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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)(376014)(7416014)(36860700013)(1800799024); DIR:OUT; SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Oct 2025 17:53:27.4927 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 04241af7-d162-4758-0f04-08de1581bba5 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: SN1PEPF0002BA4D.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB9546 Received-SPF: permerror client-ip=2a01:111:f403:c111::9; envelope-from=nicolinc@nvidia.com; helo=DM5PR21CU001.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, RCVD_IN_DNSWL_NONE=-0.0001, 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, Oct 27, 2025 at 06:38:08PM +0100, Eric Auger wrote: > > > On 10/27/25 6:13 PM, Nicolin Chen wrote: > > Hi Eric, > > > > On Mon, Oct 27, 2025 at 05:59:13PM +0100, Eric Auger wrote: > >> On 9/29/25 3:36 PM, Shameer Kolothum wrote: > >>> QEMU SMMUv3 does not enable ATS (Address Translation Services) by default. > >>> When accelerated mode is enabled and the host SMMUv3 supports ATS, it can > >>> be useful to report ATS capability to the guest so it can take advantage > >>> of it if the device also supports ATS. > >>> > >>> Note: ATS support cannot be reliably detected from the host SMMUv3 IDR > >>> registers alone, as firmware ACPI IORT tables may override them. The > >>> user must therefore ensure the support before enabling it. > >> This looks incomplete to me. ATS is a big topic in itself. I would > >> prefer we do not advertise it until we do not have full support for it > >> (including emulation). Comparing to > >> c049bf5bb9dd ("intel_iommu: Add support for ATS") which was recently > >> contributed we miss at least translation request implementations > >> (PCIIOMMUOps ats_request_translation callback implementation). > >> > >> See: > >> https://lore.kernel.org/all/20250628180226.133285-11-clement.mathieu--drif@eviden.com/#r > > In accelerated SMMUv3 case, ATS translation and invalidation are > > done by the physical SMMU. Wondering why do we need this? > > in 06/27 you still can have emulated EPs hotplugged in the loop, no? > > I remember some discussions with Peter who was also reluctant in general > to introduce some partial feature support. I think in general this is a > good policy to have features emulated and then accelerated. That's also > good for testing in case we can bring up some test env. Hmm, that sounds a legit reason, though adding the ATS support to the emulated SMMUv3 isn't seemingly a small effort... Also, do we have any emulated EP to test out ATS translation and invalidation from the emulated SMMUv3? Thanks Nicolin