KVM: split KVM runtime generation and startup

Before we used to generate the kvm command line and then just run it.
With this patch we split the generation from the time it is run,
allowing us to save it and replay it at reboot.

We must take special care about instance nics:
  - We can't include them in the saved command line, as they point to
    temporary files
  - We can't just generate them at exec time, because we would apply
    those changes, but not all the other ones, to a running instance,
    thus making it inconsistent (for example if an instance had a memory
    increased and one more nic, in a soft reboot we would add the nic, but
    not the memory)
So we'll just save the instance nic data at the time the kvm runtime
data is generated, and transform it into actual parameters at execution
time.

Reviewed-by: iustinp

diff --git a/lib/hypervisor/hv_kvm.py b/lib/hypervisor/hv_kvm.py
index a205ae4..4d999f1 100644 (file)
--- a/lib/hypervisor/hv_kvm.py
+++ b/lib/hypervisor/hv_kvm.py
@@ -178,16 +178,11 @@ class KVMHypervisor(hv_base.BaseHypervisor):
 
     return data
 
-  def StartInstance(self, instance, block_devices, extra_args):
-    """Start an instance.
+  def _GenerateKVMRuntime(self, instance, block_devices, extra_args):
+    """Generate KVM information to start an instance.
 
     """
-    temp_files = []
     pidfile = self._PIDS_DIR + "/%s" % instance.name
-    if utils.IsProcessAlive(utils.ReadPidFile(pidfile)):
-      raise errors.HypervisorError("Failed to start instance %s: %s" %
-                                   (instance.name, "already running"))
-
     kvm = constants.KVM_PATH
     kvm_cmd = [kvm]
     kvm_cmd.extend(['-m', instance.beparams[constants.BE_MEMORY]])
@@ -198,18 +193,6 @@ class KVMHypervisor(hv_base.BaseHypervisor):
     kvm_cmd.extend(['-daemonize'])
     if not instance.hvparams[constants.HV_ACPI]:
       kvm_cmd.extend(['-no-acpi'])
-    if not instance.nics:
-      kvm_cmd.extend(['-net', 'none'])
-    else:
-      nic_seq = 0
-      for nic in instance.nics:
-        script = self._WriteNetScript(instance, nic_seq, nic)
-        # FIXME: handle other models
-        nic_val = "nic,macaddr=%s,model=virtio" % nic.mac
-        kvm_cmd.extend(['-net', nic_val])
-        kvm_cmd.extend(['-net', 'tap,script=%s' % script])
-        temp_files.append(script)
-        nic_seq += 1
 
     boot_drive = True
     for cfdev, dev_path in block_devices:
@@ -248,6 +231,35 @@ class KVMHypervisor(hv_base.BaseHypervisor):
     serial_dev = 'unix:%s,server,nowait' % self._InstanceSerial(instance.name)
     kvm_cmd.extend(['-serial', serial_dev])
 
+    # Save the current instance nics, but defer their expansion as parameters,
+    # as we'll need to generate executable temp files for them.
+    kvm_nics = instance.nics
+
+    return (kvm_cmd, kvm_nics)
+
+  def _ExecuteKVMRuntime(self, instance, kvm_runtime):
+    """Execute a KVM cmd, after completing it with some last minute data
+
+    """
+    pidfile = self._PIDS_DIR + "/%s" % instance.name
+    if utils.IsProcessAlive(utils.ReadPidFile(pidfile)):
+      raise errors.HypervisorError("Failed to start instance %s: %s" %
+                                   (instance.name, "already running"))
+
+    temp_files = []
+
+    kvm_cmd, kvm_nics = kvm_runtime
+
+    if not kvm_nics:
+      kvm_cmd.extend(['-net', 'none'])
+    else:
+      for nic_seq, nic in enumerate(kvm_nics):
+        nic_val = "nic,macaddr=%s,model=virtio" % nic.mac
+        script = self._WriteNetScript(instance, nic_seq, nic)
+        kvm_cmd.extend(['-net', nic_val])
+        kvm_cmd.extend(['-net', 'tap,script=%s' % script])
+        temp_files.append(script)
+
     result = utils.RunCmd(kvm_cmd)
     if result.failed:
       raise errors.HypervisorError("Failed to start instance %s: %s (%s)" %
@@ -261,6 +273,18 @@ class KVMHypervisor(hv_base.BaseHypervisor):
     for filename in temp_files:
       utils.RemoveFile(filename)
 
+  def StartInstance(self, instance, block_devices, extra_args):
+    """Start an instance.
+
+    """
+    pidfile = self._PIDS_DIR + "/%s" % instance.name
+    if utils.IsProcessAlive(utils.ReadPidFile(pidfile)):
+      raise errors.HypervisorError("Failed to start instance %s: %s" %
+                                   (instance.name, "already running"))
+
+    kvm_runtime = self._GenerateKVMRuntime(instance, block_devices, extra_args)
+    self._ExecuteKVMRuntime(instance, kvm_runtime)
+
   def StopInstance(self, instance, force=False):
     """Stop an instance.