please try below test code piece. Hope it could help you.

Thanks& Regards,
Criping

#include <stdio.h>
#include <stdlib.h>

#include <xenctrl.h>

int main(int argc, char *argv[] )
{
    int cpu, xc_id;
    if ( argc < 2) {
        printf("Please input offline CPU-id\n");
        exit(0);
    }
    cpu = atoi(argv[1]);
    printf("Offline CPU %d\n", cpu);
    xc_id = xc_interface_open();
    xc_cpu_offline(xc_id, cpu);
    printf("CPU offlined\n");
    xc_interface_close(xc_id);
    return 0;
}

________________________________
From: xen-devel-bounces@lists.xensource.com [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of ChristieShum@gmail.com
Sent: 2009Äê5ÔÂ13ÈÕ 12:30
To: Xen-devel
Subject: Re: Re: [Xen-devel] need help about CPU offline/hotplug in Xen Unstable

Thanks a lot.
Is there a sample or tutorial for how to implement the offline process using this library?

On May 12, 2009 11:02pm, Keir Fraser <keir.fraser@eu.citrix.com> wrote:
> On 12/05/2009 15:47, "Ting Shen" christieshum@gmail.com> wrote:
>
>
>
> > Then I downloaded the stable version from xen.org http://xen.org>  and
>
> > installed.
>
> > But since the document is not updated, I don't know the detail method to
>
> > offline a physical CPU.
>
>
>
> It's available as a library function (xc_cpu_offline) but not actually
>
> plumbed into a xm command, or other tool.
>
>
>
>  -- Keir
>
>
>
>
>