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Thu, 23 Jan 2025 22:44:00 +0000 Date: Thu, 23 Jan 2025 14:43:58 -0800 From: Dan Williams To: Alejandro Lucero Palau , Dan Williams , CC: Dave Jiang , Ira Weiny , Subject: Re: [PATCH v2 3/5] cxl: Introduce 'struct cxl_dpa_partition' and 'struct cxl_range_info' Message-ID: <6792c62e340ad_20fa29438@dwillia2-xfh.jf.intel.com.notmuch> References: <173753635014.3849855.17902348420186052714.stgit@dwillia2-xfh.jf.intel.com> <173753636727.3849855.464861650807086965.stgit@dwillia2-xfh.jf.intel.com> <52174ecc-40f9-82e5-1925-dfa1b7c968da@amd.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <52174ecc-40f9-82e5-1925-dfa1b7c968da@amd.com> X-ClientProxiedBy: MW4PR02CA0003.namprd02.prod.outlook.com (2603:10b6:303:16d::30) 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_|PH7PR11MB6955:EE_ X-MS-Office365-Filtering-Correlation-Id: 1a9da599-704d-4007-f3c3-08dd3bff6de3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|366016; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?MZ7mQJn+b0ajUl+VXpOjqvbUsjseAAxgbyS7ZNAN61aksBLMZdqfbcr0Ilww?= =?us-ascii?Q?lr1jTqMUzd1OL216OEkCXMHcfnXA8z1TzxV6l7JLZ51DREz0i3I339FWDaLg?= =?us-ascii?Q?CxcPYagqzexEnRxZzx9p89IR90W0QjKJBSOjNT+mFl2jMYb8fTQk1KFOPkyz?= =?us-ascii?Q?pr177K38nBa6UdKr5fRraOq6jWECRxkolR5uzs2JZXTZmdNmfQ5ux+j/z0bB?= =?us-ascii?Q?TskQy/d3MsASC3YUCeOdQ1jDmW0vKpWw48yvWFqLJEpq7THecfblqPzQLnfn?= =?us-ascii?Q?wOMwxmsk2AhHCPa4dZ9GdudiTe2l98JpYDluYmwnXBhiinVuWwW89z4od0FH?= =?us-ascii?Q?qExah77EpOVw6bTDkNSM18rPQ6qye/+OHozDyM9vTORngky9u88bkl3ynbhJ?= =?us-ascii?Q?nwKM6fopZX1A61509y4hlvV24FBu2UhRuefl3w+wfP1ec/8BBRmj8eZQH8nQ?= =?us-ascii?Q?zKaTo1P5oFm2ZpSel4aq8yeIIj7pIa6gJnQWOJrLN213kraLVKJBnnem6EXa?= =?us-ascii?Q?q8+NjTU6gWZ5v/I0PDVtyqGal8Tn6XagNLrBlHzeQ8ZW/86qNC8npUcRpTHh?= =?us-ascii?Q?/TeZT5hJulSHv71XZi+aR1LNLEE5imODnmfnRiPWGgslLQr8GFv6SooD70xx?= =?us-ascii?Q?SIvhdRBJd3q+K6Rs2FqfWYJW9rmpDROoIG5E0qKq1HamUpQA33cB5RdqiTbv?= =?us-ascii?Q?hL+m6aNJqviUmUWcUW2H/qfxmd4MDiC8g1VBqIGiED+uyvUOOMqPsPmmCFCz?= =?us-ascii?Q?Q08OKHkp99LSRAuJ4VvJ8pu2JFVqBF8J/FTSIk63pjaKb1Wj5klyEd9ZpkUL?= =?us-ascii?Q?9R+Tfqwo5n433wPcTVvAzSIFPzvQPjBsfXsFxZz30FM+jWB0lRYsFyC9YXEb?= =?us-ascii?Q?GMuBr6mmaBGj5lhi3ocef9pHlWcQbYql5rJBIWTGiwTRdwCBMwVCOFQv6TFw?= =?us-ascii?Q?5BIFl4a56d/6N2zGt8mFnHJFenPEcnbUkKmZ41TvpelpTlA+i6/IrsGpjjHR?= =?us-ascii?Q?U/Ylt3cKuKK10sbUFFStEsQzsYOXI3bMfQyGGGcftgDr/viwosCstS9VLNB5?= =?us-ascii?Q?Dl7Q2SU8HqGuWim4pcIY3QF9JKCYQFUH3YYw06BU01vCxOC97H6PNmnC3g3I?= =?us-ascii?Q?f2HBbX+PiKAgFDo0KiEU0L4hyMKBt26Dh/8482Lk/9c2cQ5t34+JdznsE6H/?= =?us-ascii?Q?Jymgmubhb4ShkqUXcsMX3exwRmFJPF6XGrM2tvvHBz6tu6Hw9CQyIX40KGDy?