tpm: Return QMP error when TPM is disabled in build

When the management layer queries a binary built using --disable-tpm
for TPM devices, it gets confused by getting empty responses:

  { "execute": "query-tpm" }
  {
      "return": [
      ]
  }
  { "execute": "query-tpm-types" }
  {
      "return": [
      ]
  }
  { "execute": "query-tpm-models" }
  {
      "return": [
      ]
  }

To make it clearer by returning an error:
- Make the TPM QAPI schema conditional
  All of tpm.json is now 'if': 'defined(CONFIG_TPM)'.
- Adapt the HMP command
- Remove stubs which became unnecessary

The management layer now gets a 'CommandNotFound' error:

  { "execute": "query-tpm" }
  {
      "error": {
          "class": "CommandNotFound",
          "desc": "The command query-tpm has not been found"
      }
  }

Suggested-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>

MAINTAINERS

@@ -2707,7 +2707,6 @@ TPM
 M: Stefan Berger <stefanb@linux.ibm.com>
 S: Maintained
 F: tpm.c
-F: stubs/tpm.c
 F: hw/tpm/*
 F: include/hw/acpi/tpm.h
 F: include/sysemu/tpm*

monitor/hmp-cmds.c

@@ -901,6 +901,7 @@ void hmp_info_pci(Monitor *mon, const QDict *qdict)
 
 void hmp_info_tpm(Monitor *mon, const QDict *qdict)
 {
+#ifdef CONFIG_TPM
     TPMInfoList *info_list, *info;
     Error *err = NULL;
     unsigned int c = 0;
@@ -946,6 +947,9 @@ void hmp_info_tpm(Monitor *mon, const QDict *qdict)
         c++;
     }
     qapi_free_TPMInfoList(info_list);
+#else
+    monitor_printf(mon, "TPM device not supported\n");
+#endif /* CONFIG_TPM */
 }
 
 void hmp_quit(Monitor *mon, const QDict *qdict)

qapi/tpm.json

@@ -17,7 +17,9 @@
 #
 # Since: 1.5
 ##
-{ 'enum': 'TpmModel', 'data': [ 'tpm-tis', 'tpm-crb', 'tpm-spapr' ] }
+{ 'enum': 'TpmModel', 'data': [ 'tpm-tis', 'tpm-crb', 'tpm-spapr' ],
+  'if': 'defined(CONFIG_TPM)' }
+
 ##
 # @query-tpm-models:
 #
@@ -33,7 +35,8 @@
 # <- { "return": [ "tpm-tis", "tpm-crb", "tpm-spapr" ] }
 #
 ##
-{ 'command': 'query-tpm-models', 'returns': ['TpmModel'] }
+{ 'command': 'query-tpm-models', 'returns': ['TpmModel'],
+  'if': 'defined(CONFIG_TPM)' }
 
 ##
 # @TpmType:
@@ -46,7 +49,8 @@
 #
 # Since: 1.5
 ##
-{ 'enum': 'TpmType', 'data': [ 'passthrough', 'emulator' ] }
+{ 'enum': 'TpmType', 'data': [ 'passthrough', 'emulator' ],
+  'if': 'defined(CONFIG_TPM)' }
 
 ##
 # @query-tpm-types:
@@ -63,7 +67,8 @@
 # <- { "return": [ "passthrough", "emulator" ] }
 #
 ##
-{ 'command': 'query-tpm-types', 'returns': ['TpmType'] }
+{ 'command': 'query-tpm-types', 'returns': ['TpmType'],
+  'if': 'defined(CONFIG_TPM)' }
 
 ##
 # @TPMPassthroughOptions:
@@ -79,7 +84,8 @@
 ##
 { 'struct': 'TPMPassthroughOptions',
   'data': { '*path': 'str',
-            '*cancel-path': 'str' } }
+            '*cancel-path': 'str' },
+  'if': 'defined(CONFIG_TPM)' }
 
 ##
 # @TPMEmulatorOptions:
@@ -90,7 +96,8 @@
 #
 # Since: 2.11
 ##
-{ 'struct': 'TPMEmulatorOptions', 'data': { 'chardev' : 'str' } }
+{ 'struct': 'TPMEmulatorOptions', 'data': { 'chardev' : 'str' },
+  'if': 'defined(CONFIG_TPM)' }
 
 ##
 # @TpmTypeOptions:
@@ -104,7 +111,8 @@
 ##
 { 'union': 'TpmTypeOptions',
    'data': { 'passthrough' : 'TPMPassthroughOptions',
-             'emulator': 'TPMEmulatorOptions' } }
+             'emulator': 'TPMEmulatorOptions' },
+  'if': 'defined(CONFIG_TPM)' }
 
 ##
 # @TPMInfo:
@@ -122,7 +130,8 @@
 { 'struct': 'TPMInfo',
   'data': {'id': 'str',
            'model': 'TpmModel',
-           'options': 'TpmTypeOptions' } }
+           'options': 'TpmTypeOptions' },
+  'if': 'defined(CONFIG_TPM)' }
 
 ##
 # @query-tpm:
@@ -152,4 +161,5 @@
 #    }
 #
 ##
-{ 'command': 'query-tpm', 'returns': ['TPMInfo'] }
+{ 'command': 'query-tpm', 'returns': ['TPMInfo'],
+  'if': 'defined(CONFIG_TPM)' }

stubs/meson.build

@@ -38,7 +38,6 @@ stub_ss.add(files('runstate-check.c'))
 stub_ss.add(files('sysbus.c'))
 stub_ss.add(files('target-get-monitor-def.c'))
 stub_ss.add(files('target-monitor-defs.c'))
-stub_ss.add(files('tpm.c'))
 stub_ss.add(files('trace-control.c'))
 stub_ss.add(files('uuid.c'))
 stub_ss.add(files('vmgenid.c'))

stubs/tpm.c

@@ -1,25 +0,0 @@
-/*
- * TPM stubs
- *
- * This work is licensed under the terms of the GNU GPL, version 2 or later.
- * See the COPYING file in the top-level directory.
- */
-
-#include "qemu/osdep.h"
-#include "qapi/qapi-commands-tpm.h"
-#include "hw/acpi/tpm.h"
-
-TPMInfoList *qmp_query_tpm(Error **errp)
-{
-    return NULL;
-}
-
-TpmTypeList *qmp_query_tpm_types(Error **errp)
-{
-    return NULL;
-}
-
-TpmModelList *qmp_query_tpm_models(Error **errp)
-{
-    return NULL;
-}