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CTRY:US; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:mail.nvidia.com; PTR:dc7edge1.nvidia.com; CAT:NONE; SFS:(13230040)(1800799024)(36860700013)(82310400026)(7416014)(376014); DIR:OUT; SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Aug 2025 15:31:13.6624 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c216d29a-8717-4c15-ad8f-08dde57ec1e3 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: CH2PEPF00000146.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4202 Received-SPF: permerror client-ip=2a01:111:f403:200a::623; envelope-from=nicolinc@nvidia.com; helo=NAM12-MW2-obe.outbound.protection.outlook.com X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FORGED_SPF_HELO=1, SPF_HELO_PASS=-0.001, SPF_NONE=0.001 autolearn=no 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 Wed, Aug 27, 2025 at 02:32:42PM +0200, Eric Auger wrote: > On 8/27/25 2:30 PM, Yi Liu wrote: > > On 2025/8/27 19:22, Eric Auger wrote: > >>> TBH. I'm hesitating to name it as get_viommu_cap. The scope is a little > >>> larger than what we want so far. So I'm wondering if it can be done > >>> in a > >>> more straightforward way. e.g. just a bool op named > >>> iommu_nested_wanted(). Just an example, maybe better naming. We can > >>> extend the op to be returning a u64 value in the future when we see > >>> another request on VFIO from vIOMMU. > >> personnally I am fine with the bitmask which looks more future proof. > > > > not quite sure if there is another info that needs to be checked in > > this "VFIO asks vIOMMU" manner. Have you seen one beside this > > nested hwpt requirement by vIOMMU? > > I don't remember any at this point. But I guess with ARM CCA device > passthrough we might have other needs Yea. A Realm vSMMU instance won't allocate IOAS/HWPT. So it will ask the core to bypass those allocations, via the same op. I don't know: does "get_viommu_flags" sound more fitting to have a clear meaning of "want"? VIOMMU_FLAG_WANT_NESTING_PARENT VIOMMU_FLAG_WANT_NO_IOAS At least, the 2nd one being a "cap" wouldn't sound nice to me.. Nicolin