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Thu, 9 Apr 2026 17:04:47 -0700 Date: Thu, 9 Apr 2026 17:04:46 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: "Tian, Kevin" , "will@kernel.org" , "robin.murphy@arm.com" , "bhelgaas@google.com" , "joro@8bytes.org" , "praan@google.com" , "baolu.lu@linux.intel.com" , "miko.lenczewski@arm.com" , "linux-arm-kernel@lists.infradead.org" , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "Williams, Dan J" , "jonathan.cameron@huawei.com" , Vikram Sethi , "linux-cxl@vger.kernel.org" Subject: Re: [PATCH v3 1/3] PCI: Allow ATS to be always on for CXL.cache capable devices Message-ID: References: <20260409225252.GU3357077@nvidia.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: <20260409225252.GU3357077@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF000044A8:EE_|CY1PR12MB9560:EE_ X-MS-Office365-Filtering-Correlation-Id: 7c627250-c6f6-43bf-0732-08de9694d285 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|36860700016|82310400026|1800799024|18002099003|22082099003|56012099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: W4/PHzH13j0NB7Nu1Ss4Q/DOUMEaWz6o/kWpL5K8NTsGwxWRnf/KfGYagAdWExN0e0MpWGilXm9VWnXPCnDxtBT+oYeAueXW4SdyQRuz5ekfZnyGSAeQMjvsOV5leyGk5JpQhKfI+zky8h5T62TiLialG4QIZaLvShVTSVBe+dPlYMZrhCcPH1vnrE7sU89eubyViYTT5D8c4F0qy3Pr2gZn1Q+AEqTRNh/j1MGM2iQ8jn3fPm2tEFsV+RT9rDY2GrK0voZeTJ4e8f/nEVKUkJAk6ANd5ZfjtrXEJsAa/x9Zc7FLSkMQx6uzDQVdgImLRetpq0Xm2qjNT4AGYBji8sq3/XrDHz9toNhQrIqftybPPnY8H3yA7KoSgijb7g8UCEbCd963GaOjybRT4y/bu+HisXEDMlNQiuPcHetMlFdYLDCUZWUy0s9kTJmuLRS8 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Apr 2026 00:05:06.2560 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 7c627250-c6f6-43bf-0732-08de9694d285 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF000044A8.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY1PR12MB9560 On Thu, Apr 09, 2026 at 07:52:52PM -0300, Jason Gunthorpe wrote: > On Thu, Apr 09, 2026 at 03:45:26PM -0700, Nicolin Chen wrote: > > > One question regarding VM case: if a device is ats_always_on, while > > VM somehow doesn't set nested_domain->enable_ats. Should the kernel > > at least spit a warning, given that it would surely fail the device? > > No, just let break, the resulting failure has to be contained to the > VM or the platform is broken.. > > The HV can't turn on ATS because we it can't know what invalidations > to push so not much other choice. I see. Thanks Nicolin