# virsh dumpxml avocado-vt-vm1 --xpath //disk
<disk type="file" device="disk">
  <driver name="qemu" type="qcow2"/>
  <source file="/var/lib/libvirt/images/guest.qcow2"/>
  <backingStore/>
  <target dev="vda" bus="virtio"/>
  <address type="pci" domain="0x0000" bus="0x04" slot="0x00" function="0x0"/>
</disk>
<disk type="file" device="disk">
  <driver name="qemu" type="raw"/>
  <source file="/var/lib/libvirt/images/guest.disk"/>
  <target dev="vdb" bus="virtio"/>
  <address type="pci" domain="0x0000" bus="0x09" slot="0x00" function="0x0"/>
</disk>

# virsh snapshot-create-as avocado-vt-vm1 s2 --memspec file=/tmp/guest.mem --diskspec vda,file=/tmp/guest.s2
Domain snapshot s2 created

# virsh snapshot-list avocado-vt-vm1 
 Name   Creation Time               State
---------------------------------------------
 s2     2025-07-16 07:47:18 -0400   running

# virsh snapshot-revert avocado-vt-vm1 s2
error: Failed to revert snapshot s2
error: unsupported configuration: cannot generate external snapshot name for disk 'vdb': collision with disk 'vda'

# virsh domstate avocado-vt-vm1 --reason 
shut off (from snapshot)

# cat /var/log/libvirt/qemu/avocado-vt-vm1.log
2025-07-16 11:28:09.863+0000: 624328: info : libvirt version: 11.3.0, package: 1.el10 (Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>, 2025-05-06-07:27:27, )
2025-07-16 11:28:09.863+0000: 624328: info : hostname: $hostname
2025-07-16 11:28:09.863+0000: 624328: info : virObjectUnref:378 : OBJECT_UNREF: obj=0x7f5c580078c0
char device redirected to /dev/pts/5 (label charserial0)
2025-07-16 11:30:19.583+0000: shutting down, reason=from snapshot
2025-07-16T11:30:19.585751Z qemu-kvm: terminating on signal 15 from pid 624226 (/usr/sbin/virtqemud)