Re: [Qemu-arm] [Qemu-devel] VCPU hotplug on KVM/ARM

[Marc Zyngier]

On 01/03/18 13:32, David Hildenbrand wrote:
> On 01.03.2018 11:05, Peter Maydell wrote:
>> On 1 March 2018 at 09:50, Igor Mammedov <address@hidden> wrote:
>>> In QEMU on x86 (and I think ppc, s390 as well), we create vCPUs on demand.>>
>>> It would be nice if ARM would be able to do that too,
>>> so that it could take advantage of the same code.
>>
>> It's not clear to me how that would work, given that for
>> instance the interrupt controller wants to know up-front
>> how many CPUs it has to deal with.
>>
> 
> So how is cpu hotplug handled in HW? Or doesn't it even exist there?

I don't know of any physical system offering that facility.

> (we have max_cpus for the interrupt controller, but not sure if that is
> what we want)
We'd need something along those lines. Each CPU has a notional point to
point link to the interrupt controller (to the redistributor, to be
precise), and this entity must pre-exist.

Thanks,

        M.
-- 
Jazz is not dead. It just smells funny...