linux-kernel - [PATCH 0/6] riscv: Add helpers use_alternative

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Message-Id: <20250820-riscv-altn-helper-wip-v1-0-c3c626c1f7e6@iscas.ac.cn>
Date: Wed, 20 Aug 2025 21:44:44 +0800
From: Vivian Wang <wangruikang@...as.ac.cn>
To: Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Alexandre Ghiti <alex@...ti.fr>, Yury Norov <yury.norov@...il.com>, 
 Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Vivian Wang <wangruikang@...as.ac.cn>, Vivian Wang <uwu@...m.page>, 
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Aydın Mercan <aydin@...can.dev>
Subject: [PATCH 0/6] riscv: Add helpers use_alternative_{likely,unlikely}

There are about a dozen uses of asm goto in arch/riscv just to select
between two code paths with the alternative mechanism. Introduce helpers
similar to arm64's alternative_has_cap_{likely,unlikely} for this, and
convert the existing code to use it.

I did not use the name alternative_has_cap_{likely,unlikely} since riscv
alternatives are not all CPU capabilities.

In each case, I have tried to preserve the existing logic while picking
between "likely" and "unlikely".

These patches are also available at:

https://github.com/dramforever/linux/tree/riscv/altn-helper/v1

---
Vivian Wang (6):
      riscv: Introduce use_alternative_{likely,unlikely}
      riscv: pgtable: Convert to use_alternative_unlikely
      riscv: checksum: Convert to use_alternative_likely
      riscv: hweight: Convert to use_alternative_likely
      riscv: bitops: Convert to use_alternative_likely
      riscv: cmpxchg: Convert to use_alternative_likely

 arch/riscv/include/asm/alternative-macros.h |  73 ++++++++++++++++
 arch/riscv/include/asm/arch_hweight.h       |  42 ++++------
 arch/riscv/include/asm/bitops.h             | 112 +++++++++++--------------
 arch/riscv/include/asm/checksum.h           |  13 +--
 arch/riscv/include/asm/cmpxchg.h            | 125 ++++++++++++++--------------
 arch/riscv/include/asm/pgtable.h            |  15 ++--
 arch/riscv/lib/csum.c                       |  65 ++++++---------
 arch/riscv/mm/pgtable.c                     |  22 +++--
 8 files changed, 247 insertions(+), 220 deletions(-)
---
base-commit: 062b3e4a1f880f104a8d4b90b767788786aa7b78
change-id: 20250820-riscv-altn-helper-wip-00af3a552c37

Best regards,
-- 
Vivian "dramforever" Wang