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Tsirkin" , Miguel Ojeda , Robin Murphy , rust-for-linux@vger.kernel.org, Sagi Grimberg , Stefano Stabellini , Steven Rostedt , virtualization@lists.linux.dev, Will Deacon , xen-devel@lists.xenproject.org Subject: Re: [PATCH v4 01/16] dma-mapping: introduce new DMA attribute to indicate MMIO memory Message-ID: <20250828130329.GA9469@nvidia.com> References: <08e044a00a872932e106f7e27449a8eab2690dbc.1755624249.git.leon@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <08e044a00a872932e106f7e27449a8eab2690dbc.1755624249.git.leon@kernel.org> X-ClientProxiedBy: YT4PR01CA0331.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:10a::27) To CH3PR12MB8659.namprd12.prod.outlook.com (2603:10b6:610:17c::13) Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR12MB8659:EE_|CY1PR12MB9583:EE_ X-MS-Office365-Filtering-Correlation-Id: 2e8ce38d-1495-4e9c-fbd5-08dde633497c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|1800799024|376014|366016; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?1ckjCiMh3aH7YHuAcYKILzSmiSeqWlaX0cjU6lr4SyHlEcJpmEAmCeyOV40z?= =?us-ascii?Q?9e1fR89T7j6Xp4z815rEDhXVCgZIIo5/9Sb04mNpuRfGYPRBY9zvqpgOkh35?= =?us-ascii?Q?/IOPcsnkEdYIiouJI/wlLh7BnCc/nEB/fa3oJleLj3SXEa/1YouLRDZ/ieHd?= =?us-ascii?Q?Fhgn69Lu1zSjAD4cDL8F4xerway++pdKYp7fMh6cIZ+VlW6jycFV1P5MXmgS?= =?us-ascii?Q?mGoV98JXp74/ppnciUAThGSQzIxV/501z03pCA1eCrV3j/v+1Br3yDy4QJxW?= =?us-ascii?Q?frMzh866Wke8P8HGgSkgaXpOEwgWy3NKvZOWom5IlZaQ7STgDF21n3deg2Bn?= =?us-ascii?Q?smMK5qJYmUv/jkHZMtLRoXgBwR9hcu6+SvkgrewPkzyqBlRl6GTkMCr3k5VU?= =?us-ascii?Q?Giq4WnZqwKFeLOQps32EJCGUMPry83QrPBaNQL6gWIPmnMvFyZSyAVDm33RB?= =?us-ascii?Q?Nsr45KQ1aoLyewrNb+mw5B+uzTtLwjFV+N2mOUGeVFIHf75PqWqyy4eoQWco?= =?us-ascii?Q?wsPshiiaB2TYJsV+YT+NrgZovS94Jcb5smuzQLTnPPYLsbEfZgq8vP23JNE5?= =?us-ascii?Q?0oIZWVjvcbOUXUQ2nxNg9O6CsRDFOnW6vwXQ8hIeYJ0z7OlEC4uo+6X9hqsK?= =?us-ascii?Q?y4Gl1D9IPDsnjZEc5PABOo7nWuuY9OkIfi+DzpgT6SH8PGC8O9gsn12QD9iD?= =?us-ascii?Q?VHCXBZ/dky8PMllRareAMm9eiICY+eX+htBuOVv6YHLr+eHCDo5EzEJso+ZA?= =?us-ascii?Q?DvjhpqVdbeaZwt7TnBuqzgfG4taKsF9UKdhPYrjQQNQ/d/iHvMNy0gtC9jDv?= =?us-ascii?Q?A8wYHhwRWc07lOdovRO6IA4mL9B02+icHfZr1/KGehCEHBqrBFbeO6zOVurf?= =?us-ascii?Q?ISrwNfw+VWQFC2e2Jxr7QeagvEtwLbOPYlUsVvv5ouP/fmLkb9L+vQsiADaQ?= =?us-ascii?Q?0KFF0SxzmH8inER9VlRkWQj0uNmQsVFoU7A7VEop+6CPD+kMmtDkfsXixQKw?= =?us-ascii?Q?2IiT0TOhGwzqVh1hNf2+uFaw4c9EhIXWPBB8fpLj+KDyJZCRxevz6pgajGiD?= =?us-ascii?Q?6e7tp4RsiOIP/Xavv4sXZ1KwcKti2bFyaaRW9q3aE5/5bOj7YvQSlvTJyFcy?= =?us-ascii?Q?kpYDF/yTAwhXZyFXDbgZ9IjCIjLtGugtDk4bAJjQ/gr1GrnLqqhzXPE57QWJ?= =?us-ascii?Q?tvusWzcZabNSlAxrYhLQt9cEh/6g/IXqiyuBEp/8uUB53JY5tovj1FwY7dBa?= =?us-ascii?Q?POWqTvzzR9OjJNSNOYA1vFMFL0NX1qP4KFiAOxEPvZl/bNot7SBXmSsUqQRb?= =?us-ascii?Q?i2roYAb0OOObJ5qpVpyF/VUBMiTm/Ffg65Y6dDlp3oYLtb98fMfrqLNlir5o?= =?us-ascii?Q?69dWufR7H944Ebi7jgYNTTnrOi+apHLvwcBfiNyXb6pO8LPkL+toURxOapMC?= =?us-ascii?Q?txtSAZPvR0gYWoN6ASv0OhUDjZNkxjBzocQbB3nXsjABL9de5niWUn4J1UsY?= =?us-ascii?Q?1AM2M6EZA2k2+hd/hd6eZSjh1JlTWb6QuWfgRP1wqdgQbsfEPseK/hCvJ0i4?= =?us-ascii?Q?kzEeLZAg6e2kdvXAlIY=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2e8ce38d-1495-4e9c-fbd5-08dde633497c X-MS-Exchange-CrossTenant-AuthSource: CH3PR12MB8659.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Aug 2025 13:03:31.1146 (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: RspixjdFPbAilZf2tLBPnkO+nFqvF4XSCsFdPZ/SEHIuDVu4IvPjaklp3X5pg66+ X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY1PR12MB9583 On Tue, Aug 19, 2025 at 08:36:45PM +0300, Leon Romanovsky wrote: > From: Leon Romanovsky > > This patch introduces the DMA_ATTR_MMIO attribute to mark DMA buffers > that reside in memory-mapped I/O (MMIO) regions, such as device BARs > exposed through the host bridge, which are accessible for peer-to-peer > (P2P) DMA. > > This attribute is especially useful for exporting device memory to other > devices for DMA without CPU involvement, and avoids unnecessary or > potentially detrimental CPU cache maintenance calls. > > DMA_ATTR_MMIO is supposed to provide dma_map_resource() functionality > without need to call to special function and perform branching by > the callers. 'branching when processing generic containers like bio_vec by the callers' Many of the existing dma_map_resource() users already know the thing is MMIO and don't have branching.. > Signed-off-by: Leon Romanovsky > --- > Documentation/core-api/dma-attributes.rst | 18 ++++++++++++++++++ > include/linux/dma-mapping.h | 20 ++++++++++++++++++++ > include/trace/events/dma.h | 3 ++- > rust/kernel/dma.rs | 3 +++ > 4 files changed, 43 insertions(+), 1 deletion(-) Reviewed-by: Jason Gunthorpe Jason