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Tue, 27 Jan 2026 09:11:16 -0800 Date: Tue, 27 Jan 2026 09:11:14 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , Subject: Re: [PATCH v2 06/10] iommu/arm-smmu-v3: Allocate vmid in arm_vsmmu_init Message-ID: References: <3f7c5b84c4f8605688ac08fc2ea2dab08a3c5c0c.1769044718.git.nicolinc@nvidia.com> <20260126211636.GB1134360@nvidia.com> <20260127151138.GI1134360@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260127151138.GI1134360@nvidia.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF00001CE9:EE_|PH7PR12MB7259:EE_ X-MS-Office365-Filtering-Correlation-Id: 1b677a56-28b6-4a5c-bac8-08de5dc720de X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|36860700013|7416014|376014|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?ZdG+QFzFHXJuereYuTwwDfx5lDfTnUMXFL4yp6W/rvmHF+/4e5ATDyflot1O?= =?us-ascii?Q?gcc+XXxk07QwgJvYB/wrgfsEYbUZ2nuSkAr235aPo5EUebKU+ot6DgbGM7o9?= =?us-ascii?Q?GT7KpblII0m4G8NYvOufKkpiOFG1cAELVsnNsseTWyhcYFlcDzjMMpMHL0s7?= =?us-ascii?Q?zErmwOKrBQJ8jiemHCVm1UsnxONBxhFD0MAtkz3qQQC6/9UdyuopoVqYSkUp?= =?us-ascii?Q?QisW6FrXZzfa2GI9hrD1TXBf4rRRZm+MN/tcBRDzq0pIcNLriP0rU8aiA4XH?= =?us-ascii?Q?mYPnzmtfBCuTB4Ce+SANXenuDrRmw45Y7Fr96XaepAStibNuzGFT+SOlt+BH?= =?us-ascii?Q?KZKx2BshEunI74yOtfi3FRjCLm9WufKP8Rb/6hD67TmKwxaNZGgs9lo8vmzO?= =?us-ascii?Q?Yd4eaJBIPOU0pCfvLn2AbxgLviWnat1co8d4SSXOOWz986N04Ljs4JCm0eD7?= =?us-ascii?Q?ADbu0UsuhswYZnby8DNc6mY98qV11OBwIfjrlSIioW9Zb+NvEzNfVm7pzdy6?= =?us-ascii?Q?vi1an//Dkop3Wk/oJeQRZ2RzOvEUsZg+5cCuNQqCEbHi2WVKhAruLlV12jbN?= =?us-ascii?Q?iII5n3hLiBNN4MV/20vN4J1fP37LOmQSNEm9mOlv1DnXzzfmDuCZ+FUkv/VI?= =?us-ascii?Q?giowJfyPjxBZ30lNN3q8xxbIwxff9F+nJxaUJkohp0aMlEytzg4Ren5YO+Wp?= =?us-ascii?Q?nKvnpi10uo+SU8WFilgLsNZo6wzEaEPCC2X9p/IrHFknTx0kR3Rwao4R8Vm+?= =?us-ascii?Q?T4EUxuZ1ssuIu11wMq6dZMs8dvv/KyD+zeE7IRA57Wr0VloqGG/0cQfeO6nS?= =?us-ascii?Q?bIojFdEo5kWD/TuAfzutkDgIMA39QLTizmaqRmn2pBTqcLbiSWRF9W4zutHE?= =?us-ascii?Q?8WZ1hZC9bcXAmfopZtT5mYuSbFEgVC47Rx5/ZrLlcPjfbOv0QW1ALILnlefc?= =?us-ascii?Q?OZLm3GuFEpz0Lyo/uBg4399qYYUcbEIxcJ+9R6JtxU9VTZeMlqLhnteyFrPl?= =?us-ascii?Q?or3YD7VTPZe09mlSGrLCeB+JZCV18IdORoWcGa7FnzOHPX0fOgKhhpJIlHrg?= =?us-ascii?Q?U9pa3wJT+yxt8vYzMmB+wr7gV11jNs1FSMlOXURUx093DvPq9Wc9khzbNYNs?= =?us-ascii?Q?zR3J0xN34rraT26Q1ZiYynRGC9rtzcJidf9ggGBHEucDDOnNak+V/XNfc/tR?= =?us-ascii?Q?p08hi5v+u8UyjJqjv49AfDFTwb9AEoOmh7iYxEzFku+u2JyqI9dmW0xfgDaG?= =?us-ascii?Q?XHKhHd1Wej6GZgar8q0lbdzw5OwfxGiInQ5wFOL//+P62tNC59HscAp7XQdc?= =?us-ascii?Q?GTR9pztSfXAqQdTa9tp4nUeCqnDNmNQd8D8f2Q0Sco0mlu50sV5koFp7B6qH?= =?us-ascii?Q?u7AlS4gBpQadqQAMK/P/i9W0HgK7DvxZrTsbAu4fgG77nuvu2YcBoMEHBq8J?