hwclock failed to open in Xen guest with error: 'No usable clock interface found'

Issue

• Xen Server domU reports following error when executing hwclock command:

  # hwclock --debug
  hwclock from util-linux-2.13-pre7
  hwclock: Open of /dev/rtc failed, errno=19: No such device.
  No usable clock interface found.
  Cannot access the Hardware Clock via any known method.
  

• But, in the Hypervisor (dom0) this problem doesnt occur while running the hwclock command.