riscv: Add Zicclsm to cpufeature and hwprobe

Zicclsm requires misaligned support for all regular load and store
instructions, both scalar and vector, but not AMOs or other
specialized forms of memory access, to main memory regions with both
the cacheability and coherence PMAs, as defined in the profiles spec.
Even though mandated, misaligned loads and stores might execute
extremely slowly. Standard software distributions should assume their
existence only for correctness, not for performance.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Tested-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Jesse Taube <jesse@rivosinc.com>
[andrew.jones: Rebased, rewrote doc text, minor commit message revisions]
Signed-off-by: Andrew Jones <andrew.jones@oss.qualcomm.com>
Signed-off-by: Guodong Xu <docular.xu@gmail.com>
Link: https://patch.msgid.link/20260701-rva23u64-hwprobe-v2-v5-5-2c61f94a695a@gmail.com
[pjw@kernel.org: updated to apply; added Andrew's username to his tag comments]
Signed-off-by: Paul Walmsley <pjw@kernel.org>

Documentation/arch/riscv/hwprobe.rst

@@ -401,3 +401,7 @@ The following keys are defined:
     as defined in version 1.0 of the RISC-V Control-flow Integrity (CFI)
     extensions specification, ratified in commit 302a2d45c243
     ("Update build-pdf.yml") of riscv-cfi.
+
+  * :c:macro:`RISCV_HWPROBE_EXT_ZICCLSM`: The Zicclsm extension is supported,
+    as defined in the RISC-V Profiles specification starting from commit
+    b1d80660 ("Updated to ratified state.")

arch/riscv/include/asm/hwcap.h

@@ -118,6 +118,7 @@
 #define RISCV_ISA_EXT_SSCCFG		109
 #define RISCV_ISA_EXT_SMCDELEG		110
 #define RISCV_ISA_EXT_SSQOSID		111
+#define RISCV_ISA_EXT_ZICCLSM		112
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 

arch/riscv/include/uapi/asm/hwprobe.h

@@ -116,6 +116,7 @@ struct riscv_hwprobe {
 #define RISCV_HWPROBE_KEY_ZICBOP_BLOCK_SIZE	15
 #define RISCV_HWPROBE_KEY_IMA_EXT_1		16
 #define		RISCV_HWPROBE_EXT_ZICFISS	(1ULL << 0)
+#define		RISCV_HWPROBE_EXT_ZICCLSM	(1ULL << 1)
 
 /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
 

arch/riscv/kernel/cpufeature.c

@@ -525,6 +525,7 @@ 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(zicclsm, RISCV_ISA_EXT_ZICCLSM),
 	__RISCV_ISA_EXT_DATA(ziccrse, RISCV_ISA_EXT_ZICCRSE),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicfilp, RISCV_ISA_EXT_ZICFILP, riscv_xlinuxenvcfg_exts,
 					  riscv_cfilp_validate),

arch/riscv/kernel/sys_hwprobe.c

@@ -202,6 +202,7 @@ 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. */