[Pkg-libvirt-maintainers] Bug#742076: Bug#742076: libvirt-bin: setvcpus command fails to shrink the numbers of vcpu

[Guido Günther]

On Thu, Mar 20, 2014 at 11:34:09AM +0100, Sdkfz262 wrote:
> Hi Guido,
> 
> And thanks for that quick feedback. From what you wrote and the post you
> linked Yesterday I understand that's not a bug, or at least not a Debian
> bug, but something which requires (as of now) more configuration than a
> simple "setvcpus" while the guest is running.
> 
> I gave a try to your suggestion (that is: reboot the guest) and the
> situation didn't change : vcpuinfo or vcpucount still gives me back 1 vcpu,
> while the guest sees (and uses) 2 vcpus.
> 
> I think it's related to the fact that the definition file wasn't
> (automatically) changed, even with that "setvcpus <domain> 1" command. It's
> still
> 
> "<vcpu placement='static'>2</vcpu>"
> 
> and there is no "current" flag as stated in the post you linked (<vcpu
> placement='static' current='1'>2</vcpu>)
> 
> Unless I'm mistaken, that means that the only way to modify the number of
> cpus a guest can run on is to shutdown the guest, modify the definition file
> and switch it on back.

Can you try the to change the vcpus while the vm is shutdown? You can
also use "virsh edit <domain>". You should rather not change the
definition file by hand.
Cheers,
 -- Guido