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Message-ID: <20251120132046.GU17968@ziepe.ca>
Date: Thu, 20 Nov 2025 09:20:46 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Christian König <christian.koenig@....com>
Cc: Leon Romanovsky <leon@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
Logan Gunthorpe <logang@...tatee.com>, Jens Axboe <axboe@...nel.dk>,
Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
Will Deacon <will@...nel.org>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jonathan Corbet <corbet@....net>,
Sumit Semwal <sumit.semwal@...aro.org>, Kees Cook <kees@...nel.org>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
Ankit Agrawal <ankita@...dia.com>,
Yishai Hadas <yishaih@...dia.com>,
Shameer Kolothum <skolothumtho@...dia.com>,
Kevin Tian <kevin.tian@...el.com>,
Alex Williamson <alex@...zbot.org>,
Krishnakant Jaju <kjaju@...dia.com>, Matt Ochs <mochs@...dia.com>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-block@...r.kernel.org, iommu@...ts.linux.dev,
linux-mm@...ck.org, linux-doc@...r.kernel.org,
linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linaro-mm-sig@...ts.linaro.org, kvm@...r.kernel.org,
linux-hardening@...r.kernel.org, Alex Mastro <amastro@...com>,
Nicolin Chen <nicolinc@...dia.com>
Subject: Re: [Linaro-mm-sig] [PATCH v8 06/11] dma-buf: provide phys_vec to
scatter-gather mapping routine
On Thu, Nov 20, 2025 at 08:08:27AM +0100, Christian König wrote:
> >> The exporter should be able to decide if it actually wants to use
> >> P2P when the transfer has to go through the host bridge (e.g. when
> >> IOMMU/bridge routing bits are enabled).
> >
> > Sure, but this is a simplified helper for exporters that don't have
> > choices where the memory comes from.
>
> That is extremely questionable as justification to put that in common DMA-buf code.
FWIW we already have patches for a RDMA exporter lined up to use it as
well. That's two users already...
Jason
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