RE: [PATCH v5 10/11] iommu/vt-d: Add nested domain allocation

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Thursday, September 21, 2023 3:55 PM
> 
> 
> +	if (hwpt_type != IOMMU_HWPT_TYPE_DEFAULT &&
> +	    hwpt_type != IOMMU_HWPT_TYPE_VTD_S1)
> +		return ERR_PTR(-EINVAL);
> +
> +	if ((hwpt_type == IOMMU_HWPT_TYPE_DEFAULT) == !!parent)
> +		return ERR_PTR(-EINVAL);

this is probably too strict. What about intel-iommu driver supports a
IOMMU_HWPT_TYPE_VTD_S2 later for some tweak w/o nesting?

let's make the parent match specific to VTD_S1 type.

> +
> +	if (parent && request_nest_parent)
> +		return ERR_PTR(-EINVAL);

this check should be moved to iommufd?