Added handler for setting virtio block cache to none.

cloudcontrol/node/hypervisor/__init__.py

@@ -139,6 +139,8 @@ class Handler(HostHandler):
         self.main.reset_handler('drbd_sync_status', self.drbd_sync_status)
         self.main.reset_handler('drbd_shutdown', self.drbd_shutdown)
         self.main.reset_handler('vm_open_console', self.vm_open_console)
+        self.main.reset_handler('vm_disable_virtio_cache',
+                                self.vm_disable_virtio_cache)
 
         # if everything went fine, unregister the timer
         self.timer.stop()
@@ -202,6 +204,7 @@ class Handler(HostHandler):
         self.main.remove_handler('drbd_sync_status')
         self.main.remove_handler('drbd_shutdown')
         self.main.remove_handler('vm_open_console')
+        self.main.remove_handler('vm_disable_virtio_cache')
         # launch connection timer
         self.timer.start()
 
@@ -470,6 +473,44 @@ class Handler(HostHandler):
         proto = conn.create_tunnel(endpoint=endpoint, on_close=on_close)
         return proto.label
 
+    def vm_disable_virtio_cache(self, name):
+        """Set virtio cache to none on VM disks.
+
+        :param name: VM name
+        """
+        vm = self.hypervisor.domains[name]
+
+        # get VM XML
+        try:
+            xml = vm.lv_dom.XMLDesc(0)
+        except libvirt.libvirtError:
+            logger.exception('Error while getting domain XML from libvirt, %s',
+                             vm.name)
+            raise
+
+        xml_tree = et.ElementTree()
+        xml_tree.parse(StringIO(xml))
+        for disk in xml_tree.findall('devices/disk'):
+            # check that disk is virtio
+            target = disk.find('target')
+            if target is None or target.get('bus') != 'virtio':
+                continue
+            # modify cache attr
+            driver = disk.find('driver')
+            assert driver is not None
+            driver.set('cache', 'none')
+            logger.debug('Set cache attribute for disk %s of VM %s',
+                         target.get('dev'), name)
+
+        # write back the XML tree
+        out = StringIO()
+        xml_tree.write(out)  # check encoding is fine
+        try:
+            self.hypervisor.vir_con.defineXML(out.getvalue())
+        except libvirt.libvirtError:
+            logger.exception('Cannot update XML file for domain %s', name)
+            raise
+
     def vol_create(self, pool, name, size):
         logger.debug('Volume create %s, pool %s, size %s', name, pool, size)
         try: