vmm: Move DeviceManager into an Arc<Mutex<>>

In anticipation of the support for device hotplug, this commit moves the
DeviceManager object into an Arc<Mutex<>> when the DeviceManager is
being created. The reason is, we need the DeviceManager to implement the
BusDevice trait and then provide it to the IO bus, so that IO accesses
related to device hotplug can be handled correctly.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/cpu.rs

@@ -494,7 +494,7 @@ impl CpuManager {
     pub fn new(
         boot_vcpus: u8,
         max_vcpus: u8,
-        device_manager: &DeviceManager,
+        device_manager: &Arc<Mutex<DeviceManager>>,
         guest_memory: GuestMemoryAtomic<GuestMemoryMmap>,
         fd: Arc<VmFd>,
         cpuid: CpuId,
@@ -503,6 +503,7 @@ impl CpuManager {
         let mut vcpu_states = Vec::with_capacity(usize::from(max_vcpus));
         vcpu_states.resize_with(usize::from(max_vcpus), VcpuState::default);
 
+        let device_manager = device_manager.lock().unwrap();
         let cpu_manager = Arc::new(Mutex::new(CpuManager {
             boot_vcpus,
             max_vcpus,