Re: [Qemu-devel] [PATCH qom v1 1/1] qom/object.c: Split out object and class caches.

[Peter Crosthwaite]

Hi

On Wed, Dec 4, 2013 at 1:40 AM, Paolo Bonzini <address@hidden> wrote:
> Il 28/11/2013 05:27, Peter Crosthwaite ha scritto:
>> The object-cast and class-cast caches cannot be shared because class
>> caching is conditional on the target type not being an interface and
>> object caching is unconditional. Leads to a bug when a class cast
>> to an interface follows an object cast to the same interface type:
>>
>> FooObject = FOO(obj);
>> FooClass = FOO_GET_CLASS(obj);
>>
>> Where TYPE_FOO is an interface. The first (object) cast will be
>> successful and cache the casting result (i.e. TYPE_FOO will be cached).
>> The second (class) cast will then check the shared cast cache
>> and register a hit. The issue is, when a class cast hits in the cache
>> it just returns a pointer cast of the input class (i.e. the concrete
>> class).
>>
>> When casting to an interface, the cast itself must return the
>> interface class, not the concrete class. The implementation of class
>> cast caching already ensures that the returned cast result is only
>> a pointer cast before caching. The object cast logic however does
>> not have this check.
>>
>> Resolve by just splitting the object and class caches.
>>
>> Signed-off-by: Peter Crosthwaite <address@hidden>
>
> Cc: address@hidden

Nathan just tested some Microblaze ethernet use cases and this is
needed to get it working. Please apply to stable as critical bugfix.

Regards,
Peter

> Reviewed-by: Paolo Bonzini <address@hidden>
>