On Wed, Jun 24, 2020 at 01:55:15AM -0700, Liu Yi L wrote:
> +/*
> + * struct iommu_nesting_info - Information for nesting-capable IOMMU.
> + *				user space should check it before using
> + *				nesting capability.
> + *
> + * @size:	size of the whole structure
> + * @format:	PASID table entry format, the same definition with
> + *		@format of struct iommu_gpasid_bind_data.
> + * @features:	supported nesting features.
> + * @flags:	currently reserved for future extension.
> + * @data:	vendor specific cap info.
> + *
> + * +---------------+----------------------------------------------------+
> + * | feature       |  Notes                                             |
> + * +===============+====================================================+
> + * | SYSWIDE_PASID |  Kernel manages PASID in system wide, PASIDs used  |
> + * |               |  in the system should be allocated by host kernel  |
> + * +---------------+----------------------------------------------------+
> + * | BIND_PGTBL    |  bind page tables to host PASID, the PASID could   |
> + * |               |  either be a host PASID passed in bind request or  |
> + * |               |  default PASIDs (e.g. default PASID of aux-domain) |
> + * +---------------+----------------------------------------------------+
> + * | CACHE_INVLD   |  mandatory feature for nesting capable IOMMU       |
> + * +---------------+----------------------------------------------------+

This feature description is vague about what CACHE_INVLD does and how to
use it. If I understand correctly, the presence of this feature means
that VFIO_IOMMU_NESTING_OP_CACHE_INVLD must be used?

The same kind of clarification could be done for SYSWIDE_PASID and
BIND_PGTBL too.

Stefan