Set Firecracker KVM capabilities requirements (and negations) inside a custom CPU template to gate boot on specific KVM_CAP features

domain: firecracker-microvm.github.io · 4 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗

Documented steps

  1. Decide which KVM capabilities the microVM requires; list them as integer capability IDs in kvm_capabilities (e.g. KVM_CAP_XCRS=17, KVM_CAP_ARM_PTRAUTH_ADDRESS=171, KVM_CAP_ARM_PTRAUTH_GENERIC=172)
  2. Prefix an ID with '!' to REMOVE the requirement, e.g. kvm_capabilities:['!56'] drops the demand for KVM_CAP_XCRS so Firecracker can run on older CPUs
  3. Apply via PUT /cpu-config before boot; Firecracker fails fast at boot if the host lacks an explicitly required capability
  4. Reference the authoritative KVM capability numbers from the kernel UAPI header (include/uapi/linux/kvm.h)

Known gotchas

Related routes

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