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Thu, 27 Apr 2023 10:24:58 -0700 Date: Thu, 27 Apr 2023 10:24:57 -0700 From: Nicolin Chen To: Robin Murphy CC: Baolu Lu , Jason Gunthorpe , "iommu@lists.linux.dev" , Joerg Roedel , Will Deacon , Kevin Tian , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] iommu/vt-d: Remove unnecessary locking in intel_irq_remapping_alloc() Message-ID: References: <20230314051836.23817-1-baolu.lu@linux.intel.com> <09e4ce6e-0341-8590-b933-795ee28326a3@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1NAM11FT040:EE_|SA3PR12MB8809:EE_ X-MS-Office365-Filtering-Correlation-Id: 7f97d654-90f4-438c-29e1-08db47445a3e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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:(13230028)(4636009)(396003)(39860400002)(346002)(376002)(136003)(451199021)(46966006)(40470700004)(36840700001)(86362001)(53546011)(41300700001)(26005)(9686003)(2906002)(47076005)(55016003)(5660300002)(8676002)(40480700001)(8936002)(336012)(426003)(40460700003)(34020700004)(478600001)(33716001)(83380400001)(7636003)(356005)(54906003)(186003)(82740400003)(36860700001)(82310400005)(6916009)(4326008)(316002)(70206006)(70586007);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Apr 2023 17:25:09.9491 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 7f97d654-90f4-438c-29e1-08db47445a3e 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: CO1NAM11FT040.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR12MB8809 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 27, 2023 at 10:35:11AM +0100, Robin Murphy wrote: > On 2023-04-27 04:37, Nicolin Chen wrote: > > On Thu, Apr 27, 2023 at 11:20:40AM +0800, Baolu Lu wrote: > > > > > > Attaching WARNINGs: > > > > [ 19.680725] ------------[ cut here ]------------ > > > > [ 19.681083] WARNING: CPU: 0 PID: 561 at include/linux/mmap_lock.h:161 track_pfn_remap+0xf5/0x100 > > > > > > [ 19.684817] Call Trace: > > > > [ 19.684893] > > > > [ 19.684967] remap_pfn_range+0x3e/0xa0 > > > > [ 19.685084] vfio_pci_mmap_fault+0x8a/0x160 [vfio_pci_core] > > > > > I took a quick look. It seems that above warnings are irrelevant to this > > > commit. Can you please simply revert this commit and check whether there > > > are any changes? > > > > I tried on top of the v6.3-rc5 tag. The warnings were triggered > > constantly. And reverting the commit fixes it: > > nicolinc@Asurada-Nvidia:~/work/mkt/images/nicolinc/src/kernel$ git log --oneline -2 > > cb3dc9b2417e (HEAD -> v6.3-rc5) Revert "iommu/vt-d: Remove unnecessary locking in intel_irq_remapping_alloc()" > > 7e364e56293b (tag: v6.3-rc5, jgg/linus) Linux 6.3-rc5 > > > > I don't think the commit is the causation yet there seems to be > > a strong correlation here... > > The correlation is probably that you're now getting to see a genuine > warning from lockdep_assert_held(), since intel-iommu is no longer > causing debug_locks to be turned off earlier. Hmm, looks like so. The mmap_lock is held with a read permission, in arch/x86/mm/fault.c file, v.s. the expectation of a write one by remap_pfn_range(). Thanks Nicolin