Re: [Qemu-devel] VCPU Hot-Unplug Feature

[Eduardo Otubo]

On Mon, May 04, 2015 at 09=34=21PM +0300, Fahri Cihan Demirci wrote:
> Hello Alexandre,
> 
> Thank you for your response. I came upon that patch on the Libvirt mailing 
> list, too. However, the following comment makes me think that it's not likely 
> to be merged:
> 
> https://www.redhat.com/archives/libvir-list/2015-February/msg00415.html
> 
> Also, later in the thread, the author of the patch seems to confirm that the 
> plan for hotplug in QEMU is not compatible with that patch:
> 
> https://www.redhat.com/archives/libvir-list/2015-March/msg01169.html
> 
> So, I think Libvirt developers have decided to wait until there is a 
> generalized groundwork for VCPU hot-unplug in the QEMU code base. That's why 
> I decided to inquire and offer help for QEMU developers, since the ball seems 
> to be in their court now.

We're very interested in having this feature upstream as well. As Fahri
stated above, I also would like to offer help to get it pushed.

What's the current status?

Regards,

> 
> Thanks a lot for your time.
> 
> 
> On Mon, May 04, 2015 at 07:49:08PM +0200, Alexandre DERUMIER wrote:
> > Hi,
> > 
> > they are a lot of patches sent on the mailing list recently,
> > 
> > cpu hotplug|unplug with device_add|del
> > 
> > https://www.redhat.com/archives/libvir-list/2015-February/msg00084.html
> > 
> > 
> > 
> > ----- Mail original -----
> > De: "Fahri Cihan Demirci" <address@hidden>
> > À: "qemu-devel" <address@hidden>
> > Envoyé: Lundi 4 Mai 2015 18:24:43
> > Objet: [Qemu-devel] VCPU Hot-Unplug Feature
> > 
> > Hello, 
> > 
> > We are interested in being able to remove a VCPU from an active Libvirt 
> > domain running under QEMU/KVM. However, currently that does not seem to be 
> > possible because QEMU does not provide an interface for hot-unplugging a 
> > VCPU. The corresponding feature page [1] on the QEMU wiki mentions the 
> > cpu-add interface and the generalized device add/del interface. So, my 
> > question is, is there someone working on a cpu-remove interface or making 
> > progress in the generalized device add/del interface to hot-unplug VCPUS? 
> > If you are in any way interested in or planning such a feature, we may 
> > provide feedback, testing or help in the development effort. Any other 
> > input, guidance or corrections would be also most welcome. Thank you. 
> > 
> > [1] http://wiki.qemu.org/Features/CPUHotplug 
> > 
> > 
> > Best regards, 
> > Fahri Cihan Demirci 
> 

-- 
Eduardo Otubo
ProfitBricks GmbH

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