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Wed, 1 Apr 2026 05:27:22 +0000 From: Dan Williams Date: Tue, 31 Mar 2026 22:27:19 -0700 To: , , , , , , , , , CC: Alejandro Lucero , Jonathan Cameron , Davidlohr Bueso , "Ben Cheatham" Message-ID: <69ccacb7961fe_1b0cc6100b4@dwillia2-mobl4.notmuch> In-Reply-To: <20260330143827.1278677-11-alejandro.lucero-palau@amd.com> References: <20260330143827.1278677-1-alejandro.lucero-palau@amd.com> <20260330143827.1278677-11-alejandro.lucero-palau@amd.com> Subject: Re: [PATCH v25 10/11] cxl: Avoid dax creation for accelerators Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW4P220CA0026.NAMP220.PROD.OUTLOOK.COM (2603:10b6:303:115::31) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) 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: PH8PR11MB8107:EE_|IA0PR11MB7281:EE_ X-MS-Office365-Filtering-Correlation-Id: 30ef1036-35bf-4604-87fb-08de8faf59dd X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|1800799024|376014|921020|18002099003|22082099003|56012099003; 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> > + /* > + * HDM-D[B] (device-memory) regions have accelerator specific usage. > + * Skip device-dax registration. > + */ > + if (cxlr->type == CXL_DECODER_DEVMEM) > + return 0; > + It is possible for a general memory expander to also be CXL_DECODER_DEVMEM. Imagine a memory expander that could back invalidate on decoder change. See my reply to patch5 for the changes to cxl_region_probe() when an accelerator driver wants to own mapping a resulting region. Also note that cxl_region_has_memdev_attach() arranges for memory notifiers and poison to be setup. This is for accelerators that may use devm_memremap_pages() and accelerators that may implement a full CXL mailbox for whatever reason. A CXL mailbox remains the only generic mechanism for determining the DPA layout of a device.