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Thu, 23 Jun 2022 19:44:01 -0700 Date: Thu, 23 Jun 2022 19:44:00 -0700 From: Nicolin Chen To: Baolu Lu , CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v3 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group Message-ID: References: <20220623200029.26007-1-nicolinc@nvidia.com> <20220623200029.26007-2-nicolinc@nvidia.com> <270eec00-8aee-2288-4069-d604e6da2925@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <270eec00-8aee-2288-4069-d604e6da2925@linux.intel.com> X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 771209c9-cd43-40df-d84d-08da558b67d9 X-MS-TrafficTypeDiagnostic: CY5PR12MB6057:EE_ 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:12.22.5.236;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:InfoNoRecords;CAT:NONE;SFS:(13230016)(4636009)(376002)(136003)(39860400002)(396003)(346002)(40470700004)(36840700001)(46966006)(316002)(53546011)(81166007)(7406005)(26005)(7416002)(8936002)(336012)(356005)(36860700001)(4326008)(70206006)(5660300002)(70586007)(82740400003)(47076005)(9686003)(186003)(86362001)(33716001)(40460700003)(110136005)(83380400001)(2906002)(478600001)(426003)(82310400005)(41300700001)(55016003)(54906003)(40480700001)(966005)(8676002)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Jun 2022 02:44:05.6241 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 771209c9-cd43-40df-d84d-08da558b67d9 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[12.22.5.236];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT016.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6057 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Fri, Jun 24, 2022 at 09:35:49AM +0800, Baolu Lu wrote: > External email: Use caution opening links or attachments > > > On 2022/6/24 04:00, Nicolin Chen wrote: > > diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c > > index e1cb51b9866c..5386d889429d 100644 > > --- a/drivers/iommu/mtk_iommu_v1.c > > +++ b/drivers/iommu/mtk_iommu_v1.c > > @@ -304,7 +304,7 @@ static int mtk_iommu_v1_attach_device(struct iommu_domain *domain, struct device > > /* Only allow the domain created internally. */ > > mtk_mapping = data->mapping; > > if (mtk_mapping->domain != domain) > > - return 0; > > + return -EMEDIUMTYPE; > > > > if (!data->m4u_dom) { > > data->m4u_dom = dom; > > This change looks odd. It turns the return value from success to > failure. Is it a bug? If so, it should go through a separated fix patch. Makes sense. I read the commit log of the original change: https://lore.kernel.org/r/1589530123-30240-1-git-send-email-yong.wu@mediatek.com It doesn't seem to allow devices to get attached to different domains other than the shared mapping->domain, created in the in the mtk_iommu_probe_device(). So it looks like returning 0 is intentional. Though I am still very confused by this return value here, I doubt it has ever been used in a VFIO context. Young, would you please give us some input? Overall, I feel it's better to play it safe here by dropping this part. If we later confirm there is a need to fix it, we will do that in a separate patch anyway. Thanks Nic