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Managing node labeling for obsolete CPU models

You can schedule a virtual machine (VM) on a node as long as the VM CPU model and policy are supported by the node.

About node labeling for obsolete CPU models

The OpenShift Virtualization Operator uses a predefined list of obsolete CPU models to ensure that a node supports only valid CPU models for scheduled VMs.

By default, the following CPU models are eliminated from the list of labels generated for the node:

Obsolete CPU models 
"486"
Conroe
athlon
core2duo
coreduo
kvm32
kvm64
n270
pentium
pentium2
pentium3
pentiumpro
phenom
qemu32
qemu64

This predefined list is not visible in the HyperConverged CR. You cannot remove CPU models from this list, but you can add to the list by editing the spec.obsoleteCPUs.cpuModels field of the HyperConverged CR.

About node labeling for CPU features

Through the process of iteration, the base CPU features in the minimum CPU model are eliminated from the list of labels generated for the node.

For example:

  • An environment might have two supported CPU models: Penryn and Haswell.

  • If Penryn is specified as the CPU model for minCPU, each base CPU feature for Penryn is compared to the list of CPU features supported by Haswell.

    CPU features supported by Penryn 
    apic
clflush
cmov
cx16
cx8
de
fpu
fxsr
lahf_lm
lm
mca
mce
mmx
msr
mtrr
nx
pae
pat
pge
pni
pse
pse36
sep
sse
sse2
sse4.1
ssse3
syscall
tsc
    CPU features supported by Haswell 
    aes
apic
avx
avx2
bmi1
bmi2
clflush
cmov
cx16
cx8
de
erms
fma
fpu
fsgsbase
fxsr
hle
invpcid
lahf_lm
lm
mca
mce
mmx
movbe
msr
mtrr
nx
pae
pat
pcid
pclmuldq
pge
pni
popcnt
pse
pse36
rdtscp
rtm
sep
smep
sse
sse2
sse4.1
sse4.2
ssse3
syscall
tsc
tsc-deadline
x2apic
xsave

  • If both Penryn and Haswell support a specific CPU feature, a label is not created for that feature. Labels are generated for CPU features that are supported only by Haswell and not by Penryn.

    Node labels created for CPU features after iteration 
    aes
avx
avx2
bmi1
bmi2
erms
fma
fsgsbase
hle
invpcid
movbe
pcid
pclmuldq
popcnt
rdtscp
rtm
sse4.2
tsc-deadline
x2apic
xsave

Configuring obsolete CPU models

You can configure a list of obsolete CPU models by editing the HyperConverged custom resource (CR).

Procedure

  • Edit the HyperConverged custom resource, specifying the obsolete CPU models in the obsoleteCPUs array. For example:

    apiVersion: hco.kubevirt.io/v1beta1
kind: HyperConverged
metadata:
  name: kubevirt-hyperconverged
  namespace: openshift-cnv
spec:
  obsoleteCPUs:
    cpuModels: (1)
      - "<obsolete_cpu_1>"
      - "<obsolete_cpu_2>"
    minCPUModel: "<minimum_cpu_model>" (2)
    1 Replace the example values in the cpuModels array with obsolete CPU models. Any value that you specify is added to a predefined list of obsolete CPU models. The predefined list is not visible in the CR.
    2 Replace this value with the minimum CPU model that you want to use for basic CPU features. If you do not specify a value, Penryn is used by default.