The attribute name called 'alias name' can not be applied to xen hypervisor

Software environment

• Operating system: Ubuntu20.04
• Architecture: AMD64
• kernel version: 5.4.0-80-generic
• libvirt version: 7.0.0
• Hypervisor and version: xen-4.13.4-pre

Description of problem

Steps to reproduce

1. Try to assign an "alias name" to a device in libvirt configuration file.
2. But the attribute is not valid for the xen vm.

Additional information

I had launched a xen vm successfully by libvirt using the configuration file as below. In the configuration file, I had added the attribute name called "alias name" for the disk, but when I reopened the configuration file again I found that the alias name is missing for the xen vm. But there is no problem when I use this attribute for type-2 hypervisor(kvm). Is there any suggestion for this problem? Very appreciate to get the respond for this problem. Thanks a lot.

<disk type='file' device='disk'>
  <driver name='tap' type='raw'/>
  <source file='/x86/libvirt-xen/disk1.img'/>
  <target dev='xvda' bus='xen'/>
  <alias name='ua-xvda'/>
  <address type='drive' controller='0' bus='0' target='0' unit='0'/>
</disk>