libvirt: allow querying devices from the persistent domain

This patch adds from_persistent_config kwargs to get_interface_by_cfg()
and get_disk() so that the caller can specify which domain config the
devices is read from. Currently, if there was both a live domain and a
persistent domain then nova only reads from the live domain. In a later
patch during device detach these calls will be used to detach from the
persistent domain separately from the live domain.

Change-Id: I86153d31b02e6b74b42d53a6800297cbd0e5cbb4
Related-Bug: #1882521

Author: Balazs Gibizer

nova/tests/unit/virt/libvirt/test_driver.py

@@ -24034,6 +24034,41 @@ def test_get_disk_xml(self):
 
         self.assertIsNone(guest.get_disk('vdc'))
 
+        dom.XMLDesc.assert_has_calls([mock.call(0)] * 3)
+
+    def test_get_disk_xml_from_persistent_config(self):
+        dom_xml = """
+              <domain type="kvm">
+                <devices>
+                  <disk type="file">
+                     <source file="disk1_file"/>
+                     <target dev="vda" bus="virtio"/>
+                     <serial>0e38683e-f0af-418f-a3f1-6b67ea0f919d</serial>
+                  </disk>
+                  <disk type="block">
+                    <source dev="/path/to/dev/1"/>
+                    <target dev="vdb" bus="virtio" serial="1234"/>
+                  </disk>
+                </devices>
+              </domain>
+              """
+
+        diska_xml = """<disk type="file" device="disk">
+  <source file="disk1_file"/>
+  <target bus="virtio" dev="vda"/>
+  <serial>0e38683e-f0af-418f-a3f1-6b67ea0f919d</serial>
+</disk>"""
+
+        dom = mock.MagicMock()
+        dom.XMLDesc.return_value = dom_xml
+        guest = libvirt_guest.Guest(dom)
+
+        actual_diska_xml = guest.get_disk(
+            'vda', from_persistent_config=True).to_xml()
+        self.assertXmlEqual(diska_xml, actual_diska_xml)
+        dom.XMLDesc.assert_called_once_with(
+            fakelibvirt.VIR_DOMAIN_XML_INACTIVE)
+
     def test_vcpu_model_from_config(self):
         drv = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
         vcpu_model = drv._cpu_config_to_vcpu_model(None, None)

nova/tests/unit/virt/libvirt/test_guest.py

@@ -540,6 +540,49 @@ def test_get_devices(self):
         self.assertIsNotNone(
             self.guest.get_interface_by_cfg(cfg))
         self.assertIsNone(self.guest.get_interface_by_cfg(None))
+        self.domain.XMLDesc.assert_has_calls([mock.call(0)] * 6)
+
+        # now check if the persistent config can be queried too
+        self.domain.XMLDesc.reset_mock()
+        devs = self.guest.get_all_devices(
+            devtype=None, from_persistent_config=True)
+        self.domain.XMLDesc.assert_called_once_with(
+            fakelibvirt.VIR_DOMAIN_XML_INACTIVE)
+
+    def test_get_interface_by_cfg_persistent_domain(self):
+        self.domain.XMLDesc.return_value = """<domain>
+  <devices>
+    <interface type="bridge">
+      <mac address="fa:16:3e:f9:af:ae"/>
+      <model type="virtio"/>
+      <driver name="qemu"/>
+      <source bridge="qbr84008d03-11"/>
+      <target dev="tap84008d03-11"/>
+    </interface>
+  </devices>
+</domain>"""
+        cfg = vconfig.LibvirtConfigGuestInterface()
+        cfg.parse_str("""
+            <interface type="bridge">
+              <mac address="fa:16:3e:f9:af:ae"/>
+              <model type="virtio"/>
+              <driver name="qemu"/>
+              <source bridge="qbr84008d03-11"/>
+              <target dev="tap84008d03-11"/>
+              </interface>""")
+        self.assertIsNotNone(
+            self.guest.get_interface_by_cfg(
+                cfg, from_persistent_config=True))
+        self.assertIsNone(
+            self.guest.get_interface_by_cfg(
+                vconfig.LibvirtConfigGuestInterface(),
+                from_persistent_config=True))
+        self.domain.XMLDesc.assert_has_calls(
+            [
+                mock.call(fakelibvirt.VIR_DOMAIN_XML_INACTIVE),
+                mock.call(fakelibvirt.VIR_DOMAIN_XML_INACTIVE),
+            ]
+        )
 
     def test_get_interface_by_cfg_vhostuser(self):
         self.domain.XMLDesc.return_value = """<domain>

nova/virt/libvirt/guest.py

@@ -227,19 +227,22 @@ def get_interfaces(self):
 
         return interfaces
 
-    def get_interface_by_cfg(self, cfg):
+    def get_interface_by_cfg(self, cfg, from_persistent_config=False):
         """Lookup a full LibvirtConfigGuestDevice with
         LibvirtConfigGuesDevice generated
         by nova.virt.libvirt.vif.get_config.
 
         :param cfg: config object that represents the guest interface.
         :type cfg: a subtype of LibvirtConfigGuestDevice object
+        :param from_persistent_config: query the device from the persistent
+            domain instead of the live domain configuration
         :returns: nova.virt.libvirt.config.LibvirtConfigGuestDevice instance
             if found, else None
         """
 
         if cfg:
-            interfaces = self.get_all_devices(type(cfg))
+            interfaces = self.get_all_devices(
+                type(cfg), from_persistent_config)
             for interface in interfaces:
                 # NOTE(leehom) LibvirtConfigGuest get from domain and
                 # LibvirtConfigGuest generated by
@@ -312,13 +315,16 @@ def get_config(self):
         config.parse_str(self._domain.XMLDesc(0))
         return config
 
-    def get_disk(self, device):
+    def get_disk(self, device, from_persistent_config=False):
         """Returns the disk mounted at device
 
         :returns LivirtConfigGuestDisk: mounted at device or None
         """
+        flags = 0
+        if from_persistent_config:
+            flags |= libvirt.VIR_DOMAIN_XML_INACTIVE
         try:
-            doc = etree.fromstring(self._domain.XMLDesc(0))
+            doc = etree.fromstring(self._domain.XMLDesc(flags))
         except Exception:
             return None
 
@@ -343,18 +349,24 @@ def get_all_disks(self):
 
         return self.get_all_devices(vconfig.LibvirtConfigGuestDisk)
 
-    def get_all_devices(self, devtype=None):
+    def get_all_devices(self, devtype=None, from_persistent_config=False):
         """Returns all devices for a guest
 
         :param devtype: a LibvirtConfigGuestDevice subclass class
-
+        :param from_persistent_config: query the device from the persistent
+            domain (i.e. inactive XML configuration that'll be used on next
+            start of the domain) instead of the live domain configuration
         :returns: a list of LibvirtConfigGuestDevice instances
         """
 
+        flags = 0
+        if from_persistent_config:
+            flags |= libvirt.VIR_DOMAIN_XML_INACTIVE
+
         try:
             config = vconfig.LibvirtConfigGuest()
             config.parse_str(
-                self._domain.XMLDesc(0))
+                self._domain.XMLDesc(flags))
         except Exception:
             return []