Description of problem: During the final step of FFWD2 the live migration fails to migrate instances from OSP13 EL7.8 hybrid state to OSP16.1 compute with the error: ERROR nova.virt.libvirt.driver [...] CPU doesn't have compatibility. internal error: Unknown CPU feature arch-facilities This is due to RHEL7 naming the feature 'arch-facilities' vs RHEL8 naming the feature 'arch-capabilities'. A suggested workaround is to remove the 'arch-facilities' feature from /usr/share/libvirt/cpu_map.xml in the libvirt container on the RHEL7 source when switching it into hybrid mode. While a workaround through documentation is possible, the process to do this is better handled through automation to prevent mistakes.
To be more precise, the workaround: 1. On the El-7 host, double-check none of the EL7 instance XML contain 'arch-facilities' CPU feature. Normally, the guests do _not_ have it. 2. Run `virsh capabilities | grep arch-facilities` — it will be present. 3. Comment out 'arch-facilities' in /usr/share/libvirt/cpu_share.xml 4. Restart 'libvirtd' and 'nova-compute' service (both are needed). 5. Then run `virsh capabilities`, again: it will now be absent (expected). 6. Now migrate the guest from EL7 to EL8: it must succeed. (Thanks: Jiri Denemark from libvirt team.)
*** This bug has been marked as a duplicate of bug 1867128 ***