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Wed, 9 Jul 2025 05:46:18 -0700 From: Dragos Tatulea To: , , Andrew Lunn , "David S. Miller" , "Eric Dumazet" , Jakub Kicinski , Paolo Abeni , Simon Horman , Jens Axboe , Simona Vetter , Willem de Bruijn , Kaiyuan Zhang CC: Dragos Tatulea , , , Tariq Toukan , , , Subject: [PATCH net] net: Allow non parent devices to be used for ZC DMA Date: Wed, 9 Jul 2025 15:40:57 +0300 Message-ID: <20250709124059.516095-2-dtatulea@nvidia.com> X-Mailer: git-send-email 2.50.0 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-NV-OnPremToCloud: AnonymousSubmission X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWH0EPF000971E7:EE_|SJ0PR12MB6901:EE_ X-MS-Office365-Filtering-Correlation-Id: 9fffd56d-8d06-420c-1f28-08ddbee6a761 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|36860700013|7416014|376014|921020; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?39MQE0IcwC35P2jLSjCOAAC82/hYWKGg7id8HzEILhlW2Srr6LWOkuA0g+VR?= =?us-ascii?Q?i2jzQley2Ich6TL6t58HpslrSfljMWK8r7Lw0r9M+ty4zdsqp5zT6FHg9XXC?= =?us-ascii?Q?goOY32GxrrL7/JtPt4Gk7USKLbszIfZGrIzYG49INfoVmf6mvCQHyVZKQnpF?= =?us-ascii?Q?v/gENjq0f6b1SMpqbr7LxR+azQv8Ia4qepn4fA+GZe0C8rT+SWQkJHOU4tE3?= =?us-ascii?Q?NzgAA/eotScNmbWt2WosX+1mFNsii6BmhwsmitYKd2zNT8JvQ1fUj9bGwFbQ?= =?us-ascii?Q?V3Kje2xb/cSUJ6FNJis42MMWBFTUuKpNbaRZZTK/ZprQrzFIHfhRiB1eUmCe?= =?us-ascii?Q?3owBo8FWFFu80Tq0CzRTddbg1LU7inLagdC2FdCojz1FNbHr8YE9VNVPqeU5?= =?us-ascii?Q?g/F4Af7aquPGQ0OD4SusGM+deSMjEIma6uOyUVkAkn1nPEP0kV1MSZot7uYJ?= =?us-ascii?Q?y9WRLhS0EZ+qXaT2Z1KTNSKeqAHWQj6tjLDbn99DqXas9scNC2NXOZ5JNrkC?= =?us-ascii?Q?1NIN3qjKwWq6Dmjnn/B5/77niFDA/B46v82dsAJDDoB8dZSmM9hc8l1AHO8T?= =?us-ascii?Q?hgAkSWVetA5bxhRu4+3utJNBTYbeYcLkDlSi1e5zc9mOm8n24aBHdcvpk1YN?= =?us-ascii?Q?YgBjWLsaxls9GkOOKQYF0tteMbufmZHOy2UXvF++pFQd1it4et6/HzLxnkty?= =?us-ascii?Q?LgDVTzmRCi+zz01IIDCUhVk92fkj0LJesXbUGUdv4YC6QMdYJObabMo/14Le?= =?us-ascii?Q?4sAcOtn/NnOsdnEwfzJiVTo45neu4J9Pilov63ldqNXdVem2K+VPD9i4Ef99?= =?us-ascii?Q?ugVanhR5wfbU4zNsByDkW5Ro73f0+52YCsPNTScGS4erzMkNWpf+wenF6TRX?= =?us-ascii?Q?nCFPP+pM4PI1bOV3UWh/yyXnkHg18bpt4erSLvlf7NHWrxsIk8b7wf+rxIq1?= =?us-ascii?Q?bg3v6bjFs29KK5pJZBIBQW177u6uj9tYkqSxKaRZ1CqryZFDWCUa7FA1GJ1x?= =?us-ascii?Q?kkZE4syRtiWsSeZFGL4Kb2unO3QtLjnwNVviOyLKuCarLou/jOOIm8T8oWY2?= =?us-ascii?Q?hg9CQft4FktCOdchTjgR4+ePBH0rDdTmQQ8wmj3Wj0eUD6FEW8M02nltgI/m?= =?us-ascii?Q?19Knc4OAQSddcJmoOp1asD6PMPaAEKJsMDop9Xbnc4H5KdxP/1sSXukRGW18?= =?us-ascii?Q?OT4XyuUazjrB7tCHIcbdFwYv7AF5zxWWN/wcslXhkjIcYSTB3Yd6sSPOV8DI?= =?us-ascii?Q?AeerwEXCLNx9No5fK/HQLIFSQN9o099tAj2hMemJwsqwGAeW0xSB+ADKwVVx?= =?us-ascii?Q?NzRVuyxoUqvB7hpilquwuEu6C+BRb9MEVmWF8NiFJaDZ0+SeVl03jYYkkKR2?= =?us-ascii?Q?JjoqAJrG0Vb+hXsRl4qbUP/bfSGIItyeYzFt7S29uStpZrB5DcXnFHUEwAnd?= =?us-ascii?Q?rWZB7RSp/fg5rsdBBvl4hObgbPLoUunWnGRDO7ZPqNFTJfEQpoiddDXx+RwC?= =?us-ascii?Q?dii8ACUNBbjtuPZohS7a8PCN8MS9FhXfCdOA8G3lMzMkox/jzXTtUp9UqcCD?= =?us-ascii?Q?KH/CfBnVZanPR+2wINs=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(1800799024)(82310400026)(36860700013)(7416014)(376014)(921020);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Jul 2025 12:46:41.5466 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 9fffd56d-8d06-420c-1f28-08ddbee6a761 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: MWH0EPF000971E7.