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Thu, 26 Sep 2024 23:02:38 -0700 Date: Thu, 26 Sep 2024 23:02:37 -0700 From: Nicolin Chen To: Yi Liu CC: , , , , , , , , , , , , , , , , , , 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> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF000044FC:EE_|IA0PR12MB8976:EE_ X-MS-Office365-Filtering-Correlation-Id: 2c42109f-fac4-4218-0d6a-08dcdeba04b3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|82310400026|1800799024|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?sFR//xfocYupMilAgcKfJ1p+iXNcD3C4NMcqdNM0016XYJDerjqh1XqqxeUk?= =?us-ascii?Q?D1jB7HLFaVO6YFC1p0ZNjnxjc1N4AzE0vVOSj0pQY2eBlz0UrIgSLUU7+bS2?= =?us-ascii?Q?6FvfrxLMS+oVevxbSg+pJjUFJq6tCyq3T1/6T+1pBIWmlO9+GRIrp3FstFv3?= =?us-ascii?Q?cJrzn6hr2HPzfF0gljMgzftCQfgQwMrcH3eMFZZZZev1m1n5VhCcvgLumL3s?= =?us-ascii?Q?73P+oTNP09ZyX3WDP9gh33vo8kQnhFKU8DTZsxo9XHq/nKrLgWgOZEJsiO2y?= =?us-ascii?Q?q/Np0Lu8iE/Y77Zkyj47z1ZLoAA2CQFLsmu0ObEozBHo/3XtAbsk6ZVDu3LZ?= =?us-ascii?Q?mcN9ZaolNr68rsW2NBuSTRI0dzcqEz6ZZ8faWx+qcK8RzR+bzS3uMar4aXQy?= =?us-ascii?Q?gjnMn+2GlzuzK/r1oLGbNi57Nu5+87NAVfJvB3cRe1w5wz7OvC+FN4cWwCJ5?= =?us-ascii?Q?1kq1KaPirrTeC7Wf643Vq9ZAhQ5CSjAtig9pgYwRH8zbCIDxRtEvHzFKr3yK?= =?us-ascii?Q?Op1HGXMeN/WDAf3DC2zUFJ0QXVhM4eJCJCaMEEFhqEPOlvrCWrehZp73FkVT?= =?us-ascii?Q?qhH6/Zya5zsNRCkyGBhS/yHkEeftdxvC5WOotyJ6kJSvu0a+MYu1nidxK8DU?= =?us-ascii?Q?kZB3lEYwnLM10V74htO3H6BIgh2/f0vX/dnne3KLAWk/JgspB5vRJ3CikXfD?= =?us-ascii?Q?jPyZu72gNBRBs/Eg/+qdmR9Dzt8rmuc/gEjb+ZbuilXCXbUGj7BFCV76UmsX?= =?us-ascii?Q?qIcHwbib0/169YeDzyWFzBnRsIgSZD0BIpw+hAhwxv0TpCVGy1HLYSvohrlv?= =?us-ascii?Q?UU3rAWgker2Gk3a+VYV+D3GqvIcNAAgb/sSu0prZ27IKjEXq1axLpRqAlt1h?= =?us-ascii?Q?3ebiJrYIVCT+pHX4oAVOmQWo6k0mKKuu/2UtFPzVu6gqbsVmKsBtRfk/Mv5Y?= =?us-ascii?Q?xrn0s+sacSdaMdRXkaTMuC1a5tjT42axx6m5d6+Hiux1TrC9yC6HdRJjIonj?= =?us-ascii?Q?ERgVamBjRcjM4MLcUC/587JgHM4/AzDNRNHsp44SsyN5DPEVaw3e8vkunZWz?= =?us-ascii?Q?1v+Avv65Rsr5WZNFdRBGwpydNkxh+2upguxNuYbIFMVVMYWXj+3/0O8sz7D2?= =?us-ascii?Q?MIgE3uzLpaIdxSPOsY1NcKDXpzg/HF322G0Y+u8vIA+Vn5eBbqwRX0UU0FtW?= =?us-ascii?Q?GMl6tHlLdt2nPvOfSGvlb4EpjRuNjC7gdGK5W8933CmmXC+Z22ex7LwTGdB/?= =?us-ascii?Q?rsXwiCWUx3rf9xtrafpddz1uj2pHTevSpF4BNTq36a3+xUIamL3w57lnPT+y?= =?us-ascii?Q?Dd1nbTb55cwZNcFFsbKU4Oyc/xd7m+3gwGOsckQRtB6sNx4YTewWJ+tXsyv/?= =?us-ascii?Q?SDoBim871LmjlVbwUMgcMEwCAZH7DKy7twE3DbBzEJS6VrmXa003Sg5j73WK?= =?us-ascii?Q?L0xKlczd60Et5YC5E9H6yu/GwM1isTpP?= X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(376014)(7416014)(82310400026)(1800799024)(36860700013);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Sep 2024 06:02:50.2956 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2c42109f-fac4-4218-0d6a-08dcdeba04b3 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: CO1PEPF000044FC.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB8976 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240926_230308_957475_B2F90F8A X-CRM114-Status: GOOD ( 22.54 ) 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 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. QEMU then does the routing to assign PCI buses and IORT (or DT). This part is suggested now to move to libvirt though. So, I think at the end of the day, libvirt would run the sys check and assign a device to the corresponding pci bus backed by the correct IOMMU. This gives an example showing two devices behind iommu0 and third device behind iommu1 are assigned to a VM: -device pxb-pcie.id=pcie.viommu0,bus=pcie.0.... \ # bus for viommu0 -device pxb-pcie.id=pcie.viommu1,bus=pcie.0.... \ # bus for viommu1 -device pcie-root-port,id=pcie.viommu0p0,bus=pcie.viommu0... \ -device pcie-root-port,id=pcie.viommu0p1,bus=pcie.viommu0... \ -device pcie-root-port,id=pcie.viommu1p0,bus=pcie.viommu1... \ -device vfio-pci,bus=pcie.viommu0p0... \ # connect to bus for viommu0 -device vfio-pci,bus=pcie.viommu0p1... \ # connect to bus for viommu0 -device vfio-pci,bus=pcie.viommu1p0... # connect to bus for viommu1 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. Thanks Nic