vmm: Add a VM stop method

In order to transfer the control loop to a separate VMM thread, we want
to shrink the VM control loop to a bare minimum.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

vmm/src/lib.rs

@@ -25,6 +25,9 @@ pub enum Error {
 
     /// Cannot start a VM.
     VmStart(vm::Error),
+
+    /// Cannot stop a VM.
+    VmStop(vm::Error),
 }
 pub type Result<T> = result::Result<T, Error>;
 
@@ -35,6 +38,7 @@ impl Display for Error {
         match self {
             VmNew(e) => write!(f, "Can not create a new virtual machine: {:?}", e),
             VmStart(e) => write!(f, "Can not start a new virtual machine: {:?}", e),
+            VmStop(e) => write!(f, "Can not stop a virtual machine: {:?}", e),
         }
     }
 }
@@ -44,9 +48,12 @@ pub fn start_vm_loop(config: Arc<VmConfig>) -> Result<()> {
         let mut vm = Vm::new(config.clone()).map_err(Error::VmNew)?;
 
         if vm.start().map_err(Error::VmStart)? == ExitBehaviour::Shutdown {
+            vm.stop().map_err(Error::VmStop)?;
             break;
         }
 
+        vm.stop().map_err(Error::VmStop)?;
+
         #[cfg(not(feature = "acpi"))]
         break;
     }

vmm/src/vm.rs

@@ -909,6 +909,10 @@ impl Vm {
             }
         }
 
+        Ok(exit_behaviour)
+    }
+
+    pub fn stop(&mut self) -> Result<()> {
         if self.on_tty {
             // Don't forget to set the terminal in canonical mode
             // before to exit.
@@ -941,7 +945,7 @@ impl Vm {
             thread.join().map_err(|_| Error::ThreadCleanup)?
         }
 
-        Ok(exit_behaviour)
+        Ok(())
     }
 
     fn os_signal_handler(signals: Signals, console_input_clone: Arc<Console>) {