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Tue, 1 Sep 2026 14:08:53 +0000 Received: from LV8PR12MB9620.namprd12.prod.outlook.com ([fe80::299d:f5e0:3550:1528]) by LV8PR12MB9620.namprd12.prod.outlook.com ([fe80::299d:f5e0:3550:1528%4]) with mapi id 15.21.0360.008; Tue, 1 Sep 2026 14:08:53 +0000 Date: Tue, 1 Sep 2026 11:08:51 -0300 From: Jason Gunthorpe To: Christian =?utf-8?B?S8O2bmln?= Cc: Leon Romanovsky , Bjorn Helgaas , Logan Gunthorpe , Jonathan Corbet , Shuah Khan , Sumit Semwal , linux-pci@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org Subject: Re: [PATCH 2/2] dma-buf: Document how exporters and importers agree on mapping lifetime Message-ID: <20260901140851.GA2771412@nvidia.com> References: <20260825-document-dma-buf-v1-0-5ecfb3e1371c@nvidia.com> <20260825-document-dma-buf-v1-2-5ecfb3e1371c@nvidia.com> <2776f9b0-c299-45ff-bf82-89b95e73fd60@amd.com> <20260826124341.GD42790@unreal> <39dc2f46-08c8-4eff-aa22-a7c67b5c7040@amd.com> <20260826140234.GE42790@unreal> <783c4c15-b8c6-4e9a-96fe-451d7c3ea302@amd.com> Content-Type: text/plain; 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For the importer there are clearly different things that imply different HW capabilities: pinned means the importer doesn't provide any way to stop DMA revocable means the importer must be able to stop DMA and possibly suffer user visble errors in the process movable means the importer must be able to pause DMA and never suffer errors while the memory location is moving. The whole reason we have these levels is because they reflect very real levels of HW support on the importer side. I think it is worth documenting it at least for the sake of people implementing importer HW to understand the rules Yes you can use the APIs more flexilby, but not beyound the HW enforced limits above. > Completely revoking is just a special case of moving the backing > store to an inaccessible place and not making it accessible again on > the next map call. In a very general abstract sense maybe, but that model doesn't match how the importer HW implementations work. Jason