netdev - Re: [PATCH net-next 1/4] arm64: barrier: add DGH macros to control memory accesses merging

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Message-ID: <20210730093921.GA8570@arm.com>
Date:   Fri, 30 Jul 2021 10:39:21 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Guangbin Huang <huangguangbin2@...wei.com>
Cc:     davem@...emloft.net, kuba@...nel.org, will@...nel.org,
        maz@...nel.org, mark.rutland@....com, dbrazdil@...gle.com,
        qperret@...gle.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        lipeng321@...wei.com
Subject: Re: [PATCH net-next 1/4] arm64: barrier: add DGH macros to control
 memory accesses merging

On Fri, Jul 30, 2021 at 11:14:21AM +0800, Guangbin Huang wrote:
> From: Xiongfeng Wang <wangxiongfeng2@...wei.com>
> 
> DGH prohibits merging memory accesses with Normal-NC or Device-GRE
> attributes before the hint instruction with any memory accesses
> appearing after the hint instruction. Provide macros to expose it to the
> arch code.
> 
> Signed-off-by: Xiongfeng Wang <wangxiongfeng2@...wei.com>
> Signed-off-by: Cheng Jian <cj.chengjian@...wei.com>
> Signed-off-by: Yufeng Mo <moyufeng@...wei.com>
> ---
>  arch/arm64/include/asm/assembler.h | 7 +++++++
>  arch/arm64/include/asm/barrier.h   | 1 +
>  2 files changed, 8 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index 89faca0e740d..5a3348b5e9f3 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -90,6 +90,13 @@
>  	.endm
>  
>  /*
> + * Data gathering hint
> + */
> +	.macro	dgh
> +	hint	#6
> +	.endm

Do we need this macro? It doesn't seem to be used anywhere.

-- 
Catalin