linux-kernel - Re: [PATCH v2 5/8] dma-mapping: Support batch mode for dma_direct_sync_sg_for

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Message-ID: <20251227200933.GO11869@unreal>
Date: Sat, 27 Dec 2025 22:09:33 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Barry Song <21cnbao@...il.com>
Cc: catalin.marinas@....com, m.szyprowski@...sung.com, robin.murphy@....com,
	will@...nel.org, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xenproject.org, Barry Song <baohua@...nel.org>,
	Ada Couprie Diaz <ada.coupriediaz@....com>,
	Ard Biesheuvel <ardb@...nel.org>, Marc Zyngier <maz@...nel.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Ryan Roberts <ryan.roberts@....com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Tangquan Zheng <zhengtangquan@...o.com>
Subject: Re: [PATCH v2 5/8] dma-mapping: Support batch mode for
 dma_direct_sync_sg_for_*

On Sat, Dec 27, 2025 at 11:52:45AM +1300, Barry Song wrote:
> From: Barry Song <baohua@...nel.org>
> 
> Instead of performing a flush per SG entry, issue all cache
> operations first and then flush once. This ultimately benefits
> __dma_sync_sg_for_cpu() and __dma_sync_sg_for_device().
> 
> Cc: Leon Romanovsky <leon@...nel.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Ada Couprie Diaz <ada.coupriediaz@....com>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Anshuman Khandual <anshuman.khandual@....com>
> Cc: Ryan Roberts <ryan.roberts@....com>
> Cc: Suren Baghdasaryan <surenb@...gle.com>
> Cc: Tangquan Zheng <zhengtangquan@...o.com>
> Signed-off-by: Barry Song <baohua@...nel.org>
> ---
>  kernel/dma/direct.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)

<...>

> -		if (!dev_is_dma_coherent(dev)) {
> +		if (!dev_is_dma_coherent(dev))
>  			arch_sync_dma_for_device(paddr, sg->length,
>  					dir);
> -			arch_sync_dma_flush();
> -		}
>  	}
> +	if (!dev_is_dma_coherent(dev))
> +		arch_sync_dma_flush();

This patch should be squashed into the previous one. You introduced
arch_sync_dma_flush() there, and now you are placing it elsewhere.

Thanks