Virtualization is increasingly utilized for consolidating server resources to improve efficiency by conserving power and space. However, significant hurdles remain in achieving satisfactory performance in a virtualized system. Notably, virtualization of network I/O continues to be a performance barrier. The driver domain model of I/O virtualization suffers from an inherent network performance disadvantage due to the necessity of scheduling a driver domain. However, this virtualization model is desirable because of its fault tolerance and isolation properties. In this work, I argue that it is possible to overcome the barrier of network I/O performance while maintaining domain protection by providing a i mechanism which enables guests to operate the driver domain on their own behalf without the intervention of the scheduler. I describe my implementation of the worldswitch mechanism and evaluate its performance. I show that with the worldswitch enabled, guests achieve higher bandwidth and lower latency than in an unmodified system.