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Tue, 24 Feb 2026 10:43:03 -0800 Date: Tue, 24 Feb 2026 10:43:00 -0800 From: Nicolin Chen To: Jonathan Cameron CC: , , , , , , , , , , , , , , Subject: Re: [PATCH v2 1/3] PCI: Allow ATS to be always on for CXL.cache capable devices Message-ID: References: <20260224115534.00000ac7@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260224115534.00000ac7@huawei.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF00020E60:EE_|DS7PR12MB6069:EE_ X-MS-Office365-Filtering-Correlation-Id: f52aedb8-bd0a-44a0-3d51-08de73d49a44 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|7416014|376014|82310400026|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?3H0OXsbIJ9hQhKlyxwg0Bz9OWOQms73AtTUVNwgkmcYmoIor5Zciie1p9dz/?= =?us-ascii?Q?8yN6iT1uXC9SK1UviGtJFHpJgprhWUSqUGPBxq1SgyAYuXKyw18HdkBKZ0jQ?= =?us-ascii?Q?VkKsCigTYhp0KEbqgKEKDWgOtMU/e+oBstqgHujpYXdfZIeMq5KRJvN3fy5d?= =?us-ascii?Q?YR1Q9ZLFyp8iM30RR/7Jf93QIeust7YcOJ2azAbTY4NwSf0ARSvEqq04MVGO?= =?us-ascii?Q?5iqj49rAbRfX+k9P6mt9COx0fEFVqZAWSH65mOs3S60JkSK4KC+Ti44wCv0w?= =?us-ascii?Q?XN+gMIfb2CayTfFtkKPcWUrXyLzfB6uZoO93KT9uAenpOgIKgZf11UZeUSSr?= =?us-ascii?Q?5G2G1UZKG76AFrvZIe3zopOguDUtcn14ze9WS8gPA4tg155QaywPnIxPcubM?= =?us-ascii?Q?ihx1cn+1JqZ3A8W286cJabOd2S9BavaUGZTPWWcBz3yoaUu+njqa5MPEijvP?= =?us-ascii?Q?iBtlFHZSO1C5wSjVBZv9JDsf9E/xS3aPZZhehxwUtF7/yu8cYc4I5zvwD+Qx?= =?us-ascii?Q?s7pDUq/QecZb+QukzaSN1CLzNUh9pPxdWufu6m/fP7qbtMrE3uiESp98iAe5?= =?us-ascii?Q?LEs83gMc0mjpv7ASARnpTyEZaIkifS6E4C8RklfIJD5Lcewd76LE4MuZoQ5g?= =?us-ascii?Q?WLvw5exzc6+G3Jp8FYSKu7NkUh7Oc814innkuE6FJ2+R/5rpkesLziYHb4cK?= =?us-ascii?Q?/zT++hJG4AnHNU3RuXO1XCtj5gTtrgAEFVYXO28WKSmdejowP9EqKcoxnMkF?= =?us-ascii?Q?PKgzLod2j+utegWkzJeAMebcsgPbQ/9vlxaYhwBAHW8R6Mwuj9aUAkmiAmQj?= =?us-ascii?Q?Ym6YeLvb9fPyHjn2X+gQDnP2cQmPNpmBD2ZLfuz6w+5ujuZfoDw5VX8ByDli?= =?us-ascii?Q?9wsW38UiVGOfaos2AquJ3YTMeC2Hgu3rLalEAELv3dxgOQTTxSIiPO0BIYqf?= =?us-ascii?Q?BsdMwU4naluKdyT55KrUkH/gUB2h3V4DnSbDscN6HS0zo17e62J+lc9xB/JX?= =?us-ascii?Q?KRDpgujrTS71Je9UtP69YQeukk4IiYQNP78lCjniiRtXs5aKqZdkclBtvXI5?= =?us-ascii?Q?fiRtmD9pmW7nZiFGneFL3IGOcL2WDMi744KpY39eoyYNOj/9H/TptjAYNg2K?= =?us-ascii?Q?r8ixczbeT8cU46Nm6Wp2US0LL9nyT7iNtElC7Vf6+xDAhesVzVN8fHcMjtOA?= =?us-ascii?Q?IPx2rMiS7kxiUoyb31LNfOfO2E/JcZUSZBiIntl5OujDypJjgObaq9zpquE0?= =?us-ascii?Q?kBVtk1aeg5bhxaERIE8KA8Bl6l3R8YKBh1UtD2L3g+7CZsMnM0Ij+O7tLc3Q?= =?us-ascii?Q?/LKbuSnL6z+GtQ5ZcFnXVRNjEMBqONcg57H/n++tyS7wrC6gs+wqNbMAvNv1?