Hi Stefan, > From: Stefan Hajnoczi <stefanha@xxxxxxxxx> > Sent: Monday, June 29, 2020 5:25 PM > > 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. For SYSWIDE_PASID and BIND_PGTBL, yes, presence of the feature bit means must use. So the two are requirements to user space if it wants to setup nesting. While for CACHE_INVLD, it's kind of availability here. How about removing CACHE_INVLD as presence of BIND_PGTBL should indicates support of CACHE_INVLD? Regards, Yi Liu > Stefan
