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([2620:10d:c092:600::1:4dfd]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-60fc81a70e4sm6850991a12.0.2025.07.08.03.46.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Jul 2025 03:46:18 -0700 (PDT) Message-ID: Date: Tue, 8 Jul 2025 11:47:46 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC net-next 1/4] net: Allow non parent devices to be used for ZC DMA To: Mina Almasry , Dragos Tatulea Cc: Parav Pandit , Jakub Kicinski , Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Saeed Mahameed , Tariq Toukan , Cosmin Ratiu , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20250702172433.1738947-1-dtatulea@nvidia.com> <20250702172433.1738947-2-dtatulea@nvidia.com> <20250702113208.5adafe79@kernel.org> <20250702135329.76dbd878@kernel.org> <22kf5wtxym5x3zllar7ek3onkav6nfzclf7w2lzifhebjme4jb@h4qycdqmwern> Content-Language: en-US From: Pavel Begunkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 7/7/25 22:55, Mina Almasry wrote: > On Mon, Jul 7, 2025 at 2:35 PM Dragos Tatulea wrote: ...>> Right. My patches show that. But the issue raised by Parav is different: >> different queues can belong to different DMA devices from different >> PFs in the case of Multi PF netdev. >> >> io_uring can do it because it maps individual buffers to individual >> queues. So it would be trivial to get the DMA device of each queue through >> a new queue op. >> > > Right, devmem doesn't stop you from mapping individual buffers to > individual queues. It just also supports mapping the same buffer to > multiple queues. AFAIR, io_uring also supports mapping a single buffer > to multiple queues, but I could easily be very wrong about that. It's It doesn't, but it could benefit from sharing depending on userspace, so it might eventually come to the same problem. -- Pavel Begunkov