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[142.162.112.119]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-89a3140f7ebsm74752146d6.6.2026.03.09.06.20.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Mar 2026 06:20:38 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vzaXG-0000000G7pH-11Zd; Mon, 09 Mar 2026 10:20:38 -0300 Date: Mon, 9 Mar 2026 10:20:38 -0300 From: Jason Gunthorpe To: Marek Szyprowski Cc: Leon Romanovsky , Robin Murphy , "Michael S. Tsirkin" , Petr Tesarik , Jonathan Corbet , Shuah Khan , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, virtualization@lists.linux.dev, linux-rdma@vger.kernel.org Subject: Re: [PATCH 2/3] dma-mapping: Clarify valid conditions for CPU cache line overlap Message-ID: <20260309132038.GL1687929@ziepe.ca> References: <20260307-dma-debug-overlap-v1-0-c034c38872af@nvidia.com> <20260307-dma-debug-overlap-v1-2-c034c38872af@nvidia.com> <20260308181920.GH1687929@ziepe.ca> <20260308184902.GR12611@unreal> <20260308230916.GI1687929@ziepe.ca> <20260309090342.GS12611@unreal> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Mar 09, 2026 at 01:30:24PM +0100, Marek Szyprowski wrote: > My question here is if RDMA works on any non-coherent DMA systems? The in kernel components do work, like storage, nvme over fabrics, netdev. The user API (uverbs) does not work at all, and has never worked. I think DRM has similar issues too where most of their DMA API usage is OK but some places where they interact win pin_user_pages() have the same issues as RDMA. This is why I'd like a new attribute DMA_ATTR_REQUIRE_COHERENCE that these special cases can use to fail instead of data corrupt. Jason