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

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Message-Id: <20240131-disable_misaligned_probe_config-v1-1-98d155e9cda8@rivosinc.com>
Date: Wed, 31 Jan 2024 22:40:22 -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>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH 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 | 6 ++++++
 arch/riscv/lib/csum.c               | 5 +----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index 5a626ed2c47a..dfdcca229174 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -28,7 +28,9 @@ struct riscv_isainfo {
 
 DECLARE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
 
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 DECLARE_PER_CPU(long, misaligned_access_speed);
+#endif
 
 /* Per-cpu ISA extensions. */
 extern struct riscv_isainfo hart_isa[NR_CPUS];
@@ -137,4 +139,8 @@ static __always_inline bool riscv_cpu_has_extension_unlikely(int cpu, const unsi
 
 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);
+}
 #endif
diff --git a/arch/riscv/lib/csum.c b/arch/riscv/lib/csum.c
index af3df5274ccb..399fa09bf4cb 100644
--- a/arch/riscv/lib/csum.c
+++ b/arch/riscv/lib/csum.c
@@ -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