= =?us-ascii?Q?SOwFWg3SnLj/HON4X8rOXZ7CLwXgeg8XmHF4wlwQMALxtq2Dv3nybLrUUPAL?= =?us-ascii?Q?K7fYYQTtEowncmBydu/1Fjk8qWIySZQO+mTYwktulel6kE0UMD9tmGEHINV9?= =?us-ascii?Q?yKy/sBmBfeSrckasqDjfaz0DI4pw87u3C6OVvvWP0ZDqOBtivbus4j+IGVoC?= =?us-ascii?Q?yhNzz+bmIT0jxC/BamCaS0VF7+IKH9GV/NVcxRh8hoOlLMaa//fjnQBbXa7D?= =?us-ascii?Q?QojfWgZemYC6REhsXE/jUbXBr6ANvGnvVrvPGMPe7uEsX5KaMtFEJHjWpxQa?= =?us-ascii?Q?J/HJeA=3D=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230040)(36860700013)(7416014)(376014)(82310400026)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: gqOMf7vIn11I+gUa24sgOtdjAvpz09FzUJd20nje4Y0UhrHriW+xt8pFzL8jwDLSPZ04RbL30xirvbx00TMegBH29l4RPWjPdrGQ+fQR9o0peStkgKtOFgm9V6SbpJJyxaIo8Bz02lyOvXNp7QH9RTIGVLOkeigDGdwB2yNnb/42JwTQoI3Z7l8wNEUK954y5jlUOtrP1GEautQlAnwnxWdS1xkm44SFwJf1XPHOrvPc+dMtkDciJEpiAed6WDrSXevi5kWxgZzPwm0ZKU3QlVGrjf61xvEQ2BVZwBr3HY57fU8m7DdJKqpVQqd+YALboi22M5/hw72KFIgKxAw7K98pOCz1fGTfTPZclMZ7Ygp65YgLLXj3geGLi0P28ztXjfpXTFmnbR+h3Co+0FFpE/FnXgNsfiw/EW3/HeB4m1X+6d7edKLo3Az7tTEAKeQe X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Feb 2026 18:43:28.9742 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f52aedb8-bd0a-44a0-3d51-08de73d49a44 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BL6PEPF00020E60.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB6069 On Tue, Feb 24, 2026 at 11:55:34AM +0000, Jonathan Cameron wrote: > On Mon, 23 Feb 2026 14:52:20 -0800 > Nicolin Chen wrote: > > +/* > > + * CXL r4.0, sec 3.2.5.13 Memory Type on CXL.cache notes: to source requests on > > + * CXL.cache, devices need to get the Host Physical Address (HPA) from the Host > > + * by means of an ATS request on CXL.io. > > + * > > + * In other world, CXL.cache devices cannot access physical memory without ATS. > > Maybe tweak that to "host physical memory" > > There are too many physical memories in CXL land... > > > + */ > > +static bool pci_cxl_ats_always_on(struct pci_dev *pdev) > > +{ > > + int offset; > > + u16 cap; > > + > > + offset = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL, > > + PCI_DVSEC_CXL_DEVICE); > > + if (!offset) > > + return false; > > + > > + pci_read_config_word(pdev, offset + PCI_DVSEC_CXL_CAP, &cap); > > + if (cap & PCI_DVSEC_CXL_CACHE_CAPABLE) > > + return true; > > Could just do > > return cap & PCI_DVSEC_CXL_CACHE_CAPABLE; > > Unless the thinking is there may be other stuff that comes here. I will fix both. Thanks for the review! Nicolin