Violet：在RISC-V上为M模式RTOS实现全虚拟化

中文摘要 AI 辅助

在嵌入式系统中，可能需要复杂的配置，例如实时操作系统（RTOS）与通用操作系统（GPOS）的同时执行，或多个RTOS实例的运行。为了满足ARM和x86等架构的这些需求，嵌入式系统虚拟机监控器已被研究和开发。RISC-V在嵌入式系统中的应用日益增长，也面临着类似的需求。然而，RISC-V的虚拟化支持仅针对U模式（应用程序运行的模式）和S模式（通用操作系统运行的模式）作为虚拟化级别。M模式（FreeRTOS或Zephyr等RTOS运行的模式）被排除在虚拟化之外。这意味着，与ARM等架构类似，使用基于虚拟化支持特性的方法在虚拟机（VM）上运行RTOS是不可能的。因此，本文提出了Violet虚拟机监控器。Violet结合了RISC-V的虚拟化特性与基于软件的模拟，使得未经修改的M模式RTOS得以执行。评估使用RISC-V架构测试验证了M模式模拟功能的有效性。此外，该方案在SiFive HiFive Premier P550硬件上实现，证明了现有RTOS可以在Violet的VM上运行，并且与Linux等GPOS共存也是可能的。性能评估还量化了M模式模拟在M模式CSR访问、定时器中断延迟和上下文切换方面引入的开销。

英文摘要

In embedded systems, complex configurations may be required, such as the simultaneous execution of a real-time operating system (RTOS) and a general-purpose operating system (GPOS), or the operation of multiple RTOS instances. Embedded system hypervisors have been studied and developed to meet these requirements for architectures like ARM and x86. RISC-V is experiencing growing adoption in embedded systems and faces similar needs. However, RISC-V's virtualization support targets only U-mode (where applications run) and S-mode (where general-purpose OSs run) as virtualization levels. The M-mode, where RTOSs like FreeRTOS or Zephyr run, is excluded from virtualization. This means that, similar to architectures like ARM, running an RTOS on a Virtual Machine (VM) using methods based on virtualization support features is impossible. Therefore, this paper proposes the Violet hypervisor. Violet combines RISC-V's virtualization features with software-based emulation, enabling the execution of unmodified M-mode RTOSs. Evaluation verified the validity of the M-mode emulation functionality using RISC-V architecture tests. Furthermore, this was implemented on the SiFive HiFive Premier P550 hardware, demonstrating that existing RTOSs can run on Violet's VM and that coexistence with GPOSs like Linux is also possible. The performance evaluation also quantified the overhead introduced by M-mode emulation on M-mode CSR accesses, timer interrupt latency, and context switching.

发表机构

• Ritsumeikan University（立命馆大学）
• Information Technology R&D Center, Mitsubishi Electric Corporation（三菱电机株式会社信息技术研发中心）

机构由 AI 辅助整理，请以论文原文为准。