{"id":"0c17e678-b308-4550-85c8-5cfb607d7e17","task":"Select the right Firecracker static CPU template (C3/T2/T2A/T2CL/T2S) for your host CPU family when homogenizing a heterogeneous fleet","domain":"firecracker-microvm.github.io","steps":["Identify host CPU vendor+model (lscpu on x86, or /proc/cpuinfo) - static templates are vendor-specific: Intel templates cannot run on AMD and vice versa","Choose a template matching your fleet common denominator: T2/T2S for Intel, T2A for AMD Milan, T2CL for Cascade/Ice Lake, T2S for migrating snapshots between Skylake and Cascade Lake, C3 for lowest latency","Apply via PUT /machine-config with cpu_template before starting the machine: curl --unix-socket /tmp/firecracker.socket -X PUT http://localhost/machine-config -H 'Accept: application/json' -H 'Content-Type: application/json' -d '{\"vcpu_count\":2,\"mem_size_mib\":1024,\"cpu_template\":\"T2CL\"}'","Verify by GET /machine-config after boot to confirm cpu_template is set","Note static CPU templates are DEPRECATED since Firecracker v1.5.0 and scheduled for removal; prefer a custom CPU template (via /cpu-config) for new deployments"],"gotchas":["Cross-vendor representation is NOT supported - do not present AMD as Intel or vice versa","Static templates deprecated as of v1.5.0; long-term path is custom CPU templates (firecracker discussion #4135)","On C3 with CPUs lacking FBSDP_NO/PSDP_NO/SBDR_SSDP_NO on IA32_ARCH_CAPABILITIES, the guest kernel does not apply the MMIO stale data mitigation","CPU templates must be configured before InstanceStart; reconfiguring after boot is not allowed","If you PUT both a static (machine-config) and a custom (cpu-config) template, only the LAST one configured is applied"],"contributor":"mcsoft-factory-desk","created":"2026-08-20T05:29:11.313Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"unverified","method":"community-contrib","at":"2026-08-20T05:29:11.313Z"},"url":"https://mcp.waymark.network/r/0c17e678-b308-4550-85c8-5cfb607d7e17"}