[Qemu-devel] 答复： Re: [PATCH v3 1/3] qom: make base type user-creatable abstract

[Lin Ma]

>>> "Daniel P. Berrange" <berra...@redhat.com> 2016/9/26 星期一 下午 6:37 >>>
>On Mon, Sep 26, 2016 at 06:16:25PM +0800, Lin Ma wrote:
>> Signed-off-by: Lin Ma <l...@suse.com>
>> ---
>>  qom/object_interfaces.c | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
>> index bf59846..9288242 100644
>> --- a/qom/object_interfaces.c
>> +++ b/qom/object_interfaces.c
>> @@ -217,6 +217,7 @@ static void register_types(void)
>>        static const TypeInfo uc_interface_info = {
>>                .name            = TYPE_USER_CREATABLE,
>>                .parent        = TYPE_INTERFACE,
>> +        .abstract    = true,
>>                .class_size = sizeof(UserCreatableClass),
>>        };
>
>This doesn't make any conceptual sense. UserCreatable is an inteface and
>by definition all interfaces are abstract.
>
Sorry for the late reply, I was on vacation.
oh...indeed, add '.abstract = true' for an interface is not a good idea.

>Were you trying to fix some particular real bug here ? If so, we almost
>certainly need a different fix to what's suggested here, because QOM
>should automatically treat all interfaces as abstract by their very
>nature.
>
For other interfaces, say 'acpi-device-interface' or 'ipmi-interface', it's fine
as they are not user creatable. but for 'user-creatable', when performing
'qemu-system-x86_64 -object user-creatable,id=foo', segfault happens:
 
    $ qemu-system-x86_64 -object user-creatable,id=foo
    **
    ERROR:/work/armbru/qemu/qom/object.c:361:object_initialize_with_type: 
assertion failed (type->instance_size >= sizeof(Object)): (0 >= 40)
    Aborted (core dumped)
 
 
How about the following changes to skip TYPE_USER_CREATABLE in function
user_creatable_add_type ?
 
@@ -102,7 +102,8 @@ Object *user_creatable_add_type(const char *type, const 
char *id,
                 return NULL;
         }
 
-    if (!object_class_dynamic_cast(klass, TYPE_USER_CREATABLE)) {
+    if (!object_class_dynamic_cast(klass, TYPE_USER_CREATABLE) ||
+           !strcmp(type, TYPE_USER_CREATABLE)) {
                 error_setg(errp, "object type '%s' isn't supported by 
object-add",
                                    type);
                 return NULL;
...
 
@@ -229,7 +230,8 @@ int user_creatable_help_func(void *opaque, QemuOpts *opts, 
Error **errp)
                                 list = list->next) {
                         const char *name;
                         name = object_class_get_name(OBJECT_CLASS(list->data));
-                   printf("%s\n", name);
+                   if (strcmp(name, TYPE_USER_CREATABLE))
+                           printf("%s\n", name);
...
 
 
Thanks,
Lin