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.

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

The full list of supported (and work in progress) platforms is presented below:

Armv8-A AArch64

• Xilinx Zynq UltraScale+ MPSoC ZCU102/4
• Ultra96 Zynq UltraScale+ ZU3EG
• NXP MCIMX8QM-CPU
• NVIDIA Jetson TX2
• 96Boards HiKey 960
• Raspberry Pi 4
• QEMU virt
• Arm Fixed Virtual Platforms
• BeagleBone AI-64
• NXP MCIMX8M-EVK
• 96Boards ROCK960

Armv7-A / Armv8-A AArch32

• Arm Fixed Virtual Platforms
• QEMU virt
• STM32MP157-DK2

Armv8-R AArch64

• Arm Fixed Virtual Platforms

Armv8-R AArch32

• Arm Fixed Virtual Platforms
• NXP S32Z/E
• Renesas RZT2M

RISC-V RV64

• QEMU virt
• Rocket w/ H-extension
• CVA6 w/ H-extension

RISC-V RV32

• QEMU virt

Project website:

• http://www.bao-project.org/

Source code:

• https://github.com/bao-project/bao-hypervisor.git
• [email protected]:bao-project/bao-hypervisor.git

Contributing:

• Please get in touch ([email protected])

For a step-by-step guide on how to run different demo configurations of the Bao hypervisor featuring multiple guest operating systems and targeting several platforms please refer to: Bao Hypervisor Demo Guide

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.

3. José Martins and Sandro Pinto. "Static Partitioning Virtualization on RISC-V". In RISC-V Summit, virtual, 2020. https://www.youtube.com/watch?v=yuxMn4ZApEM

4. Bruno Sá, José Martins and Sandro Pinto. "A First Look at RISC-V Virtualization from an Embedded Systems Perspective". In IEEE Transactions on Computers, doi: 10.1109/TC.2021.3124320.

5. Samuel Pereira, João Sousa, Sandro Pinto, José Martins, David Cerdeira "Bao-Enclave: Virtualization-based Enclaves for Arm. In https://arxiv.org/abs/2209.05572

6. José Martins and Sandro Pinto. "Shedding Light on Static Partitioning Hypervisors for Arm-based Mixed-Criticality Systems". In RTAS 2023, San Antonio, Texas, 2023. https://arxiv.org/abs/2303.11186

7. José Martins and Sandro Pinto. "Porting of a Static Partitioning Hypervisor to Arm’s Cortex-R52" In Embedded Open Source Summit 2023, Prague, Czech Republic, 2023. https://www.youtube.com/watch?v=GmeOikZJRas