Re: [PATCH V3 0/7] mdev based hardware virtio offloading support

[Jason Wang]

On 2019/10/15 äå1:49, Stefan Hajnoczi wrote:
> On Fri, Oct 11, 2019 at 04:15:50PM +0800, Jason Wang wrote:
> > There are hardware that can do virtio datapath offloading while having
> > its own control path. This path tries to implement a mdev based
> > unified API to support using kernel virtio driver to drive those
> > devices. This is done by introducing a new mdev transport for virtio
> > (virtio_mdev) and register itself as a new kind of mdev driver. Then
> > it provides a unified way for kernel virtio driver to talk with mdev
> > device implementation.
> >
> > Though the series only contains kernel driver support, the goal is to
> > make the transport generic enough to support userspace drivers. This
> > means vhost-mdev[1] could be built on top as well by resuing the
> > transport.
> >
> > A sample driver is also implemented which simulate a virito-net
> > loopback ethernet device on top of vringh + workqueue. This could be
> > used as a reference implementation for real hardware driver.
> >
> > Consider mdev framework only support VFIO device and driver right now,
> > this series also extend it to support other types. This is done
> > through introducing class id to the device and pairing it with
> > id_talbe claimed by the driver. On top, this seris also decouple
> > device specific parents ops out of the common ones.
> I was curious so I took a quick look and posted comments.
>
> I guess this driver runs inside the guest since it registers virtio
> devices?


It could run in either guest or host. But the main focus is to run in 
the host then we can use virtio drivers in containers.


> If this is used with physical PCI devices that support datapath
> offloading then how are physical devices presented to the guest without
> SR-IOV?


We will do control path meditation through vhost-mdev[1] and 
vhost-vfio[2]. Then we will present a full virtio compatible ethernet 
device for guest.

SR-IOV is not a must, any mdev device that implements the API defined in 
patch 5 can be used by this framework.

Thanks

[1] https://lkml.org/lkml/2019/9/26/15

[2] https://patchwork.ozlabs.org/cover/984763/


> Stefan