On Thu, May 15, 2025 at 04:23:29PM -0300, Jason Gunthorpe wrote: > On Thu, May 15, 2025 at 12:21:17PM -0700, Nicolin Chen wrote: > > On Thu, May 15, 2025 at 03:56:29PM -0300, Jason Gunthorpe wrote: > > > On Thu, May 15, 2025 at 11:52:05AM -0700, Nicolin Chen wrote: > > > > On Thu, May 15, 2025 at 02:17:06PM -0300, Jason Gunthorpe wrote: > > > > > On Thu, May 08, 2025 at 08:02:39PM -0700, Nicolin Chen wrote: > > > > Should the first call return out_data_type=CMDQV while returning > > > > the arm_smmu_v3 hw_info data? Otherwise, VMM wouldn't know what > > > > to set in the input sub_data_type of the 2nd ioctl? > > > > > > No, either set a flag in the smmu_v3 hw_info, as you were doing here, > > > or just have the vmm probe it. Given the VMM is likely to be told to > > > run in vCMDQ mode on the command line try-and-fail doesn't sound so > > > bad. > > > > > > And I guess we don't need a "sub type" just a "requested type" where 0 > > > means return the best one and non-zero means return a specific one or > > > fail with EOPNOTSUPP. > > > > OK. I think this would work: > > hw_info (req_type=0) => out_data_type=SMMU_V3, flags=HAS_CMDQV > > hw_info (req_type=CMDQV) => out_data_type=CMDQV, flags=0 > > Yeah > > > Or, would it be simpler by having a sub_data_uptr: > > hw_info => out_data_type=SMMU_V3, sub_data_type=CMDQV, > > data_uptr=iommu_hw_info_arm_smmuv3, > > sub_data_uptr=iommu_hw_info_tegra241_cmdqv > > ? > > I think the former is simpler to code, you can just add the req_type > to the signatures and if the driver comes back with a type != req_type > the core code will return EOPNOTSUPP
OK. Maybe just turn the out_data_type to be bidirectional? Then we would only need to update the docs: /** * enum iommu_hw_info_type - IOMMU Hardware Info Types - * @IOMMU_HW_INFO_TYPE_NONE: Used by the drivers that do not report hardware - * info + * @IOMMU_HW_INFO_TYPE_NONE: (for output) used by the drivers that do not report + * hardware info + * @IOMMU_HW_INFO_TYPE_DEFAULT: (for input) Used to request the default type * @IOMMU_HW_INFO_TYPE_INTEL_VTD: Intel VT-d iommu info type * @IOMMU_HW_INFO_TYPE_ARM_SMMUV3: ARM SMMUv3 iommu info type + * @IOMMU_HW_INFO_TYPE_TEGRA241_CMDQV: Subtype of ARM SMMUv3 for Tegra241 CMDQV */ enum iommu_hw_info_type { IOMMU_HW_INFO_TYPE_NONE = 0, + IOMMU_HW_INFO_TYPE_DEFAULT = 0, IOMMU_HW_INFO_TYPE_INTEL_VTD = 1, IOMMU_HW_INFO_TYPE_ARM_SMMUV3 = 2, + IOMMU_HW_INFO_TYPE_TEGRA241_CMDQV =3, }; - * @out_data_type: Output the iommu hardware info type as defined in the enum - * iommu_hw_info_type. + * @data_type: Bidirectional property. + * Input the requested iommu hardware info type as defined in the + * enum iommu_hw_info_type. Requesting IOMMU_HW_INFO_TYPE_DEFAULT + * lets kernel pick the default type to output, otherwise kernel + * will validate the input type and may reject with -EOPNOTSUPP. + * Output the supported iommu hardware info type as defined in the + * same enum iommu_hw_info_type And similarly in the iommu API kdoc too. > Finally we end up with only one ioctl enum number space for the > types, which seems appealing. Yea. Avoiding a sub enum is nicer. Thanks Nicolin