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Sat, 4 Apr 2026 10:07:06 +0000 Date: Sat, 4 Apr 2026 12:07:00 +0200 From: Maciej Fijalkowski To: Jakub Kicinski CC: , , , , , , , , , Stanislav Fomichev Subject: Re: [PATCH v6 net 1/8] xsk: tighten UMEM headroom validation to account for tailroom and min frame Message-ID: References: <20260402154958.562179-1-maciej.fijalkowski@intel.com> <20260402154958.562179-2-maciej.fijalkowski@intel.com> <20260403170126.276f9623@kernel.org> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260403170126.276f9623@kernel.org> X-ClientProxiedBy: VI1PR04CA0126.eurprd04.prod.outlook.com (2603:10a6:803:f0::24) To DM4PR11MB6117.namprd11.prod.outlook.com (2603:10b6:8:b3::19) 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: DM4PR11MB6117:EE_|DS4PPF900531A26:EE_ X-MS-Office365-Filtering-Correlation-Id: 727f6e80-ecfe-47d3-de46-08de9231ed41 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|1800799024|18002099003|56012099003|22082099003; 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Furthermore if multi-buffer would come to play then > > skb_shared_info stored at the end of XSK frame would be corrupted. > > > > HW typically works with 128-aligned sizes so let us provide this value > > as bare minimum. > > > > Multi-buffer setting is known later in the configuration process so > > besides accounting for 128 bytes, let us also take care of tailroom space > > upfront. > > I guess it's a bit late to ask this, but am I the only one that has > weird feelings about shinfo living in user-mapped memory? This was the approach was picked to be consistent with XDP side and allow to use mbuf related helpers. I can imagine you would be suggesting to pick up pages from system page pool but that would be a major refactor (however I have not put much not thought into it - i'm here without a coffee and in easter mode). Outside of this rewrite this set fixes existing memory corruption, so I feel it is needed and we can think how should we address the concern you are bringing up later?