linux-kernel - [PATCH v2 1/2] riscv: lib: Introduce has_fast_misaligned

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Message-Id: <20240201-disable_misaligned_probe_config-v2-1-77c368bed7b2@rivosinc.com>
Date: Thu, 01 Feb 2024 15:30:45 -0800
From: Charlie Jenkins <charlie@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Jisheng Zhang <jszhang@...nel.org>, Evan Green <evan@...osinc.com>, 
 Clément Léger <cleger@...osinc.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH v2 1/2] riscv: lib: Introduce has_fast_misaligned_access
 function

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

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

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);

-- 
2.43.0