Re: [virtio-comment] [PROPOSAL] Virtio Over Fabrics(TCP/RDMA)

[Stefan Hajnoczi <stefanha@redhat.com>]

On Mon, Apr 24, 2023 at 11:40:02AM +0800, Jason Wang wrote:
> On Sun, Apr 23, 2023 at 7:31âPM zhenwei pi <pizhenwei@bytedance.com> wrote:
> > I develop an kernel initiator(unstable, WIP version, currently TCP/RDMA
> > supported):
> > https://github.com/pizhenwei/linux/tree/virtio-of-github
> 
> A quick glance at the code told me it's a mediation layer that convert
> descriptors in the vring to the fabric specific packet. This is the
> vDPA way.
>
> If we agree virtio of fabic is useful, we need invent facilities to
> allow building packet directly without bothering the virtqueue (the
> API is layout independent anyhow).

I agree. vrings makes sense for RDMA, but I think virtio_fabrics.c
should not be dependent on vrings.

Linux struct virtqueue is independent of vrings but the implementation
currently lives in virtio_ring.c because there has never been a
non-vring transport before.

It would be nice to implement virtqueue_add_sgs() specifically for
virtio_tcp.c without the use of vrings. Is a new struct
virtqueue_ops needed with with .add_sgs() and related callbacks?

Luckily the <linux/virtio.h> API already supports this abstraction and
changes to existing device drivers should be unnecessary or minimal.

Stefan

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