Re: [Qemu-devel] Re: [PATCH] Fix bug for vcpu hotplug

[Anthony Liguori]

On 08/19/2010 10:34 AM, Avi Kivity wrote:
>  On 08/19/2010 06:24 PM, Anthony Liguori wrote:
> > On 08/18/2010 02:33 AM, Avi Kivity wrote:
> > >  On 08/18/2010 10:17 AM, Liu, Jinsong wrote:
> > > > During test, we found qemu-kvm has a bug result in guestos shutdown 
> > > > when vcpu hotadd.
> > > > This patch is to fix the bug, allow hotplug for sysbus qdev.
> > > >
> > > > --- a/hw/qdev.c
> > > > +++ b/hw/qdev.c
> > > > @@ -108,6 +108,7 @@ DeviceState *qdev_create(BusState *bus, const 
> > > > char *name)
> > > >       if (!bus) {
> > > >           if (!main_system_bus) {
> > > >               main_system_bus = qbus_create(&system_bus_info, NULL, 
> > > > "main-system-bus");
> > > > +            main_system_bus->allow_hotplug = 1;
> > > >           }
> > > >           bus = main_system_bus;
> > > >       }
> > >
> > >
> > > Looks reasonable to me.
> >
> > Not really to me.
> >
> > SysBus does not support hotplugging and CPU hot plug shouldn't have 
> > anything to do with qdev hotplug.
> >
> > Can you explain a bit more why this is needed?
>
> On cpu hotplug an apic is added, and apics live on main_system_bus.

That's the problem then.  An APIC does not live on any bus and that's 
where the problem ought to be fixed.

Regards,

Anthony Liguori