Re: [PATCH v4 18/23] iommu/arm-smmu-v3-iommufd: Support implementation-defined hw_info

Nicolin Chen
2025-05-15T18:52:32Z

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:
> > Repurpose the @__reserved field in the struct iommu_hw_info_arm_smmuv3,
> > to an HW implementation-defined field @impl.
>
> It would be nicer to have a tegra/cmdq specific struct and a way for
> iommu_hw_info to select it. 'impl' isn't going to scale very well if
> something else wants to use this.
>
> We have out_data_type but we could have an input sub_data_type too. 0
> means what we have today, then a simple enum to select another info
> struct.

So, there will be two hw_info calls back to back right?

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?

Thanks
Nicolin