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Wed, 05 Feb 2025 04:41:05 -0800 (PST) Received: from [192.168.8.100] ([148.252.128.4]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4390d93383asm20448845e9.7.2025.02.05.04.41.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Feb 2025 04:41:04 -0800 (PST) Message-ID: <53192c45-df3c-4a65-9047-bbd59d4aee47@gmail.com> Date: Wed, 5 Feb 2025 12:41:11 +0000 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC net-next v1 5/5] net: devmem: Implement TX path To: Willem de Bruijn , Mina Almasry Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, virtualization@lists.linux.dev, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Donald Hunter , Jonathan Corbet , Andrew Lunn , David Ahern , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Stefan Hajnoczi , Stefano Garzarella , Shuah Khan , Kaiyuan Zhang , Willem de Bruijn , Samiullah Khawaja , Stanislav Fomichev , Joe Damato , dw@davidwei.uk References: <20241221004236.2629280-1-almasrymina@google.com> <20241221004236.2629280-6-almasrymina@google.com> <676dd022d1388_1d346b2947@willemb.c.googlers.com.notmuch> <6798ee97c73e1_987d9294d6@willemb.c.googlers.com.notmuch> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <6798ee97c73e1_987d9294d6@willemb.c.googlers.com.notmuch> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/28/25 14:49, Willem de Bruijn wrote: >>>> +struct net_devmem_dmabuf_binding * >>>> +net_devmem_get_sockc_binding(struct sock *sk, struct sockcm_cookie *sockc) >>>> +{ >>>> + struct net_devmem_dmabuf_binding *binding; >>>> + int err = 0; >>>> + >>>> + binding = net_devmem_lookup_dmabuf(sockc->dmabuf_id); >>> >>> This lookup is from global xarray net_devmem_dmabuf_bindings. >>> >>> Is there a check that the socket is sending out through the device >>> to which this dmabuf was bound with netlink? Should there be? >>> (e.g., SO_BINDTODEVICE). >>> >> >> Yes, I think it may be an issue if the user triggers a send from a >> different netdevice, because indeed when we bind a dmabuf we bind it >> to a specific netdevice. >> >> One option is as you say to require TX sockets to be bound and to >> check that we're bound to the correct netdev. I also wonder if I can >> make this work without SO_BINDTODEVICE, by querying the netdev the >> sock is currently trying to send out on and doing a check in the >> tcp_sendmsg. I'm not sure if this is possible but I'll give it a look. > > I was a bit quick on mentioning SO_BINDTODEVICE. Agreed that it is > vastly preferable to not require that, but infer the device from > the connected TCP sock. I wonder why so? I'd imagine something like SO_BINDTODEVICE is a better way to go. The user has to do it anyway, otherwise packets might go to a different device and the user would suddenly start getting errors with no good way to alleviate them (apart from likes of SO_BINDTODEVICE). It's even worse if it works for a while but starts to unpredictably fail as time passes. With binding at least it'd fail fast if the setup is not done correctly. -- Pavel Begunkov