linux-kernel - Re: [PATCH -next v4 5/7] arm64: mte: Clean up user tag accessors

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Date:   Fri, 13 May 2022 16:36:53 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Tong Tiangen <tongtiangen@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>
Cc:     James Morse <james.morse@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Robin Murphy <robin.murphy@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Will Deacon <will@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Kefeng Wang <wangkefeng.wang@...wei.com>,
        Xie XiuQi <xiexiuqi@...wei.com>,
        Guohanjun <guohanjun@...wei.com>
Subject: Re: [PATCH -next v4 5/7] arm64: mte: Clean up user tag accessors

On Wed, Apr 20, 2022 at 03:04:16AM +0000, Tong Tiangen wrote:
> From: Robin Murphy <robin.murphy@....com>
> 
> Invoking user_ldst to explicitly add a post-increment of 0 is silly.
> Just use a normal USER() annotation and save the redundant instruction.
> 
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> Reviewed-by: Tong Tiangen <tongtiangen@...wei.com>

When posting someone else's patch, you need to add your own
Signed-off-by tag. Please see:

  https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin

That said, the patch itself looks sane, and matches its original posting
at:

  https://lore.kernel.org/linux-arm-kernel/38c6d4b5-a3db-5c3e-02e7-39875edb3476@arm.com/

So:

  Acked-by: Mark Rutland <mark.rutland@....com>

Catalin, are you happy to pick up this patch as a cleanup?

Thanks,
Mark.

> ---
>  arch/arm64/lib/mte.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/lib/mte.S b/arch/arm64/lib/mte.S
> index 8590af3c98c0..eeb9e45bcce8 100644
> --- a/arch/arm64/lib/mte.S
> +++ b/arch/arm64/lib/mte.S
> @@ -93,7 +93,7 @@ SYM_FUNC_START(mte_copy_tags_from_user)
>  	mov	x3, x1
>  	cbz	x2, 2f
>  1:
> -	user_ldst 2f, ldtrb, w4, x1, 0
> +USER(2f, ldtrb	w4, [x1])
>  	lsl	x4, x4, #MTE_TAG_SHIFT
>  	stg	x4, [x0], #MTE_GRANULE_SIZE
>  	add	x1, x1, #1
> @@ -120,7 +120,7 @@ SYM_FUNC_START(mte_copy_tags_to_user)
>  1:
>  	ldg	x4, [x1]
>  	ubfx	x4, x4, #MTE_TAG_SHIFT, #MTE_TAG_SIZE
> -	user_ldst 2f, sttrb, w4, x0, 0
> +USER(2f, sttrb	w4, [x0])
>  	add	x0, x0, #1
>  	add	x1, x1, #MTE_GRANULE_SIZE
>  	subs	x2, x2, #1
> -- 
> 2.25.1
>