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[47.55.120.4]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4ee48d64503sm3117901cf.13.2025.11.19.11.36.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Nov 2025 11:36:38 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vLnyo-00000000bYz-0lQx; Wed, 19 Nov 2025 15:36:38 -0400 Date: Wed, 19 Nov 2025 15:36:38 -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: <20251119193638.GQ17968@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> <20251119134245.GD18335@unreal> <6714dc49-6b5c-4d58-9a43-95bb95873a97@amd.com> 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: <6714dc49-6b5c-4d58-9a43-95bb95873a97@amd.com> On Wed, Nov 19, 2025 at 03:11:01PM +0100, Christian König wrote: > I miss interpreted the call to pci_p2pdma_map_type() here in that > now the DMA-buf code decides if transactions go over the root > complex or not. Oh, that's not it at all. I think you get it, but just to be really clear: This code is taking a physical address from the exporter and determining how it MUST route inside the fabric. There is only one single choice with no optionality. The exporter already decided if it will go over the host bridge by providing an address that must use a host bridge path. > But the exporter can call pci_p2pdma_map_type() even before calling > this function, so that looks fine to me. Yes, the exporter needs to decide where the data is placed before it tries to map it into the SGT. Jason