The Odyssey of HWCAP on RISC-V platforms
summary
Linux faces many incompatible vendor extensions and an unstable ISA string, so the proposal stores rich platform info in the VDSO and publishes its address via HWCAP stores pointer at ELF load time; userspace reads per-core vdso data immediately without extra syscalls. A proof-of-concept emits extension/version/vendor fields and exposes them via string-based lookup, but discussion leans toward bitmap/key-value encoding; concerns include container masking, mmu-less systems, per-core mismatches and hypervisor virtualization.
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chapters (7)
- 0:00Introduction to HWCAP challenges
- 3:34VDSO data mechanism proposal
- 7:30Pros and cons of VDSO approach
- 13:00Alternative encoding formats
- 17:58Virtualization considerations
- 24:27VDSO format discussion
- 28:57Q&A and next steps
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