RPUGuard: Real-Time Processing Unit Virtualization for Mixed-Criticality Applications

Virtualization techniques are attracting interest in industrial applications to implement mixed-criticality systems taking full advance of modern embedded architectures, such as Multi-Processor Systems on Chip (MPSoCs). However, the virtualization support for important hardware accelerators, such as Real-Time Processing Units (RPUs), used for real-time and/or safety-critical workloads, is still overlooked. In this paper, we propose an architectural solution to virtualize RPUs in complex embedded systems. Specifically, we design and implement a component, named RPUGuard, which is able to guarantee isolated communication channels with a fixed bandwidth between virtual machines, running on regular Application Processing Units (APUs), and the RPU on the same MPSoC. We evaluated RPUGuard on the Zynq Ultrascale+ board, in the context of a challenging case study concerning the magnetic control system of the ITER experimental nuclear fusion reactor. Results demonstrate how our solution can mitigate the weaknesses of current asymmetric communication techniques, while providing isolation guarantees to critical communication channels.