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Wysocki" , Len Brown , Pavel Machek , Li Ming , Jeff Johnson , Ying Huang , Yao Xingtao , Peter Zijlstra , Greg Kroah-Hartman , Nathan Fontenot , Terry Bowman , Robert Richter , Benjamin Cheatham , Zhijian Li , Borislav Petkov , Tomasz Wolski References: <20260122045543.218194-1-Smita.KoralahalliChannabasappa@amd.com> <20260122045543.218194-7-Smita.KoralahalliChannabasappa@amd.com> <84d0ede7-b39d-4a41-b2b6-8183d9ccbb9e@amd.com> <6977fe94d8ee_309510033@dwillia2-mobl4.notmuch> <69794d438629e_1d33100f3@dwillia2-mobl4.notmuch> From: Alejandro Lucero Palau In-Reply-To: <69794d438629e_1d33100f3@dwillia2-mobl4.notmuch> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: LO0P265CA0006.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:355::17) To DM6PR12MB4202.namprd12.prod.outlook.com (2603:10b6:5:219::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6PR12MB4202:EE_|CYYPR12MB8870:EE_ X-MS-Office365-Filtering-Correlation-Id: 1aa5f1e7-1bc8-4930-641b-08de5e891a22 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|366016|7053199007; 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Forcing them to >> be compiled with the kernel would go against what distributions >> currently and widely do with initramfs. Not sure if some current "early" >> stubs could be used for this though but the information needs to be >> recollected before this code does the checks. > The simple path is "do not use EFI_MEMORY_SP for accelerator memory". Sure. That is what I hope our device will end up having ... since neither hmem nor dax is an option for us. > However, if the accelerator wants to publish memory as EFI_MEMORY_SP > then it needs to coordinate with the kernel's default behavior somehow. I think some Type2 drivers could be happy with dax and therefore using EFI_MEMORY_SP, so yes, that is what I meant: there is another option instead of forcing drivers to be present at the time of this decision. If someone reading is working on Type2 drivers and see this suitable/required, please tell. I'll be interested in doing it or helping. > That means expanding the list of drivers that dax_hmem needs to await > before it can make a determination, or teaching dax_hmem to look for a > secondary indication that it should never fall back to the default > behavior. I think waiting could be problematic as some Type2 drivers could not be automatically load. It looks like if a CXL region is not backing the Type2 CXL.mem completely should not impact dax devices and cxl regions maybe being used at Type2 driver probe. Would a warning be enough? > > Talk to your AMD peers Paul and Rajneesh about their needs. I took it on > faith that the use case was required. After reading that presentation, I think this is a different subject. Assuming case 1 there is what you have in mind, and if I understand it properly, that could be useful for companies owning the full platform, but not sure adding a specific acpi driver per device makes sense for less-powerful vendors. Anyway, I will talk with them as the memory allocation part which seems to be one thing to do by those acpi drivers is interesting. Thank you