Re: [Qemu-devel] [PATCH 07/23] target-i386: convert cpuid features into properties

[Paolo Bonzini]

Il 03/10/2012 17:03, Eduardo Habkost ha scritto:
> On Tue, Oct 02, 2012 at 05:38:45PM -0300, Eduardo Habkost wrote:
>> (Now replying on the right thread, to keep the discussion in the right
>> place. I don't know how I ended up replying to a pre-historic version of
>> the patch, sorry.)
>>
>> On Tue, Oct 02, 2012 at 05:36:59PM +0200, Igor Mammedov wrote:
>> [...]
>>> @@ -1938,6 +2043,12 @@ static void x86_cpu_initfn(Object *obj)
>>>      object_property_add(obj, "tsc-frequency", "int",
>>>                          x86_cpuid_get_tsc_freq,
>>>                          x86_cpuid_set_tsc_freq, NULL, NULL, NULL);
>>> +    x86_register_cpuid_properties(obj, feature_name);
>>> +    x86_register_cpuid_properties(obj, ext_feature_name);
>>> +    x86_register_cpuid_properties(obj, ext2_feature_name);
>>> +    x86_register_cpuid_properties(obj, ext3_feature_name);
>>> +    x86_register_cpuid_properties(obj, kvm_feature_name);
>>> +    x86_register_cpuid_properties(obj, svm_feature_name);
>>
>> Stupid question about qdev:
>>
>> - qdev_prop_set_globals() is called from device_initfn()
>> - device_initfn() is called before the child class instance_init()
>>   function (x86_cpu_initfn())
>> - So, qdev_prop_set_globals() gets called before the CPU class
>>   properties are registered.
>>
>> So this would defeat the whole point of all the work we're doing, that
>> is to allow compatibility bits to be set as machine-type global
>> properties. But I don't know what's the right solution here.
>>
>> Should the qdev_prop_set_globals() call be moved to qdev_init() instead?
>> Should the CPU properties be registered somewhere else?

Properties should be registered (for all objects, not just CPUs) in the
instance_init function.  This is device_initfn.

I would add an instance_postinit function that is called at the end of
object_initialize_with_type, that is after instance_init, and in the
opposite order (i.e. from the leaf to the root).

Paolo

> Replying to myself: it wouldn't make sense to call it on qdev_init() as
> it would overwrite properties set between the calls to object_new() and
> qdev_init().
> 
> But I still don't see what would be the proper way to solve this. I
> don't see any mechanism that would allow us to ensure the
> object_property_add() calls are made before qdev_prop_set_globals() is
> called.
>