Description of problem:
cpu_weight does not work in config file

Version-Release number of selected component (if applicable):
xen-3.0.3-25.0.3.el5

How reproducible:
cpu_weight = '128'

into your config, restart the guest.

xm sched-credit -d <guest>
{'cap': 0, 'weight': 256}

But I can set the weight by hand:
xm sched-credit -d <guest> -w 128
root@cda-gw:~# xm sched-credit -d <guest>
{'cap': 0, 'weight': 128}

  
Additional info: