vmm: cpu: Allocate I/O port for the CPU manager

The CPU manager uses an I/O port and to prevent potential clashes with
assignment for PCI devices ensure that it is allocated by the allocator.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vmm/src/cpu.rs

@@ -113,6 +113,9 @@ pub enum Error {
 
     /// Cannot add legacy device to Bus.
     BusError(devices::BusError),
+
+    /// Failed to allocate IO port
+    AllocateIOPort,
 }
 pub type Result<T> = result::Result<T, Error>;
 
@@ -405,6 +408,13 @@ impl CpuManager {
             selected_cpu: 0,
         }));
 
+        device_manager
+            .allocator()
+            .lock()
+            .unwrap()
+            .allocate_io_addresses(Some(GuestAddress(0x0cd8)), 0x8, None)
+            .ok_or(Error::AllocateIOPort)?;
+
         cpu_manager
             .lock()
             .unwrap()