Hi, The virsh vcpupin command does not work when it uses Xend(xend_internal.c). HV(xen_internal.c) works fine. I'm testing on Xen3.1.0(hypervisor_version=2, dom_interface_version=5, xendConfigVersion=4), and using current libvirt(ChangeLog revision 1.546). To solve this problem, I got the xend debug information and compared that. * in the case of executing "virsh vcpupin 63 7 1" * [2007-05-29 09:33:20 4258] DEBUG (XendDomain:1297) dom(63) cpu 7 cpumap [1](<type'str'>) * in the case of executing "xm vcpu-pin 63 7 1" * [2007-05-29 09:33:32 4258] DEBUG (XendDomain:1297) dom(63) cpu 7 cpumap [1](<type'list'>) There is one different thing. The type of cpumap is str when executing virsh command, but the type of cpumap is list when executing xm command. Do you have any idea ? Thanks, Saori Fukuta