[PATCH v2 1/6] RISC-V: Add Zicclsm to cpufeature and hwprobe

Jesse Taube
2024-06-13T19:16:57Z

> 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@rivosinc.com>
---
V1 -> V2:
- Add documentation for Zicclsm
- Move Zicclsm to correct location
---
Documentation/arch/riscv/hwprobe.rst | 3 +++
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, 7 insertions(+)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index df5045103e73..7085a694b801 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -207,6 +207,9 @@ 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.
+
* :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);
--
2.43.0