acpi: Enable DSDT for CpuManager on AArch64

Simplified definition block of CPU's on AArch64. It is not complete yet.
Guest boots. But more is to do in future:
- Fix the error in ACPI definition blocks (seen in boot messages)
- Implement CPU hot-plug controller

Signed-off-by: Michael Zhao <michael.zhao@arm.com>

vmm/src/cpu.rs

@@ -132,7 +132,7 @@ pub enum Error {
 }
 pub type Result<T> = result::Result<T, Error>;
 
-#[cfg(feature = "acpi")]
+#[cfg(all(target_arch = "x86_64", feature = "acpi"))]
 #[repr(packed)]
 struct LocalApic {
     pub r#type: u8,
@@ -394,6 +394,7 @@ pub struct CpuManager {
     seccomp_action: SeccompAction,
     vmmops: Arc<Box<dyn VmmOps>>,
     #[cfg(feature = "acpi")]
+    #[cfg_attr(target_arch = "aarch64", allow(dead_code))]
     acpi_address: GuestAddress,
 }
 
@@ -1260,12 +1261,13 @@ struct Cpu {
     cpu_id: u8,
 }
 
-#[cfg(feature = "acpi")]
+#[cfg(all(target_arch = "x86_64", feature = "acpi"))]
 const MADT_CPU_ENABLE_FLAG: usize = 0;
 
 #[cfg(feature = "acpi")]
-impl Aml for Cpu {
+impl Cpu {
-    fn to_aml_bytes(&self) -> Vec<u8> {
+    #[cfg(target_arch = "x86_64")]
+    fn generate_mat(&self) -> Vec<u8> {
         let lapic = LocalApic {
             r#type: 0,
             length: 8,
@@ -1278,11 +1280,22 @@ impl Aml for Cpu {
         mat_data.resize(std::mem::size_of_val(&lapic), 0);
         unsafe { *(mat_data.as_mut_ptr() as *mut LocalApic) = lapic };
 
+        mat_data
+    }
+}
+
+#[cfg(feature = "acpi")]
+impl Aml for Cpu {
+    fn to_aml_bytes(&self) -> Vec<u8> {
+        #[cfg(target_arch = "x86_64")]
+        let mat_data: Vec<u8> = self.generate_mat();
+
         aml::Device::new(
             format!("C{:03}", self.cpu_id).as_str().into(),
             vec![
                 &aml::Name::new("_HID".into(), &"ACPI0007"),
                 &aml::Name::new("_UID".into(), &self.cpu_id),
+                // Currently, AArch64 cannot support following fields.
                 /*
                 _STA return value:
                 Bit [0] – Set if the device is present.
@@ -1292,6 +1305,7 @@ impl Aml for Cpu {
                 Bit [4] – Set if the battery is present.
                 Bits [31:5] – Reserved (must be cleared).
                 */
+                #[cfg(target_arch = "x86_64")]
                 &aml::Method::new(
                     "_STA".into(),
                     0,
@@ -1305,8 +1319,10 @@ impl Aml for Cpu {
                 // The Linux kernel expects every CPU device to have a _MAT entry
                 // containing the LAPIC for this processor with the enabled bit set
                 // even it if is disabled in the MADT (non-boot CPU)
+                #[cfg(target_arch = "x86_64")]
                 &aml::Name::new("_MAT".into(), &aml::Buffer::new(mat_data)),
                 // Trigger CPU ejection
+                #[cfg(target_arch = "x86_64")]
                 &aml::Method::new(
                     "_EJ0".into(),
                     1,
@@ -1467,6 +1483,7 @@ impl Aml for CpuManager {
     fn to_aml_bytes(&self) -> Vec<u8> {
         let mut bytes = Vec::new();
         // CPU hotplug controller
+        #[cfg(target_arch = "x86_64")]
         bytes.extend_from_slice(
             &aml::Device::new(
                 "_SB_.PRES".into(),