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Fri, 27 Sep 2024 12:52:55 -0700 Date: Fri, 27 Sep 2024 12:52:54 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: Yi Liu , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v2 04/19] iommufd: Allow pt_id to carry viommu_id for IOMMU_HWPT_ALLOC Message-ID: References: <2d469a5279ef05820d5993df752d32239878338d.1724776335.git.nicolinc@nvidia.com> <3ddf97a3-cf5b-4907-bbe4-296456951e6b@intel.com> <20240927115925.GX9417@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20240927115925.GX9417@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWH0EPF000A672F:EE_|IA0PR12MB7507:EE_ X-MS-Office365-Filtering-Correlation-Id: acd42fac-6c26-4a66-4abe-08dcdf2dffce X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|376014|7416014|82310400026|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?55y7N6/iJe4OuGR7944iQn33Q3rWMno64wKhA+zYBSFKnKQTFXq1ACuoRYMM?= =?us-ascii?Q?v6TV1NJJSzKsrIRvQ23FZmvThh+nmG4q45oQRN9lfUoDXVXjS94qHNAygtmc?= =?us-ascii?Q?U+kdJkXVHyx5sm1MtJf7tfuYrIvQI75jCNDDFP1mCQYT/VireltkvRzg8C/R?= =?us-ascii?Q?U7p5kQ593peS3Oai3YwlMzjDuF/e6hNcIDdRgGx8DMq14VSEMlSnoNPT2mVD?= =?us-ascii?Q?KfzXJ0oNtCaSzYIAIqYsvJ41ShdU4koI9oyZeSgindxnqaP0mPNsudM40q1G?= =?us-ascii?Q?7ICHFtbvCkvRHLUfl7AaL2DeS4mEzzUnlBKFbXBsSxNjm46qXtxB95T59pru?= =?us-ascii?Q?9/SyPHThZRUljjOIEFROE+kEbaYdTvkQEy2It/Fq60DmfL1+8Xz3C27VCw9E?= =?us-ascii?Q?QlGRebpeo6igq7v+3dF9+6M8YKFCaLQFpodD9fKml0VdY0YHeZmoVcQouCeD?= =?us-ascii?Q?AZbGU32OkX+s+o/5m8K4INKGXReKk//jZa6fKsKdP4fuME/c5u5q97lpQxrc?= =?us-ascii?Q?cWfkhe626ObkBnDSyioQvJImjJ0qa+x7F2UP3LUMLL179j4XeGcIPkUKqT4v?= =?us-ascii?Q?XTo7lOXY/Yvmn5m3nJOozKS6O7FlTfus+2DMDm7maWbmyIzPNx2Wbp9pEJ+r?= =?us-ascii?Q?MHZNdYZ2fF1e/GH2cTPAiBSXE/fsddKYlwxLFNyqw71n3AKAJmOSbLSahW8J?= =?us-ascii?Q?RhRkKrDQPEK/GLs1+E7zUd+oAVVtzWoaOTtBG95Tb8ecRSvrJJj/vR5Kl/xL?= =?us-ascii?Q?ZkIQOaShLcyKEPtN0fhzqyd5qNRzk9tK9xx4vH3vGtx1PmXijBFI5ooUcdZA?= =?us-ascii?Q?D+ZQFak5EFb7CKELtWVa1GT6v+aT0u9yYMhBSdvRKCWOb+kD56gnasbZolMn?= =?us-ascii?Q?Jf8LFeiQZq82+F+86pLslSW3uGntMy2E3uKCn6zRlMlK2iADArE+Z9UsJ5B0?= =?us-ascii?Q?eUnxetoFCmg6JSlQ1RK2TYu0b9bFWTszEWujRS7RMP0FT247UhglBmlz6wwl?= =?us-ascii?Q?LhEDDllJKibHm6H2FqTVMr0AwLu3RFv62Tn3Py/h07rTtv66HkOxfewYQjM8?= =?us-ascii?Q?H43yoQEA90BwONPzpz1FMiFWSHSw59euJAQ7cNSFgfnyUUwdxxk0KeTzWJpQ?= =?us-ascii?Q?shpBTBn7oKkvFW8penUcxYHz06vwibRfN31T4Bt0WFRcZPsqIZqOCvpMDDUd?= =?us-ascii?Q?cOlCSxJ8SDHhrunzXW56MvoEMu6gydC8HqO3SYRDFXCPpHVezNR4z9uG2NGW?= =?us-ascii?Q?WOelpJv+xUwkgqPWRYQEY36vqUYREuSGpwIxFpPjkJXdMSvAAjjY5ZneSbWU?= =?us-ascii?Q?2ZNJU9xO7Jn0fVaSq/cPve+ERqPGs5eih+yirRmtmTZ8c2odn6z/QSwWyLqm?= =?us-ascii?Q?1tWdGOuaKtHSOQrMHsZZP5naNcQg?