RE: [PATCH v1 5/8] vfio/type1: Report 1st-level/stage-1 format to userspace

Liu, Yi L
2020-04-08T01:02:58Z

> From: Liu, Yi L
> Sent: Tuesday, April 7, 2020 5:43 PM
>
> > We don't, the PASID spaces are per-VM on Arm, so this function should
> > consult the IOMMU driver before setting flags. As you said on patch 3,
> > nested doesn't necessarily imply PASID support. The SMMUv2 does not
> > support PASID but does support nesting stages 1 and 2 for the IOVA space.
> > SMMUv3 support of PASID depends on HW capabilities. So I think this
> > needs to be finer grained:
> >
> > Does the container support:
> > * VFIO_IOMMU_PASID_REQUEST?
> > -> Yes for VT-d 3
> > -> No for Arm SMMU
> > * VFIO_IOMMU_{,UN}BIND_GUEST_PGTBL?
> > -> Yes for VT-d 3
> > -> Sometimes for SMMUv2
> > -> No for SMMUv3 (if we go with BIND_PASID_TABLE, which is simpler due to
> > PASID tables being in GPA space.)
> > * VFIO_IOMMU_BIND_PASID_TABLE?
> > -> No for VT-d
> > -> Sometimes for SMMUv3
> >
> > Any bind support implies VFIO_IOMMU_CACHE_INVALIDATE support.
>
> good summary. do you expect to see any
please ignore this message. I planned to ask if possible to report
VFIO_IOMMU_CACHE_INVALIDATE only (no bind support). But I stopped
typing it when I came to believe it's unnecessary to report it if
there is no bind support.

Regards,
Yi Liu