Cache Covert-Channel Mitigation in Cloud Virtualization with XEN's Credit Scheduler

Covert- and side-channels as well as techniques to establish them in cloud computing are in focus of research for quite some time. However, not many concrete mitigation methods have been developed and even less have been adapted and concretely implemented by cloud providers. Thus, we recently conceptually proposed C-3-Sched a CPU scheduling based approach to mitigate L2 cache covert-channels. Instead offlushing the cache on every context switch, we schedule trusted virtual machines to create noise which prevents potential covert-channels. Additionally, our approach aims on preserving performance by utilizing existing instead of artificial workload while reducing covert-channel related cache flushes to cases where not enough noise has been achieved. In this work we evaluate cache covert-channel mitigation and performance impact of our integration of C-3-Sched in the XEN credit scheduler. Moreover, we compare it to naive solutions and more competitive approaches.