Merge "libvirt: Disable VMCoreInfo device for SEV-encrypted instances" into stable/2024.2

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

@@ -3417,6 +3417,52 @@ class LibvirtConnTestCase(test.NoDBTestCase,
             None, None, flavor, image_meta,
         )
 
+    @mock.patch.object(
+        fakelibvirt.virConnect, '_domain_capability_features', new=
+        fakelibvirt.virConnect._domain_capability_features_with_SEV
+    )
+    @mock.patch.object(host.Host, "_check_machine_type", new=mock.Mock())
+    def test_get_guest_config_memory_encryption(self):
+        """Generate a guest with memory encryption.
+
+        This configures an memory encryption.
+        """
+        self.flags(virt_type="kvm", group='libvirt')
+
+        drvr = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), True)
+        drvr._host._supports_amd_sev = True
+        instance_ref = objects.Instance(**self.test_instance)
+        image_meta = objects.ImageMeta.from_dict({
+            "hw_architecture": fields.Architecture.X86_64,
+            "disk_format": "raw",
+            "properties": {
+                "hw_machine_type": "q35",
+                "hw_firmware_type": "uefi",
+                "hw_mem_encryption": True,
+            }
+        })
+
+        disk_info = blockinfo.get_disk_info(
+            CONF.libvirt.virt_type,
+            instance_ref,
+            image_meta,
+        )
+
+        cfg = drvr._get_guest_config(
+            instance_ref,
+            _fake_network_info(self),
+            image_meta,
+            disk_info,
+        )
+
+        # NOTE(tkajinm): vmcoreinfo should be disabled in this case
+        self.assertEqual(2, len(cfg.features))
+        for idx, device_type in enumerate([
+            vconfig.LibvirtConfigGuestFeatureACPI,
+            vconfig.LibvirtConfigGuestFeatureAPIC,
+        ]):
+            self.assertIsInstance(cfg.features[idx], device_type)
+
     def _test_sev_enabled(self, expected=None, host_sev_enabled=False,
                           enc_extra_spec=None, enc_image_prop=None,
                           hw_machine_type=None, hw_firmware_type=None):

nova/virt/libvirt/driver.py

@@ -6621,8 +6621,11 @@ class LibvirtDriver(driver.ComputeDriver):
                 fields.Architecture.I686, fields.Architecture.X86_64,
                 fields.Architecture.AARCH64,
             ):
-                guest.add_feature(
-                    vconfig.LibvirtConfigGuestFeatureVMCoreInfo())
+                # VMCoreInfo device requires DMA between guest OS and host
+                # OS, which is prohibited when guest memory is encrypted.
+                if not self._sev_enabled(flavor, image_meta):
+                    guest.add_feature(
+                        vconfig.LibvirtConfigGuestFeatureVMCoreInfo())
 
             if hide_hypervisor_id:
                 guest.add_feature(

releasenotes/notes/bug-2117170-disable-vmcoreinfo-when-memory-encryption-is-enabled-142e64f6b9ef3135.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    [`bug 2117170 <https://bugs.launchpad.net/nova/+bug/2117170>`_] Libvirt
+    driver no longer enables VMCoreInfo device when an instance has memory
+    encryption is enabled, to avoid kernel crash caused by fw_cfg device in
+    guest requiring DMA.