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Tue, 5 Mar 2024 16:42:28 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.11.0-alpha0-208-g3f1d79aedb-fm-20240301.002-g3f1d79ae Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <037496c9-f06a-4946-b903-95d87d577b89@app.fastmail.com> In-Reply-To: References: <20240305020153.2787423-1-almasrymina@google.com> <20240305020153.2787423-6-almasrymina@google.com> <5e2f9342-4ee9-4b30-9dcf-393e57e0f7c6@app.fastmail.com> Date: Tue, 05 Mar 2024 22:42:07 +0100 From: "Arnd Bergmann" To: "Mina Almasry" Cc: Netdev , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, sparclinux@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Linux-Arch , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, "David S . Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Jonathan Corbet" , "Richard Henderson" , "Ivan Kokshaysky" , "Matt Turner" , "Thomas Bogendoerfer" , "James E . J . Bottomley" , "Helge Deller" , "Andreas Larsson" , "Jesper Dangaard Brouer" , "Ilias Apalodimas" , "Steven Rostedt" , "Masami Hiramatsu" , "Mathieu Desnoyers" , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Martin KaFai Lau" , "Eduard Zingerman" , "Song Liu" , "Yonghong Song" , "John Fastabend" , "KP Singh" , "Stanislav Fomichev" , "Hao Luo" , "Jiri Olsa" , "David Ahern" , "Willem de Bruijn" , shuah , "Sumit Semwal" , =?UTF-8?Q?Christian_K=C3=B6nig?= , "Pavel Begunkov" , "David Wei" , "Jason Gunthorpe" , "Yunsheng Lin" , "Shailend Chand" , "Harshitha Ramamurthy" , "Shakeel Butt" , "Jeroen de Borst" , "Praveen Kaligineedi" , "Willem de Bruijn" , "Kaiyuan Zhang" Subject: Re: [RFC PATCH net-next v6 05/15] netdev: support binding dma-buf to netdevice Content-Type: text/plain;charset=utf-8 Content-Transfer-Encoding: quoted-printable On Tue, Mar 5, 2024, at 21:00, Mina Almasry wrote: > On Tue, Mar 5, 2024 at 1:05=E2=80=AFAM Arnd Bergmann w= rote: >> On Tue, Mar 5, 2024, at 03:01, Mina Almasry wrote: > > A key goal of this patch series is that the kernel does not try to > parse the skb frags that reside in the dma-buf for that precise > reason. This is achieved using patch "net: add support for skbs with > unreadable frags" which disables the kernel touching the payload in > these skbs, and "tcp: RX path for devmem TCP" which implements a uapi > where the kernel hands the data in the dmabuf to the userspace via a > cmsg that gives the user a pointer to the data in the dmabuf (offset + > size). > > So really AFACT the only restriction here is that the NIC should be > able to DMA into the dmabuf that we're attaching, and dma_buf_attach() > fails in this scenario so we're covered there. Ok, makes sense. Thanks for the clarification. Arnd