Bao - a lightweight static partitioning hypervisor

Introduction

Bao (from Mandarin Chinese “bǎohù”, meaning “to protect”) is a lightweight, open-source embedded hypervisor which aims at providing strong isolation and real-time guarantees. Bao provides a minimal, from-scratch implementation of the partitioning hypervisor architecture.

Designed mainly for targeting mixed-criticality systems, Bao strongly focuses on isolation for fault-containment and real-time behavior. Its implementation comprises only a minimal, thin-layer of privileged software leveraging ISA virtualization support to implement the static partitioning hypervisor architecture: resources are statically partitioned and assigned at VM instantiation time; memory is statically assigned using 2-stage translation; IO is pass-through only; virtual interrupts are directly mapped to physical ones; and it implements a 1-1 mapping of virtual to physical CPUs, with no need for a scheduler.

Bao has no external dependencies, such as on privileged VMs running untrustable, large monolithic general-purpose operating systems (e.g., Linux), and, as such, encompasses a much smaller TCB.

Bao originally targets the Armv8-A architecture, but there is experimental support for the RISC-V architecture. The full list of supported (and work in progress) platforms is presented below:

• Xilinx Zynq UltraScale+ MPSoC ZCU102 (Armv8-A)
• Xilinx Zynq UltraScale+ MPSoC ZCU104 (Armv8-A)
• Ultra96 Zynq UltraScale+ ZU3EG (Armv8-A)
• 96Boards HiKey 960 (Armv8-A)
• NXP MCIMX8M-EVK (Armv8-A) - wip
• NXP MCIMX8QM-CPU (Armv8-A) - wip
• 96Boards ROCK960 (Armv8-A) - wip
• QEMU virt (Armv8-A) - wip
• QEMU virt (RISC-V rv64) - wip

NOTE: This is work in progress! Don't expect things to be complete. Use at your own risk.

Community Resources

Project website:

• http://www.bao-project.org/

Source code:

Contributing:

• Please get in touch ([email protected])

Demos

As of now, there are two demos for the ZCU10X platforms.

For specific instructions on how to build, compile, and run please refer to:

1. ZCU10X bare metal guest demo:

• https://github.com/bao-project/zcu_baremetal_demo

1. ZCU10X Linux/FreeRTOS demo:

• https://github.com/bao-project/zcu_linux-freertos_demo

References

1. José Martins, Adriano Tavares, Marco Solieri, Marko Bertogna, and Sandro Pinto. "Bao: A Lightweight Static Partitioning Hypervisor for Modern Multi-Core Embedded Systems". In Workshop on Next Generation Real-Time Embedded Systems (NG-RES 2020). Schloss Dagstuhl-Leibniz-Zentrum für Informatik. 2020. https://drops.dagstuhl.de/opus/volltexte/2020/11779/

2. José Martins and Sandro Pinto. "Bao: a modern lightweight embedded hypervisor". In Proceedings of the Embedded World Conference, Nuremberg, Germany, 2020.