Re: [PATCH] riscv: uaccess: Allow the last potential unrolled copy

From: Alexandre Ghiti <alex@ghiti.fr>
To: Xiao Wang <xiao.w.wang@intel.com>,
	paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu
Cc: jerry.shih@sifive.com, nick.knight@sifive.com,
	ajones@ventanamicro.com, bjorn@rivosinc.com,
	andy.chiu@sifive.com, viro@zeniv.linux.org.uk,
	cleger@rivosinc.com, alexghiti@rivosinc.com,
	haicheng.li@intel.com, akira.tsukamoto@gmail.com,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: uaccess: Allow the last potential unrolled copy
Date: Fri, 3 May 2024 14:16:18 +0200	[thread overview]
Message-ID: <7ebc5b28-7115-494f-a607-e46c71214cce@ghiti.fr> (raw)
In-Reply-To: <20240313103334.4036554-1-xiao.w.wang@intel.com>

Hi Xiao,

On 13/03/2024 11:33, Xiao Wang wrote:
> When the dst buffer pointer points to the last accessible aligned addr, we
> could still run another iteration of unrolled copy.
>
> Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
> ---
>   arch/riscv/lib/uaccess.S | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
> index 2e665f8f8fcc..1399d797d81b 100644
> --- a/arch/riscv/lib/uaccess.S
> +++ b/arch/riscv/lib/uaccess.S
> @@ -103,7 +103,7 @@ SYM_FUNC_START(fallback_scalar_usercopy)
>   	fixup REG_S   t4,  7*SZREG(a0), 10f
>   	addi	a0, a0, 8*SZREG
>   	addi	a1, a1, 8*SZREG
> -	bltu	a0, t0, 2b
> +	bleu	a0, t0, 2b
>   
>   	addi	t0, t0, 8*SZREG /* revert to original value */
>   	j	.Lbyte_copy_tail

I agree it is still safe to continue for another word_copy here.

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Thanks,

Alex

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