+The optional C<readonlydisk> parameter controls what we do for
+disks which are marked E<lt>readonly/E<gt> in the libvirt XML.
+Possible values are:
+
+=over 4
+
+=item readonlydisk = \"error\"
+
+If C<readonly> is false:
+
+The whole call is aborted with an error if any disk with
+the E<lt>readonly/E<gt> flag is found.
+
+If C<readonly> is true:
+
+Disks with the E<lt>readonly/E<gt> flag are added read-only.
+
+=item readonlydisk = \"read\"
+
+If C<readonly> is false:
+
+Disks with the E<lt>readonly/E<gt> flag are added read-only.
+Other disks are added read/write.
+
+If C<readonly> is true:
+
+Disks with the E<lt>readonly/E<gt> flag are added read-only.
+
+=item readonlydisk = \"write\" (default)
+
+If C<readonly> is false:
+
+Disks with the E<lt>readonly/E<gt> flag are added read/write.
+
+If C<readonly> is true:
+
+Disks with the E<lt>readonly/E<gt> flag are added read-only.
+
+=item readonlydisk = \"ignore\"
+
+If C<readonly> is true or false:
+
+Disks with the E<lt>readonly/E<gt> flag are skipped.
+
+=back
+