Add a hypervisor constant for migration support

This variable can be used by other tools to determine in a generic way
whether a given hypervisor supports migration or not.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

lib/hypervisor/hv_base.py

@@ -101,10 +101,14 @@ class BaseHypervisor(object):
           - a function to check for parameter validity on the remote node,
             in the L{ValidateParameters} function
           - an error message for the above function
+  @type CAN_MIGRATE: boolean
+  @cvar CAN_MIGRATE: whether this hypervisor can do migration (either
+      live or non-live)
 
   """
   PARAMETERS = {}
   ANCILLARY_FILES = []
+  CAN_MIGRATE = False
 
   def __init__(self):
     pass

lib/hypervisor/hv_fake.py

@@ -40,6 +40,8 @@ class FakeHypervisor(hv_base.BaseHypervisor):
   a real virtualisation software installed.
 
   """
+  CAN_MIGRATE = True
+
   _ROOT_DIR = constants.RUN_DIR + "/ganeti-fake-hypervisor"
 
   def __init__(self):

lib/hypervisor/hv_kvm.py

@@ -44,6 +44,7 @@ from ganeti.hypervisor import hv_base
 
 class KVMHypervisor(hv_base.BaseHypervisor):
   """KVM hypervisor interface"""
+  CAN_MIGRATE = True
 
   _ROOT_DIR = constants.RUN_GANETI_DIR + "/kvm-hypervisor"
   _PIDS_DIR = _ROOT_DIR + "/pid" # contains live instances pids

lib/hypervisor/hv_xen.py

@@ -39,6 +39,7 @@ class XenHypervisor(hv_base.BaseHypervisor):
   all the functionality that is identical for both.
 
   """
+  CAN_MIGRATE = True
   REBOOT_RETRY_COUNT = 60
   REBOOT_RETRY_INTERVAL = 10