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Mon, 9 Feb 2026 09:46:54 +0000 Date: Mon, 9 Feb 2026 10:46:39 +0100 From: Larysa Zaremba To: Jakub Kicinski CC: Vladimir Oltean , , "Claudiu Manoil" , Wei Fang , Clark Wang , Andrew Lunn , "David S. Miller" , Eric Dumazet , "Paolo Abeni" , Tony Nguyen , "Przemek Kitszel" , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , "Stanislav Fomichev" , Andrii Nakryiko , "Martin KaFai Lau" , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , Simon Horman , Shuah Khan , Alexander Lobakin , "Maciej Fijalkowski" , "Bastien Curutchet (eBPF Foundation)" , Tushar Vyavahare , Jason Xing , Ricardo =?utf-8?B?Qi4gTWFybGniiJrCrnJl?= , Eelco Chaudron , Lorenzo Bianconi , "Toke Hoiland-Jorgensen" , , , , , , Aleksandr Loktionov Subject: Re: [PATCH bpf 6/6] net: enetc: use truesize as XDP RxQ info frag_size Message-ID: References: <20260205005901.gnju3zmqimtgeu2b@skbuf> <20260204173401.282899d0@kernel.org> <20260205122953.lscemcctayrvszdu@skbuf> <20260205124638.hxzvjiocephzlrk3@skbuf> <20260205134046.pggwyosutj7ggi4i@skbuf> <20260205175408.30ab72a1@kernel.org> <20260206185735.787fb0e5@kernel.org> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260206185735.787fb0e5@kernel.org> X-ClientProxiedBy: BE1P281CA0426.DEUP281.PROD.OUTLOOK.COM (2603:10a6:b10:83::11) To SN7PR11MB7540.namprd11.prod.outlook.com (2603:10b6:806:340::7) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN7PR11MB7540:EE_|PH8PR11MB7095:EE_ X-MS-Office365-Filtering-Correlation-Id: b57873a3-18ea-4ee5-5d1e-08de67c0282a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|10070799003|366016; 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Much simpler, "infinite space", and works regardless of the > > > driver. I don't mean that to suggest you implement it, purely to point > > > out that I think nobody really uses positive offsets.. So we can as > > > well switch more complicated drivers back to xdp_rxq_info_reg(). > > > > As Vladimir has mentioned, if the driver does not use header split, frags will > > have a tailroom of a size of skb_shared_info, so tail growing does work in > > practice. > > > > Allocating a page_pool buffer (given XDP queue has one attached) is certainly an > > option, although I am not sure if anyone needs it. Furthermore, growing tail > > would still fail for a single-buf case. > > sbuf is a different code path, sbuf has precise frame_sz per frame, > not a single value in rxq, no? Don't mean to argue, just making sure > my mental model is correct ;) > You are right, xdp_buff in sbuf case is self-sufficient inside of bpf ops. sbuf mostly requires memory info from XDP RxQ for proper xdp_frame handling. What I meant is that intended conditions of failure to grow tail are the same for sbuf and mbuf case, the last (which can be the same as the first) buffer needs to have enough leftover space.