feat: Add VMSizeProperties support to disable SMT/hyperthreading (rebase of #1419)#1746
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fabioaraujopt wants to merge 1 commit into
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feat: Add VMSizeProperties support to disable SMT/hyperthreading (rebase of #1419)#1746fabioaraujopt wants to merge 1 commit into
fabioaraujopt wants to merge 1 commit into
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This PR adds support for Azure VM vCore Customization feature,
allowing users to disable SMT (Simultaneous Multi-Threading, also
known as hyperthreading) on AKS nodes provisioned by Karpenter.
Changes:
- Add VMSizeProperties field to AKSNodeClassSpec API
- Support vCPUsPerCore configuration (1=SMT disabled, 2=SMT enabled)
- Add validation for vCPUsPerCore range (1-2)
- Update VM creation to apply vmSizeProperties to hardwareProfile
- Add comprehensive unit tests for API validation
- Add tests for VM creation with vmSizeProperties
- Generate updated CRDs with new field
Use case:
This feature is particularly useful for:
- CAE (Computer-Aided Engineering) workloads requiring consistent
performance without SMT overhead
- Security hardening by disabling SMT to mitigate certain CPU
vulnerabilities
- Workloads that benefit from dedicated physical cores
Example usage:
```yaml
apiVersion: karpenter.azure.com/v1beta1
kind: AKSNodeClass
metadata:
name: smt-disabled
spec:
imageFamily: AzureLinux
vmSizeProperties:
vCPUsPerCore: 1 # Disables SMT
```
Requirements:
- VM must support hyperthreading (2 threads per core)
- Can only be set at VM creation time
- Requires Azure API version 2021-07-01 or later
Related documentation:
https://learn.microsoft.com/en-us/azure/virtual-machines/vm-customization
Fixes: Feature request for SMT control in Azure Karpenter
This was referenced Jun 22, 2026
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Fixes #1541
Supersedes #1419
Summary
mainand aligned it with current provider structure.vmSizeProperties.vCPUsPerCoreto bothv1beta1andv1alpha2AKSNodeClassSpec, with validation and regenerated CRD/deepcopy artifacts.VMSizePropertiesonly in VM API (aksscriptless) path; explicitly ignore it for AKS Machine API modes (aksmachineapi,aksmachineapiheaderbatch) with test coverage.Test plan
go test ./pkg/providers/instance -run TestConvertVMSizeProperties -count=1go test ./pkg/apis/v1beta1 -run TestAPIs -count=1 -args -ginkgo.focus=VMSizeProperties(with envtest assets)go test ./pkg/apis/v1alpha2 -run TestAPIs -count=1 -args -ginkgo.focus=VMSizeProperties(with envtest assets)go test ./pkg/apis/v1alpha2 ./pkg/apis/v1beta1 -run '^$' -count=1Notes