libvirt: Skip unsupported firmware types

Ignore (1) stateless mode firmware and (2) memory device firmware which
do not include a few core keys such as nvram-template. This is
a temporal (and backportable) workaround until firmware detection using
libvirt's internal feature is implemented by [1]

[1] https://blueprints.launchpad.net/nova/+spec/libvirt-firmware-auto-selection

Closes-Bug: #2122288
Change-Id: I99bc36fdd5df816c9ae374db71e4734fb7fc467b
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

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

@@ -2035,6 +2035,7 @@ Active:          8381604 kB
                 'interface-types': ['uefi'],
                 'mapping': {
                     'device': 'flash',
+                    'mode': 'split',
                     'executable': {
                         'filename': '/usr/share/edk2/ovmf/OVMF_CODE.fd',
                         'format': 'raw',
@@ -2053,6 +2054,44 @@ Active:          8381604 kB
                 'features': ['acpi-s3', 'amd-sev', 'verbose-dynamic'],
                 'tags': [],
             },
+            # NOTE(tkajinam): The following loaders are not supported and
+            # should be ignored. https://bugs.launchpad.net/nova/+bug/2122288
+            {
+                'description': 'Sample descriptor for stateless mode',
+                'interface-types': ['uefi'],
+                'mapping': {
+                    'device': 'flash',
+                    'mode': 'stateless',
+                    'executable': {
+                        'filename': '/usr/share/edk2/ovmf/OVMF_CODE_SL.fd',
+                        'format': 'raw'
+                    }
+                },
+                'targets': [
+                    {
+                        'architecture': 'x86_64',
+                        'machines': ['pc-q35-*'],
+                    },
+                ],
+                'features': ['amd-sev', 'verbose-dynamic'],
+                'tags': [],
+            },
+            {
+                'description': 'Sample descriptor for memory device',
+                'interface-types': ['uefi'],
+                'mapping': {
+                    'device': 'memory',
+                    'filename': '/usr/share/edk2/ovmf/OVMF_MEM.fd'
+                },
+                'targets': [
+                    {
+                        'architecture': 'x86_64',
+                        'machines': ['pc-q35-*'],
+                    }
+                ],
+                'features': ['amd-sev', 'verbose-dynamic'],
+                'tags': [],
+            },
         ]
 
         def fake_get_mtype(arch, machine):

nova/virt/libvirt/host.py

@@ -2094,31 +2094,37 @@ class Host(object):
         machine = self.get_canonical_machine_type(arch, machine)
 
         for loader in self.loaders:
-            for target in loader['targets']:
-                if arch != target['architecture']:
-                    continue
+            try:
+                for target in loader['targets']:
+                    if arch != target['architecture']:
+                        continue
 
-                for machine_glob in target['machines']:
-                    # the 'machines' attribute supports glob patterns (e.g.
-                    # 'pc-q35-*') so we need to resolve these
-                    if fnmatch.fnmatch(machine, machine_glob):
-                        break
+                    for machine_glob in target['machines']:
+                        # the 'machines' attribute supports glob patterns (e.g.
+                        # 'pc-q35-*') so we need to resolve these
+                        if fnmatch.fnmatch(machine, machine_glob):
+                            break
+                    else:
+                        continue
+
+                    # if we've got this far, we have a match on the target
+                    break
                 else:
                     continue
 
-                # if we've got this far, we have a match on the target
-                break
-            else:
-                continue
+                # if we request secure boot then we should get it and vice
+                # versa
+                if has_secure_boot != ('secure-boot' in loader['features']):
+                    continue
 
-            # if we request secure boot then we should get it and vice versa
-            if has_secure_boot != ('secure-boot' in loader['features']):
+                return (
+                    loader['mapping']['executable']['filename'],
+                    loader['mapping']['nvram-template']['filename'],
+                    'requires-smm' in loader['features'],
+                )
+            except KeyError:
+                # This indicates that the description structure is new and nova
+                # does not how to handle it
                 continue
 
-            return (
-                loader['mapping']['executable']['filename'],
-                loader['mapping']['nvram-template']['filename'],
-                'requires-smm' in loader['features'],
-            )
-
         raise exception.UEFINotSupported()

releasenotes/notes/bug-2133416-80522b523ee74835.yaml

@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    [`bug 2133416 <https://bugs.launchpad.net/nova/+bug/2133416>`_] Libvirt
+    virt driver now ignores the OVMF firmware files of the following types.
+    Previously nova failed to start instances with UEFI boot when it attempts
+    to check such firmware files.
+
+    - stateless mode
+    - memory device