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR12MB6901 For zerocopy (io_uring, devmem), there is an assumption that the parent device can do DMA. However that is not always the case: ScalableFunction devices have the DMA device in the grandparent. This patch adds a helper for getting the DMA device for a netdev from its parent or grandparent if necessary. The NULL case is handled in the callers. devmem and io_uring are updated accordingly to use this helper instead of directly using the parent. Signed-off-by: Dragos Tatulea Fixes: 170aafe35cb9 ("netdev: support binding dma-buf to netdevice") Reviewed-by: Tariq Toukan --- Changes in v1: - Upgraded from RFC status. - Dropped driver specific bits for generic solution. - Implemented single patch as a fix as requested in RFC. - Handling of multi-PF netdevs will be handled in a subsequent patch series. RFC: https://lore.kernel.org/all/20250702172433.1738947-2-dtatulea@nvidia.com/ --- include/linux/netdevice.h | 14 ++++++++++++++ io_uring/zcrx.c | 2 +- net/core/devmem.c | 10 +++++++++- 3 files changed, 24 insertions(+), 2 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 5847c20994d3..1cbde7193c4d 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -5560,4 +5560,18 @@ extern struct net_device *blackhole_netdev; atomic_long_add((VAL), &(DEV)->stats.__##FIELD) #define DEV_STATS_READ(DEV, FIELD) atomic_long_read(&(DEV)->stats.__##FIELD) +static inline struct device *netdev_get_dma_dev(const struct net_device *dev) +{ + struct device *dma_dev = dev->dev.parent; + + if (!dma_dev) + return NULL; + + /* Some devices (e.g. SFs) have the dma device as a grandparent. */ + if (!dma_dev->dma_mask) + dma_dev = dma_dev->parent; + + return (dma_dev && dma_dev->dma_mask) ? dma_dev : NULL; +} + #endif /* _LINUX_NETDEVICE_H */ diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c index 797247a34cb7..93462e5b2207 100644 --- a/io_uring/zcrx.c +++ b/io_uring/zcrx.c @@ -584,7 +584,7 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx, goto err; } - ifq->dev = ifq->netdev->dev.parent; + ifq->dev = netdev_get_dma_dev(ifq->netdev); if (!ifq->dev) { ret = -EOPNOTSUPP; goto err; diff --git a/net/core/devmem.c b/net/core/devmem.c index b3a62ca0df65..881044e0ae0e 100644 --- a/net/core/devmem.c +++ b/net/core/devmem.c @@ -183,6 +183,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, { struct net_devmem_dmabuf_binding *binding; static u32 id_alloc_next; + struct device *dma_dev; struct scatterlist *sg; struct dma_buf *dmabuf; unsigned int sg_idx, i; @@ -193,6 +194,13 @@ net_devmem_bind_dmabuf(struct net_device *dev, if (IS_ERR(dmabuf)) return ERR_CAST(dmabuf); + dma_dev = netdev_get_dma_dev(dev); + if (!dma_dev) { + err = -EOPNOTSUPP; + NL_SET_ERR_MSG(extack, "Device doesn't support dma"); + goto err_put_dmabuf; + } + binding = kzalloc_node(sizeof(*binding), GFP_KERNEL, dev_to_node(&dev->dev)); if (!binding) { @@ -209,7 +217,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, binding->dmabuf = dmabuf; - binding->attachment = dma_buf_attach(binding->dmabuf, dev->dev.parent); + binding->attachment = dma_buf_attach(binding->dmabuf, dma_dev); if (IS_ERR(binding->attachment)) { err = PTR_ERR(binding->attachment); NL_SET_ERR_MSG(extack, "Failed to bind dmabuf to device"); -- 2.50.0