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Fri, 13 Mar 2026 02:03:23 +0000 From: Dan Williams Date: Thu, 12 Mar 2026 19:03:21 -0700 To: PJ Waskiewicz , Alejandro Lucero Palau , "Cheatham, Benjamin" , CC: , , , , , , , , Message-ID: <69b37069af0f8_b2b610068@dwillia2-mobl4.notmuch> In-Reply-To: References: <20260201155438.2664640-1-alejandro.lucero-palau@amd.com> <20260201155438.2664640-9-alejandro.lucero-palau@amd.com> <03ab7820-a6e0-4655-bae7-61d2d0b7dfd6@amd.com> <28148dcf-3cdc-439b-900a-a3f672a28ad1@amd.com> Subject: Re: [PATCH v23 08/22] cxl/hdm: Add support for getting region from committed decoder Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SJ0PR03CA0155.namprd03.prod.outlook.com (2603:10b6:a03:338::10) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR11MB8107:EE_|IA4PR11MB8989:EE_ X-MS-Office365-Filtering-Correlation-Id: ced694d2-f184-426d-136d-08de80a4b4d4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|366016|1800799024|18002099003|56012099003|22082099003; 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This works in my tests and it is safe > > because I check the region does exist before using it. But the error > > inside sfc should then not be fatal for cxl sfc initialization and > > fallback to the other cxl initialization possibility. > > > > So I'm running into this situation I think. > > When you're testing, are you surviving a reload of the driver? Right > now, I can load and successfully create the region0 device. However, > following the same teardown path in SFC, I cannot reload my driver > afterwards and map the region. I get: > > cxl_port endpoint5: failed to attach decoder5 to region0: -6 (ENXIO) > 0000:c1:00.0: CXL found committed decoder without a region > 0000:c1:00.0: CXL init failed > > I'd be surprised if SFC in its current patch state would survive this > same insmod/rmmod/insmod test. So over here [1] I reviewed Smita's patch to stop resetting decoders by default if they were part of region auto-assembly. While that stops resetting the decoders it does not allow the device to get a hint of where it should place its HPAs if the decoders get reset while the driver is detached. I am going to draft some patches to allow an accelerator to mark an address range as "designated" so that it can recall the memory it was assigned by boot firmware. This also dovetails with the conversation I had with Paul Blinzer at Plumbers about an ability to designate Soft Reserve memory. So a generic facility to designate memory allows accelerators to recall their address range if the decoders ever lose their configuration. It also tells the rest of the CXL subsystem "hands off, this range was accelerator designated by platform firmware". [1]: http://lore.kernel.org/69b1e0aacb9d0_2132100c5@dwillia2-mobl4.notmuch