Comment 2 for bug 1997352

This was tested using OpenStack Xena.

There were no changes to the `delete_configuration` method itself https://opendev.org/openstack/nova/blame/commit/f9dc9f259bfff5ac9424b4acb8575bf8c2463113/nova/virt/libvirt/guest.py#L298, but there was https://bugs.launchpad.net/nova/+bug/1845628 and the resulting https://review.opendev.org/c/openstack/nova/+/685678.

Going along the chain of events I believe with the switch to a non-UEFI image during REBUILD the information that there WAS an NVRAM present due to the previously used UEFI-enabled image is lost, thus the delete_configuration does to work anymore causing the rebuild to fail.

My take would be:

Why not always delete the NVRAM if the hosts has UEFI support, just in case? Is that call really that expensive? By calling "delete_configuration" I simply want to end up with a deleted configuration / domain.