Improving the Reliability of the Operating System Inside a VM

Virtualization technology can provide reusability and strong isolation between different virtual machines (VMs). However, there is no effective isolation mechanism inside a VM to solve an operating system's reliability problems, including driver faults. This paper describes Chariot, an architecture that provides effective and transparent driver isolation inside the VM, achieves fine-grained driver isolation and retains the reusability advantage of virtualization technology. First, Chariot transparently monitors an isolated driver with monitoring wrappers, and establishes an access control table (ACT) in a timely manner that records the driver write permissions. Secondly, Chariot protects the shadow page table of the VM (where the driver resides) in due time to capture its write operations. Next, the ACT examines the correctness of the write operations. Finally, if an illegal write operation is detected, Chariot recovers the faulty driver and prevents the spread of driver faults in the VM. The experimental results show that Chariot effectively isolates more than 90% of injected faults (with performance losses of 20% in most benchmarks) and effectively improves the reliability of the VM. In addition, Chariot can be easily extended to isolate new drivers and ported to other versions of OSs in the virtualization environment.