Re: [Qemu-devel] [RFC/PATCH 0/1] cpu hotplug for s390

[Andreas Färber]

Am 19.04.2013 09:51, schrieb Jens Freimann:
> On Wed, Apr 17, 2013 at 08:06:37PM +0200, Andreas Färber wrote:
>> Hi Jens,
>>
>> Am 03.04.2013 08:42, schrieb Jens Freimann:
>>> this is what our approach to CPU hotplug looks like.
>>> With respect to Igor's CPU hotplug series, how should we proceed? 
>>> Should we change the interface to 
>>> qemu_system_cpu_add_notifier/qemu_system_cpu_hotplug_request/cpu-add etc?
>>
>> I am wondering if my recent qdev/device_add fixes would allow to
>> implement CPU hot-add via device_add for s390x?
> 
> From what I've seen so far it could be possible, but...

Hm, so probably not a good idea? Just looking for a guinea pig for
infrastructure testing...

>> Background is that for x86 we currently have a flat CPU core/thread
>> namespace but would need to deal with sockets, cores and threads to get
>> topologies right. I assume there are no such issues on s390x, so that
>> the vCPU to CPUState mapping could stay 1:1?
> 
> s390 hardware today already has a topology and CPU features.  We are not 
> modelling it in QEMU right now, but want to go there in the future so that 
> there would be no simple 1:1 mapping anymore.

In that case please enlighten us how the topology model should/could
look like in the future, so that we can align this with the x86
remodelling and APIC/ID discussion.

Regards,
Andreas

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