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[146.241.41.201]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438e23d48b3sm197508285e9.5.2025.02.04.04.15.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Feb 2025 04:15:41 -0800 (PST) Message-ID: <09a0caba-db29-4100-a46d-b104b282ea0a@redhat.com> Date: Tue, 4 Feb 2025 13:15:38 +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: [PATCH net-next v3 5/6] net: devmem: Implement TX path To: Mina Almasry , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux.dev, linux-kselftest@vger.kernel.org Cc: Donald Hunter , Jakub Kicinski , "David S. Miller" , Eric Dumazet , Simon Horman , Jonathan Corbet , Andrew Lunn , Neal Cardwell , David Ahern , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Stefan Hajnoczi , Stefano Garzarella , Shuah Khan , sdf@fomichev.me, asml.silence@gmail.com, dw@davidwei.uk, Jamal Hadi Salim , Victor Nogueira , Pedro Tammela , Samiullah Khawaja , Kaiyuan Zhang References: <20250203223916.1064540-1-almasrymina@google.com> <20250203223916.1064540-6-almasrymina@google.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20250203223916.1064540-6-almasrymina@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/3/25 11:39 PM, Mina Almasry wrote: > Augment dmabuf binding to be able to handle TX. Additional to all the RX > binding, we also create tx_vec needed for the TX path. > > Provide API for sendmsg to be able to send dmabufs bound to this device: > > - Provide a new dmabuf_tx_cmsg which includes the dmabuf to send from. > - MSG_ZEROCOPY with SCM_DEVMEM_DMABUF cmsg indicates send from dma-buf. > > Devmem is uncopyable, so piggyback off the existing MSG_ZEROCOPY > implementation, while disabling instances where MSG_ZEROCOPY falls back > to copying. > > We additionally pipe the binding down to the new > zerocopy_fill_skb_from_devmem which fills a TX skb with net_iov netmems > instead of the traditional page netmems. > > We also special case skb_frag_dma_map to return the dma-address of these > dmabuf net_iovs instead of attempting to map pages. > > Based on work by Stanislav Fomichev . A lot of the meat > of the implementation came from devmem TCP RFC v1[1], which included the > TX path, but Stan did all the rebasing on top of netmem/net_iov. > > Cc: Stanislav Fomichev > Signed-off-by: Kaiyuan Zhang > Signed-off-by: Mina Almasry Very minor nit: you unexpectedly leaved a lot of empty lines after the SoB. [...] @@ -240,13 +249,23 @@ net_devmem_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd, > * binding can be much more flexible than that. We may be able to > * allocate MTU sized chunks here. Leave that for future work... > */ > - binding->chunk_pool = > - gen_pool_create(PAGE_SHIFT, dev_to_node(&dev->dev)); > + binding->chunk_pool = gen_pool_create(PAGE_SHIFT, > + dev_to_node(&dev->dev)); > if (!binding->chunk_pool) { > err = -ENOMEM; > goto err_unmap; > } > > + if (direction == DMA_TO_DEVICE) { > + binding->tx_vec = kvmalloc_array(dmabuf->size / PAGE_SIZE, > + sizeof(struct net_iov *), > + GFP_KERNEL); > + if (!binding->tx_vec) { > + err = -ENOMEM; > + goto err_free_chunks; It looks like the later error paths (in the for_each_sgtable_dma_sg() loop) could happen even for 'direction == DMA_TO_DEVICE', so I guess an additional error label is needed to clean tx_vec on such paths. /P