arch: CpuProfile enum

Introduce a CpuProfile enum that will be deserialized from the user's
selected CPU profile.

Currently we only have a "host" variant, but in the future there will
be a build script automatically constructing this enum based on
pre-generated CPU profiles.

Signed-off-by: Oliver Anderson <oliver.anderson@cyberus-technology.de>
On-behalf-of: SAP oliver.anderson@sap.com

arch/src/lib.rs

@@ -9,9 +9,11 @@
 //! Supported platforms: x86_64, aarch64, riscv64.
 
 use std::collections::BTreeMap;
+use std::str::FromStr;
 use std::sync::Arc;
 use std::{fmt, result};
 
+use serde::de::IntoDeserializer;
 use serde::{Deserialize, Serialize};
 use thiserror::Error;
 
@@ -53,6 +55,26 @@ pub enum Error {
 /// Type for returning public functions outcome.
 pub type Result<T> = result::Result<T, Error>;
 
+// If the target_arch is x86_64 we import CpuProfile from the x86_64 module, otherwise we
+// declare it here with only "host" as a selectable CPU profile. This trick is useful to prevent
+// excessive conditional compilation throughout the codebase.
+#[cfg(not(target_arch = "x86_64"))]
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+/// A [`CpuProfile`] is a mechanism for ensuring live migration compatibility
+/// between host's with potentially different CPU models.
+pub enum CpuProfile {
+    #[default]
+    Host,
+}
+
+// Note that this trait impl is architecture agnostic and may thus reside here.
+impl FromStr for CpuProfile {
+    type Err = serde::de::value::Error;
+    fn from_str(s: &str) -> result::Result<Self, Self::Err> {
+        Self::deserialize(s.into_deserializer())
+    }
+}
+
 /// Type for memory region types.
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Serialize, Deserialize)]
 pub enum RegionType {
@@ -100,8 +122,9 @@ pub mod x86_64;
 #[cfg(target_arch = "x86_64")]
 pub use x86_64::{
     _NSIG, CpuidConfig, CpuidFeatureEntry, EntryPoint, arch_memory_regions, configure_system,
-    configure_vcpu, generate_common_cpuid, generate_ram_ranges, get_host_cpu_phys_bits,
-    initramfs_load_addr, layout, layout::CMDLINE_MAX_SIZE, layout::CMDLINE_START, regs,
+    configure_vcpu, cpu_profile::CpuProfile, generate_common_cpuid, generate_ram_ranges,
+    get_host_cpu_phys_bits, initramfs_load_addr, layout, layout::CMDLINE_MAX_SIZE,
+    layout::CMDLINE_START, regs,
 };
 
 /// Safe wrapper for `sysconf(_SC_PAGESIZE)`.

arch/src/x86_64/cpu_profile/mod.rs

@@ -4,3 +4,13 @@
 //
 
 pub mod cpuid_adjustments;
+
+// TODO: Auto generate the CpuProfile enum with a build script once we introduce user facing CPU profiles.
+
+/// A [`CpuProfile`] is a mechanism for ensuring live migration compatibility
+/// between hosts with potentially different CPU models.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+pub enum CpuProfile {
+    #[default]
+    Host,
+}