[PATCH v4 1/7] RISC-V: Add Zicclsm to cpufeature and hwprobe

[Jesse Taube]

> Zicclsm Misaligned loads and stores to main memory regions with both
> the cacheability and coherence PMAs must be supported.
> Note:
> This introduces a new extension name for this feature.
> This requires misaligned support for all regular load and store
> instructions (including scalar and vector) but not AMOs or other
> specialized forms of memory access. Even though mandated, misaligned
> loads and stores might execute extremely slowly. Standard software
> distributions should assume their existence only for correctness,
> not for performance.

Detecing zicclsm allows the kernel to report if the
hardware supports misaligned accesses even if support wasn't probed.

This is useful for usermode to know if vector misaligned accesses are
supported.

Signed-off-by: Jesse Taube <jesse at rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley at microchip.com>
Reviewed-by: Andy Chiu <andy.chiu at sifive.com>
---
V1 -> V2:
 - Add documentation for Zicclsm
 - Move Zicclsm to correct location
V2 -> V3:
 - No changes
V3 -> V4:
 - Add definitions to hwprobe.rst
---
 Documentation/arch/riscv/hwprobe.rst  | 5 +++++
 arch/riscv/include/asm/hwcap.h        | 1 +
 arch/riscv/include/uapi/asm/hwprobe.h | 1 +
 arch/riscv/kernel/cpufeature.c        | 1 +
 arch/riscv/kernel/sys_hwprobe.c       | 1 +
 5 files changed, 9 insertions(+)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index df5045103e73..78acd37b6477 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -207,6 +207,11 @@ The following keys are defined:
   * :c:macro:`RISCV_HWPROBE_EXT_ZVE64D`: The Vector sub-extension Zve64d is
     supported, as defined by version 1.0 of the RISC-V Vector extension manual.
 
+  * :c:macro:`RISCV_HWPROBE_EXT_ZICCLSM`:  The Zicclsm extension is supported as
+        defined in the RISC-V RVA Profiles Specification. Misaligned support for
+        all regular load and store instructions (including scalar and vector) but
+        not AMOs or other specialized forms of memory access.
+
 * :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: Deprecated. Returns similar values to
      :c:macro:`RISCV_HWPROBE_KEY_MISALIGNED_PERF`, but the key was mistakenly
      classified as a bitmask rather than a value.
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index f64d4e98e67c..0b3bd8885a2b 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -86,6 +86,7 @@
 #define RISCV_ISA_EXT_ZVE64X		77
 #define RISCV_ISA_EXT_ZVE64F		78
 #define RISCV_ISA_EXT_ZVE64D		79
+#define RISCV_ISA_EXT_ZICCLSM		80
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
index 2fb8a8185e7a..023b7771d1b7 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -65,6 +65,7 @@ struct riscv_hwprobe {
 #define		RISCV_HWPROBE_EXT_ZVE64X	(1ULL << 39)
 #define		RISCV_HWPROBE_EXT_ZVE64F	(1ULL << 40)
 #define		RISCV_HWPROBE_EXT_ZVE64D	(1ULL << 41)
+#define		RISCV_HWPROBE_EXT_ZICCLSM	(1ULL << 42)
 #define RISCV_HWPROBE_KEY_CPUPERF_0	5
 #define		RISCV_HWPROBE_MISALIGNED_UNKNOWN	(0 << 0)
 #define		RISCV_HWPROBE_MISALIGNED_EMULATED	(1 << 0)
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 1d6e4fda00f8..83c5ae16ad5e 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -283,6 +283,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_h),
 	__RISCV_ISA_EXT_SUPERSET(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts),
 	__RISCV_ISA_EXT_SUPERSET(zicboz, RISCV_ISA_EXT_ZICBOZ, riscv_xlinuxenvcfg_exts),
+	__RISCV_ISA_EXT_DATA(zicclsm, RISCV_ISA_EXT_ZICCLSM),
 	__RISCV_ISA_EXT_DATA(zicntr, RISCV_ISA_EXT_ZICNTR),
 	__RISCV_ISA_EXT_DATA(zicond, RISCV_ISA_EXT_ZICOND),
 	__RISCV_ISA_EXT_DATA(zicsr, RISCV_ISA_EXT_ZICSR),
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index e4ec9166339f..e910e2971984 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -96,6 +96,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 		EXT_KEY(ZBB);
 		EXT_KEY(ZBS);
 		EXT_KEY(ZICBOZ);
+		EXT_KEY(ZICCLSM);
 		EXT_KEY(ZBC);
 
 		EXT_KEY(ZBKB);
-- 
2.45.2