Support use_multipath for NVME driver

Initiate connector for LibvirtNVMEVolumeDriver driver with
use_multipath argument.

Change-Id: I20f6aa2d422259601c44d024099cd5760a8e21c6

nova/tests/unit/virt/libvirt/volume/test_nvme.py

@@ -29,7 +29,21 @@ class LibvirtNVMEVolumeDriverTestCase(test_volume.LibvirtVolumeBaseTestCase):
 
         nvme.LibvirtNVMEVolumeDriver(self.fake_host)
         mock_factory.assert_called_once_with(
-            initiator.NVME, 'sudo',
+            initiator.NVME, 'sudo', use_multipath=False,
+            device_scan_attempts=3)
+
+    @mock.patch('os.path.exists', return_value=True)
+    @mock.patch('nova.utils.get_root_helper')
+    @mock.patch('os_brick.initiator.connector.InitiatorConnector.factory')
+    def test_libvirt_nvme_driver_multipath(self, mock_factory, mock_helper,
+                                           exists):
+        self.flags(num_nvme_discover_tries=3, volume_use_multipath=True,
+                   group='libvirt')
+        mock_helper.return_value = 'sudo'
+
+        nvme.LibvirtNVMEVolumeDriver(self.fake_host)
+        mock_factory.assert_called_once_with(
+            initiator.NVME, 'sudo', use_multipath=True,
             device_scan_attempts=3)
 
     @mock.patch('os_brick.initiator.connector.InitiatorConnector.factory',

nova/virt/libvirt/volume/nvme.py

@@ -33,6 +33,7 @@ class LibvirtNVMEVolumeDriver(libvirt_volume.LibvirtVolumeDriver):
 
         self.connector = connector.InitiatorConnector.factory(
             initiator.NVME, utils.get_root_helper(),
+            use_multipath=CONF.libvirt.volume_use_multipath,
             device_scan_attempts=CONF.libvirt.num_nvme_discover_tries)
 
     def connect_volume(self, connection_info, instance):

releasenotes/notes/use-multipath-0a0aa2b479e02370.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    The libvirt driver now allows using Native NVMeoF multipathing
+    for NVMeoF connector, via the configuration attribute in nova-cpu.conf
+    ``[libvirt]/volume_use_multipath``, defaulting to False (disabled).
+