xapi: Fix live block migration

Fixes bug 1040332.

Xapi VM.migrate_send and VM.assert_can_migrate calls require that
vdi_map parameter is a (source_vdi_ref -> target_sr_ref) mapping, for block
live migration to work, as of XenServer 6.0 RC1.

On the destination side:
This fix modifies the check_can_live_migrate_destination call, so that the
value returned contains the "destination_sr_ref" (XenAPI specific data is
stored under the "migrate_send_data key").

On the source side:
check_can_live_migrate_source and live_migrate calls assemble the
vdi_map by mapping all the local sr contained vdis of the VM to
destination_sr_ref, and passing this parameter to the VM.migrate_send and
VM.assert_can_migrate Xapi calls.

Change-Id: I95f3dca651d2e72fc727646580092a25f558d6ba

nova/tests/xenapi/test_vm_utils.py

@@ -0,0 +1,48 @@
+from nova.tests.xenapi import stubs
+from nova.virt.xenapi import driver as xenapi_conn
+from nova.virt.xenapi import fake
+from nova.virt.xenapi import vm_utils
+
+
+class GetInstanceForVdisForSrTestCase(stubs.XenAPITestBase):
+    def setUp(self):
+        super(GetInstanceForVdisForSrTestCase, self).setUp()
+        self.flags(disable_process_locking=True,
+                   instance_name_template='%d',
+                   firewall_driver='nova.virt.xenapi.firewall.'
+                                   'Dom0IptablesFirewallDriver',
+                   xenapi_connection_url='test_url',
+                   xenapi_connection_password='test_pass',)
+
+    def tearDown(self):
+        super(GetInstanceForVdisForSrTestCase, self).tearDown()
+
+    def test_get_instance_vdis_for_sr(self):
+        vm_ref = fake.create_vm("foo", "Running")
+        sr_ref = fake.create_sr()
+
+        vdi_1 = fake.create_vdi('vdiname1', sr_ref)
+        vdi_2 = fake.create_vdi('vdiname2', sr_ref)
+
+        for vdi_ref in [vdi_1, vdi_2]:
+            fake.create_vbd(vm_ref, vdi_ref)
+
+        stubs.stubout_session(self.stubs, fake.SessionBase)
+        driver = xenapi_conn.XenAPIDriver(False)
+
+        result = list(vm_utils.get_instance_vdis_for_sr(
+            driver._session, vm_ref, sr_ref))
+
+        self.assertEquals([vdi_1, vdi_2], result)
+
+    def test_get_instance_vdis_for_sr_no_vbd(self):
+        vm_ref = fake.create_vm("foo", "Running")
+        sr_ref = fake.create_sr()
+
+        stubs.stubout_session(self.stubs, fake.SessionBase)
+        driver = xenapi_conn.XenAPIDriver(False)
+
+        result = list(vm_utils.get_instance_vdis_for_sr(
+            driver._session, vm_ref, sr_ref))
+
+        self.assertEquals([], result)