libvirt: persist volume attachments into config

When you attach a volume to a running instance, only the running
xml is updated in libvirt. This is due to the usage of the
VIRT_DOMAIN_AFFECT_CURRENT flag passed to attach device. What we
really want is to affect both the config and the running xml. There
is no combination of flags that works in all states, so we explicitly
set the right combination of flags depending on the running state
of the vm.

Includes a test to test_virt_drivers to ensure the flags are passed
correctly.

Fixes bug 1071069

Change-Id: I1992748b08daf99cf03dfeb0937ad42457fff1a3

nova/tests/fakelibvirt.py

@@ -73,6 +73,8 @@ def _reset():
 VIR_DOMAIN_UNDEFINE_MANAGED_SAVE = 1
 
 VIR_DOMAIN_AFFECT_CURRENT = 0
+VIR_DOMAIN_AFFECT_LIVE = 1
+VIR_DOMAIN_AFFECT_CONFIG = 2
 
 VIR_CPU_COMPARE_ERROR = -1
 VIR_CPU_COMPARE_INCOMPATIBLE = 0
@@ -337,7 +339,10 @@ def attachDevice(self, xml):
         self._def['devices']['disks'] += [disk_info]
         return True
 
-    def attachDeviceFlags(self, xml, _flags):
+    def attachDeviceFlags(self, xml, flags):
+        if (flags & VIR_DOMAIN_AFFECT_LIVE and
+            self._state != VIR_DOMAIN_RUNNING):
+            raise libvirtError("AFFECT_LIVE only allowed for running domains!")
         self.attachDevice(xml)
 
     def detachDevice(self, xml):

nova/tests/test_virt_drivers.py

@@ -360,6 +360,18 @@ def test_attach_detach_volume(self):
                                       instance_ref['name'],
                                       '/mnt/nova/something')
 
+    @catch_notimplementederror
+    def test_attach_detach_different_power_states(self):
+        instance_ref, network_info = self._get_running_instance()
+        self.connection.power_off(instance_ref)
+        self.connection.attach_volume({'driver_volume_type': 'fake'},
+                                      instance_ref['name'],
+                                      '/mnt/nova/something')
+        self.connection.power_on(instance_ref)
+        self.connection.detach_volume({'driver_volume_type': 'fake'},
+                                      instance_ref['name'],
+                                      '/mnt/nova/something')
+
     @catch_notimplementederror
     def test_get_info(self):
         instance_ref, network_info = self._get_running_instance()

nova/virt/libvirt/driver.py

@@ -646,7 +646,13 @@ def attach_volume(self, connection_info, instance_name, mountpoint):
             self._conn.defineXML(domxml)
         else:
             try:
-                flags = (libvirt.VIR_DOMAIN_AFFECT_CURRENT)
+                # NOTE(vish): We can always affect config because our
+                #             domains are persistent, but we should only
+                #             affect live if the domain is running.
+                flags = libvirt.VIR_DOMAIN_AFFECT_CONFIG
+                state = LIBVIRT_POWER_STATE[virt_dom.info()[0]]
+                if state == power_state.RUNNING:
+                    flags |= libvirt.VIR_DOMAIN_AFFECT_LIVE
                 virt_dom.attachDeviceFlags(conf.to_xml(), flags)
             except Exception, ex:
                 if isinstance(ex, libvirt.libvirtError):
@@ -704,7 +710,13 @@ def detach_volume(self, connection_info, instance_name, mountpoint):
                 domxml = virt_dom.XMLDesc(libvirt.VIR_DOMAIN_XML_SECURE)
                 self._conn.defineXML(domxml)
             else:
-                flags = (libvirt.VIR_DOMAIN_AFFECT_CURRENT)
+                # NOTE(vish): We can always affect config because our
+                #             domains are persistent, but we should only
+                #             affect live if the domain is running.
+                flags = libvirt.VIR_DOMAIN_AFFECT_CONFIG
+                state = LIBVIRT_POWER_STATE[virt_dom.info()[0]]
+                if state == power_state.RUNNING:
+                    flags |= libvirt.VIR_DOMAIN_AFFECT_LIVE
                 virt_dom.detachDeviceFlags(xml, flags)
         except libvirt.libvirtError as ex:
             # NOTE(vish): This is called to cleanup volumes after live