Clarify supported CPU models for CPU templates

.buildkite/pipeline_cpu_template.py

@@ -70,7 +70,6 @@ class BkStep(str, Enum):
             "m5n.metal",
             "m6i.metal",
             "m6a.metal",
-            "m7a.metal-48xl",
         ],
     },
 }

CHANGELOG.md

@@ -26,6 +26,10 @@ and this project adheres to
   WAITPKG CPUID bit in CPUID normalization. The feature enables a guest to put a
   physical processor into an idle state, which is undesirable in a FaaS
   environment since that is what the host wants to decide.
+- [#5142](https://github.com/firecracker-microvm/firecracker/pull/5142):
+  Clarified what CPU models are supported by each existing CPU template.
+  Firecracker exits with an error if a CPU template is used on an unsupported
+  CPU model.
 
 ### Deprecated
 

docs/cpu_templates/cpu-templates.md

@@ -48,14 +48,14 @@ Firecracker supports two types of CPU templates:
 
 At the moment the following set of static CPU templates are supported:
 
-| CPU template | CPU vendor | CPU model             |
-| ------------ | ---------- | --------------------- |
-| C3           | Intel      | any                   |
-| T2           | Intel      | any                   |
-| T2A          | AMD        | Milan                 |
-| T2CL         | Intel      | Cascade Lake or newer |
-| T2S          | Intel      | any                   |
-| V1N1         | ARM        | Neoverse V1           |
+| CPU template | CPU vendor | CPU model                       |
+| ------------ | ---------- | ------------------------------- |
+| C3           | Intel      | Skylake, Cascade Lake, Ice Lake |
+| T2           | Intel      | Skylake, Cascade Lake, Ice Lake |
+| T2A          | AMD        | Milan                           |
+| T2CL         | Intel      | Cascade Lake, Ice Lake          |
+| T2S          | Intel      | Skylake, Cascade Lake           |
+| V1N1         | ARM        | Neoverse V1                     |
 
 T2 and C3 templates are mapped as close as possible to AWS T2 and C3 instances
 in terms of CPU features. Note that on a microVM that is lauched with the C3
@@ -71,8 +71,8 @@ a performance assessment if they wish to use the T2S template. Note that
 Firecracker expects the host to always be running the latest version of the
 microcode.
 
-The T2CL template is mapped to be close to Intel Cascade Lake. It is not safe to
-use it on Intel CPUs older than Cascade Lake (such as Skylake).
+The T2CL template is mapped to be close to Intel Cascade Lake. It is only safe
+to use it on Intel Cascade Lake and Ice Lake.
 
 The only AMD template is T2A. It is considered safe to be used with AMD Milan.
 

src/vmm/src/arch/x86_64/cpu_model.rs

@@ -2,7 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use std::arch::x86_64::__cpuid as host_cpuid;
-use std::cmp::{Eq, Ordering, PartialEq, PartialOrd};
+use std::cmp::{Eq, PartialEq};
 
 /// Structure representing x86_64 CPU model.
 #[derive(Debug, Eq, PartialEq)]
@@ -19,6 +19,42 @@ pub struct CpuModel {
     pub stepping: u8,
 }
 
+/// Family / Model / Stepping for Intel Skylake
+pub const SKYLAKE_FMS: CpuModel = CpuModel {
+    extended_family: 0x0,
+    extended_model: 0x5,
+    family: 0x6,
+    model: 0x5,
+    stepping: 0x4,
+};
+
+/// Family / Model / Stepping for Intel Cascade Lake
+pub const CASCADE_LAKE_FMS: CpuModel = CpuModel {
+    extended_family: 0x0,
+    extended_model: 0x5,
+    family: 0x6,
+    model: 0x5,
+    stepping: 0x7,
+};
+
+/// Family / Model / Stepping for Intel Ice Lake
+pub const ICE_LAKE_FMS: CpuModel = CpuModel {
+    extended_family: 0x0,
+    extended_model: 0x6,
+    family: 0x6,
+    model: 0xa,
+    stepping: 0x6,
+};
+
+/// Family / Model / Stepping for AMD Milan
+pub const MILAN_FMS: CpuModel = CpuModel {
+    extended_family: 0xa,
+    extended_model: 0x0,
+    family: 0xf,
+    model: 0x1,
+    stepping: 0x1,
+};
+
 impl CpuModel {
     /// Get CPU model from current machine.
     pub fn get_cpu_model() -> Self {
@@ -27,19 +63,6 @@ impl CpuModel {
         let eax = unsafe { host_cpuid(0x1) }.eax;
         CpuModel::from(&eax)
     }
-
-    /// Check if the current CPU model is Intel Cascade Lake or later.
-    pub fn is_at_least_cascade_lake(&self) -> bool {
-        let cascade_lake = CpuModel {
-            extended_family: 0,
-            extended_model: 5,
-            family: 6,
-            model: 5,
-            stepping: 7,
-        };
-
-        self >= &cascade_lake
-    }
 }
 
 impl From<&u32> for CpuModel {
@@ -54,59 +77,22 @@ impl From<&u32> for CpuModel {
     }
 }
 
