vmm: Remove IO bus strong reference from Vm

The Vm structure was used to store a strong reference to the IO bus.
This is not needed anymore since the AddressManager is logically the
one holding this strong reference. This has been made possible by the
introduction of Weak references on the Bus structure itself.

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

vmm/src/device_manager.rs

@@ -474,7 +474,6 @@ impl DeviceManager {
         _exit_evt: &EventFd,
         reset_evt: &EventFd,
         vmm_path: PathBuf,
-        io_bus: &Arc<devices::Bus>,
     ) -> DeviceManagerResult<Arc<Mutex<Self>>> {
         let mut virtio_devices: Vec<(Arc<Mutex<dyn vm_virtio::VirtioDevice>>, bool)> = Vec::new();
         let migratable_devices: Vec<Arc<Mutex<dyn Migratable>>> = Vec::new();
@@ -486,7 +485,7 @@ impl DeviceManager {
 
         let address_manager = Arc::new(AddressManager {
             allocator,
-            io_bus: Arc::clone(io_bus),
+            io_bus: Arc::new(devices::Bus::new()),
             mmio_bus: Arc::new(devices::Bus::new()),
             vm_fd: vm_fd.clone(),
         });

vmm/src/vm.rs

@@ -222,8 +222,6 @@ pub struct Vm {
     state: RwLock<VmState>,
     cpu_manager: Arc<Mutex<cpu::CpuManager>>,
     memory_manager: Arc<Mutex<MemoryManager>>,
-    // Hold the strong reference onto the IO bus.
-    _io_bus: Arc<devices::Bus>,
 }
 
 impl Vm {
@@ -331,8 +329,6 @@ impl Vm {
             .ok_or(Error::CreateSystemAllocator)?,
         ));
 
-        let io_bus = Arc::new(devices::Bus::new());
-
         let memory_config = config.lock().unwrap().memory.clone();
 
         let memory_manager = MemoryManager::new(
@@ -355,7 +351,6 @@ impl Vm {
             &exit_evt,
             &reset_evt,
             vmm_path,
-            &io_bus,
         )
         .map_err(Error::DeviceManager)?;
 
@@ -384,7 +379,6 @@ impl Vm {
             state: RwLock::new(VmState::Created),
             cpu_manager,
             memory_manager,
-            _io_bus: io_bus,
         })
     }