Currently, when hot-plugging an interface to a running guest VM, a `RestartRequired` condition is updated in the VM spec.
This mostly affects the UI users, as the UI limits the ability to use the guest until this condition is filled, i.e. until the VM is restarted. 

OCP 4.19.0-ec.3
CNV v4.19.0 (brew.registry.redhat.io/rh-osbs/iib:935792)

100%

1.
Create a new namespace to work in.
You can apply the following ProjectRequest for that:
apiVersion: project.openshift.io/v1
kind: ProjectRequest
metadata:
  name: l2-bridge-test-bridge-nic-hot-plug

2.
Create a linux-bridge on the cluster workers. This can be done by applying a NodeNetworkConfigurationPolicy like the following:

apiVersion: nmstate.io/v1
kind: NodeNetworkConfigurationPolicy
metadata:
  name: hot-plug-br-nncp
spec:
  desiredState:
    interfaces:
    - bridge:
        options:
          stp:
            enabled: false
        port:
        - name: enp9s0
      ipv4:
        auto-dns: true
        dhcp: true
        enabled: true
      ipv6:
        auto-dns: true
        autoconf: false
        dhcp: false
        enabled: false
      name: hot-plug-br
      state: up
      type: linux-bridge
  nodeSelector:
    node-role.kubernetes.io/worker: ""

3.
Create a NetworkAttachmentDefinition that connects to the linux-bridge:
apiVersion: k8s.cni.cncf.io/v1
kind: NetworkAttachmentDefinition
metadata:
  name: hot-plug-br-nad
  namespace: l2-bridge-test-bridge-nic-hot-plug
spec:
  config: '{"name": "hot-plug-br", "plugins": [{"type": "bridge", "bridge": "hot-plug-br"}],
    "cniVersion": "0.3.1"}'

4.
Create a simple fedora VM. You can use the attached vm-for-hot-plug.yaml, which is created without any secondary interface.

5.
Start the created VM (virtctl start hot-plug-test-vm).

6.
After the VM is up and running - hot-plug an interface to it (the interface is supposed to be backed by the bridge node interface you created, via the NAD).
This can be done by editing the *VM* (not VMI) spec and adding the following:
spec:
  template:
    spec:
      domain:
        devices:
          interfaces:
          - bridge: {}
            name: hot-plug-iface
      networks:
      - multus:                                                                                                                                                                                                                                               
          networkName: hot-plug-br-nad
        name: hot-plug-iface

7.
Check {.status.conditions} in the VM spec.

A `RestartRequired` condition was added:
  {
    "lastProbeTime": null,
    "lastTransitionTime": "2025-03-19T16:02:37Z",
    "message": "a non-live-updatable field was changed in the template spec",
    "status": "True",
    "type": "RestartRequired"
  }

Restart is not required to complete the hot-plug, thus this condition shouldn't be there.

For QE: For verifying - you can run the *setup* steps of `test_vmi_spec_updated_with_hot_plugged_interface`, and check the conditions in the VM spec (not VMI).