The node-labeller will only label a node with Skylake, Cascadelake or Icelake CPUs if the Node CPU has 'mpx' feature. This is incorrect, as not every model of those CPUs has this feature, MPX has been long deprecated and removed, even from the Linux kernel and QEMU. Also see https://www.phoronix.com/news/Intel-MPX-Is-Dead.

The code that is doing this is [1]. It expects all features from /usr/share/libvirt/cpu_map/[CPU Model].xml to be present on the node CPU in order to label it. This is incorrect, some features may be missing, such as MPX.

According to the libvirt team, in [2], kubevirt should not even be reading /usr/share/libvirt/cpu_map/[CPU Model].xml, so this logic shouldn't exist and better ways to determine the CPU model should be used. Also, some flags may be missing, sometimes microcode updates disable features due to security flaws and other reasons, MPX is not the first and likely won't be the last edge case.

4.14, 4.13 (probably all)

Always

$ ssh core@blue.shift.home.arpa cat /proc/cpuinfo | grep mpx
$ 
$ ssh core@blue.shift.home.arpa cat /proc/cpuinfo | grep name | head -n 1
model name	: 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz

$ oc get node blue.shift.home.arpa -o yaml | grep cpu-model.node
    cpu-model.node.kubevirt.io/Broadwell-noTSX: "true"
    cpu-model.node.kubevirt.io/Broadwell-noTSX-IBRS: "true"
    cpu-model.node.kubevirt.io/Haswell-noTSX: "true"
    cpu-model.node.kubevirt.io/Haswell-noTSX-IBRS: "true"
    cpu-model.node.kubevirt.io/IvyBridge: "true"
    cpu-model.node.kubevirt.io/IvyBridge-IBRS: "true"
    cpu-model.node.kubevirt.io/Nehalem: "true"
    cpu-model.node.kubevirt.io/Nehalem-IBRS: "true"
    cpu-model.node.kubevirt.io/Opteron_G1: "true"
    cpu-model.node.kubevirt.io/Penryn: "true"
    cpu-model.node.kubevirt.io/SandyBridge: "true"
    cpu-model.node.kubevirt.io/SandyBridge-IBRS: "true"
    cpu-model.node.kubevirt.io/Westmere: "true"
    cpu-model.node.kubevirt.io/Westmere-IBRS: "true"

$ oc rsh virt-launcher-rhvm-mfd6f virsh domcapabilities | grep -E 'Cascade|Sky' | grep yes
      <model usable='yes' vendor='Intel'>Skylake-Server-noTSX-IBRS</model>
      <model usable='yes' vendor='Intel'>Skylake-Client-noTSX-IBRS</model>
      <model usable='yes' vendor='Intel'>Cascadelake-Server-noTSX</model>

{"component":"virt-handler","level":"warning","msg":"CPU model Skylake-Server-noTSX-IBRS is missing required feature mpx","pos":"node_labeller.go:414","timestamp":"2024-01-19T00:24:35.332857Z"}
{"component":"virt-handler","level":"warning","msg":"CPU model Skylake-Client-noTSX-IBRS is missing required feature mpx","pos":"node_labeller.go:414","timestamp":"2024-01-19T00:24:35.332885Z"}
{"component":"virt-handler","level":"warning","msg":"CPU model Opteron_G2 is missing required feature svm","pos":"node_labeller.go:414","timestamp":"2024-01-19T00:24:35.332923Z"}
{"component":"virt-handler","level":"warning","msg":"CPU model Cascadelake-Server-noTSX is missing required feature mpx","pos":"node_labeller.go:414","timestamp":"2024-01-19T00:24:35.332973Z"}
{"component":"virt-handler","level":"warning","msg":"CPU model Skylake-Server-noTSX-IBRS is missing required feature mpx","pos":"node_labeller.go:414","timestamp":"2024-01-19T00:24:35.337136Z"}
{"component":"virt-handler","level":"warning","msg":"CPU model Skylake-Client-noTSX-IBRS is missing required feature mpx","pos":"node_labeller.go:414","timestamp":"2024-01-19T00:24:35.337173Z"}
{"component":"virt-handler","level":"warning","msg":"CPU model Opteron_G2 is missing required feature svm","pos":"node_labeller.go:414","timestamp":"2024-01-19T00:24:35.337210Z"}
{"component":"virt-handler","level":"warning","msg":"CPU model Cascadelake-Server-noTSX is missing required feature mpx","pos":"node_labeller.go:414","timestamp":"2024-01-19T00:24:35.337262Z"}

Node is missing Skylake, Cascadelake and Icelake Labels
Customer cannot expose these models to VMs.

Nodes are correctly labeled with CPUs it supports.