linux-kernel - Re: [PATCH v3] riscv: fix using wrong load type

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Message-ID: <B1669DA80470EE6A+aKQldVbfZ9rnlD9o@LT-Guozexi>
Date: Tue, 19 Aug 2025 15:19:17 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Jimmy Ho <jimmy.ho@...ive.com>, linux-riscv@...ts.infradead.org
Cc: troy.mitchell@...ux.spacemit.com, ziyao@...root.org,
	paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
	alex@...ti.fr, cyrilbur@...storrent.com, cleger@...osinc.com,
	charlie@...osinc.com, kees@...nel.org, ben.dooks@...ethink.co.uk,
	jszhang@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] riscv: fix using wrong load type

On Tue, Aug 19, 2025 at 03:13:18PM +0800, Jimmy Ho wrote:
> thread_info.cpu field is 32 bits wide,
> but is accessed using an XLEN-bit load, which might be 64bit load, fix it
> 
> Changes in v3:
> - replace space with tab to keep it aligned with code block
> - Add "Fixes" tag
Please add previous version link.

> 
> Changes in v2:
> - add a comment to explain why use lw instead of REG_L.
> - correct commit message
ditto.

Additionally, I see a patch here that serves the same purpose as yours,
but it's more comprehensive and was submitted earlier.

In any case, if you'd like to proceed, here is the:
Acked-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
> 
> Fixes: 503638e0babf3 ("riscv: Stop emitting preventive sfence.vma for new vmalloc mappings")
> Signed-off-by: Jimmy Ho <jimmy.ho@...ive.com>
> ---
>  arch/riscv/kernel/entry.S | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 3a0ec6fd5956..492ae936dccd 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -45,8 +45,10 @@
>  	 * Computes:
>  	 * a0 = &new_vmalloc[BIT_WORD(cpu)]
>  	 * a1 = BIT_MASK(cpu)
> +	 * 
> +	 * using lw instead of REG_L is because the thread_info.cpu field is 32 bits wide
>  	 */
> -	REG_L 	a2, TASK_TI_CPU(tp)
> +	lw	a2, TASK_TI_CPU(tp)
>  	/*
>  	 * Compute the new_vmalloc element position:
>  	 * (cpu / 64) * 8 = (cpu >> 6) << 3
> -- 
> 2.39.3
> 
>