-impl From<&CpuModel> for u32 {
-    fn from(cpu_model: &CpuModel) -> Self {
-        (u32::from(cpu_model.extended_family) << 20)
-            | (u32::from(cpu_model.extended_model) << 16)
-            | (u32::from(cpu_model.family) << 8)
-            | (u32::from(cpu_model.model) << 4)
-            | u32::from(cpu_model.stepping)
-    }
-}
-
-impl PartialOrd for CpuModel {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        Some(u32::from(self).cmp(&u32::from(other)))
-    }
-}
-
-impl Ord for CpuModel {
-    fn cmp(&self, other: &Self) -> Ordering {
-        u32::from(self).cmp(&u32::from(other))
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
 
-    const SKYLAKE: CpuModel = CpuModel {
-        extended_family: 0,
-        extended_model: 5,
-        family: 6,
-        model: 5,
-        stepping: 4,
-    };
-
-    const CASCADE_LAKE: CpuModel = CpuModel {
-        extended_family: 0,
-        extended_model: 5,
-        family: 6,
-        model: 5,
-        stepping: 7,
-    };
-
     #[test]
     fn cpu_model_from() {
         let skylake_eax = 0x00050654;
-        assert_eq!(u32::from(&SKYLAKE), skylake_eax);
-        assert_eq!(CpuModel::from(&skylake_eax), SKYLAKE);
-    }
+        assert_eq!(CpuModel::from(&skylake_eax), SKYLAKE_FMS);
 
-    #[test]
-    fn cpu_model_ord() {
-        assert_eq!(SKYLAKE, SKYLAKE);
-        assert!(SKYLAKE < CASCADE_LAKE);
-        assert!(CASCADE_LAKE > SKYLAKE);
+        let cascade_lake_eax = 0x00050657;
+        assert_eq!(CpuModel::from(&cascade_lake_eax), CASCADE_LAKE_FMS);
+
+        let ice_lake_eax = 0x000606a6;
+        assert_eq!(CpuModel::from(&ice_lake_eax), ICE_LAKE_FMS);
+
+        let milan_eax = 0x00a00f11;
+        assert_eq!(CpuModel::from(&milan_eax), MILAN_FMS);
     }
 }

src/vmm/src/arch/x86_64/vcpu.rs

@@ -832,17 +832,6 @@ mod tests {
         (kvm, vm, vcpu)
     }
 
-    fn is_at_least_cascade_lake() -> bool {
-        CpuModel::get_cpu_model()
-            >= (CpuModel {
-                extended_family: 0,
-                extended_model: 5,
-                family: 6,
-                model: 5,
-                stepping: 7,
-            })
-    }
-
     fn create_vcpu_config(
         kvm: &Kvm,
         vcpu: &KvmVcpu,
@@ -915,24 +904,46 @@ mod tests {
         // Test configure while using the T2S template.
         let t2a_res = try_configure(&kvm, &mut vcpu, StaticCpuTemplate::T2A);
 
+        let cpu_model = CpuModel::get_cpu_model();
         match &cpuid::common::get_vendor_id_from_host().unwrap() {
             cpuid::VENDOR_ID_INTEL => {
-                assert!(t2_res);
-                assert!(c3_res);
-                assert!(t2s_res);
-                if is_at_least_cascade_lake() {
-                    assert!(t2cl_res);
-                } else {
-                    assert!(!t2cl_res);
-                }
+                assert_eq!(
+                    t2_res,
+                    StaticCpuTemplate::T2
+                        .get_supported_cpu_models()
+                        .contains(&cpu_model)
+                );
+                assert_eq!(
+                    c3_res,
+                    StaticCpuTemplate::C3
+                        .get_supported_cpu_models()
+                        .contains(&cpu_model)
+                );
+                assert_eq!(
+                    t2s_res,
+                    StaticCpuTemplate::T2S
+                        .get_supported_cpu_models()
+                        .contains(&cpu_model)
+                );
+                assert_eq!(
+                    t2cl_res,
+                    StaticCpuTemplate::T2CL
+                        .get_supported_cpu_models()
+                        .contains(&cpu_model)
+                );
                 assert!(!t2a_res);
             }
             cpuid::VENDOR_ID_AMD => {
                 assert!(!t2_res);
                 assert!(!c3_res);
                 assert!(!t2s_res);
                 assert!(!t2cl_res);
-                assert!(t2a_res);
+                assert_eq!(
+                    t2a_res,
+                    StaticCpuTemplate::T2A
+                        .get_supported_cpu_models()
+                        .contains(&cpu_model)
+                );
             }
             _ => {
                 assert!(!t2_res);

src/vmm/src/cpu_config/test_utils.rs

@@ -9,7 +9,7 @@ use crate::cpu_config::templates::CustomCpuTemplate;
 pub fn get_json_template(filename: &str) -> CustomCpuTemplate {
     let json_path = [
         env!("CARGO_MANIFEST_DIR"),
-        "../../tests/data/static_cpu_templates",
+        "../../tests/data/custom_cpu_templates",
         filename,
     ]
     .iter()