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Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Andrew Lunn , Jens Axboe , Cosmin Ratiu , Tariq Toukan , Pavel Begunkov , Mina Almasry , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "io-uring@vger.kernel.org" Subject: RE: [PATCH v2 net-next] net: Allow SF devices to be used for ZC DMA Thread-Topic: [PATCH v2 net-next] net: Allow SF devices to be used for ZC DMA Thread-Index: AQHb8kYbLM5zoGcCakGbq+Zrkt38erQyZkUAgAA6FgCAAI2+gIABctUAgAABBIA= Date: Wed, 16 Jul 2025 11:23:13 +0000 Message-ID: References: <20250711092634.2733340-2-dtatulea@nvidia.com> <20250714181136.7fd53312@kernel.org> <20250715060649.03b3798c@kernel.org> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; x-ms-publictraffictype: Email x-ms-traffictypediagnostic: CY8PR12MB7195:EE_|DM3PR12MB9434:EE_ x-ms-office365-filtering-correlation-id: d4551435-6927-4fd0-518f-08ddc45b2731 x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0;ARA:13230040|10070799003|366016|1800799024|376014|7416014|38070700018; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: CY8PR12MB7195.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: d4551435-6927-4fd0-518f-08ddc45b2731 X-MS-Exchange-CrossTenant-originalarrivaltime: 16 Jul 2025 11:23:13.4709 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: GC2Tkr5fba85V8t+M1zFnsVIEPHsrHJFQbEwmBwx8/4zv11Hdbja/Qk67Ge7xNvP+EdIPJUyslCKrMHEIW64EQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM3PR12MB9434 > From: Christoph Hellwig > Sent: 16 July 2025 04:44 PM >=20 > On Tue, Jul 15, 2025 at 06:06:49AM -0700, Jakub Kicinski wrote: > > On Mon, 14 Jul 2025 21:39:30 -0700 Christoph Hellwig wrote: > > > > LGTM, but we need a better place for this function. netdevice.h is > > > > included directly by 1.5k files, and indirectly by probably another= 5k. > > > > It's not a great place to put random helpers with 2 callers. > > > > Maybe net/netdev_rx_queue.h and net/core/netdev_rx_queue.c? > > > > I don't think it needs to be a static inline either. > > > > > > The whole concept is also buggy. Trying to get a dma-able device by > > > walking down from an upper level construct like the netdevice can't > > > work reliably. You'll need to explicitly provide the dma_device > > > using either a method or a pointer to it instead of this guesswork. > > > > Yeah, I'm pretty sure we'll end up with a method in queue ops. > > But it's not that deep, an easy thing to change. >=20 > Why not get this right now instead of adding more of the hacky parent > walking? The previous RFC version (v1) [1], the driver was explicitly providing dma_= dev=20 at device level. Queue level is even better; it will address the Netdev with two pci devs so= cket direct use case too. Not sure how difficult it is.=20 Dragos can you please evaluate? I believe the dma_mask check in [1] should be removed regardless. [1] https://lore.kernel.org/netdev/20250702172433.1738947-2-dtatulea@nvidia= .com/