vmm: vm: Factorize the KVM setup code

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

vmm/src/vm.rs

@@ -251,12 +251,7 @@ pub struct Vm {
 }
 
 impl Vm {
-    pub fn new(
+    fn kvm_new() -> Result<(Kvm, Arc<VmFd>)> {
-        config: Arc<Mutex<VmConfig>>,
-        exit_evt: EventFd,
-        reset_evt: EventFd,
-        vmm_path: PathBuf,
-    ) -> Result<Self> {
         let kvm = Kvm::new().map_err(Error::KvmNew)?;
 
         // Check required capabilities:
@@ -272,14 +267,6 @@ impl Vm {
             return Err(Error::CapabilityMissing(Cap::SplitIrqchip));
         }
 
-        let kernel = File::open(&config.lock().unwrap().kernel.as_ref().unwrap().path)
-            .map_err(Error::KernelFile)?;
-
-        let initramfs = match &config.lock().unwrap().initramfs {
-            Some(initramfs) => Some(File::open(&initramfs.path).map_err(Error::InitramfsFile)?),
-            None => None,
-        };
-
         let fd: VmFd;
         loop {
             match kvm.create_vm() {
@@ -303,7 +290,6 @@ impl Vm {
         fd.set_tss_address(arch::x86_64::layout::KVM_TSS_ADDRESS.raw_value() as usize)
             .map_err(Error::VmSetup)?;
 
-        let mut cpuid_patches = Vec::new();
         // Create split irqchip
         // Only the local APIC is emulated in kernel, both PICs and IOAPIC
         // are not.
@@ -312,6 +298,31 @@ impl Vm {
         cap.args[0] = ioapic::NUM_IOAPIC_PINS as u64;
         fd.enable_cap(&cap).map_err(Error::VmSetup)?;
 
+        Ok((kvm, fd))
+    }
+
+    pub fn new(
+        config: Arc<Mutex<VmConfig>>,
+        exit_evt: EventFd,
+        reset_evt: EventFd,
+        vmm_path: PathBuf,
+    ) -> Result<Self> {
+        let (kvm, fd) = Vm::kvm_new()?;
+
+        let kernel = File::open(&config.lock().unwrap().kernel.as_ref().unwrap().path)
+            .map_err(Error::KernelFile)?;
+
+        let initramfs = config
+            .lock()
+            .unwrap()
+            .initramfs
+            .as_ref()
+            .map(|i| File::open(&i.path))
+            .transpose()
+            .map_err(Error::InitramfsFile)?;
+
+        let mut cpuid_patches = Vec::new();
+
         // Patch tsc deadline timer bit
         cpuid_patches.push(cpu::CpuidPatch {
             function: 1,