What were you trying to do that didn't work?

Error msg prompts when attaching virtio-mem device to persistent guest config without memory slot.

Please provide the package NVR for which bug is seen:

 # rpm -q libvirt
libvirt-9.5.0-7.el9_3.x86_64

How reproducible:

100%

Steps to reproduce

1. Define a guest with below config xml:

<maxMemory unit="KiB">20485760</maxMemory>
<memory unit="KiB">2097152</memory>
<currentMemory unit="KiB">2097152</currentMemory>

...

<numa>
      <cell id="0" cpus="0-5" memory="2097152" unit="KiB"/>
</numa>

2. Prepare a virtio-mem device with below config xml:

 # cat mem.xml 
<memory model='virtio-mem'> 
  <target> 
    <size unit='MiB'>512</size> 
    <block unit='KiB'>2048</block>
    <requested unit='MiB'>512</requested> 
    <node>0</node> 
  </target> 
</memory>

3. Attach the virtio-mem device from step2:

 # virsh attach-device vm1 mem.xml --config
error: Failed to attach device from mem.xml
error: unsupported configuration: no free memory device slot available

Expected results

The virtio-mem device should be attached successfully.

Actual results

Error msg "no free memory device slot available" prompts while attaching.

Additional info:

If define the guest with below config xml:

<maxMemory unit="KiB">20485760</maxMemory>
<memory unit="KiB">2097152</memory>
<currentMemory unit="KiB">2097152</currentMemory>

...
<numa>
      <cell id="0" cpus="0-5" memory="2097152" unit="KiB"/>
</numa>

...

<memory model='virtio-mem'> 
  <target> 
    <size unit='MiB'>512</size> 
    <block unit='KiB'>2048</block>
    <requested unit='MiB'>512</requested> 
    <node>0</node> 
  </target> 
</memory>

The the guest config could be defined:

 # virsh define vm1.xml
Domain 'vm1' defined from vm1.xml

Then attach the virtio-mem device with --config, we could get successful result:

 # virsh attach-device vm1 mem.xml --config
Device attached successfully