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

[Anthony Liguori]

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.

Regards,

Anthony Liguori