linux-kernel - Re: [PATCH v7 1/4] riscv: lib: Introduce has_fast_unaligned

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Date: Thu, 7 Mar 2024 07:49:17 +0000
From: Conor Dooley <conor.dooley@...rochip.com>
To: Charlie Jenkins <charlie@...osinc.com>
CC: 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>, <linux-riscv@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 1/4] riscv: lib: Introduce has_fast_unaligned_access
 function

On Wed, Mar 06, 2024 at 12:00:01PM -0800, Charlie Jenkins wrote:

$subject: riscv: lib: Introduce has_fast_unaligned_access function

nit - s/ function/()/ & put the () after function names in commit
messages please.

> 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>

Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

Cheers,
Conor.

> ---
>  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
> 

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