= =?us-ascii?Q?Dr2Wwf3GrrvCudMph9DZQV5GGRtNvsgoa4gfn7UzttPELNPJwrDB6vUDE+2X?= =?us-ascii?Q?EP8lIJTMQgdSC+vzYOh/Lm0chkr65d8nS4lBZ4zoe/yASNUVqsxCBsQ1nh4s?= =?us-ascii?Q?EHgWZRiJq1MZ2guSlvQW4l8SVwgIZE000JnOnLQcsUPuXIFPxX9/Z1i4oXhy?= =?us-ascii?Q?MrWO4KEOB41sLvn2WFVzVwDQ+74oLwCLybjKIXA6xXqPlS0b0P1KhCasYHiD?= =?us-ascii?Q?oQDXRA=3D=3D?= X-Forefront-Antispam-Report: CIP:216.228.118.232;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge1.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(36860700013)(7416014)(376014)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Jan 2026 17:11:36.4319 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1b677a56-28b6-4a5c-bac8-08de5dc720de X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF00001CE9.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB7259 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260127_091148_108509_4223441A X-CRM114-Status: GOOD ( 22.64 ) 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 Tue, Jan 27, 2026 at 11:11:38AM -0400, Jason Gunthorpe wrote: > On Mon, Jan 26, 2026 at 07:06:24PM -0800, Nicolin Chen wrote: > > On Mon, Jan 26, 2026 at 05:16:36PM -0400, Jason Gunthorpe wrote: > > > On Wed, Jan 21, 2026 at 05:24:24PM -0800, Nicolin Chen wrote: > > > > VMID owned by a vSMMU should be allocated in the viommu_init callback, as > > > > HW like tegra241-cmdqv needs to setup VINTF with the VMID. > > > > > > Even the architected SMMU needs this, the VMS (not implemented in > > > Linux) should all share the same VMID for the same VM. > > > > But for standard SMMU, the allocation/sharing could happen at the > > device attachment to a nested (maybe bypass proxy) domain, right? > > > > vmid is only needed for STE (attach) and invalidation. > > > > Or do you see some other case where vmid must be allocated during > > viommu_init? > > It has to be tied to the VSMMU, it doesn't matter if a single VMID is > allocated on-demand for the VSMMU or for the lifetime, it has to be a > single ID and shared across all STEs. Attachment threads are mutexed. Any device that attaches firstly will allocate a shareable tag and add it to the array. Any other device will get the tag from the array and reuse it. And nothing will change this. > It is easy to understand that lifecycle by just allocating it for the > lifetime of the VSMMU.. Yea, it makes sense for that matter. So, perhaps: VMID owned by a vSMMU should be allocated in the viommu_init callback for - a straightforward lifecycle for a VMID used by a vSMMU - HW like tegra241-cmdqv needs to setup VINTF with the VMID Thanks Nicolin