Linux Kernel Continues Prepping For RISC-V's Updated Supervisor Binary Interface
Written by Michael Larabel in Hardware on 12 February 2020 at 06:30 AM EST. 4 Comments
HARDWARE --
RISC-V's Supervisor Binary Interface "SBI" is the interface between the platform-specific firmware and the running operating system or hypervisor for interacting with the supervisor execution environment in the higher privileged mode. The Linux kernel has been working to support a newer version of the SBI that is more extensible moving forward.

The RISC-V Supervisor Binary Interface v0.2 now has extendability in mind with the ability to add extensions in the future while maintaining backwards compatibility. Linux kernel patches continue to be worked on in supporting this updated SBI interface for the Linux kernel.

In addition to supporting SBI v0.2 itself, the Linux kernel patches also are implementing extensions for handling RISC-V CPU hot-plugging and HSM. HSM in this context is the Hart State Management Extension to allow the supervisor to request higher privilege modes to start/stop harts.

Supporting the newer RISC-V SBI is important for allowing future extensions and this standard being important for allowing RISC-V support to play nicely across the RISC-V hardware ecosystem. The most recent version of these Linux RISC-V SBI patches can be found here while we wait to see if the work gets buttoned up in time for Linux 5.7. The Supervisor Binary Interface specification can be read on GitHub for those interested.
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