= =?us-ascii?Q?VY1RzBHnjTQVvbEs5h17xbBVLxImtstk/RNNKET/UMu0FS3PYw4AeHetN+L/?= =?us-ascii?Q?wh85lfZnG4kcyLRI+3LTdrVonaVYn1/1AXH4pkfq97NJdDNqc4zKqNZG3Mh6?= =?us-ascii?Q?96T34jgnghVYfwVg9RhqgQZ/zScoLqFEpAbjZ8mFdYLNp+lpMybHEv1wVqrk?= =?us-ascii?Q?7xVyx2NKmqJKhN2W3R7XUVWjs6etQHD1X5wNQpkhZd0u3bG1yp4+4NwNvPYy?= =?us-ascii?Q?cVp3KBYZU/7CPeNT1ZGCBdSKkXfOOXOPDVtDsI7GdLRfmC94ZEDRb9nPCC9y?= =?us-ascii?Q?kHqWaqKxPlNG6LbNSyK4NxP3QTSQPocTtxPjN+SF7YG9TxDO8hGgq9NBAM7J?= =?us-ascii?Q?uQ=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 1a9da599-704d-4007-f3c3-08dd3bff6de3 X-MS-Exchange-CrossTenant-AuthSource: PH8PR11MB8107.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jan 2025 22:44:00.4325 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: FGwgiAKRF78gCV5LtKArcUqZwXOgkrMTAQcLh8XJJnjEcbTRdQ6mKvG/qryVkL5VGVGqnjwEvIGRUBgcqC78FIn6H9qIXovuBIrldrO7528= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR11MB6955 X-OriginatorOrg: intel.com Alejandro Lucero Palau wrote: > > > > > -static inline struct resource *to_ram_res(struct cxl_dev_state *cxlds) > > + > > +/* Static RAM is only expected at partition 0. */ > > > This may be seen silly but Static Ram as SRAM has connotations which > could confuse people. > > Maybe better to use Static partition for RAM. Without the DCD code upstream even "Static partition" is "confusing", "what's a non-static partition?". At some point people need to be trusted to have context and share in the responsibility to resolve their own confusion. > It is far more concerning to me though Ira's comment about how can we be > sure there is going to be only one RAM or one PMEM partition. Simply put, we can't. Use cases evolve in unpredictable ways and folks will show up to address those new use case when they arrive. I do not lose sleep over it due to the open ecosystem, and in this case, economics: - open ecosystem means someone can see us chatting about theoretical devices that complicate the implementation and either chime in and say "we have such a use case, here are the patches", or "it looks like mainline does not care about that particular degree of spec freedom, do we really want to go there with our device?". - on economics: It is hard enough to get developers to care about NUMA effects let alone heterogenous memory performance within a single device. It would mean building a complicated device with heterogeneous media, or mixed memory controllers. The Type-2 series confirmed that single range RAM accelerator support is all that is needed for now. My bar is "as simple as possible, but no simpler" especially when it comes to user ABI extensions, because ABIs are forever.