nova.patch

diff --git a/nova/virt/block_device.py b/nova/virt/block_device.py
index e86abb7..75d8808 100644
--- a/nova/virt/block_device.py
+++ b/nova/virt/block_device.py
@@ -338,6 +338,8 @@ class DriverVolumeBlockDevice(DriverBlockDevice):
         if 'serial' not in connection_info:
             connection_info['serial'] = self.volume_id
         self._preserve_multipath_id(connection_info)
+        original_info = self['connection_info']
+        connection_info['_original_info'] = original_info
         self['connection_info'] = connection_info
 
     def save(self):
diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index e77eace..a882b56 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -6827,10 +6827,18 @@ class LibvirtDriver(driver.ComputeDriver):
         for vol in block_device_mapping:
             # Retrieve connection info from Cinder's initialize_connection API.
             # The info returned will be accurate for the source server.
-            volume_id = vol['connection_info']['serial']
-            connection_info = volume_api.initialize_connection(context,
-                                                               volume_id,
-                                                               connector)
+            if '_original_info' in vol['connection_info']:
+                # don't call Cinder if we already have the source host
+                # information
+                connection_info = vol['connection_info']['_original_info']
+                del vol['connection_info']['_original_info']
+            else:
+                # we don't have the source host's connection_info
+                # so we have to ask Cinder for it.
+                volume_id = vol['connection_info']['serial']
+                connection_info = volume_api.initialize_connection(context,
+                                                                   volume_id,
+                                                                   connector)
 
             # TODO(leeantho) The following multipath_id logic is temporary
             # and will be removed in the future once os-brick is updated