linux-kernel - [PATCH 3/8] riscv: cpufeature: Enforce Ziccrse dependency on Zalrsc

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Message-Id: <20260207-isa-ext-parse-export-v1-3-a64d3a8bc20a@riscstar.com>
Date: Sat, 07 Feb 2026 18:27:57 +0800
From: Guodong Xu <guodong@...cstar.com>
To: Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>, 
 Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>, 
 Jonathan Corbet <corbet@....net>, Shuah Khan <skhan@...uxfoundation.org>, 
 Conor Dooley <conor@...nel.org>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 linux-doc@...r.kernel.org, Guodong Xu <guodong@...cstar.com>
Subject: [PATCH 3/8] riscv: cpufeature: Enforce Ziccrse dependency on
 Zalrsc

Ziccrse guarantees RsrvEventual for cacheable coherent main memory,
a property that is only meaningful when LR/SC instructions are present.
Since Zalrsc is the extension that provides LR/SC (also implied by A),
add a validation callback to enforce this dependency.

Introduce riscv_ext_zalrsc_depends() following the naming convention
used by other pure dependency checks like riscv_ext_f_depends().

Signed-off-by: Guodong Xu <guodong@...cstar.com>
---
 arch/riscv/kernel/cpufeature.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 3d3af82a53250f29204a3fb138feaf520a878d0e..68c94fe29cd1b26925fa38a5c877d699bbc88e25 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -338,6 +338,15 @@ static int riscv_ext_supm_validate(const struct riscv_isa_ext_data *data,
 	return -EPROBE_DEFER;
 }
 
+static int riscv_ext_zalrsc_depends(const struct riscv_isa_ext_data *data,
+				    const unsigned long *isa_bitmap)
+{
+	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZALRSC))
+		return 0;
+
+	return -EPROBE_DEFER;
+}
+
 static const unsigned int riscv_a_exts[] = {
 	RISCV_ISA_EXT_ZAAMO,
 	RISCV_ISA_EXT_ZALRSC,
@@ -543,7 +552,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts, riscv_ext_zicbom_validate),
 	__RISCV_ISA_EXT_DATA_VALIDATE(zicbop, RISCV_ISA_EXT_ZICBOP, riscv_ext_zicbop_validate),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicboz, RISCV_ISA_EXT_ZICBOZ, riscv_xlinuxenvcfg_exts, riscv_ext_zicboz_validate),
-	__RISCV_ISA_EXT_DATA(ziccrse, RISCV_ISA_EXT_ZICCRSE),
+	__RISCV_ISA_EXT_DATA_VALIDATE(ziccrse, RISCV_ISA_EXT_ZICCRSE, riscv_ext_zalrsc_depends),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicfilp, RISCV_ISA_EXT_ZICFILP, riscv_xlinuxenvcfg_exts,
 					  riscv_cfilp_validate),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicfiss, RISCV_ISA_EXT_ZICFISS, riscv_xlinuxenvcfg_exts,

-- 
2.43.0