Re: [Qemu-devel] [PATCH 1/7] Introduce a new bus "ICC" to connect APIC

[Anthony Liguori]

On 02/16/2012 06:50 AM, Jan Kiszka wrote:
> On 2012-02-16 13:42, Anthony Liguori wrote:
> > On 02/16/2012 05:25 AM, Jan Kiszka wrote:
> > > On 2012-02-16 00:16, Igor Mammedov wrote:
> > > > Introduce a new structure CPUS as the controller of ICC (INTERRUPT
> > > > CONTROLLER COMMUNICATIONS), and new bus "ICC" to hold APIC,instead
> > > > of sysbus. So we can support APIC hot-plug feature.
> > > >
> > > > This is repost of original patch for qemu-kvm rebased on current qemu:
> > > > http://lists.nongnu.org/archive/html/qemu-devel/2011-11/msg01478.html
> > > > All credits to Liu Ping Fan for writing it.
> > > >
> > > > V2 changes:
> > > >     - cpusockets_init: cpu_sockets is not yet initialized, use cpus that
> > > >       we got as input param instead for qbus_create, this makes cpus
> > > >       apics visible in "info qtree" monitor command
> > > >     - fix format error spotted by Jan and missed by checkpatch
> > > >     - cpu_has_apic_feature: return bool instead of int
> > >
> > > This patch surely no longer applies. And the ICC requires QOM conversion.
> >
> > Also, post-QOM, I don't think having an ICC bus makes a whole lot of sense.
> >
> > The LAPIC can be made a child of the CPU device with a bidirectional link.
>
> We do have a bus here, the IO-APICs are attached to it as well.


Isn't that a bus protocol that's specific to the LAPICs/IO-APICs?  I don't think 
that you would logically model the CPU as part of it.

I wonder if modeling inter-lapic communication via a bus is a bit overkill 
compared to what we do today (just a for() loop when needed).

Regards,

Anthony Liguori

 But we
> can surely save that dummy cpusockets device.
>
> Jan