libvirt: drop MIN_QEMU_DISCARD_VERSION

We now require a minimum QEMU version (2.1.0) that is
high enough such that we can drop this compatibility
code.

Change-Id: If07c6f242f6b7ad50f51587bbbdb480153a77694

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

@@ -290,22 +290,3 @@ class LibvirtVolumeTestCase(LibvirtISCSIVolumeBaseTestCase):
         conf = libvirt_driver.get_config(connection_info, self.disk_info)
         tree = conf.format_dom()
         self.assertIsNone(tree.find("driver[@discard]"))
-
-    @mock.patch('nova.virt.libvirt.host.Host.has_min_version')
-    def test_libvirt_volume_driver_discard_true_bad_version(
-            self, mock_has_min_version):
-        # Check the discard attrib is not present in driver section
-        mock_has_min_version.return_value = False
-        libvirt_driver = volume.LibvirtVolumeDriver(self.fake_host)
-        connection_info = {
-            'driver_volume_type': 'fake',
-            'data': {
-                'device_path': '/foo',
-                'discard': True,
-            },
-            'serial': 'fake_serial',
-        }
-
-        conf = libvirt_driver.get_config(connection_info, self.disk_info)
-        tree = conf.format_dom()
-        self.assertIsNone(tree.find("driver[@discard]"))

nova/virt/libvirt/driver.py

@@ -212,8 +212,6 @@ NEXT_MIN_QEMU_VERSION = (2, 5, 0)
 # Libvirt version 1.2.17 is required for successful block live migration
 # of vm booted from image with attached devices
 MIN_LIBVIRT_BLOCK_LM_WITH_VOLUMES_VERSION = (1, 2, 17)
-# libvirt discard feature
-MIN_QEMU_DISCARD_VERSION = (1, 6, 0)
 # While earlier versions could support NUMA reporting and
 # NUMA placement, not until 1.2.7 was there the ability
 # to pin guest nodes to host nodes, so mandate that. Without
@@ -3471,14 +3469,6 @@ class LibvirtDriver(driver.ComputeDriver):
 
     def _get_guest_disk_config(self, instance, name, disk_mapping, inst_type,
                                image_type=None):
-        if CONF.libvirt.hw_disk_discard:
-            if not self._host.has_min_version(hv_ver=MIN_QEMU_DISCARD_VERSION,
-                                              hv_type=host.HV_DRIVER_QEMU):
-                msg = (_('Volume sets discard option, qemu %(qemu)s'
-                         ' or later is required.') %
-                      {'qemu': MIN_QEMU_DISCARD_VERSION})
-                raise exception.Invalid(msg)
-
         disk = self.image_backend.by_name(instance, name, image_type)
         if (name == 'disk.config' and image_type == 'rbd' and
                 not disk.exists()):

nova/virt/libvirt/volume/volume.py

@@ -26,15 +26,12 @@ from nova.i18n import _LW
 from nova import profiler
 from nova.virt.libvirt import config as vconfig
 import nova.virt.libvirt.driver
-from nova.virt.libvirt import host
 from nova.virt.libvirt import utils as libvirt_utils
 
 LOG = logging.getLogger(__name__)
 
 CONF = nova.conf.CONF
 
-SHOULD_LOG_DISCARD_WARNING = True
-
 
 @profiler.trace_cls("volume_api")
 class LibvirtBaseVolumeDriver(object):
@@ -96,23 +93,7 @@ class LibvirtBaseVolumeDriver(object):
 
         # Configure usage of discard
         if data.get('discard', False) is True:
-            min_qemu = nova.virt.libvirt.driver.MIN_QEMU_DISCARD_VERSION
+            conf.driver_discard = 'unmap'
-            if self.host.has_min_version(
-                    hv_ver=min_qemu,
-                    hv_type=host.HV_DRIVER_QEMU):
-                conf.driver_discard = 'unmap'
-            else:
-                global SHOULD_LOG_DISCARD_WARNING
-                if SHOULD_LOG_DISCARD_WARNING:
-                    SHOULD_LOG_DISCARD_WARNING = False
-                    LOG.warning(_LW('Unable to attach %(type)s volume '
-                                    '%(serial)s with discard enabled: qemu '
-                                    '%(qemu)s or later is required.'),
-                                {
-                        'qemu': min_qemu,
-                        'serial': conf.serial,
-                        'type': connection_info['driver_volume_type']
-                    })
 
         return conf