Comment 33 for bug 1873809

@Stéphane, the uncompress message appears to be something that may happen if blocks are not aligned but not harming anything. By now I have played around with both a self created secureboot VM on bionic and also (following your turorial) a LXD 4.0 vM. And for both I could not repeat what you saw. Both booted. There is a minor issue for people creating their own VMs and using a graphical interface (like virt-manager). The kvm kernel has no framebuffer devices enabled so one does not see anything if one does not enable a serial console.

For LXD, when I repeated the steps from https://discuss.linuxcontainers.org/t/running-virtual-machines-with-lxd-4-0/7519 I saw one crash not finding the root disk after the initial lxc start when I ran lxc console. But that was with the generic kernel and that seems to be handled by the panic handler. Attaching to he console a second time I saw cloud-init finishing and then I installed the proposed kvm kernel in that running vm and rebooted. And this gave me a working boot:

ubuntu@ubuntu:~$ uname -a
Linux ubuntu 5.4.0-1017-kvm #17-Ubuntu SMP Mon Jun 15 13:05:31 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
ubuntu@ubuntu:~$ dmesg|grep secure
[ 0.000000] secureboot: Secure boot enabled
[ 0.260090] secureboot: Secure boot enabled