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Tue, 13 Sep 2022 13:14:26 -0700 Date: Tue, 13 Sep 2022 13:14:24 -0700 From: Nicolin Chen To: Jean-Philippe Brucker CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH 4/5] iommu: Regulate errno in ->attach_dev callback functions Message-ID: References: <20220913082448.31120-1-nicolinc@nvidia.com> <20220913082448.31120-5-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: DM6NAM11FT072:EE_|BY5PR12MB4260:EE_ X-MS-Office365-Filtering-Correlation-Id: 4703a67a-e720-4dfa-0d73-08da95c48ffc 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:12.22.5.235;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:InfoNoRecords;CAT:NONE;SFS:(13230022)(4636009)(376002)(136003)(39860400002)(346002)(396003)(451199015)(36840700001)(46966006)(40470700004)(356005)(186003)(26005)(83380400001)(426003)(336012)(8936002)(7406005)(36860700001)(81166007)(41300700001)(86362001)(55016003)(478600001)(40460700003)(8676002)(2906002)(47076005)(5660300002)(54906003)(316002)(9686003)(7416002)(82740400003)(6916009)(70586007)(4326008)(82310400005)(70206006)(33716001)(40480700001)(36900700001)(67856001);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Sep 2022 20:14:28.7041 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4703a67a-e720-4dfa-0d73-08da95c48ffc X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[12.22.5.235];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT072.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR12MB4260 Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org Hi Jean, On Tue, Sep 13, 2022 at 01:27:03PM +0100, Jean-Philippe Brucker wrote: > External email: Use caution opening links or attachments > > > Hi Nicolin, > > On Tue, Sep 13, 2022 at 01:24:47AM -0700, Nicolin Chen wrote: > > Following the new rules in include/linux/iommu.h kdocs, update all drivers > > ->attach_dev callback functions to return ENODEV error code for all device > > specific errors. It particularly excludes EINVAL from being used for such > > error cases. For the same purpose, also replace one EINVAL with ENOMEM in > > mtk_iommu driver. > > > > Note that the virtio-iommu does a viommu_domain_map_identity() call, which > > returns either 0 or ENOMEM at this moment. Change to "return ret" directly > > to allow it to pass an EINVAL in the future. > [...] > > diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c > > index 80151176ba12..874c01634d2b 100644 > > --- a/drivers/iommu/virtio-iommu.c > > +++ b/drivers/iommu/virtio-iommu.c > > @@ -696,7 +696,7 @@ static int viommu_domain_finalise(struct viommu_endpoint *vdev, > > if (ret) { > > ida_free(&viommu->domain_ids, vdomain->id); > > vdomain->viommu = NULL; > > - return -EOPNOTSUPP; > > + return ret; > > I think in the future it will be too easy to forget about the constrained > return value of attach() while modifying some other part of the driver, > and let an external helper return EINVAL. So I'd rather not propagate ret > from outside of viommu_domain_attach() and finalise(). > > For the same reason I do prefer this solution over EMEDIUMTYPE, because > it's too tempting to use exotic errno when they seem appropriate instead > of boring ENODEV and EINVAL. The alternative would be adding a special > purpose code to linux/errno.h, similarly to EPROBE_DEFER, but that might > be excessive. > > Since we can't guarantee that APIs like virtio or ida won't ever return > EINVAL, we should set all return values: Thanks for the inputs. Assuming your attached patch isn't officially sent, I will group it into my next version. Similarly, I will also double check other drivers, to make sure all of them have explicit return values, other than "ret".