This paper addresses the I/O latency issue within Xen-ARM. Although Xen-ARM's split driver presents reliable driver isolation, it requires additional inter-VM scheduling. Consequently, the credit scheduler within Xen-ARM results in unsatisfactory I/O latency for real-time guest OS. This paper analyzes the I/O latency in Xen-ARM's interrupt path, and proposes a new scheduler to bound I/O latency. Our scheduler dynamically assigns priorities to guest OSs so that Xen-ARM ensures to schedule the most urgent task within the system. The experimental results show that Xen-ARM with our new scheduler reduces delay spikes, latency larger than 1ms, from 16% to 1% while retaining the split driver model.