Towards Temporal and Spatial Isolation in Memory Hierarchies for Mixed-Criticality Systems with Hypervisors

In mixed-criticality systems, applications with different levels of criticality are integrated on the same computational platform. Without a proper isolation of the different applications of such a mixed-criticality system certification gets expensive, because it has to be shown that application components of lower criticality do not hamper the correct operation of the critical applications. Therefore, all components – even the less critical ones – have to be certified for the highest criticality level. The use of hypervisors promises to shield applications of different criticality from each other, thus keepting certification cost reasonable. Indeed hypervisors can provide spatial isolation. Further they can prohibit certain types of temporal interference. We show, however, that full temporal isolation is only achievable if the hypervisor is run on appropriate hardware. We discuss hardware mechanisms that thwart respectlively facilitate temporal isolation. This way we provide a guideline for the sharing of resources and the realization of memory hierarchies for mixedcriticality multi-core systems. Keywords—mixed-criticality systems; partitioning; multi-core; isolation; time predictability; memory hierarchy;