arch, vmm: Pass cpu topology configuation to FDT

In an Arm system, the hierarchy of CPUs is defined through three
entities that are used to describe the layout of physical CPUs in
the system:

- cluster
- core
- thread

All these three entities have their own FDT node field. Therefore,
This commit adds an AArch64-specific helper to pass the config from
the Cloud Hypervisor command line to the `configure_system`, where
eventually the `create_fdt` is called.

Signed-off-by: Henry Wang <Henry.Wang@arm.com>

vmm/src/cpu.rs

@@ -978,6 +978,14 @@ impl CpuManager {
             .collect()
     }
 
+    #[cfg(target_arch = "aarch64")]
+    pub fn get_vcpu_topology(&self) -> Option<(u8, u8, u8)> {
+        self.config
+            .topology
+            .clone()
+            .map(|t| (t.threads_per_core, t.cores_per_die, t.packages))
+    }
+
     #[cfg(feature = "acpi")]
     pub fn create_madt(&self) -> Sdt {
         use crate::acpi;

vmm/src/vm.rs

@@ -1072,6 +1072,7 @@ impl Vm {
     fn configure_system(&mut self) -> Result<()> {
         let cmdline_cstring = self.get_cmdline()?;
         let vcpu_mpidrs = self.cpu_manager.lock().unwrap().get_mpidrs();
+        let vcpu_topology = self.cpu_manager.lock().unwrap().get_vcpu_topology();
         let mem = self.memory_manager.lock().unwrap().boot_guest_memory();
         let initramfs_config = match self.initramfs {
             Some(_) => Some(self.load_initramfs(&mem)?),
@@ -1129,6 +1130,7 @@ impl Vm {
             &mem,
             &cmdline_cstring,
             vcpu_mpidrs,
+            vcpu_topology,
             device_info,
             &initramfs_config,
             &pci_space,
@@ -2653,6 +2655,7 @@ mod tests {
             &mem,
             &CString::new("console=tty0").unwrap(),
             vec![0],
+            Some((0, 0, 0)),
             &dev_info,
             &*gic,
             &None,