Comment 22 for bug 1885662

Hello Christian,

I wrote a test script to run the migrations you suggested in a reproducible manner, (sorry for taking so long, it took me quite a while to deal with all libvirt/QEMU/OVMF quirks)

Here is the summary:

Migration of default "--boot uefi" guests:

focal -> focal(upgraded) [OK]
focal (upgraded) -> focal [FAIL] (see notes)
bionic -> focal [OK]
bionic -> focal (upgraded) [OK]
focal -> jammy [OK]
focal (upgraded) -> jammy [OK]
bionic -> focal -> jammy [OK]
bionic -> focal (upgraded) -> jammy [OK]

Migration of "--boot loader=OVMF_CODE.fd/OVMF_VARS.fd" guests (simulates created guests before the update):

focal -> focal(upgraded) [OK]
focal (upgraded) -> focal [OK]
bionic -> focal [OK]
bionic -> focal (upgraded) [OK]
focal -> jammy [OK]
focal (upgraded) -> jammy [OK]
bionic -> focal -> jammy [OK]
bionic -> focal (upgraded) -> jammy [OK]

Notes:
The reason why focal (upgraded) -> focal migration fails in the default "--boot uefi" scenario is; the upgraded host creates the guest with the new "_4M" images (because fw descriptors are now pointing to the 4M images), and the non-upgraded focal simply doesn't have them, hence the migration fails. VM stays on the source host, untouched.

You can find the test script and test reports in the following attachment.