linux-kernel - [PATCH v5 1/2] riscv: lib: Introduce has_fast_unaligned

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Message-Id: <20240227-disable_misaligned_probe_config-v5-1-b6853846e27a@rivosinc.com>
Date: Tue, 27 Feb 2024 15:13:13 -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>, 
 Eric Biggers <ebiggers@...nel.org>, 
 Elliot Berman <quic_eberman@...cinc.com>, Charles Lohr <lohr85@...il.com>, 
 Conor Dooley <conor.dooley@...rochip.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH v5 1/2] riscv: lib: Introduce has_fast_unaligned_access
 function

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@...osinc.com>
Reviewed-by: Evan Green <evan@...osinc.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