[OSDOCS-16009]: Adding evictionStrategy docs

Author: lahinson

hosted_control_planes/hcp-manage/hcp-manage-virt.adoc

@@ -60,6 +60,8 @@ include::modules/hcp-virt-attach-nvidia-gpus.adoc[leveloffset=+1]
 
 include::modules/hcp-virt-attach-nvidia-gpus-np-api.adoc[leveloffset=+1]
 
+include::modules/hcp-virt-evict-vms.adoc[leveloffset=+1]
+
 include::modules/hcp-topology-spread-constraint.adoc[leveloffset=+1]
 
 [role="_additional-resources"]

modules/hcp-virt-evict-vms.adoc

@@ -0,0 +1,82 @@
+// Module included in the following assemblies:
+//
+// * hosted_control_planes/hcp-manage/hcp-manage-virt.adoc
+
+:_mod-docs-content-type: PROCEDURE
+[id="hcp-virt-evict-vms_{context}"]
+= Evicting KubeVirt virtual machines
+
+In cases where KubeVirt virtual machines (VMs) cannot be live migrated, such as when you use GPU passthrough, the VMs must be evicted at the same time as the `NodePool` resource of the hosted cluster. Otherwise, the compute nodes might be shut down without being drained from the workload. This might also happen when you are upgrading the {VirtProductName} Operator. To achieve a synchronized restart, you can set the `evictionStrategy` parameter on the `hyperconverged` resource to ensure that only VMs that are drained from workloads are rebooted. 
+
+.Procedure
+
+. Enter the following command:
++
+[source,terminal]
+----
+$ oc explain hyperconverged.spec.evictionStrategy
+----
++
+.Example output
+[source,terminal]
+----
+GROUP:      hco.kubevirt.io
+KIND:       HyperConverged
+VERSION:    v1beta1FIELD: evictionStrategy <string>
+ENUM:
+    None
+    LiveMigrate
+    LiveMigrateIfPossible
+    External
+DESCRIPTION:
+    EvictionStrategy defines at the cluster level if the VirtualMachineInstance
+    should be
+    migrated instead of shut-off in case of a node drain. If the
+    VirtualMachineInstance specific
+    field is set it overrides the cluster level one.
+    Allowed values:
+    - `None` no eviction strategy at cluster level.
+    - `LiveMigrate` migrate the VM on eviction; a not live migratable VM with no
+    specific strategy will block the drain of the node util manually evicted.
+    - `LiveMigrateIfPossible` migrate the VM on eviction if live migration is
+    possible, otherwise directly evict.
+    - `External` block the drain, track eviction and notify an external
+    controller.
+    Defaults to LiveMigrate with multiple worker nodes, None on single worker
+    clusters. 
+----
+
+. Patch the `hyperconverged` resource by entering the following command:
++
+[source,terminal]
+----
+$ oc -n openshift-cnv patch hyperconverged kubevirt-hyperconverged \
+  --type=merge \
+  -p '{"spec": {"evictionStrategy": "External"}}'
+----
+
+. Patch the workload update strategy and the workload update methods by entering the following command:
++
+[source,terminal]
+----
+$ oc -n openshift-cnv patch hyperconverged kubevirt-hyperconverged \
+  --type=merge \
+  -p '{"spec": {"workloadUpdateStrategy": {"workloadUpdateMethods": ["LiveMigrate","Evict"]}}}'
+----
++
+Patching to `LiveMigrate` and `Evict` should live migrate VMs if possible and only evict VMs that are not able to be live migrated.
+
+.Verification
+
+* Check whether the patch command was applied properly by entering the following command:
++
+[source,terminal]
+----
+$ oc -n openshift-cnv get hyperconverged kubevirt-hyperconverged -ojsonpath='{.spec.evictionStrategy}'
+----
++
+.Example output
+[source,terminal]
+----
+External
+----