Re: [PATCH] cpu hotplug issue

Gleb Natapov
2011-07-21T12:40:35Z

On Thu, Jul 21, 2011 at 02:35:09PM +0200, Jan Kiszka wrote:
> On 2011-07-21 14:25, Gleb Natapov wrote:
> > On Thu, Jul 21, 2011 at 02:22:07PM +0200, Jan Kiszka wrote:
> >> On 2011-07-21 13:06, Vasilis Liaskovitis wrote:
> >>> More precisely: To enable cpu-hotplug at each bisect stage, I apply
> >>> this patch derived from:
> >>> http://lists.gnu.org/archive/html/qemu-devel/2010-08/msg00850.html
> >>>
> >>> diff --git a/hw/qdev.c b/hw/qdev.c
> >>> index 1aa1ea0..aed48ce 100644
> >>> --- a/hw/qdev.c
> >>> +++ b/hw/qdev.c
> >>> @@ -327,6 +327,7 @@ BusState *sysbus_get_default(void)
> >>> if (!main_system_bus) {
> >>> main_system_bus = qbus_create(&system_bus_info, NULL,
> >>> "main-system-bus");
> >>> + main_system_bus->allow_hotplug = 1;
> >>
> >> BTW, this reminds me why "fixing" CPU hotplug won't help a lot. We
> > I do not see relation between qdev not allowing cpu hotplug bug
>
> It's not a bug, it's a feature: The system bus we attach APICs to so far
> is a statically configured beast, intentionally hotplug-incapable.
> Hacking this away in qemu-kvm will be a step towards where we came from
> and will break sooner or later again. We need a CPU/APIC bus, also for
> other reasons, that can then be made hotplug-capable.
>
Agree. I was calling the whole situation the "bug", not this missing line in
qdev in particular.

> > and cpu been
> > created with incorrect state bug. Fixing of former will not magically
> > make later disappear. Both should be solved.
>
> The issues hidden by the topology design problem should be solved
> nevertheless, that's true.
>
> Jan
>
> --
> Siemens AG, Corporate Technology, CT T DE IT 1
> Corporate Competence Center Embedded Linux

--
Gleb.