Hi Zhu,

          I am testing the hot unplug feature using your github branch 'cpu-hotplug'. It is working fine when first time I added and deleted cpu. But when I tried to add cpu second time, it showed me the following error:
(qemu) device_add kvm64-x86_64-cpu,apic-id=1,id=cpu1

           Duplicate ID 'cpu1' for device

I guess you should use iasl and regenerate the ACPI tables.

You can refer to the following issue:
http://lists.nongnu.org/archive/html/qemu-devel/2014-09/msg02993.html

I get from one of your patch (https://patchwork.ozlabs.org/patch/439485/) commit message that cpu is not literally removed from qemu but guest is unable to use it anymore. Do you know the way how I can reuse that cpu which has already added and deleted once. Or unparking the cpu mechanism.

Thanks,

Mohsin Kazmi