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Sun, 31 Aug 2025 19:59:58 -0700 Received: from drhqmail201.nvidia.com (10.126.190.180) by drhqmail201.nvidia.com (10.126.190.180) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.14; Sun, 31 Aug 2025 19:59:57 -0700 Received: from Asurada-Nvidia (10.127.8.14) by mail.nvidia.com (10.126.190.180) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.14 via Frontend Transport; Sun, 31 Aug 2025 19:59:57 -0700 Date: Sun, 31 Aug 2025 19:59:55 -0700 From: Nicolin Chen To: "Duan, Zhenzhong" CC: "Liu, Yi L" , Eric Auger , "qemu-devel@nongnu.org" , "alex.williamson@redhat.com" , "clg@redhat.com" , "mst@redhat.com" , "jasowang@redhat.com" , "peterx@redhat.com" , "ddutile@redhat.com" , "jgg@nvidia.com" , "joao.m.martins@oracle.com" , "clement.mathieu--drif@eviden.com" , "Tian, Kevin" , "Peng, Chao P" Subject: Re: [PATCH v5 02/21] hw/pci: Introduce pci_device_get_viommu_cap() Message-ID: References: <32c0a5e1-6529-4978-a0e1-32940e806dc0@intel.com> <1ee98764-d57f-4ff9-9018-f07d8ee5d68d@intel.com> <153e1475-6678-415c-86bf-b7251cb59f3f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; 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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)(82310400026)(1800799024)(7416014)(376014)(36860700013); DIR:OUT; SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Sep 2025 03:00:30.4480 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 3a3680df-e496-495d-50af-08dde903b61b 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: DS1PEPF00017090.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB9347 Received-SPF: permerror client-ip=40.107.243.44; envelope-from=nicolinc@nvidia.com; helo=NAM12-DM6-obe.outbound.protection.outlook.com X-Spam_score_int: 7 X-Spam_score: 0.7 X-Spam_bar: / X-Spam_report: (0.7 / 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=2.807, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.01, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, 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 Mon, Sep 01, 2025 at 02:35:29AM +0000, Duan, Zhenzhong wrote: > >> I just noticed this change will conflict with your suggestion of using > >HW_NESTED terminology. > >> Let me know if you agree with this change or not? > > > >It wouldn't necessarily conflict. VIOMMU_FLAG_WANT_NESTING_PARENT > >is a request, interchangeable with VIOMMU_FLAG_SUPPORT_HW_NESTED, > >i.e. a cap. > > > >At the end of the day, they are fundamentally the same thing that > >is to tell the core to allocate a nesting parent HWPT. The former > >one is just more straightforward, avoiding confusing terms such as > >"stage-1" and "nested". > > > >IMHO, you wouldn't even need the comments in the other thread, as > >the flag explains clearly what it wants and what the core is doing. > > > >Also, once you use the "want" one, the "HW_NESTED" terminology will > >not exist in the code. > > OK, will use the *_flags and _WANT_* style, do you have suggestions > for the name of vfio_device_viommu_get_nested() since "HW_NESTED" > terminology will not exist, what about vfio_device_get_viommu_flags_W_N_P()? I don't see it very necessary to have a specific API per flag. So, it could be just: uint64_t viommu_flags = vfio_device_get_viommu_flags(vbasedev); if (viommu_flags & VIOMMU_FLAG_WANT_NEST_PARENT) { flags |= IOMMU_HWPT_ALLOC_NEST_PARENT; } ? Thanks Nic