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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.
note

The defaultCPUModel is case sensitive and must match a CPU model supported by nodes in your cluster.

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:

    $ 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:

    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):

    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.