Re: [PATCH] tpm: Return QMP error when TPM is disabled in build

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 6/9/21 6:01 PM, Marc-André Lureau wrote:
> Hi
> 
> On Wed, Jun 9, 2021 at 7:33 PM Philippe Mathieu-Daudé <philmd@redhat.com
> <mailto:philmd@redhat.com>> wrote:
> 
>     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": [
>           ]
>       }
> 
>     Make it clearer by returning an error, mentioning the feature is
>     disabled:
> 
>       { "execute": "query-tpm" }
>       {
>           "error": {
>               "class": "GenericError",
>               "desc": "this feature or command is not currently supported"
>           }
>       }
> 
>     Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com
>     <mailto:philmd@redhat.com>>
> 
> 
> Why not make the qapi schema conditional?

I'm getting:

qapi/qapi-commands-tpm.c:123:13: error: ‘qmp_marshal_output_TPMInfoList’
defined but not used [-Werror=unused-function]
  123 | static void qmp_marshal_output_TPMInfoList(TPMInfoList *ret_in,
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
qapi/qapi-commands-tpm.c:73:13: error: ‘qmp_marshal_output_TpmTypeList’
defined but not used [-Werror=unused-function]
   73 | static void qmp_marshal_output_TpmTypeList(TpmTypeList *ret_in,
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
qapi/qapi-commands-tpm.c:23:13: error: ‘qmp_marshal_output_TpmModelList’
defined but not used [-Werror=unused-function]
   23 | static void qmp_marshal_output_TpmModelList(TpmModelList *ret_in,
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Fixed doing:

-- >8 --
diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
index 0e13d510547..85e332a5979 100644
--- a/scripts/qapi/commands.py
+++ b/scripts/qapi/commands.py
@@ -91,6 +91,7 @@ def gen_call(name: str,
 def gen_marshal_output(ret_type: QAPISchemaType) -> str:
     return mcgen('''

+__attribute__((unused))
 static void qmp_marshal_output_%(c_name)s(%(c_type)s ret_in,
                                 QObject **ret_out, Error **errp)
 {
---

But I doubt this is correct... I suppose gen_marshal_output() should
be elided if no command use the type? The enum is used however:

include/sysemu/tpm.h-37-struct TPMIfClass {
include/sysemu/tpm.h-38-    InterfaceClass parent_class;
include/sysemu/tpm.h-39-
include/sysemu/tpm.h:40:    enum TpmModel model;
include/sysemu/tpm.h-41-    void (*request_completed)(TPMIf *obj, int ret);
include/sysemu/tpm.h-42-    enum TPMVersion (*get_version)(TPMIf *obj);
include/sysemu/tpm.h-43-};
include/sysemu/tpm.h-44-