If you are used to being able to apply QoS policies to interfaces, it is somewhat surprising when you go to apply one to a subinterface and are greated with an error message:
CBWFQ : Not supported on subinterfaces
Never fear, there is a documented work around. You basically have to trick the router into believing CBWFQ is not being applied to the subinterface. Cisco's fancy term for this is a hierarchical policy.
Here's a link with specific examples: Applying QoS Features to Ethernet Subinterfaces