Hi, I’m Jonathan Neuschäfer (jn__ on IRC) and my GSoC project for this year is to improve coreboot’s support for RISC-V platforms. RISC-V is a new instruction set architecture (ISA) that can be implemented without paying license fees and is relatively simple.
Coreboot has already been ported to RISC-V in 2014, and has since received a bunch of patches, but since the RISC-V Privileged ISA Specification (which defines things like interrupt handling and virtual memory) is still in flux, it has become unbootable again.
My first first goal last week was to run coreboot in SPIKE, the official RISC-V emulator, and get some console output. I checked out commit 419f1b5f3 (current master) of the riscv-tools repository and built SPIKE from there.
After I patched a few outdated instructions and worked around the fact that the RISC-V binutils port currently included in coreboot targets a newer version of the RISC-V Privileged Spec by hardcoding some Control and Status Register numbers, I finally got coreboot booting until the point where it would jump into a payload, had I specified one.
All patches can be found under the riscv topic on gerrit.
Plans for this week
This week I will update my SPIKE to a version that supports the upcoming Privileged Spec 1.9, which will be released in the next couple weeks. This has the advantage that I don’t need to patch instructions because GCC encodes them differently than SPIKE decodes them. Additionally, I’ll try to get Linux to boot in SPIKE, under coreboot.