linux-kernel - Re: [PATCH v2 6/8] dma-mapping: Support batch mode for dma_direct_{map,unmap}

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Message-ID: <20251227201406.GP11869@unreal>
Date: Sat, 27 Dec 2025 22:14:06 +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 6/8] dma-mapping: Support batch mode for
 dma_direct_{map,unmap}_sg

On Sat, Dec 27, 2025 at 11:52:46AM +1300, Barry Song wrote:
> From: Barry Song <baohua@...nel.org>
> 
> Leon suggested extending a flush argument to

Let's move this sentence out of the commit message and place it in the
changelog instead.

> dma_direct_unmap_phys(), dma_direct_map_phys(), and
> dma_direct_sync_single_for_cpu(). For single-buffer cases, this
> would use flush=true, while for SG cases flush=false would be
> used, followed by a single flush after all cache operations are
> issued in dma_direct_{map,unmap}_sg().
> 
> This ultimately benefits dma_map_sg() and dma_unmap_sg().
> 
> 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  | 17 +++++++++++++----
>  kernel/dma/direct.h  | 16 ++++++++++------
>  kernel/dma/mapping.c |  6 +++---
>  3 files changed, 26 insertions(+), 13 deletions(-)

Thanks,
Reviewed-by: Leon Romanovsky <leon@...nel.org>