/usr/sbin/xm is in xen-utils-common 4.1.4-3+deb7u9.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/sbin/../lib/xen-common/bin/xen-toolstack-wrapper
/usr/sbin/../lib/xen-common/bin/xen-toolstack-wrapper