Re: [Qemu-devel] [PATCH v3] apic: bump emulated lapic version to 0x14 on pc machines >= 2.1

[Alexander Graf <agraf@suse.de>]

On 01.05.14 19:22, Gabriel L. Somlo wrote:
> On Wed, Apr 30, 2014 at 09:44:32PM +0200, Alexander Graf wrote:
>>> diff --git a/hw/intc/apic.c b/hw/intc/apic.c
>>> index 2f40cba..4480bc4 100644
>>> --- a/hw/intc/apic.c
>>> +++ b/hw/intc/apic.c
>>> @@ -32,6 +32,8 @@
>>>   #define SYNC_TO_VAPIC                   0x2
>>>   #define SYNC_ISR_IRR_TO_VAPIC           0x4
>>> +uint8_t apic_version = 0x14;
>> Is there any way to make this a qdev/qom device property rather than
>> a global?
> If there is, and anyone with a better understanding of qom/qdev
> has an example I could follow, that would be much appreciated!
>
> As far as I could comprehend it since I started looking at it last
> night, the apic_class_init() functions run before pci_init() in
> pc_[q35|piix].c knows which machine type we have, but the
> apic_realize() functions (which appear to be the actual apic
> "constructors") run after that.
>
> The obvious alternative to having one global apic version would be
> to add a field to APICCommonClass or APICCommonState, and then somehow
> modify the default (set in apic_class_init()) from pci_init()
> according to the machine version; After that, each apic may refer to
> its private data member "version" when needed.
>
> So, is qom/qdev basically boiling down to a set of macros that can
> translate something like "qom_set_property(apic_instance, version, 0x14);"
> into "apic_instance.version = 0x14;" ?

With qdev we basically had an array of constructor parameters in the 
qdev definition. You could set these from the outside between create and 
init, basically:

   dev = dev_create()
   set_prop(dev, "foo", bar);
   dev_init(dev)

which semantically translated to

   dev = new dev(foo = bar);

The way to do this with QOM is similar, but I keep forgetting the 
details. I'm sure you'll easily find out :).


Alex