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Wed, 18 Mar 2026 16:35:02 -0700 Date: Wed, 18 Mar 2026 16:35:01 -0700 From: Nicolin Chen To: Bjorn Helgaas CC: , , , , , , Subject: Re: [PATCH rc] PCI: Fix nested pci_dev_reset_iommu_prepare/done() Message-ID: References: <20260318220028.1146905-1-nicolinc@nvidia.com> <20260318225705.GA479639@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@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: <20260318225705.GA479639@bhelgaas> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MW1PEPF00016160:EE_|DS5PPFA33D606F8:EE_ X-MS-Office365-Filtering-Correlation-Id: 926d6627-f6c0-4cac-3da1-08de85470510 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|82310400026|36860700016|1800799024|18002099003|56012099003|22082099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(376014)(82310400026)(36860700016)(1800799024)(18002099003)(56012099003)(22082099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: OwnKFwjGpsYpXOIWGhFpSQCnH/RIQg+7sGupTalj2q7lvaDZbPfDS/AS6x/T7aUx1VnU9jELd3mVCQaBt/p8bUwdRbnXRpHPvXqnZYt2obM85n6Unj7rxvSKl7bmmIkSXuyo+sbzCaAeqoBVlMuHbpPab7zlXWsIFU7m28DBp9Aw+O7k/P5xo7bGB4IidQ7R6Ya9U/rOaxl2l45LmZbHuAgizqqQEb0FFIE353OxL1oNvEDAUoTNV6njocO2j+jBHGkdp2PLliHHnkAZc0UYdqhS9biX1OU6YwBg6s87p9lRVwo0NQrDunlAojrnSnqC2Dhqc18+NdY3TmVyGHAfff1vKjH7/YcfieHV3SYaMyEOWEc2/KLBjd7ykhxTMBR04/cZpc6/d5wUQm0L2aVf23c2r582z5M3caBZAhbfqFSNIyoGLgoeVSLU/PrZht8R X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Mar 2026 23:35:20.6603 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 926d6627-f6c0-4cac-3da1-08de85470510 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: MW1PEPF00016160.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS5PPFA33D606F8 Hi Bjorn, On Wed, Mar 18, 2026 at 05:57:05PM -0500, Bjorn Helgaas wrote: > On Wed, Mar 18, 2026 at 03:00:28PM -0700, Nicolin Chen wrote: > > Shuai found that cxl_reset_bus_function() calls pci_reset_bus_function() > > internally while both are calling pci_dev_reset_iommu_prepare/done(). > > > > This results in a nested pci_dev_reset_iommu_prepare/done() call: > > cxl_reset_bus_function(): > > pci_dev_reset_iommu_prepare(); // outer > > pci_reset_bus_function(): > > pci_dev_reset_iommu_prepare(); // inner (re-entry) > > ... > > pci_dev_reset_iommu_done(); // inner > > pci_dev_reset_iommu_done(); // outer > > > > However, pci_dev_reset_iommu_prepare() doesn't allow a re-entry for now. > > > > Digging further, I found that most functions in pci_dev_specific_reset() > > except reset_ivb_igd() are calling pcie_flr() that has nested those two > > functions as well. > > > > Drop the outer callbacks in: > > - cxl_reset_bus_function() > > - pci_dev_specific_reset() > > > > Replace with adding the callbacks in: > > + reset_ivb_igd() > > This needs to say clearly what the issue is. Deadlock? Crash? > Corruption? > > I guess it's a deadlock when the second call to > pci_dev_reset_iommu_prepare() acquires the group->mutex? It will trigger a WARN_ON and fail the inner reset function: /* Re-entry is not allowed */ if (WARN_ON(group->resetting_domain)) return -EBUSY; > Since f5b16b802174 appeared in v7.0-rc1 (merged by Joerg), I guess > this fix also needs to be in v7.0 -- please confirm. Yes. I marked it "PATCH rc", hoping to cover that. I'll send a v2 explicitly mentioning the WARN_ON and -EBUSY failure. Nicolin