vmm: Remove all Weak references from CpuManager

Now that the BusDevice devices are stored as Weak references by the
IO and MMIO buses, there's no need to use Weak references from the
CpuManager anymore.

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

vmm/src/cpu.rs

@@ -20,7 +20,7 @@ use libc::{c_void, siginfo_t};
 use std::cmp;
 use std::os::unix::thread::JoinHandleExt;
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::sync::{Arc, Barrier, Mutex, Weak};
+use std::sync::{Arc, Barrier, Mutex};
 use std::thread;
 use std::{fmt, io, result};
 use vm_device::{Migratable, MigratableError, Pausable, Snapshotable};
@@ -372,7 +372,7 @@ impl Vcpu {
 pub struct CpuManager {
     boot_vcpus: u8,
     max_vcpus: u8,
-    io_bus: Weak<devices::Bus>,
+    io_bus: Arc<devices::Bus>,
     mmio_bus: Arc<devices::Bus>,
     ioapic: Option<Arc<Mutex<ioapic::Ioapic>>>,
     vm_memory: GuestMemoryAtomic<GuestMemoryMmap>,
@@ -507,7 +507,7 @@ impl CpuManager {
         let cpu_manager = Arc::new(Mutex::new(CpuManager {
             boot_vcpus,
             max_vcpus,
-            io_bus: Arc::downgrade(&device_manager.io_bus()),
+            io_bus: device_manager.io_bus(),
             mmio_bus: device_manager.mmio_bus().clone(),
             ioapic: device_manager.ioapic().clone(),
             vm_memory: guest_memory,
@@ -531,8 +531,6 @@ impl CpuManager {
             .lock()
             .unwrap()
             .io_bus
-            .upgrade()
-            .unwrap()
             .insert(cpu_manager.clone(), 0x0cd8, 0xc)
             .map_err(Error::BusError)?;
 
@@ -563,7 +561,7 @@ impl CpuManager {
             let mut vcpu = Vcpu::new(
                 cpu_id,
                 &self.fd,
-                self.io_bus.clone().upgrade().unwrap(),
+                self.io_bus.clone(),
                 self.mmio_bus.clone(),
                 ioapic,
                 creation_ts,