RE: [PATCH v3 13/14] vfio: Document dual stage control

["Liu, Yi L" <yi.l.liu@intel.com>]

> From: Stefan Hajnoczi <stefanha@gmail.com>
> Sent: Monday, June 29, 2020 5:22 PM
> 
> On Wed, Jun 24, 2020 at 01:55:26AM -0700, Liu Yi L wrote:
> > +Details can be found in Documentation/userspace-api/iommu.rst. For
> > +Intel VT-d, each stage 1 page table is bound to host by:
> > +
> > +    nesting_op->flags = VFIO_IOMMU_NESTING_OP_BIND_PGTBL;
> > +    memcpy(&nesting_op->data, &bind_data, sizeof(bind_data));
> > +    ioctl(container->fd, VFIO_IOMMU_NESTING_OP, nesting_op);
> > +
> > +As mentioned above, guest OS may use stage 1 for GIOVA->GPA or GVA->GPA.
> > +GVA->GPA page tables are available when PASID (Process Address Space
> > +GVA->ID)
> > +is exposed to guest. e.g. guest with PASID-capable devices assigned.
> > +For such page table binding, the bind_data should include PASID info,
> > +which is allocated by guest itself or by host. This depends on
> > +hardware vendor e.g. Intel VT-d requires to allocate PASID from host.
> > +This requirement is defined by the Virtual Command Support in VT-d
> > +3.0 spec, guest software running on VT-d should allocate PASID from
> > +host kernel. To allocate PASID from host, user space should +check
> > +the IOMMU_NESTING_FEAT_SYSWIDE_PASID
> 
> s/+check/check/g

got it.

> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

thanks :-)

Regards,
Yi Liu