Re: [PATCH] cpu hotplug issue

Jan Kiszka
2011-07-21T12:35:15Z

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.

> 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

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