Re: [Qemu-devel] status of cpu hotplug work for x86_64?

[Anshul Makkar]

Hi,

But where are the patches. The links shared are just sites where
discussion about patches is going on.  Are there any public
repositories from where I can find proper patches ?

Thanks
Anshul Makkar.

On Fri, May 2, 2014 at 3:35 PM, Igor Mammedov <address@hidden> wrote:
> On Fri, 2 May 2014 14:10:35 +0200
> Vasilis Liaskovitis <address@hidden> wrote:
>
>> Hi,
>>
>> On Mon, Apr 28, 2014 at 11:58:38AM -0600, Chris Friesen wrote:
>> > Hi,
>> >
>> > I'm trying to figure out what the current status is for cpu hotplug
>> > and hot-remove on x86_64.
>> >
>> > As far as I can tell, it seems like currently there is a QMP
>> > "cpu-add" command but no matching remove...is that correct?
>>
>> correct. "cpu-add" is the way to hot-add CPUs.
>> There is no support for cpu hot-remove at this point.
>>
>> The latest patchset for cpu hot-remove that I know of is:
>> http://lists.gnu.org/archive/html/qemu-devel/2013-12/msg04266.html
>>
>> If I understand correctly the biggest hurdle is supporting vcpu destruction
>> during the VM lifetime on the kvm host side. The corresponding kvm patches 
>> have
>> not been accepted:
>> http://comments.gmane.org/gmane.comp.emulators.kvm.devel/114347
>>
>> So I have the same question as you: Is there any plan to support cpu 
>> hot-remove?
> Besides above mentioned series and KVM side of the problem there are
> several not yet addressed QEMU issues:
>   - remove dependency on cpu_index for X86 cpu (arbitrary CPU add/rm)
>   - need an interface to specify apic id when adding CPU
>     -  clean way would be -device x86-cpu-foo,{apic-id=xxx || 
> node=foo,socket=x,core=y,thread=z}
>     -  x86 cpu subclasses by Eduardo were merged in the last release so
>        on the road to "-device x86-cpu-foo" only conversion to of CPU 
> features to properties
>        is left (I need to rebase and respin it)
>   - fix vmstate register/unregister (migration and arbitrary CPU add/rm)
>
> As for plans QEMU side of work could be done without KVM support first and 
> then
> once KVM would be able to unplug VCPUs it could be added to QEMU without much 
> issues.
>
>
>>
>> thanks,
>>
>> - Vasilis
>
>