[v2,1/2] riscv: lib: Introduce has_fast_misaligned_access function

Commit Message

Charlie Jenkins Feb. 1, 2024, 11:30 p.m. UTC

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

Signed-off-by: Charlie Jenkins <[e-mail]>
---
 arch/riscv/include/asm/cpufeature.h | 15 ++++++++++-----
 arch/riscv/lib/csum.c               |  7 ++-----
 2 files changed, 12 insertions(+), 10 deletions(-)

Comments

Eric Biggers Feb. 2, 2024, 10:49 p.m. UTC | #1

On Thu, Feb 01, 2024 at 03:30:45PM -0800, Charlie Jenkins wrote:
> -	if (((unsigned long)buff & OFFSET_MASK) == 0)
> +	if (has_fast_misaligned_accesses() || (((unsigned long)buff & OFFSET_MASK) == 0b101))
>  		return do_csum_no_alignment(buff, len);

Why did the 0 change into 0b101?

- Eric

Charlie Jenkins Feb. 2, 2024, 11:11 p.m. UTC | #2

On Fri, Feb 02, 2024 at 02:49:39PM -0800, Eric Biggers wrote:
> On Thu, Feb 01, 2024 at 03:30:45PM -0800, Charlie Jenkins wrote:
> > -	if (((unsigned long)buff & OFFSET_MASK) == 0)
> > +	if (has_fast_misaligned_accesses() || (((unsigned long)buff & OFFSET_MASK) == 0b101))
> >  		return do_csum_no_alignment(buff, len);
> 
> Why did the 0 change into 0b101?
> 
> - Eric

Whoops, thank you.

- Charlie

Patch

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index 5a626ed2c47a..eb3ac304fc42 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
@@ -28,8 +28,6 @@  struct riscv_isainfo {
 
 DECLARE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
 
-DECLARE_PER_CPU(long, misaligned_access_speed);
-
 /* Per-cpu ISA extensions. */
 extern struct riscv_isainfo hart_isa[NR_CPUS];
 
@@ -53,6 +51,15 @@  static inline bool check_unaligned_access_emulated(int cpu)
 static inline void unaligned_emulation_finish(void) {}
 #endif
 
+DECLARE_PER_CPU(long, misaligned_access_speed);
+
+DECLARE_STATIC_KEY_FALSE(fast_misaligned_access_speed_key);
+
+static __always_inline bool has_fast_misaligned_accesses(void)
+{
+	return static_branch_likely(&fast_misaligned_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/lib/csum.c b/arch/riscv/lib/csum.c
index af3df5274ccb..ea2f668fab71 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_misaligned_accesses() || (((unsigned long)buff & OFFSET_MASK) == 0b101))
 		return do_csum_no_alignment(buff, len);
 
 	return do_csum_with_alignment(buff, len);