diff --git a/nova/tests/unit/virt/libvirt/test_driver.py b/nova/tests/unit/virt/libvirt/test_driver.py
index d2998bfbe590..298b182ec034 100755
--- a/nova/tests/unit/virt/libvirt/test_driver.py
+++ b/nova/tests/unit/virt/libvirt/test_driver.py
@@ -5826,6 +5826,38 @@ class LibvirtConnTestCase(test.NoDBTestCase,
         self.assertEqual(conf.cpu.cores, 1)
         self.assertEqual(conf.cpu.threads, 1)
 
+    def test_get_guest_cpu_config_host_passthrough_aarch64(self):
+        expected = {
+            fields.Architecture.X86_64: "host-model",
+            fields.Architecture.I686: "host-model",
+            fields.Architecture.PPC: "host-model",
+            fields.Architecture.PPC64: "host-model",
+            fields.Architecture.ARMV7: "host-model",
+            fields.Architecture.AARCH64: "host-passthrough",
+        }
+        for guestarch, expect_mode in expected.items():
+            caps = vconfig.LibvirtConfigCaps()
+            caps.host = vconfig.LibvirtConfigCapsHost()
+            caps.host.cpu = vconfig.LibvirtConfigCPU()
+            caps.host.cpu.arch = guestarch
+            with mock.patch.object(host.Host, "get_capabilities",
+                                   return_value=caps):
+                drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+                if caps.host.cpu.arch == fields.Architecture.AARCH64:
+                    drvr._has_uefi_support = mock.Mock(return_value=True)
+                instance_ref = objects.Instance(**self.test_instance)
+                image_meta = objects.ImageMeta.from_dict(self.test_image_meta)
+
+                disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type,
+                                                    instance_ref,
+                                                    image_meta)
+                conf = drvr._get_guest_config(instance_ref,
+                                              _fake_network_info(self, 1),
+                                              image_meta, disk_info)
+                self.assertIsInstance(conf.cpu,
+                                      vconfig.LibvirtConfigGuestCPU)
+                self.assertEqual(conf.cpu.mode, expect_mode)
+
     def test_get_guest_cpu_config_host_model(self):
         drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
         instance_ref = objects.Instance(**self.test_instance)
diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index ce24cd2be9bc..4209af1a62b0 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -3551,7 +3551,23 @@ class LibvirtDriver(driver.ComputeDriver):
         if (CONF.libvirt.virt_type == "kvm" or
             CONF.libvirt.virt_type == "qemu"):
             if mode is None:
-                mode = "host-model"
+                caps = self._host.get_capabilities()
+                # AArch64 lacks 'host-model' support because neither libvirt
+                # nor QEMU are able to tell what the host CPU model exactly is.
+                # And there is no CPU description code for ARM(64) at this
+                # point.
+
+                # Also worth noting: 'host-passthrough' mode will completely
+                # break live migration, *unless* all the Compute nodes (running
+                # libvirtd) have *identical* CPUs.
+                if caps.host.cpu.arch == fields.Architecture.AARCH64:
+                    mode = "host-passthrough"
+                    LOG.info('CPU mode "host-passthrough" was chosen. Live '
+                             'migration can break unless all compute nodes '
+                             'have identical cpus. AArch64 does not support '
+                             'other modes.')
+                else:
+                    mode = "host-model"
             if mode == "none":
                 return vconfig.LibvirtConfigGuestCPU()
         else:
diff --git a/releasenotes/notes/aarch64-set-proper-cpu-mode-8455bad7d69dc6fd.yaml b/releasenotes/notes/aarch64-set-proper-cpu-mode-8455bad7d69dc6fd.yaml
new file mode 100644
index 000000000000..6458fbe74c8e
--- /dev/null
+++ b/releasenotes/notes/aarch64-set-proper-cpu-mode-8455bad7d69dc6fd.yaml
@@ -0,0 +1,13 @@
+---
+upgrade:
+  - |
+    On AArch64 architecture ``cpu_mode`` for libvirt is set to ``host-passthrough``
+    by default.
+
+    AArch64 currently lacks ``host-model`` support because neither libvirt nor
+    QEMU are able to tell what the host CPU model exactly is and there is no
+    CPU description code for ARM(64) at this point.
+
+    .. warning:: ``host-passthrough`` mode will completely break live
+       migration, *unless* all the Compute nodes (running libvirtd) have
+       *identical* CPUs.