Comment 4 for bug 2003226

Hello,

sorry for the delay, busy schedule ....

so , i finally had time to do some tests, and i got some new informations :

- i reinstalled 2 of my virtualization servers on ubuntu 18.04.6
     - 1 older ( Intel Xeon E5-2640 v4 2.40GHz )
     - 1 newer ( Intel Xeon Gold 5215 2.50GHz )

- first, i can confirm that with ubuntu 18.04.6 ( kernel 4.15.0-204 ) i do not have the problem
  i can migrate VM from new system to older system and reverse without any issue.

- i installed (manually) a kernel 5.15.0-56 ( ubuntu 2204 ) on both 1804 servers,
  and reboot to this kernel ( without changing anything else )

- with kernel 5.15.0-56, i can reproduce the problem each time :
    - migrate VM from older system to newer always works
    - migrate VM from newer system to older always crash the VM

     this is a bit different though, the VM is tagged as "paused",
     and if i try to virsh resume, i got :
        error: Failed to resume domain devansible01
        error: internal error: unable to execute QEMU command 'cont': Resetting the Virtual Machine is required

     the only thing i can do is virsh destroy and virsh start

since i did not change qemu version, i seems that this is a kernel issue.

i plan to do the opposite test : reinstall both servers in ubuntu 2204, and downgrade the kernel
hopefully by the end of the week, i will let you know.

Best regards.