Configure CPU models¶

You can configure CPU models for your virtual machines at both the cluster level and individual VM level. Set a cluster-wide default CPU model to automatically apply to all new VMs, or configure a specific CPU model for individual VMs to override the cluster default.

Configure the default CPU model¶

Use the defaultCPUModel setting in the HyperConverged custom resource (CR) to define a cluster-wide default CPU model.

When you set a cluster-wide default CPU model:

• Every new virtual machine (VM) that does not have an explicit CPU model defined receives a node selector for the chosen CPU model.
• Only nodes labeled with cpu-model.node.kubevirt.io/<cpuModel> are eligible to run VMs using the default model.
• Nodes that do not support the selected CPU model are not considered during VM scheduling.

A CPU model configured at the VM level always takes precedence over the cluster-wide default CPU model.

Prerequisites

• Install the OpenShift CLI (oc).

Procedure

1. Open the HyperConverged CR by running the following command:
   terminal

   $ oc edit hyperconvergeds.v1beta1.hco.kubevirt.io kubevirt-hyperconverged -n openshift-cnv

2. Add the defaultCPUModel field to the CR and set the value to the name of a CPU model that exists in the cluster:
   yaml

   apiVersion: hco.kubevirt.io/v1beta1
   kind: HyperConverged
   metadata:
    name: kubevirt-hyperconverged
    namespace: openshift-cnv
   spec:
     defaultCPUModel: "EPYC-IBPB"

   where:

   EPYC-IBPB

   Specifies a CPU model that is supported by nodes in your cluster.

3. Apply the YAML file to your cluster.

Configure a CPU model per-VM¶

You can specify a named CPU model in the virtual machine (VM) specification. This per-VM configuration takes precedence over any cluster-wide default CPU model.

The VM CPU model depends on the availability of CPU models within the VM and the cluster.

• If the VM does not have a defined CPU model, the defaultCPUModel is automatically set using the CPU model defined at the cluster-wide level.
• If both the VM and the cluster have a defined CPU model, the VM’s CPU model takes precedence.
• If neither the VM nor the cluster have a defined CPU model, the host-model is automatically set using the CPU model defined at the host level.

Prerequisites

• Install the OpenShift CLI (oc).

Procedure

1. To configure a named CPU model for a specific VM, edit the VirtualMachine custom resource (CR):
   yaml

   apiVersion: kubevirt.io/v1
   kind: VirtualMachine
   metadata:
     name: myvm
   spec:
     template:
       spec:
         domain:
           cpu:
             model: Conroe

   • spec.template.spec.domain.cpu.model defines the named CPU model for the VM.
2. Apply the CR to your cluster.