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Wed, 26 Feb 2025 10:57:01 -0800 Date: Wed, 26 Feb 2025 10:57:00 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , , , , , , , , Subject: Re: [PATCH v2 7/7] iommu: Turn iova_cookie to dma-iommu private pointer Message-ID: References: <949e28875e01646feac5c4951b63723579d29b36.1740014950.git.nicolinc@nvidia.com> <20250221143959.GA272220@nvidia.com> <20250226173610.GE28425@nvidia.com> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250226173610.GE28425@nvidia.com> X-NV-OnPremToCloud: AnonymousSubmission X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH2PEPF000000A0:EE_|PH7PR12MB9202:EE_ X-MS-Office365-Filtering-Correlation-Id: a4558011-5267-4504-4f27-08dd56976366 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|82310400026|1800799024|376014|7416014; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Feb 2025 18:57:16.2459 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a4558011-5267-4504-4f27-08dd56976366 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CH2PEPF000000A0.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB9202 On Wed, Feb 26, 2025 at 01:36:10PM -0400, Jason Gunthorpe wrote: > On Tue, Feb 25, 2025 at 06:25:27PM -0800, Nicolin Chen wrote: > > On Fri, Feb 21, 2025 at 10:39:59AM -0400, Jason Gunthorpe wrote: > > > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > > > index 99dd72998cb7f7..082274e8ba6a3d 100644 > > > --- a/include/linux/iommu.h > > > +++ b/include/linux/iommu.h > > > @@ -1534,12 +1534,16 @@ void iommu_debugfs_setup(void); > > > static inline void iommu_debugfs_setup(void) {} > > > #endif > > > > > > -#ifdef CONFIG_IOMMU_DMA > > > +#if defined(CONFIG_IOMMU_DMA) && IS_ENABLED(CONFIG_IRQ_MSI_IOMMU) > > > int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base); > > > +void iommu_put_msi_cookie(struct iommu_domain *domain); > > > #else /* CONFIG_IOMMU_DMA */ > > > static inline int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base) > > > { > > > - return -ENODEV; > > > + return 0; > > > > Should we keep the -ENODEV here for !CONFIG_IOMMU_DMA? > > My feeling was if the system doesn't have an IRQ driver that needs > MSI_IOMMU but does have a IOMMU driver that reports SW_MSI reserved > regions then iommufd/vfio should not fail. OK, I see. But we are also changing the behavior for the !CONFIG_IOMMU_DMA configuration, in which case all other iommu functions seem to return -ENODEV. And I assume we would need a justification for such a change? Perhaps, this can be explicit, just to keep the consistency: /* NOP if IOMMU driver reports SW_MSI reserved regions */ return IS_ENABLED(CONFIG_IOMMU_DMA) ? 0 : -ENODEV; > I don't think it is realistic that we'd ever hit this return. Yea, the only caller is VFIO, where there are quite a few IOMMU functions calls before reaching to this one. So, it would have been just returned with any -ENODEV prior. Thanks Nicolin