crash from bootloader.
Luckily I was able to interrupt the boot very early and select old loader.
It seems similar topic was mentioned on FreeBSD forums: https://forums.freebsd.org/threads/upgrade-disaster-11-2-release-12-0-release.68680/
(In reply to martin ilavsky from comment #0)
Do you mind to test with current? if it is ok, then we need to pick those changes over to 12..
I downloaded the current snapshot build: https://download.freebsd.org/ftp/snapshots/amd64/13.0-CURRENT/kernel.txz from Dec 13,2018. Used /boot from this snapshot, but kept /boot/kernel from my 12.0.
Boot went ok.
(In reply to martin ilavsky from comment #2)
Ok, so it is fixed in current. Thats good.
Yes, it seems so. In above test I used 13 current. I did additional tests with official /boot and /boot/kernel/.
With 12.0-RELEASE system hung, got no info at all.
With 12-stable I got to the menu where it failed kernel was missing. Indeed, snapshot kernel.txz from Dec 13 doesn't have kernel/kernel inside (am I missing something?).
I did another test and used my own kernel but with 12-stable /boot -- all went ok.
I confirm that 12-stable has this issue fixed.