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Mon, 30 Jan 2023 11:38:50 -0800 Date: Mon, 30 Jan 2023 11:38:49 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: , , , Subject: Re: [PATCH v2 2/3] iommufd/device: Make hwpt_list list_add/del symmetric Message-ID: References: <6f388b1f20622957518ec5a9ddc7f0037e7671c4.1674939002.git.nicolinc@nvidia.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: DM6NAM11FT037:EE_|MN2PR12MB4341:EE_ X-MS-Office365-Filtering-Correlation-Id: 1b30a70c-e360-4906-b610-08db02f9a2ff 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:216.228.118.232;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge1.nvidia.com;CAT:NONE;SFS:(13230025)(4636009)(39860400002)(346002)(136003)(376002)(396003)(451199018)(36840700001)(46966006)(40470700004)(41300700001)(336012)(7636003)(40460700003)(36860700001)(82740400003)(86362001)(33716001)(54906003)(82310400005)(8936002)(6862004)(6636002)(5660300002)(316002)(55016003)(356005)(40480700001)(426003)(47076005)(2906002)(83380400001)(9686003)(4326008)(26005)(478600001)(186003)(70586007)(70206006)(8676002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jan 2023 19:39:00.6430 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1b30a70c-e360-4906-b610-08db02f9a2ff 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: DM6NAM11FT037.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB4341 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 30, 2023 at 03:07:50PM -0400, Jason Gunthorpe wrote: > On Mon, Jan 30, 2023 at 11:03:09AM -0800, Nicolin Chen wrote: > > On Mon, Jan 30, 2023 at 10:59:32AM -0400, Jason Gunthorpe wrote: > > > On Sat, Jan 28, 2023 at 01:18:10PM -0800, Nicolin Chen wrote: > > > > Since the list_del() of hwpt_item is done in iommufd_device_detach(), move > > > > its list_add_tail() to a similar place in iommufd_device_do_attach(). > > > > > > > > Also move and place the mutex outside the iommufd_device_auto_get_domain() > > > > and iommufd_device_do_attach() calls, to serialize attach/detach routines. > > > > This adds an additional locking protection so that the following patch can > > > > safely remove devices_lock. > > > > > > That should be two patches then, this is just moving one line of code > > > from what I can tell? > > > > The mutex is used to protect the list. So moving the list means > > we'd need to the mutex too. What this patch does is to enlarge > > the protection scope a bit to cover iommufd_device_do_attach() > > and iommufd_device_auto_get_domain(). > > That doesn't explain why iommufd_device_auto_get_domain was changed > around, it already had the lock That is trying to make the code look like this: iommufd_device_attach { ... case IOMMUFD_OBJ_HW_PAGETABLE: + mutex_lock(&hwpt->ioas->mutex); rc = iommufd_device_do_attach(idev, hwpt); + mutex_unlock(&hwpt->ioas->mutex); ... case IOMMUFD_OBJ_IOAS: ... + mutex_lock(&ioas->mutex); rc = iommufd_device_auto_get_domain(idev, ioas); + mutex_unlock(&ioas->mutex); ... } If you don't think that's necessary, I can make things intact in iommufd_device_auto_get_domain(). Thanks Nic