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Introduction

RP016​

RP016 is a project aiming to extend OpenSBI with features to support running typical TEE stacks. This project is being implemented by RISCstar.

OpenSBI is an implementation of the RISC-V Supervisor Binary Interface specification that is key to some of the OP-TEE feature enablement RISCstar will do. RISCstar will implement the needed OpenSBI feature enhancements required to provide the core infrastructure to support the execution at S-Mode of a trusted execution environment (TEE) such as the open source TEE, OP-TEE.

RISCstar is working collaboratively with RISE to develop the required features in OpenSBI. Our plans are targeted to meet the goal of enabling RISE member engineers to quickly try our code and provide feedback. We emphasize quick execution, integration and delivery, with upstreaming as a parallel background effort.

The project is split into multiple milestones:

  • Milestone 1: Baseline Setup - There were no upstream deliverables for M1. M1 was completed December 16, 2025
  • Milestone 2: Support for External Interrupts using the APLIC - Documentation and the latest patch series were sent to the OpenSBI mailing list on May 4, 2026. This is currently in the later stages of active upstream review. Acceptance and merging of the M2 patch set should be soon, subject to maintainer review timelines and feedback.
  • Milestone 3: Interrupt driven OpenSBI Domain Context Switching. The latest M3 patch series was posted to the OpenSBI mailing list on May 14, 2026 and is under review.
  • Milestone 4: Generic support for platform specific system level hardware isolation features. The latest documentation and patch series was sent to the OpenSBI mailing list on May 4, 2026 and is under review. Acceptance and merging of the M4 patch set should be soon, subject to maintainer review timelines and feedback.
  • Milestone 5: Support for WorldGuard based system level hardware isolation. The latest M5 patch series was posted to the OpenSBI mailing list on May 14, 2026 and is under review.
  • Milestone 6: Floating Point and Vector Context management. The last M6 patch series was sent to the OpenSBI mailing list on May 16, 2026 and accepted. This is now upstream.

For each milestone, RISCstar will follow open source development best practices, and maintain feature branches for our changes, develop test plans for the features implemented and any other documentation needed. We will ensure the code upstreamed is of the highest quality and follows the requirements needed to upstream it to the relevant open source project.