linux-kernel - Re: [PATCH v3 0/3] Optimize GCD performance on RISC-V by selecting implementation at runtime

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: 
 <175486034374.1221929.15171575812600532444.git-patchwork-notify@kernel.org>
Date: Sun, 10 Aug 2025 21:12:23 +0000
From: patchwork-bot+linux-riscv@...nel.org
To: Kuan-Wei Chiu <visitorckw@...il.com>
Cc: linux-riscv@...ts.infradead.org, paul.walmsley@...ive.com,
 palmer@...belt.com, aou@...s.berkeley.edu, alex@...ti.fr,
 akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
 jserv@...s.ncku.edu.tw, eleanor15x@...il.com
Subject: Re: [PATCH v3 0/3] Optimize GCD performance on RISC-V by selecting
 implementation at runtime

Hello:

This series was applied to riscv/linux.git (fixes)
by Andrew Morton <akpm@...ux-foundation.org>:

On Fri,  6 Jun 2025 21:47:55 +0800 you wrote:
> The current implementation of gcd() selects between the binary GCD and
> the odd-even GCD algorithm at compile time, depending on whether
> CONFIG_CPU_NO_EFFICIENT_FFS is set. On platforms like RISC-V, however,
> this compile-time decision can be misleading: even when the compiler
> emits ctz instructions based on the assumption that they are efficient
> (as is the case when CONFIG_RISCV_ISA_ZBB is enabled), the actual
> hardware may lack support for the Zbb extension. In such cases, ffs()
> falls back to a software implementation at runtime, making the binary
> GCD algorithm significantly slower than the odd-even variant.
> 
> [...]

Here is the summary with links:
  - [v3,1/3] lib/math/gcd: Use static key to select implementation at runtime
    https://git.kernel.org/riscv/c/b3d5fd6f82dd
  - [v3,2/3] riscv: Optimize gcd() code size when CONFIG_RISCV_ISA_ZBB is disabled
    https://git.kernel.org/riscv/c/26b537edc533
  - [v3,3/3] riscv: Optimize gcd() performance on RISC-V without Zbb extension
    https://git.kernel.org/riscv/c/36e224168721

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html