2026-06-09 –, Plenary
RVA23, ratified by RISC-V International in October 2024, defines the mandatory extension baseline for application-class RISC-V. Eighteen months on, is the profile real inside the software stack? This talk answers from one vantage point — the Linux kernel — through a shipping part.
SpacemiT's K3 is the first mass-produced RVA23 SoC. Bringing it up in mainline (RISCstar with SpacemiT), we found the kernel's RVA23 mandatory coverage stuck near 68% for a year, with bindings missing several extensions. Over several revisions those gaps closed, and Linux v7.0 reached 100%.
From that experience, I examine how the community decides what "supporting" an extension means: a data-backed classification by whether an extension adds architectural state the OS must save and restore — showing roughly two-thirds are stateless and only need to be discoverable, not implemented. This explains the principles maintainers apply.
I then cover two complementary halves now in review for v7.1.
1) Runtime detection: a unified series, carried forward from Andrew Jones' (Qualcomm) RFC, resolving rva23u64/rva23s64 base behaviour and exporting it via /proc/cpuinfo and hwprobe.
2) Compile-time specialisation, presented by co-speaker Charlie Jenkins (Meta), builds the kernel for RVA23. I share review feedback — including Paul Walmsley's call for hardware measurements — answered with numbers from the K3.
Complete mainline RVA23 lets distributions ship generic images and reduce fragmentation; Ubuntu 26.04 has adopted it while Debian, Fedora and Red Hat wait.
By sharing the technical considerations and review discussions from the kernel community, this talk aims to:
1) help community and SoC vendors better understand what is expected when bringing RVA23-compliant hardware to mainline Linux.
2) It also provides feedback to the RISC-V profile specification process on how profile definitions interact with kernel design constraints. (that's a more ambitious goal).
My target audience include: Linux kernel and boot firmware developers working on RISC-V architecture support, SoC vendors planning RVA23-compliant products, distribution (such as Debian, Fedora) maintainers interested in generic RISC-V image support, and RISC-V profile specification contributors.
Guodong Xu is a RISC-V International Advocate and Director of Software Engineering at RISCstar Solutions, with over 20 years of Linux kernel development experience. Previously at Motorola (mobile phone low-level software) and Linaro (Sr. Tech Lead, 10+ years), he now works on RISC-V upstream kernel enablement — including SpacemiT K1/K3 SoC support and RVA23 profile extensions.
Charlie has been a contributor to the Linux kernel for the last 3 years, focusing on bringing RISC-V support to be on-par with x86 and ARM.