Hello, Having just upgraded a Xen host from bullseye to bookworm, I got to experience this, too. My UEFI HVM domU guests did not boot to OS, and issue presentation was either attempting to boot from network with iPXE [despite not having network boot enabled in domU config...], or with network interfaces commented out, booting to the EDK2 UEFI shell.
This involved debugging the QEMU process startup to try to find what was not honouring the domU boot configuration, finding what packages were modified and split between bullseye and bookworm, identifying that OVMF is a package dependency, and reverting it to package version 2020.11-2+deb11u2 from http://snapshot.debian.org/package/edk2/2020.11-2%2Bdeb11u2/#ovmf_2020.11-2:2b:deb11u2 After reverting the package and rebooting the affected domU instances, the guests proceeded to boot as expected. I then came over to file a bug for this behaviour, and have found that the bug already exists, from over a year ago...if I only know what the problem was from the beginning... David Comeau (SaturnNiGHTS)
