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[47.55.120.4]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8b3295c13ccsm148498285a.26.2025.11.20.05.20.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Nov 2025 05:20:46 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vM4ac-00000000gLM-0tBz; Thu, 20 Nov 2025 09:20:46 -0400 Date: Thu, 20 Nov 2025 09:20:46 -0400 From: Jason Gunthorpe To: Christian =?utf-8?B?S8O2bmln?= Cc: Leon Romanovsky , Bjorn Helgaas , Logan Gunthorpe , Jens Axboe , Robin Murphy , Joerg Roedel , Will Deacon , Marek Szyprowski , Andrew Morton , Jonathan Corbet , Sumit Semwal , Kees Cook , "Gustavo A. R. Silva" , Ankit Agrawal , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , Krishnakant Jaju , Matt Ochs , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, iommu@lists.linux.dev, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, kvm@vger.kernel.org, linux-hardening@vger.kernel.org, Alex Mastro , Nicolin Chen Subject: Re: [Linaro-mm-sig] [PATCH v8 06/11] dma-buf: provide phys_vec to scatter-gather mapping routine Message-ID: <20251120132046.GU17968@ziepe.ca> References: <20251111-dmabuf-vfio-v8-0-fd9aa5df478f@nvidia.com> <20251111-dmabuf-vfio-v8-6-fd9aa5df478f@nvidia.com> <8a11b605-6ac7-48ac-8f27-22df7072e4ad@amd.com> <20251119132511.GK17968@ziepe.ca> <69436b2a-108d-4a5a-8025-c94348b74db6@amd.com> <20251119193114.GP17968@ziepe.ca> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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