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Tue, 5 May 2026 14:44:30 -0700 Date: Tue, 5 May 2026 14:44:27 -0700 From: Nicolin Chen To: Pranjal Shrivastava CC: Jason Gunthorpe , , Will Deacon , Joerg Roedel , Robin Murphy , Mostafa Saleh , "Samiullah Khawaja" , Daniel Mentz , "Pasha Tatashin" , David Matlack Subject: Re: [PATCH rc v2] iommu/arm-smmu-v3: Fix inconsistent ATS state tracking Message-ID: References: <20260504163842.2692314-1-praan@google.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN1PEPF0000468D:EE_|SJ0PR12MB7081:EE_ X-MS-Office365-Filtering-Correlation-Id: 743b444b-df6c-45ed-510e-08deaaef842f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|82310400026|36860700016|376014|1800799024|56012099003|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: xzwWLPdIJFmN0qMNVdiRJ7/nXyUSuQt0jtrO2DaBwwOyCvMZ35HEm+QjOfEEZKpqzuWjtSRL2wZmHYs+eRf3t76n/asOGX+fa/CwzLr1Tn3ro5Cn095VuAVE4VQ0+lg3qgmS2e9lJDobxYWpPPwzt+zbXnc02TSbny+XAL4PBOrhrrAkD1F2Fa7vXvk9Qx+iL0G+SRtTrhoyHUj/r5Cw5nn6N0v3XNcgN6ShIQTILIS6liZB5CYiTZkzIrGuUwllyJOrLc0JOK8b3ZLkCF0o8mYXJqzDD//Y8LmmEsDMisefWombA05Wit57fMYomymjcupIRC1qdUxLDIUNpsHZ7d9xdiMfZjm7TpXSr0xSUp5RVjLT+nYNvMeKdy1Dr5jVfZiyx9kK3sUrciD6H3fu+uWFOqlsU868qFnqGjQpcB7qJYI7frsjfTFWAiX4HVW5 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 May 2026 21:44:42.3449 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 743b444b-df6c-45ed-510e-08deaaef842f X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN1PEPF0000468D.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR12MB7081 On Tue, May 05, 2026 at 09:23:15PM +0000, Pranjal Shrivastava wrote: > On Tue, May 05, 2026 at 01:21:37PM -0700, Nicolin Chen wrote: > > /** > > * pci_prepare_ats - Setup the PS for ATS > > * @dev: the PCI device > > * @ps: the IOMMU page shift > > * > > * This must be done by the IOMMU driver on the PF before any VFs are created to > > * ensure that the VF can have ATS enabled. > > > > But it returns 0 directly on dev->is_virtfn. > > > > I wonder if this function itself should just fail if dev->is_virtfn > > and !pci_physfn(dev)->ats_stu? > > > > Just wondering if there's a use-case that might break? Well, even a break would be what the kdoc statement demands :-/ > Otherwise, in > current context I agree that we should fail if ats_stu == 0 / mis-match Yea, should check mis-match. "== 0" doesn't guarantee the enable success. > > Then, arm_smmu_probe_device() must fail if pci_prepare_ats() fails. > > I don't think probe device should fail, we should just mark that ATS > isn't supported for the function? right? PF must be probed() first with ats_stu set correctly. If VF gets probed before that or with a different ats_stu, something must be wrong. Again, following the kdoc statement, VF should not be "created" in this case. Or should we read it differently? :-/ Nicolin