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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: 17 Jun 2025 03:15:01.2070 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 629cdba8-2a4d-4a7e-b317-08ddad4d25c0 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: BN1PEPF00006003.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4218 Received-SPF: permerror client-ip=2a01:111:f403:2415::60f; envelope-from=nicolinc@nvidia.com; helo=NAM11-DM6-obe.outbound.protection.outlook.com X-Spam_score_int: -39 X-Spam_score: -4.0 X-Spam_bar: ---- X-Spam_report: (-4.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.892, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Jun 16, 2025 at 08:15:11AM +0000, Duan, Zhenzhong wrote: > >IIUIC, the guest kernel cmdline can switch the mode between the > >stage1 (nesting) and stage2 (legacy/emulated VT-d), right? > > Right. E.g., kexec from "intel_iommu=on,sm_on" to "intel_iommu=on,sm_off", > Then first kernel will run in scalable mode and use stage1(nesting) and > second kernel will run in legacy mode and use stage2. In scalable mode, guest kernel has a stage1 (nested) domain and host kernel has a stage2 (nesting parent) domain. In this case, the VFIO container IOAS could be the system AS corresponding to the kernel-managed stage2 domain. In legacy mode, guest kernel has a stage2 (normal) domain while host kernel has a stage2 (shadow) domain? In this case, the VFIO container IOAS should be the iommu AS corresponding to the kernel guest-level stage2 domain (or should it be shadow)? The ARM model that Shameer is proposing only allows a nested SMMU when such a legacy mode is off. This simplifies a lot of things. But the difficulty of the VT-d model is that it has to rely on a guest bootcmd during runtime.. Nicolin