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

As subject

Please provide the package NVR for which bug is seen:

libvirt-10.0.0-2.el9.x86_64
qemu-kvm-8.2.0-3.el9.x86_64

How reproducible:

100%

Steps to reproduce

1. Prepare a domain
2. Prepare the iommu XML and cold-plug it to the domain

cat /tmp/iommu.xml
 <iommu model='virtio'/>

virsh attach-device rhel /tmp/iommu.xml --config 
error: Failed to attach device from /tmp/iommu.xml
error: Operation not supported: persistent attach of device 'iommu' is not supported

Expected results

As above

Actual results

No error