Re: [virtio-dev] [PATCH v5 01/10] vhost-user: add vhost-user device type

[Nikos Dragazis <ndragazis@arrikto.com>]

On 23/7/20 9:15 Ï.Î., Stefan Hajnoczi wrote:

> On Fri, Jul 17, 2020 at 02:17:13PM +0300, Nikos Dragazis wrote:
> > On 17/7/20 12:26 Î.Î., Stefan Hajnoczi wrote:
> >
> > > On Thu, Jul 16, 2020 at 05:45:47PM +0100, Alex BennÃe wrote:
> > > > Nikos Dragazis <ndragazis@arrikto.com> writes:
> > > > > diff --git a/virtio-vhost-user.tex b/virtio-vhost-user.tex
> > > > > new file mode 100644
> > > > > index 0000000..ac96dc2
> > > > > --- /dev/null
> > > > > +++ b/virtio-vhost-user.tex
> > > > > @@ -0,0 +1,292 @@
> > > > > +\section{Vhost-user Device Backend}\label{sec:Device Types / Vhost-user Device Backend}
> > > > > +
> > > > > +The vhost-user device backend facilitates vhost-user device emulation through
> > > > > +vhost-user protocol exchanges and access to shared memory.  Software-defined
> > > > > +networking, storage, and other I/O appliances can provide services through this
> > > > > +device.
> > > > > +
> > > > > +This section relies on definitions from the \hyperref[intro:Vhost-user
> > > > > +Protocol]{Vhost-user Protocol}.  Knowledge of the vhost-user protocol is a
> > > > > +prerequisite for understanding this device.
> > > > > +
> > > > > +The \hyperref[intro:Vhost-user Protocol]{Vhost-user Protocol} was originally
> > > > > +designed for processes on a single system communicating over UNIX domain
> > > > > +sockets.  The virtio vhost-user device backend allows the vhost-user slave to
> > > > > +communicate with the vhost-user master over the device instead of a UNIX domain
> > > > > +socket.  This allows the slave and master to run on two separate
> > > > > systems such
> > > > I realise we already have the terms master/slave baked into the
> > > > vhost-user spec but perhaps we could find better wording? The vhost
> > > > documentation describes thing in terms of who owns the virtqueues (the
> > > > drive) and who processes the requests (the device). There may be better
> > > > terminology to use.
> > > "backend" is now commonly used instead of "slave". There is no new term
> > > for "master" yet. I suggest replacing "slave" with "backend" in this
> > > patch.
> > Makes sense. Some observations:
> >
> > 1. Since "backend" is used instead of "slave", why "frontend" is not
> >  ÂÂ used instead of "master"? Also, why does the vhost-user spec use the
> >  ÂÂ terms"slave" and "backend" interchangeably and doesn't just drop the
> >  ÂÂ term"slave"completely?
> Using "frontend" and "backend" sounds good. Do you want to send a patch
> to qemu.git docs/interop/vhost-user.rst?

OK, I will.

> The vhost-user spec grew organically and few people have spent time on
> polishing it, making it consistent, etc.
>
> Stefan