I am writing a simple python script for migrating vm's based on zfs zvol's. Either I am doing something wrong or python migrateSetMaxSpeed not taking effect: no mater what value I specify (except for 0), I end up with 10 Mib/s migration speed. The code is:

def virt_migrate(domain):
    conn = libvirt.open('qemu:///system')
    domain_obj = conn.lookupByName(domain)
    dst='qemu+ssh://root@%s/system' % args.remote
    domain_obj.migrateSetMaxSpeed(40,0)
    new_dom = domain_obj.migrateToURI(dst,libvirt.VIR_MIGRATE_LIVE | libvirt.VIR_MIGRATE_PEER2PEER | libvirt.VIR_MIGRATE_NON_SHARED_INC | libvirt.VIR_MIGRATE_PERSIST_DEST | libvirt.VIR_MIGRATE_UNDEFINE_SOURCE, None, 0)
    conn.close()