The RISC-V platform requirements for OpenSBI can change over time with advances in RISC-V specifications and ecosystem.
To handle this, we have two types of RISC-V platform requirements:
Currently, we don't have any Release specific platform requirements but such platform requirements will be added in future.
The base RISC-V platform requirements for OpenSBI are as follows:
At least rv32ima or rv64ima required on all HARTs
At least one HART should have S-mode support because:
The MTVEC CSR on all HARTs must support direct mode
The PMP CSRs are optional. If PMP CSRs are not implemented then OpenSBI cannot protect M-mode firmware and secured memory regions
The TIME CSR is optional. If TIME CSR is not implemented in hardware then a 64-bit MMIO counter is required to track time and emulate TIME CSR
Hardware support for injecting M-mode software interrupts on a multi-HART platform
The RISC-V extensions not covered by rv32ima or rv64ima are optional for OpenSBI. Although, OpenSBI will detect and handle some of these optional RISC-V extensions at runtime.
The optional RISC-V extensions handled by OpenSBI at runtime are: