Xentry: Hypervisor-Level Soft Error Detection

Cloud data centers leverage virtualization to share commodity hardware resources, where virtual machines (VMs) achieve fault isolation by containing VM failures within the virtualization boundary. However, hypervisor failure induced by soft errors will most likely affect multiple, if not all, VMs on a single physical host. Existing fault detection techniques are not well equipped to handle such hypervisor failures. In this paper, we propose a new soft error detection framework, Xentry (a sentry on soft error for Xen), that focuses on limiting error propagation within and from the hypervisor. In particular, we have designed a VM transition detection technique to identify incorrect control flow before VM execution resumes, and a runtime detection technique to shorten detection latency. This framework requires no hardware modification and has been implemented in the Xen hypervisor. The experiment results show that Xentry incurs very small performance overhead and detects over 99% of the injected faults.