Symptom
You're trying to upgrade to version 6.3 and you're getting the following message about "Update eligibility problems"
Explanation
- Existing VM should continue work as they were. The alert is telling if you have image without virtio-blk driver and you want to create new VM from that image, it probably will hit difficulty to boot. In order to make it works, you should mark the image properties as hw_machine_type=pc, then only provision the new VM with the image you intended to use.
Finding out affected image
for i in $(openstack image list -c ID -f value); do echo === image $i ===; openstack image show $i | grep hw_disk_bus | grep -v 'virtio'; done
Details on the workaround can be found here.