[Qemu-devel] How to enable the realtime features of qemu?

[cauchy-love]

Hi,
   I have noticed that the recent qemu provide realtime features as the qemu 
help outputs something like "run qemu with realtime features". But there is 
little information about that area. I would be much appreciated if someone can 
provide the detailed information (i.e., system configuration, usage) about 
qemu's realtime features.
  Thanks,
Yi