= X-Forefront-Antispam-Report: CIP:216.228.118.233;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge2.nvidia.com;CAT:NONE;SFS:(13230040)(36860700013)(376014)(7416014)(82310400026)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Sep 2024 19:53:03.7218 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: acd42fac-6c26-4a66-4abe-08dcdf2dffce X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.233];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: MWH0EPF000A672F.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB7507 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240927_125328_798986_2CDE8F08 X-CRM114-Status: GOOD ( 30.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 27, 2024 at 08:59:25AM -0300, Jason Gunthorpe wrote: > On Thu, Sep 26, 2024 at 11:02:37PM -0700, Nicolin Chen wrote: > > On Fri, Sep 27, 2024 at 01:38:08PM +0800, Yi Liu wrote: > > > > > Does it mean each vIOMMU of VM can only have > > > > > one s2 HWPT? > > > > > > > > Giving some examples here: > > > > - If a VM has 1 vIOMMU, there will be 1 vIOMMU object in the > > > > kernel holding one S2 HWPT. > > > > - If a VM has 2 vIOMMUs, there will be 2 vIOMMU objects in the > > > > kernel that can hold two different S2 HWPTs, or share one S2 > > > > HWPT (saving memory). > > > > > > So if you have two devices assigned to a VM, then you may have two > > > vIOMMUs or one vIOMMU exposed to guest. This depends on whether the two > > > devices are behind the same physical IOMMU. If it's two vIOMMUs, the two > > > can share the s2 hwpt if their physical IOMMU is compatible. is it? > > > > Yes. > > > > > To achieve the above, you need to know if the physical IOMMUs of the > > > assigned devices, hence be able to tell if physical IOMMUs are the > > > same and if they are compatible. How would userspace know such infos? > > > > My draft implementation with QEMU does something like this: > > - List all viommu-matched iommu nodes under /sys/class/iommu: LINKs > > - Get PCI device's /sys/bus/pci/devices/0000:00:00.0/iommu: LINK0 > > - Compare the LINK0 against the LINKs > > > > We so far don't have an ID for physical IOMMU instance, which can > > be an alternative to return via the hw_info call, otherwise. > > We could return the sys/class/iommu string from some get_info or > something I had a patch doing an ida alloc for each iommu_dev and returning the ID via hw_info. It wasn't useful at that time, as we went for fail-n-retry for S2 HWPT allocations on multi-pIOMMU platforms. Perhaps that could be cleaner than returning a string? > > For compatibility to share a stage-2 HWPT, basically we would do > > a device attach to one of the stage-2 HWPT from the list that VMM > > should keep. This attach has all the compatibility test, down to > > the IOMMU driver. If it fails, just allocate a new stage-2 HWPT. > > Ideally just creating the viommu should validate the passed in hwpt is > compatible without attaching. I think I should add a validation between hwpt->domain->owner and dev_iommu_ops(idev->dev) then! Thanks Nicolin