linux-kernel - [PATCH 5/8] riscv: hwprobe: Add support for probing Zicclsm

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Message-Id: <20260207-isa-ext-parse-export-v1-5-a64d3a8bc20a@riscstar.com>
Date: Sat, 07 Feb 2026 18:27:59 +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 5/8] riscv: hwprobe: Add support for probing Zicclsm

Zicclsm guarantees that misaligned loads and stores to main memory
regions are supported. This is a mandatory extension in the RVA23U64
user-mode profile.

Export Zicclsm through hwprobe to help userspace check the existence of
this capability.

"Misaligned vector accesses are only supported if Zicclsm extension
is supported", as clarified in:

commit 982a7eb97be6 ("Documentation: RISC-V: uabi: Only scalar
misaligned loads are supported")

Link: https://lore.kernel.org/all/20240524185600.5919-1-palmer@rivosinc.com/
Link: https://lore.kernel.org/all/20240524-ruckus-trickily-1cda26c1a455@spud/
Signed-off-by: Guodong Xu <guodong@...cstar.com>
---
 Documentation/arch/riscv/hwprobe.rst  | 4 ++++
 arch/riscv/include/uapi/asm/hwprobe.h | 1 +
 arch/riscv/kernel/sys_hwprobe.c       | 1 +
 3 files changed, 6 insertions(+)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index 8430bc94fdba073e1e3ded973322c773c598a0b5..198b31bc9a20c2739988849cf7d2948a4fe1bdc4 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -395,3 +395,7 @@ The following keys are defined:
   * :c:macro:`RISCV_HWPROBE_IMA_B`: The B extension is supported, as defined
     by version 20240411 of the RISC-V Instruction Set Manual, Volume I
     Unprivileged Architecture.
+
+  * :c:macro:`RISCV_HWPROBE_EXT_ZICCLSM`: The Zicclsm extension for main
+    memory that must support misaligned loads and stores, as ratified in
+    RISC-V Profiles Version 1.0.
diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
index e7bd2e9ea33459572d01495f4063e32e3207e48f..323c488de5548883ddceac256bf312ec854ee899 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -117,6 +117,7 @@ struct riscv_hwprobe {
 #define RISCV_HWPROBE_KEY_IMA_EXT_1		16
 #define		RISCV_HWPROBE_EXT_ZICFISS	(1ULL << 0)
 #define		RISCV_HWPROBE_IMA_B		(1ULL << 1)
+#define		RISCV_HWPROBE_EXT_ZICCLSM	(1ULL << 2)
 
 /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
 
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index 491af3c5b66a0cb30471dafc8b31c70df2f9bed1..6997c6007a8e86dff85b5b83d14924e7c2466eb2 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -208,6 +208,7 @@ static void hwprobe_isa_ext1(struct riscv_hwprobe *pair,
 		 * in the hart_isa bitmap, are made.
 		 */
 		EXT_KEY(isainfo->isa, ZICFISS, pair->value, missing);
+		EXT_KEY(isainfo->isa, ZICCLSM, pair->value, missing);
 	}
 
 	/* Now turn off reporting features if any CPU is missing it. */

-- 
2.43.0