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

Jerry Shih
2023-11-22T07:58:24Z

On Nov 22, 2023, at 07:51, Eric Biggers <ebiggers@kernel.org> wrote:
> On Wed, Nov 01, 2023 at 09:03:33PM -0700, Eric Biggers wrote:
>>
>> 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).

It doesn't fit all v1.0 spec.
The `Zvkb` is missed in binutils. It's the subset of `Zvbb`. We needs some extra
works if user just try to use `Zvkb`.
https://github.com/riscv/riscv-crypto/blob/main/doc/vector/riscv-crypto-vector-zvkb.adoc
Some crypto algorithms are already checking for `Zvkb` instead of `Zvbb`.

> 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?

Yes, we could.
But we need to handle the extensions checking for toolchains like:
https://github.com/torvalds/linux/commit/b6fcdb191e36f82336f9b5e126d51c02e7323480
I could do that, but I think I need some times to test the builds. And it will introduce
more dependency patch which is not related to actual crypto algorithms and the
gluing code in kernel. I will send another patch for toolchain part after the v2 patch.
And I am working for v2 patch with your new review comments. The v2 will still
use `perlasm`.
And we could move this discussion to this thread.
https://lore.kernel.org/all/20231025183644.8735-1-jerry.shih@sifive.com/

-Jerry