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Thu, 12 Mar 2026 22:45:30 -0700 Received: from Asurada-Nvidia (10.127.8.14) by mail.nvidia.com (10.126.190.182) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.20 via Frontend Transport; Thu, 12 Mar 2026 22:45:29 -0700 Date: Thu, 12 Mar 2026 22:45:28 -0700 From: Nicolin Chen To: Nilay Shroff CC: , , , , , , , , Subject: Re: [PATCH] powerpc/iommu: fix lockdep warning during PCI enumeration Message-ID: References: <20260310082129.3630996-1-nilay@linux.ibm.com> Precedence: bulk X-Mailing-List: stable@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: <20260310082129.3630996-1-nilay@linux.ibm.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PEPF00000012:EE_|DS2PR12MB9565:EE_ X-MS-Office365-Filtering-Correlation-Id: f8f4aa2f-c61a-4db9-c841-08de80c3c117 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|36860700016|1800799024|82310400026|56012099003|22082099003|18002099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 74DKkHtsLINejtmkkoxM7rVOiUGF2Arpfgqq2zRr68Shmhzb8lx3lnivnREsZtCUsdxrTAdIU+QSPQwFSpsT0+10WTKSbGfu0G6eaOjh13MEvRqPgqih2UKDQz+iziV4cJvNhQb5kJXQM3m6vhHIDLAXtxEQ/DMuWPHdbsr5f/wDr5dCSor9m3hMxbj4ghZ5vk577Fh34Rkn+PUnG3g/JEtQwHfsgUl+KFS1RiuG4Aalx84Sv0yueHbn05LEnWro5wWxmOgcPmOJUz7LrRQaPAubX6bhAc7PqErsqXnfu0QiO/jTXIfbGaJZpVjn0/c2jd64M1H5IJBs3aasU82wTgLK8EGil2mEdkChJkRbiho+G8bNxTEgdbUqAg9CYy17nyCG8xXbSlgtOjLydWvcdiSoCKr41sbdRsNwUhF3wXTEIh9iNkIw31THx86tlpNK X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Mar 2026 05:45:37.8188 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f8f4aa2f-c61a-4db9-c841-08de80c3c117 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: CH3PEPF00000012.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS2PR12MB9565 On Tue, Mar 10, 2026 at 01:51:24PM +0530, Nilay Shroff wrote: > Commit a75b2be249d6 ("iommu: Add iommu_driver_get_domain_for_dev() > helper") introduced iommu_driver_get_domain_for_dev() for driver > code paths that hold iommu_group->mutex while attaching a device > to an IOMMU domain. > > The same commit also added a lockdep assertion in > iommu_get_domain_for_dev() to ensure that callers do not hold > iommu_group->mutex when invoking it. > > On powerpc platforms, when PCI device ownership is switched from > BLOCKED to the PLATFORM domain, the attach callback > spapr_tce_platform_iommu_attach_dev() still calls > iommu_get_domain_for_dev(). This happens while iommu_group->mutex > is held during domain switching, which triggers the lockdep warning > below during PCI enumeration: > > WARNING: drivers/iommu/iommu.c:2252 at iommu_get_domain_for_dev+0x38/0x80, CPU#2: swapper/0/1 > Modules linked in: > CPU: 2 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0-rc2+ #35 PREEMPT > Hardware name: IBM,9105-22A Power11 (architected) 0x820200 0xf000007 of:IBM,FW1120.00 (RB1120_115) hv:phyp pSeries > NIP: c000000000c244c4 LR: c00000000005b5a4 CTR: c00000000005b578 > REGS: c00000000a7bf280 TRAP: 0700 Not tainted (7.0.0-rc2+) > MSR: 8000000002029033 CR: 22004422 XER: 0000000a > CFAR: c000000000c24508 IRQMASK: 0 > GPR00: c00000000005b5a4 c00000000a7bf520 c000000001dc8100 0000000000000001 > GPR04: c00000000f972f10 0000000000000000 0000000000000000 0000000000000001 > GPR08: 0000001ffbc60000 0000000000000001 0000000000000000 0000000000000000 > GPR12: c00000000005b578 c000001fffffe480 c000000000011618 0000000000000000 > GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > GPR20: ffffffffffffefff 0000000000000000 c000000002d30eb0 0000000000000001 > GPR24: c0000000017881f8 0000000000000000 0000000000000001 c00000000f972e00 > GPR28: c00000000bbba0d0 0000000000000000 c00000000bbba0d0 c00000000f972e00 > NIP [c000000000c244c4] iommu_get_domain_for_dev+0x38/0x80 > LR [c00000000005b5a4] spapr_tce_platform_iommu_attach_dev+0x2c/0x98 > Call Trace: > iommu_get_domain_for_dev+0x68/0x80 (unreliable) > spapr_tce_platform_iommu_attach_dev+0x2c/0x98 > __iommu_attach_device+0x44/0x220 > __iommu_device_set_domain+0xf4/0x194 > __iommu_group_set_domain_internal+0xec/0x228 > iommu_setup_default_domain+0x5f4/0x6a4 > __iommu_probe_device+0x674/0x724 > iommu_probe_device+0x50/0xb4 > iommu_add_device+0x48/0x198 > pci_dma_dev_setup_pSeriesLP+0x198/0x4f0 > pcibios_bus_add_device+0x80/0x464 > pci_bus_add_device+0x40/0x100 > pci_bus_add_devices+0x54/0xb0 > pcibios_init+0xd8/0x140 > do_one_initcall+0x8c/0x598 > kernel_init_freeable+0x3ec/0x850 > kernel_init+0x34/0x270 > ret_from_kernel_user_thread+0x14/0x1c > > Fix this by using iommu_driver_get_domain_for_dev() instead of > iommu_get_domain_for_dev() in spapr_tce_platform_iommu_attach_dev(), > which is the appropriate helper for callers holding the group mutex. > > Cc: stable@vger.kernel.org > Fixes: a75b2be249d6 ("iommu: Add iommu_driver_get_domain_for_dev() helper") > Signed-off-by: Nilay Shroff Reviewed-by: Nicolin Chen