KubeDescheduler is an optional operator that can be installed also on clusters with KubeVirt.
If installed on the cluster, its configuration should be tuned for KubeVirt enabling an alpha feature.

KubeDescheduler operator can only be configured via a CR of kind KubeDescheduler named cluster in namespace openshift-kube-descheduler-operator.
HCO will monitor it and it will eventually raise MisconfiguredDescheduler alert if the descheduler is not properly configured.
The linked runbook should instruct the cluster admin to merge something like:

apiVersion: operator.openshift.io/v1
kind: KubeDescheduler
metadata:
  name: cluster
  namespace: openshift-kube-descheduler-operator
spec:
  profileCustomizations:
    devEnableEvictionsInBackground: true