[libvirt] libvirt/libxl implemetation of get_online_cpu / virNodeGetCPUMap?

Hi, A recent OpenStack nova commit make use of virNodeGetCPUMap to get the list of online cpu of a host. But this API is not implemented for the libvirt xen driver. The commit: Add handling for offlined CPUs to the nova libvirt driver. https://review.openstack.org/gitweb?p=openstack/nova.git;a=commitdiff;h=0696... Is there a need to use this under Xen? (Is it possible to have offline CPU?). What libxl API those provide this information, if it exist? I found libxl_get_online_cpus() but that not enough. They want a bitmap. Thanks, -- Anthony PERARD