lion VS riscv-formal

I've been starting to dabble with digital logic design via Clash (https://clash-lang.org/), and there is a very cool-looking RISC-V SoC project done in that tool that looks fairly serious: https://github.com/standardsemiconductor/lion.

That’s fascinating about the M1. In retrospect it seems like kind of a no-brainer but I doubt I would have thought of it.

SPARC had different memory models at different ISA revs IIRC: it’s been like 20 years since I was dealing with SPARC so I might be misremembering the details. Alpha would have been a better example.

RISC-V is really interesting. I’ve been slowly working through this: https://github.com/standardsemiconductor/lion, highly recommend!

Interesting. Actually, you may be just the person to answer my question: Is it possible/plausible to run a Cardano node on Lion OS on a RISC-V machine? IMO, it would be great for the community if we could run all Cardano stake pools on end to end formally verified machines using open source core and hardware.

Lion: A formally verified, 5-stage pipeline RISC-V core\ (30 comments)

In addition, you can actually set the riscv-formal suite to verify correctness by k-induction: https://github.com/SymbioticEDA/riscv-formal/pull/28 https://symbiyosys.readthedocs.io/en/latest/quickstart.html#beyond-bounded-model-checks although I concur that by looking at https://github.com/standardsemiconductor/lion/blob/main/lion-formal/app/Main.hs the lion core is only verified with BMC.

You might be able to hook up your simulator to risc v-formal https://github.com/SymbioticEDA/riscv-formal

Then we have RISC, which wrote their own formal verification toolchain here. They just generate Verilog with a Python script. AFAICT this would be really hard to adapt to an assembler. Fortunately the ISA is simple to implement.

Your question is certainly not dumb; on the contrary, it is very important! I suppose the developers are responsible for verifying the formal verifier and ensuring it covers the spec. Maybe there is a way to formally verify the formal verifier? Either way, I must give a shout out to the riscv-formal project and its contributors; the project was instrumental to the development of Lion.

Not trying to put words in your mouth, but I do want to clarify something for this audience: the bound in the BMC done by the riscv-formal suite is on the number of cycles, not on the number of bits. Case in point, when you try to BMC the (M)ultiply extensions with the riscv-formal suite, you're actually not allowed to use multiplication because the state space blows up: https://github.com/SymbioticEDA/riscv-formal/blob/master/docs/rvfi.md#alternative-arithmetic-operations

Use riscv-formal. It will save a ton of headaches trying to track down a bad instruction. It can generate a module that does checks on the fly during normal sims.

I recommend SymbiYosys for formally testing your CPU before ever placing it into a simulation. You can use the riscv-formal property set to get you started, but I'd personally go for an inductive proof of some type and the riscv-formal property set may not get you that far.