RE: [PATCH v1 3/8] vfio/type1: Report PASID alloc/free support to userspace

[Liu, Yi L]

> From: Tian, Kevin <kevin.tian@xxxxxxxxx>
> Sent: Monday, March 30, 2020 5:44 PM
> To: Liu, Yi L <yi.l.liu@xxxxxxxxx>; alex.williamson@xxxxxxxxxx;
> Subject: RE: [PATCH v1 3/8] vfio/type1: Report PASID alloc/free support to
> userspace
> 
> > From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> > Sent: Sunday, March 22, 2020 8:32 PM
> >
> > From: Liu Yi L <yi.l.liu@xxxxxxxxx>
> >
> > This patch reports PASID alloc/free availability to userspace (e.g.
> > QEMU) thus userspace could do a pre-check before utilizing this feature.
> >
> > Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> > CC: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > Cc: Eric Auger <eric.auger@xxxxxxxxxx>
> > Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> > ---
> >  drivers/vfio/vfio_iommu_type1.c | 28 ++++++++++++++++++++++++++++
> >  include/uapi/linux/vfio.h       |  8 ++++++++
> >  2 files changed, 36 insertions(+)
> >
> > diff --git a/drivers/vfio/vfio_iommu_type1.c
> > b/drivers/vfio/vfio_iommu_type1.c index e40afc0..ddd1ffe 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c
> > @@ -2234,6 +2234,30 @@ static int vfio_iommu_type1_pasid_free(struct
> > vfio_iommu *iommu,
> >  	return ret;
> >  }
> >
> > +static int vfio_iommu_info_add_nesting_cap(struct vfio_iommu *iommu,
> > +					 struct vfio_info_cap *caps)
> > +{
> > +	struct vfio_info_cap_header *header;
> > +	struct vfio_iommu_type1_info_cap_nesting *nesting_cap;
> > +
> > +	header = vfio_info_cap_add(caps, sizeof(*nesting_cap),
> > +				   VFIO_IOMMU_TYPE1_INFO_CAP_NESTING,
> > 1);
> > +	if (IS_ERR(header))
> > +		return PTR_ERR(header);
> > +
> > +	nesting_cap = container_of(header,
> > +				struct vfio_iommu_type1_info_cap_nesting,
> > +				header);
> > +
> > +	nesting_cap->nesting_capabilities = 0;
> > +	if (iommu->nesting) {
> 
> Is it good to report a nesting cap when iommu->nesting is disabled? I suppose the
> check should move before vfio_info_cap_add...

oops, yes it.

> 
> > +		/* nesting iommu type supports PASID requests (alloc/free)
> > */
> > +		nesting_cap->nesting_capabilities |=
> > VFIO_IOMMU_PASID_REQS;
> 
> VFIO_IOMMU_CAP_PASID_REQ? to avoid confusion with ioctl cmd
> VFIO_IOMMU_PASID_REQUEST...

got it.

Thanks,
Yi Liu