[Qemu-devel] Re: [PATCH v2 0/7] APIC/IOAPIC cleanup

[Jan Kiszka]

Avi Kivity wrote:
>  On 08/23/2010 12:06 AM, Anthony Liguori wrote:
>> On 08/22/2010 03:33 PM, Avi Kivity wrote:
>>>  On 08/22/2010 11:03 PM, Anthony Liguori wrote:
>>>> On 08/22/2010 02:44 PM, Avi Kivity wrote:
>>>>>> No more MI diamond and all devices have DeviceStates. 
>>>>>> Coincidentally, it matches more closely how hardware works..
>>>>>>
>>>>>
>>>>>
>>>>> Well, I agree, but I honestly lost the context.  How does this
>>>>> relate to the APIC and cpu hotplug?
>>>>
>>>> My original assertion was that the local APIC is not a DeviceState,
>>>> but rather it's a CPU feature.
>>>>
>>>> If you look at some of the magic that apic.c has to do in the IO
>>>> callbacks, it should be clear that it's special. 
>>>
>>> It's special in that it is connected to a cpu core.  So's the RTL8139
>>> device, on one hand connected to a PCI bus, on the other hand
>>> connected to a PHY (netdev in qemu).
>>>
>>>> In the not too distant future, I'd like to move apic.c to
>>>> target-i386.  There should be no need to explicitly instantiate it
>>>> when you instantiate a CPU.
>>>
>>> But then there's a need explicitly not to instantiate it when using
>>> -isapc.
>>
>> No.  isapc has nothing to do with whether a CPU has a local APIC.
>>
>> You don't instantiate the local APIC if you create a 486 CPU.  If you
>> create an isapc with a pentium processor, it's going to have a local
>> APIC although it's irrelevant as it's fully compatible with the 486.
>>
> 
> Okay, okay.  "But then there's a need explicitly not to instantiate it
> when modelling a 486 or lower".

...plus the need to instantiate it (as a dedicated device) when modeling
486 SMP.

Jan

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