On 8/5/22 11:25, Jin Huang wrote:
> Hi, libvirt-users
> 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/
> <https://stevescargall.com/2022/06/10/using-linux-kernel-memory-tiering/>
>

What you want to configure is so called HMAT (Heterogeneous Memory
Attribute Table). It can be configured by leaving out the @cpus
attribute completely. For instance like this:

<cpu mode='host-model' check='partial'>
    <numa>
      <cell id='0' cpus='0-5' memory='512000' unit='KiB' discard='yes'>
        <distances>
          <sibling id='0' value='10'/>
          <sibling id='1' value='21'/>
        </distances>
        <cache level='3' associativity='direct' policy='writeback'>
          <size value='10' unit='KiB'/>
          <line value='8' unit='B'/>
        </cache>
        <cache level='1' associativity='direct' policy='writeback'>
          <size value='8' unit='KiB'/>
          <line value='5' unit='B'/>
        </cache>
      </cell>
      <cell id='1' memory='512000' unit='KiB'>
        <distances>
          <sibling id='0' value='21'/>
          <sibling id='1' value='10'/>
        </distances>
      </cell>
      <interconnects>
        <latency initiator='0' target='0' cache='1' type='access'
value='5'/>
        <bandwidth initiator='0' target='0' type='access' value='204800'
unit='KiB'/>
      </interconnects>
    </numa>
  </cpu>


This was introduced in libvirt-6.6.0 so you may need to upgrade.

Michal