Re: [PATCH v4 00/12] RISC-V: support some cryptography accelerations

Eric Biggers
2023-11-21T23:51:11Z

On Wed, Nov 01, 2023 at 09:03:33PM -0700, Eric Biggers wrote:
> >
> > There is no public assembler supports the vector-crypto asm mnemonics.
> > We should still use `opcode` for vector-crypto instructions. But we might
> > use asm for standard rvv parts.
> > In order to reuse the codes in OpenSSL as much as possible, we still use
> > the `riscv.pm` for all standard rvv and vector-crypto instructions. If the asm
> > mnemonic is still a better approach, I will `rewrite` all standard rvv parts
> > with asm mnemonics in next patch.
>
> Tip-of-tree gcc + binutils seems to support them. Building some of the sample
> code from the riscv-crypto repository:
>
> $ riscv64-linux-gnu-as --version
> GNU assembler (GNU Binutils) 2.41.50.20231021
> $ riscv64-linux-gnu-gcc --version
> riscv64-linux-gnu-gcc (GCC) 14.0.0 20231021 (experimental)
> $ riscv64-linux-gnu-gcc -march=rv64ivzvkned -c riscv-crypto/doc/vector/code-samples/zvkned.s
>
> And tip-of-tree clang supports them experimentally:
>
> $ clang --version
> clang version 18.0.0 (https://github.com/llvm/llvm-project 30416f39be326b403e19f23da387009736483119)
> $ clang -menable-experimental-extensions -target riscv64-linux-gnu -march=rv64ivzvkned1 -c riscv-crypto/doc/vector/code-samples/zvkned.s
>
> It would be nice to use a real assembler, so that people won't have to worry
> about potential mistakes or inconsistencies in the perl-based "assembler". Also
> keep in mind that if we allow people to compile this code without the real
> assembler support from the beginning, it might end up staying that way for quite
> a while in order to avoid breaking the build for people.
>
> Ultimately it's up to you though; I think that you and others who have been
> working on RISC-V crypto can make the best decision about what to do here. I
> also don't want this patchset to be delayed waiting for other projects, so maybe
> that indeed means the perl-based "assembler" needs to be used for now.
>

Just wanted to bump up this discussion again. In binutils, the vector crypto
v1.0.0 support was released 4 months ago in 2.41. See the NEWS file at
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob_plain;f=binutils/NEWS;hb=refs/heads/binutils-2_41-branch

* The RISC-V port now supports the following new standard extensions:
- Zicond (conditional zero instructions)
- Zfa (additional floating-point instructions)
- Zvbb, Zvbc, Zvkg, Zvkned, Zvknh[ab], Zvksed, Zvksh, Zvkn, Zvknc, Zvkng,
Zvks, Zvksc, Zvkg, Zvkt (vector crypto instructions)

That's every extension listed in the vector crypto v1.0.0 specification
(https://github.com/riscv/riscv-crypto/releases/download/v1.0.0/riscv-crypto-spec-vector.pdf).

LLVM still has the vector crypto extensions marked as "experimental" extensions.
However, there is an open pull request to mark them non-experimental:
https://github.com/llvm/llvm-project/pull/69000

Could we just go ahead and remove riscv.pm, develop with binutils for now, and
prioritize getting the LLVM support finished?

- Eric