How could I set up a memory-only and no-cpu NUMA node for the qemu-VM with the XML file?

Seems each NUMA cell has to be bundled with some specific cpuids.

If I write the element like this, it is wrong.

<cpu mode='host-passthrough'>

  <numa>

    <cell id='0' cpus='0-3' memory='16' unit='GiB'/>

    <cell id='1' cpus='null' memory='16' unit='GiB'/>

  </numa>

</cpu>

Also if I ignore the cpus item, it is not acceptable for the virsh command.

The reason I want the memory-only node is that I want to set up multiple memory tiers for the VM, just like https://stevescargall.com/2022/06/10/using-linux-kernel-memory-tiering/