Light-Weighted Virtualization Layer for Multicore Processor-Based Embedded Systems

The real-time resource management in the Linux kernel is dramatically improving due to the effective contribution of the realtime Linux community. However, reusing existing real-time applications in embedded systems is required to develop commercial products without significantly increasing their cost because existing real-time applications run on real-time OSes whose OS API is significantly different from the POSIX interface. A virtual machine monitor that executes multiple operating systems simultaneously is a promising solution, but existing virtual machine monitors such as Xen and KVM are hard to be used for embedded systems due to their complexities and throughput oriented designs. In this paper, we introduce a lightweight processor abstraction layer named vlk. vlk provides virtual CPUs (vCPUs) for respective guest OSes, and schedules them according to their priorities. In a typical case, vlk schedules Linux with a low priority and an RTOS with a high priority. Two important features of vlk are an interrupt prioritizing mechanism and a vCPU migration mechanism that improves real-time capabilities in order to make the virtualization layer more suitable for embedded systems. We also discuss why the traditional virtual machine monitor design is not appropriate for embedded systems, and how the features of vlk allow us to design modern complex embedded systems with less efforts.