Description of problem:

The checkpoint-create-as, checkpoint-create and backup-begin all failed. but checkpoint creation worked in 8.1.0. backup-begin worked in a hotfix build libvirt-5.10.0-150_inc_backup.scrmod+el8.2.0+5151+ef7ede69.x86_64.rpm


Version-Release number of selected component (if applicable):
libvirt-6.0.0-4.module+el8.2.0+5642+838f3513.x86_64
qemu-kvm-4.2.0-9.module+el8.2.0+5699+b5331ee5.x86_64
kernel-4.18.0-151.el8.x86_64

How reproducible:

100%

Steps to Reproduce:
1.
Guest xml snippet:
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/tmp/nfs/vm1.qcow2' index='1'/>
      <backingStore/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </disk>

# virsh checkpoint-create-as vm1 cp1 --diskspec vda
error: Operation not supported: incremental backup is not supported yet

[root@dell-per730-66 ~]# cat cp.xml
<domaincheckpoint>
  <name>check_full</name>
</domaincheckpoint>

[root@dell-per730-66 ~]# cat bkup.xml
<domainbackup mode='push'>
  <disks>
    <disk name='vda' type='file'>
      <target file='/home/images/vda.full.backup'/>
      <driver type='qcow2'/>
    </disk>
  </disks>
</domainbackup>

[root@dell-per730-66 ~]# virsh checkpoint-create vm1 cp.xml
error: Operation not supported: incremental backup is not supported yet


[root@dell-per730-66 ~]# virsh backup-begin vm1 bkup.xml  cp.xml


error: Operation not supported: incremental backup is not supported yet


2.
3.

Actual results:
As above

Expected results:
Domain checkpoint creation should be supported.

Additional info: