vmm: Simplify the VM start flow

We can integrate the kernel loading into the VM start method.
The VM start flow is then: Vm::new() -> vm.start(), which feels more
natural.

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

vmm/src/lib.rs

@@ -26,9 +26,6 @@ pub enum Error {
 
     /// Cannot start a VM.
     VmStart(vm::Error),
-
-    /// Cannot load a kernel.
-    LoadKernel(vm::Error),
 }
 pub type Result<T> = result::Result<T, Error>;
 
@@ -39,7 +36,6 @@ 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),
-            LoadKernel(e) => write!(f, "Can not load a guest kernel: {:?}", e),
         }
     }
 }
@@ -60,9 +56,7 @@ pub fn boot_kernel(config: VmConfig) -> Result<()> {
         let vmm = Vmm::new()?;
         let mut vm = Vm::new(&vmm.kvm, &config).map_err(Error::VmNew)?;
 
-        let entry = vm.load_kernel().map_err(Error::LoadKernel)?;
-
-        if vm.start(entry).map_err(Error::VmStart)? == ExitBehaviour::Shutdown {
+        if vm.start().map_err(Error::VmStart)? == ExitBehaviour::Shutdown {
             break;
         }