linux-kernel - [PATCH v4 5/5] riscv: cmpxchg: Use riscv_has_extension

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Message-Id: <20251020-riscv-altn-helper-wip-v4-5-ef941c87669a@iscas.ac.cn>
Date: Mon, 20 Oct 2025 17:10:00 +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>, Paul Walmsley <pjw@...nel.org>
Cc: Charlie Jenkins <charlie@...osinc.com>, 
 Xiao Wang <xiao.w.wang@...el.com>, 
 Christoph Müllner <christoph.muellner@...ll.eu>, 
 Vivian Wang <wangruikang@...as.ac.cn>, Vivian Wang <uwu@...m.page>, 
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 5/5] riscv: cmpxchg: Use riscv_has_extension_likely

Use riscv_has_extension_likely() to check for RISCV_ISA_EXT_ZAWRS,
replacing the use of asm goto with ALTERNATIVE.

The "likely" variant is used to match the behavior of the original
implementation using ALTERNATIVE("j %l[no_zawrs]", "nop", ...).

Signed-off-by: Vivian Wang <wangruikang@...as.ac.cn>
---
 arch/riscv/include/asm/cmpxchg.h | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
index 122e1485d39a..8712cf9c69dc 100644
--- a/arch/riscv/include/asm/cmpxchg.h
+++ b/arch/riscv/include/asm/cmpxchg.h
@@ -373,9 +373,10 @@ static __always_inline void __cmpwait(volatile void *ptr,
 	u32 *__ptr32b;
 	ulong __s, __val, __mask;
 
-	asm goto(ALTERNATIVE("j %l[no_zawrs]", "nop",
-			     0, RISCV_ISA_EXT_ZAWRS, 1)
-		 : : : : no_zawrs);
+	if (!riscv_has_extension_likely(RISCV_ISA_EXT_ZAWRS)) {
+		ALT_RISCV_PAUSE();
+		return;
+	}
 
 	switch (size) {
 	case 1:
@@ -437,11 +438,6 @@ static __always_inline void __cmpwait(volatile void *ptr,
 	default:
 		BUILD_BUG();
 	}
-
-	return;
-
-no_zawrs:
-	ALT_RISCV_PAUSE();
 }
 
 #define __cmpwait_relaxed(ptr, val) \

-- 
2.51.0