Re: [PATCH/RFC 7/9] Virtual network guest device driver

Rusty Russell
2007-05-14T02:39:15Z

On Sun, 2007-05-13 at 11:49 -0500, Anthony Liguori wrote:
> Dor Laor wrote:
> > Furthermore,
> >
> >> the plan is to completely rearchitect the netback/netfront protocol for
> >> the next Xen release (this effort is referred to netchannel2).
> > It's looks like generalizing all the level 0,1,2 features plus
> > performance optimizations. It's not something we couldn't upgrade to.
>
> I'm curious what Rusty thinks as I do not know nearly enough about the
> networking subsystem to make an educated statement here. Would it be
> better to just try and generalize netback/netfront or build something
> from scratch? Could the lguest driver be generalized more easily?

In turn, I'm curious as to Herbert's opinions on this.

The lguest netdriver has only two features: it's small, and it does
multi-way inter-guest networking as well as guest<->host. It's not
clear how much the latter wins in real life over a point-to-point comms
system.

My interest is in a common low-level transport. My experience is that
it's easy to create an efficient comms channel between a guest and host
(ie. one side can access the others' memory), but it's worthwhile trying
for a model which transparently allows untrusted comms (ie.
hypervisor-assisted to access the other guest's memory). That's easier
if you only want point-to-point (see lguest's io.c for a more general
solution).

Cheers,
Rusty.