Windows instances require the timezone to be "localtime"

This was relatively simple to fix, assuming that the image used
to boot the windows instance has the os_type set to "windows".
The use of os_type in this manner is consistent with the
existing use in the Xen hypervisor driver.

DocImpact: if you're booting windows instances, then you need to
set the os_type image property in glance to "windows". Otherwise
your instances will have their clock timezone set to UTC, which
has unexpected side effects in windows.

Change-Id: Id6759a290ed25c9add97ac61bb7d165b3fb908b2
Closes-Bug: 1231254

nova/tests/virt/libvirt/test_libvirt.py

@@ -722,6 +722,21 @@ def test_get_guest_config(self):
         self.assertEquals(cfg.clock.timers[1].tickpolicy,
                           "catchup")
 
+    def test_get_guest_config_windows(self):
+        conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+        instance_ref = db.instance_create(self.context, self.test_instance)
+        instance_ref['os_type'] = 'windows'
+
+        disk_info = blockinfo.get_disk_info(CONF.libvirt_type,
+                                            instance_ref)
+        cfg = conn.get_guest_config(instance_ref,
+                                    _fake_network_info(self.stubs, 1),
+                                    None, disk_info)
+
+        self.assertEquals(type(cfg.clock),
+                          vconfig.LibvirtConfigGuestClock)
+        self.assertEquals(cfg.clock.offset, "localtime")
+
     def test_get_guest_config_with_two_nics(self):
         conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
         instance_ref = db.instance_create(self.context, self.test_instance)

nova/virt/libvirt/driver.py

@@ -2886,8 +2886,17 @@ def get_guest_config(self, instance, network_info, image_meta,
             guest.acpi = True
             guest.apic = True
 
+        # NOTE(mikal): Microsoft Windows expects the clock to be in
+        # "localtime". If the clock is set to UTC, then you can use a
+        # registry key to let windows know, but Microsoft says this is
+        # buggy in http://support.microsoft.com/kb/2687252
         clk = vconfig.LibvirtConfigGuestClock()
-        clk.offset = "utc"
+        if instance['os_type'] == 'windows':
+            LOG.info(_('Configuring timezone for windows instance to '
+                       'localtime'), instance=instance)
+            clk.offset = 'localtime'
+        else:
+            clk.offset = 'utc'
         guest.set_clock(clk)
 
         if CONF.libvirt_type == "kvm":