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[142.162.112.119]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-896f79d34bcsm39740876d6.0.2026.02.09.10.13.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Feb 2026 10:13:04 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vpVkt-0000000EmNV-2zIP; Mon, 09 Feb 2026 14:13:03 -0400 Date: Mon, 9 Feb 2026 14:13:03 -0400 From: Jason Gunthorpe To: Zhiping Zhang Cc: Leon Romanovsky , Bjorn Helgaas , linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org, Keith Busch , Yochai Cohen , Yishai Hadas , Bjorn Helgaas Subject: Re: [RFC 0/2] Retrieve tph from dmabuf for PCIe P2P memory access Message-ID: <20260209181303.GB943673@ziepe.ca> References: <20260209175317.1713406-1-zhipingz@meta.com> Precedence: bulk X-Mailing-List: netdev@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: <20260209175317.1713406-1-zhipingz@meta.com> On Mon, Feb 09, 2026 at 09:53:10AM -0800, Zhiping Zhang wrote: > Currently, the steering tag can be used for a CPU on the motherboard; the > ACPI check is in place to query and obtain the supported tph settings. Here > we intend to use the tph info to improve RDMA NIC memory access on a vfio-based > accelerator device via PCIe peer-to-peer. When an applicantion register a > RDMA memory region with DMABUF for the RDMA NIC to access the device memory, > the tph associated with the memory region can be retrieved and used to set the > steering tag / process hint (ph). The tph contains additional instructions > or hints to the GPU or accelerator device for advanced memory operations, > such as, read cache selection. > > Note this RFC is for the discussion on the direction and is not intended to be > a complete implementation. Once the direction is agreed on, we will work on the > implementation or a real patch set. you didn't cc the DRM people who really need to look at any changes to the dmabuf contract. Jason