linux-kernel - Re: [PATCH v4 16/21] crypto/arm64: sm3 - Switch to 'ksimd' scoped guard API

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Message-ID: <20251031135235.000007cb@huawei.com>
Date: Fri, 31 Oct 2025 13:52:35 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Ard Biesheuvel <ardb+git@...gle.com>
CC: <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<linux-crypto@...r.kernel.org>, <herbert@...dor.apana.org.au>,
	<ebiggers@...nel.org>, Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH v4 16/21] crypto/arm64: sm3 - Switch to 'ksimd' scoped
 guard API

On Fri, 31 Oct 2025 11:39:15 +0100
Ard Biesheuvel <ardb+git@...gle.com> wrote:

> From: Ard Biesheuvel <ardb@...nel.org>
> 
> Switch to the more abstract 'scoped_ksimd()' API, which will be modified
> in a future patch to transparently allocate a kernel mode FP/SIMD state
> buffer on the stack, so that kernel mode FP/SIMD code remains
> preemptible in principe, but without the memory overhead that adds 528
> bytes to the size of struct task_struct.
> 
> Reviewed-by: Eric Biggers <ebiggers@...nel.org>
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Hi Ard,

Trivial comment inline.

> ---
>  arch/arm64/crypto/sm3-ce-glue.c   | 15 ++++++++-------
>  arch/arm64/crypto/sm3-neon-glue.c | 16 ++++++----------
>  2 files changed, 14 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/arm64/crypto/sm3-ce-glue.c b/arch/arm64/crypto/sm3-ce-glue.c
> index eac6f5fa0abe..24c1fcfae072 100644
> --- a/arch/arm64/crypto/sm3-ce-glue.c
> +++ b/arch/arm64/crypto/sm3-ce-glue.c
> @@ -5,7 +5,6 @@
>   * Copyright (C) 2018 Linaro Ltd <ard.biesheuvel@...aro.org>
>   */
>  
> -#include <asm/neon.h>
>  #include <crypto/internal/hash.h>
>  #include <crypto/sm3.h>
>  #include <crypto/sm3_base.h>
> @@ -13,6 +12,8 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  
> +#include <asm/simd.h>
> +
>  MODULE_DESCRIPTION("SM3 secure hash using ARMv8 Crypto Extensions");
>  MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@...aro.org>");
>  MODULE_LICENSE("GPL v2");
> @@ -25,18 +26,18 @@ static int sm3_ce_update(struct shash_desc *desc, const u8 *data,
>  {
>  	int remain;
>  
> -	kernel_neon_begin();
> -	remain = sm3_base_do_update_blocks(desc, data, len, sm3_ce_transform);
> -	kernel_neon_end();
> +	scoped_ksimd() {

Why does this get brackets unlike other cases?

> +		remain = sm3_base_do_update_blocks(desc, data, len, sm3_ce_transform);
> +	}
>  	return remain;
>  }
>  
>  static int sm3_ce_finup(struct shash_desc *desc, const u8 *data,
>  			unsigned int len, u8 *out)
>  {
> -	kernel_neon_begin();
> -	sm3_base_do_finup(desc, data, len, sm3_ce_transform);
> -	kernel_neon_end();
> +	scoped_ksimd() {
> +		sm3_base_do_finup(desc, data, len, sm3_ce_transform);
> +	}
>  	return sm3_base_finish(desc, out);
>  }
>  
> diff --git a/arch/arm64/crypto/sm3-neon-glue.c b/arch/arm64/crypto/sm3-neon-glue.c
> index 6c4611a503a3..15f30cc24f32 100644
> --- a/arch/arm64/crypto/sm3-neon-glue.c
> +++ b/arch/arm64/crypto/sm3-neon-glue.c
> @@ -5,7 +5,7 @@
>   * Copyright (C) 2022 Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
>   */
>  
> -#include <asm/neon.h>
> +#include <asm/simd.h>
>  #include <crypto/internal/hash.h>
>  #include <crypto/sm3.h>
>  #include <crypto/sm3_base.h>
> @@ -20,20 +20,16 @@ asmlinkage void sm3_neon_transform(struct sm3_state *sst, u8 const *src,
>  static int sm3_neon_update(struct shash_desc *desc, const u8 *data,
>  			   unsigned int len)
>  {
> -	int remain;
> -
> -	kernel_neon_begin();
> -	remain = sm3_base_do_update_blocks(desc, data, len, sm3_neon_transform);
> -	kernel_neon_end();
> -	return remain;
> +	scoped_ksimd()
> +		return sm3_base_do_update_blocks(desc, data, len,
> +						 sm3_neon_transform);
>  }
>  
>  static int sm3_neon_finup(struct shash_desc *desc, const u8 *data,
>  			  unsigned int len, u8 *out)
>  {
> -	kernel_neon_begin();
> -	sm3_base_do_finup(desc, data, len, sm3_neon_transform);
> -	kernel_neon_end();
> +	scoped_ksimd()
> +		sm3_base_do_finup(desc, data, len, sm3_neon_transform);
>  	return sm3_base_finish(desc, out);
>  }
>