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Thu, 21 May 2026 14:59:26 -0700 Date: Thu, 21 May 2026 14:59:25 -0700 From: Nicolin Chen To: Bjorn Helgaas CC: , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v6 1/3] PCI: Add pci_ats_required() for CXL.cache capable devices Message-ID: References: <20260521213123.GA186424@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260521213123.GA186424@bhelgaas> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS1PEPF00017094:EE_|CH3PR12MB9454:EE_ X-MS-Office365-Filtering-Correlation-Id: b6fdac66-e07b-4a21-74f9-08deb784439d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|1800799024|82310400026|7416014|376014|56012099003|22082099003|18002099003|4143699003|11063799006; X-Microsoft-Antispam-Message-Info: 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 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)(36860700016)(1800799024)(82310400026)(7416014)(376014)(56012099003)(22082099003)(18002099003)(4143699003)(11063799006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: IGoMt7o/1TqrXPnXB7cXLH0jGmAeVqAcAu0XVJESXhmACZeOBB2BMPRfxZfuRP5hkVOy/QSqY5W9GXZYu7/+RnBHHPpK2epqdHlBrXq/Hgl2ZhYdf5/Elf10mScA26DmeiTQr9w4w+u1PrfzTAuVVv9v+Uq92EZGraO2PQ8s4syuYTyB0TMtSiUT7c8sHprJRAhBX/tS0JSUEmXfqDkNo2z0UqaR0i4VpyTHoxEO2QpmIYKAduFZ5EO68AWoZpDxJB3tVPhiw7qtSgpSpdVgEntWQ1Ffw5wlZ7MEjwM654duayXsOsjNRgxdN0fS29/SpoMFWWrCTUYYLfBuaC0PiVoXowWMFXAIvSOzsZWNgj2af+v677bWFuP+l76OOH20Hcz+AfbT3+6XsjnP1fANFUyWRbqdw01vuLjQYtTM+ey/4rBZAmGP1BZ0UnRSQHdW X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 May 2026 21:59:42.9621 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b6fdac66-e07b-4a21-74f9-08deb784439d 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: DS1PEPF00017094.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB9454 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260521_145953_597978_1AA04703 X-CRM114-Status: GOOD ( 19.48 ) 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 Thu, May 21, 2026 at 04:31:23PM -0500, Bjorn Helgaas wrote: > On Thu, May 21, 2026 at 02:07:34PM -0700, Nicolin Chen wrote: > > On Thu, May 21, 2026 at 03:57:23PM -0500, Bjorn Helgaas wrote: > > > On Thu, May 21, 2026 at 01:34:20PM -0700, Nicolin Chen wrote: > > > > +bool pci_ats_required(struct pci_dev *pdev) > > > > +{ > > > > + if (!pci_ats_supported(pdev)) > > > > + return false; > > > > + > > > > + /* A VF inherits its PF's requirement for ATS function */ > > > > + if (pdev->is_virtfn) > > > > + pdev = pci_physfn(pdev); > > > > + > > > > + return pci_cxl_ats_required(pdev); > > > > > > I acked this before I saw this sashiko feedback, which looks like a > > > legit issue to me: > > > > > > Will this VF inheritance logic ever be reached? > > > > > > According to the PCIe SR-IOV specification (section 9.3.3.1), VFs do > > > not implement the ATS Extended Capability, which means pdev->ats_cap > > > is always 0 for VFs. > > Huh. I wish sashiko would include the spec revision because that sure > looks wrong. In PCIe r7.0, there is no sec 9.3.3.1. In PCIe r6.0, > sec 9.3.3.1 is the SR-IOV Extended Capability, which doesn't mention > ATS. In both, sec 10.5.1 is the ATS Extended Capability and says both > PFs and VFs can implement it. I am glad you checked the spec. I should have done the same. > So I think this is OK as-is: > > Acked-by: Bjorn Helgaas Thanks! Nicolin