[PATCH v5 1/2] riscv: lib: Introduce has_fast_unaligned_access function

Charlie Jenkins
2024-02-27T23:15:01Z

Create has_fast_unaligned_access to avoid needing to explicitly check
the fast_misaligned_access_speed_key static key.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
---
arch/riscv/include/asm/cpufeature.h | 11 ++++++++---
arch/riscv/kernel/cpufeature.c | 6 +++---
arch/riscv/lib/csum.c | 7 ++-----
3 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index 5a626ed2c47a..466e1f591919 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -1,6 +1,6 @@
/* SPDX-License-Identifier: GPL-2.0-only */
/*
- * Copyright 2022-2023 Rivos, Inc
+ * Copyright 2022-2024 Rivos, Inc
*/

#ifndef _ASM_CPUFEATURE_H
@@ -53,6 +53,13 @@ static inline bool check_unaligned_access_emulated(int cpu)
static inline void unaligned_emulation_finish(void) {}
#endif

+DECLARE_STATIC_KEY_FALSE(fast_unaligned_access_speed_key);
+
+static __always_inline bool has_fast_unaligned_accesses(void)
+{
+ return static_branch_likely(&fast_unaligned_access_speed_key);
+}
+
unsigned long riscv_get_elf_hwcap(void);

struct riscv_isa_ext_data {
@@ -135,6 +142,4 @@ static __always_inline bool riscv_cpu_has_extension_unlikely(int cpu, const unsi
return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
}

-DECLARE_STATIC_KEY_FALSE(fast_misaligned_access_speed_key);
-
#endif
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 89920f84d0a3..7878cddccc0d 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -810,14 +810,14 @@ static void check_unaligned_access_nonboot_cpu(void *param)
check_unaligned_access(pages[cpu]);
}

-DEFINE_STATIC_KEY_FALSE(fast_misaligned_access_speed_key);
+DEFINE_STATIC_KEY_FALSE(fast_unaligned_access_speed_key);

static void modify_unaligned_access_branches(cpumask_t *mask, int weight)
{
if (cpumask_weight(mask) == weight)
- static_branch_enable_cpuslocked(&fast_misaligned_access_speed_key);
+ static_branch_enable_cpuslocked(&fast_unaligned_access_speed_key);
else
- static_branch_disable_cpuslocked(&fast_misaligned_access_speed_key);
+ static_branch_disable_cpuslocked(&fast_unaligned_access_speed_key);
}

static void set_unaligned_access_static_branches_except_cpu(int cpu)
diff --git a/arch/riscv/lib/csum.c b/arch/riscv/lib/csum.c
index af3df5274ccb..7178e0acfa22 100644
--- a/arch/riscv/lib/csum.c
+++ b/arch/riscv/lib/csum.c
@@ -3,7 +3,7 @@
* Checksum library
*
* Influenced by arch/arm64/lib/csum.c
- * Copyright (C) 2023 Rivos Inc.
+ * Copyright (C) 2023-2024 Rivos Inc.
*/
#include <linux/bitops.h>
#include <linux/compiler.h>
@@ -318,10 +318,7 @@ unsigned int do_csum(const unsigned char *buff, int len)
* branches. The largest chunk of overlap was delegated into the
* do_csum_common function.
*/
- if (static_branch_likely(&fast_misaligned_access_speed_key))
- return do_csum_no_alignment(buff, len);
-
- if (((unsigned long)buff & OFFSET_MASK) == 0)
+ if (has_fast_unaligned_accesses() || (((unsigned long)buff & OFFSET_MASK) == 0))
return do_csum_no_alignment(buff, len);

return do_csum_with_alignment(buff, len);

--
2.43.2