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Wed, 20 May 2026 10:29:20 -0700 Date: Wed, 20 May 2026 10:29:19 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: Bjorn Helgaas , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v4 1/3] PCI: Allow ATS to be always on for CXL.cache capable devices Message-ID: References: <20260519222335.GK3602937@nvidia.com> <20260519234801.GA21369@bhelgaas> <20260520000504.GQ3602937@nvidia.com> <20260520142043.GT3602937@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260520142043.GT3602937@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS3PEPF0000C380:EE_|CH3PR12MB7594:EE_ X-MS-Office365-Filtering-Correlation-Id: 7faf40c4-f505-4a70-4eed-08deb6955d7a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|7416014|1800799024|82310400026|376014|18002099003|22082099003|56012099003|5023799004|4143699003|11063799006|6133799003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: RiO5myyfoAj4dwRZwjqLKmXPKU5hHER85jdkhnWP0/dl4l8wIUuVsDABDN0xG2mnx2HhhNfcMjBGVDru+lbkoaid1pyqsZltgTtzOWeMRLEdDSnVgvFxGflZ8V6sAoCIbKOBOUHNcBp7gialX6fiBoQkMnTwjwBZf9Wq3OVT3mYW3nDp3MN7qEIGohlen/LrpC4idzmUD9JZp7/m5bLzyWfhEZSd0Z3mdK48duTVlgwNX4jMrq6VuYLbdXHg8OFKQjOlQt3oBvtpOcYSJLROmjapo08mexWDLKNSoseT8PgZ4K/gAmz+/GRFE7s7uu9Lt6CAElcNg1e3prz1atHG/30kIbLo31V5fGcMwQL7v4+rpJDIjiDusC2tWKcLqu7tlVnfLwn6Nb/fKCInLcaBFPEhAR/TYdSl3kdtzwiEylQF2PHF5ar5osjlSOyxSZj6 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 May 2026 17:29:36.6373 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 7faf40c4-f505-4a70-4eed-08deb6955d7a X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.233];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DS3PEPF0000C380.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB7594 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260520_103016_039066_FD41F7E3 X-CRM114-Status: GOOD ( 14.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 20, 2026 at 11:20:43AM -0300, Jason Gunthorpe wrote: > On Tue, May 19, 2026 at 06:04:18PM -0700, Nicolin Chen wrote: > > > > Yeah, that's fair, so let's rename it to > > > > > > pci_translated_required() > > > > > > ie the device requires translated requests to function. This is what > > > CXL.cache implies (IIRC I was told the spec specifically says this) > > > > > > Requiring translated requests implies you have to enable ATS in the > > > system. > > > > Perhaps we could let IOMMU drivers check: > > pci_cxl_is_cache_capable() || pci_dev_specific_is_pre_cxl() > > directly? > > I'd rather have a single function. OK. Can we use pci_ats_required()? CXL spec explicitly used "ATS" when stating the requirement of CXL.cache). And it'd fit into the existing pci_ats_ functions. Nicolin