Re: (proposal) RE: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs

joro
2020-11-03T09:52:22Z

On Mon, Oct 12, 2020 at 08:38:54AM +0000, Tian, Kevin wrote:
> > From: Jason Wang <jasowang@redhat.com>

> > Jason suggest something like /dev/sva. There will be a lot of other
> > subsystems that could benefit from this (e.g vDPA).

Honestly, I fail to see the benefit of offloading these IOMMU specific
setup tasks to user-space.

The ways PASID and the device partitioning it allows are used are very
device specific. A GPU will be partitioned completly different than a
network card. So the device drivers should use the (v)SVA APIs to setup
the partitioning in a way which makes sense for the device.

And VFIO is of course a user by itself, as it allows assigning device
partitions to guests. Or even allow assigning complete devices and allow
the guests to partition it themselfes.

So having said this, what is the benefit of exposing those SVA internals
to user-space?

Regards,

Joerg