refactor: move get_manufacturer_id_from_host() to regs.rs

Just make this a method on `Aarch64RegisterVec`, and make it return
`Option`, because there was only a single error case, and the error
message was additionall never displayed because the only call site
ignores errors beyond acknowledging that they happened.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

src/vmm/src/arch/aarch64/regs.rs

@@ -260,6 +260,14 @@ impl Aarch64RegisterVec {
             data: &mut self.data,
         }
     }
+
+    /// Extract the Manufacturer ID from a VCPU state's registers.
+    /// The ID is found between bits 24-31 of MIDR_EL1 register.
+    pub fn manifacturer_id(&self) -> Option<u32> {
+        self.iter()
+            .find(|reg| reg.id == MIDR_EL1)
+            .map(|reg| ((reg.value::<u64, 8>() >> 24) & 0xFF) as u32)
+    }
 }
 
 impl Serialize for Aarch64RegisterVec {

src/vmm/src/arch/aarch64/vcpu.rs

@@ -45,22 +45,6 @@ pub enum VcpuArchError {
     GetMidrEl1(String),
 }
 
-/// Extract the Manufacturer ID from a VCPU state's registers.
-/// The ID is found between bits 24-31 of MIDR_EL1 register.
-///
-/// # Arguments
-///
-/// * `regs` - reference [`Aarch64RegisterVec`] structure with all registers of a VCPU.
-pub fn get_manufacturer_id_from_state(regs: &Aarch64RegisterVec) -> Result<u32, VcpuArchError> {
-    let midr_el1 = regs.iter().find(|reg| reg.id == MIDR_EL1);
-    match midr_el1 {
-        Some(register) => Ok(((register.value::<u64, 8>() >> 24) & 0xFF) as u32),
-        None => Err(VcpuArchError::GetMidrEl1(
-            "Failed to find MIDR_EL1 in vCPU state!".to_string(),
-        )),
-    }
-}
-
 /// Extract the Manufacturer ID from the host.
 /// The ID is found between bits 24-31 of MIDR_EL1 register.
 pub fn get_manufacturer_id_from_host() -> Result<u32, VcpuArchError> {

src/vmm/src/persist.rs

@@ -17,7 +17,7 @@ use userfaultfd::{FeatureFlags, Uffd, UffdBuilder};
 use vmm_sys_util::sock_ctrl_msg::ScmSocket;
 
 #[cfg(target_arch = "aarch64")]
-use crate::arch::aarch64::vcpu::{get_manufacturer_id_from_host, get_manufacturer_id_from_state};
+use crate::arch::aarch64::vcpu::get_manufacturer_id_from_host;
 use crate::builder::{self, BuildMicrovmFromSnapshotError};
 use crate::cpu_config::templates::StaticCpuTemplate;
 #[cfg(target_arch = "x86_64")]
@@ -331,24 +331,24 @@ pub fn validate_cpu_vendor(microvm_state: &MicrovmState) {
 #[cfg(target_arch = "aarch64")]
 pub fn validate_cpu_manufacturer_id(microvm_state: &MicrovmState) {
     let host_cpu_id = get_manufacturer_id_from_host();
-    let snapshot_cpu_id = get_manufacturer_id_from_state(&microvm_state.vcpu_states[0].regs);
+    let snapshot_cpu_id = microvm_state.vcpu_states[0].regs.manifacturer_id();
     match (host_cpu_id, snapshot_cpu_id) {
-        (Ok(host_id), Ok(snapshot_id)) => {
+        (Ok(host_id), Some(snapshot_id)) => {
             info!("Host CPU manufacturer ID: {host_id:?}");
             info!("Snapshot CPU manufacturer ID: {snapshot_id:?}");
             if host_id != snapshot_id {
                 warn!("Host CPU manufacturer ID differs from the snapshotted one",);
             }
         }
-        (Ok(host_id), Err(_)) => {
+        (Ok(host_id), None) => {
             info!("Host CPU manufacturer ID: {host_id:?}");
             warn!("Snapshot CPU manufacturer ID: couldn't get from the snapshot");
         }
-        (Err(_), Ok(snapshot_id)) => {
+        (Err(_), Some(snapshot_id)) => {
             warn!("Host CPU manufacturer ID: couldn't get from the host");
             info!("Snapshot CPU manufacturer ID: {snapshot_id:?}");
         }
-        (Err(_), Err(_)) => {
+        (Err(_), None) => {
             warn!("Host CPU manufacturer ID: couldn't get from the host");
             warn!("Snapshot CPU manufacturer ID: couldn't get from the snapshot");
         }