Re: [Qemu-devel] Insane virtio-serial semantics

[Anthony Liguori]

On 12/08/2011 04:11 AM, Markus Armbruster wrote:
> Anthony Liguori<address@hidden>  writes:
> > And yes, I can't help but think of Dave Millers comments long ago that
> > any PV transport is eventually going to reinvent TCP, poorly.
>
> No doubt then, no doubt now.  But if I remember correctly, we didn't
> create virtio-serial because we thought we could do better than TCP/IP.
> We thought we need a zero-config communication channel that doesn't
> interfere in any way with the guest's networking.  Since the network
> folks were unwilling to give us one ("use TCP already"), we looked for
> another bare metal thing to imitate, and chose serial lines.
>
> Now, comparing serial lines to TCP/IP makes no sense.  Different layers.

virtio-serial is not a serial line.  It attempts to have connection semantics 
(like a socket) which is what the fundamental problem is.

It probably makes sense to have a virtio-serial2 that is exposed to the guest as 
a tty device and stick strictly to serial semantics.

> Layering a real network protocol on top of serial line is possible; SLIP
> exists.  But as long as we insist on "don't interfere in any way with
> the guest's networking", we can't use TCP, and thus are doomed to
> reinvent it, poorly.

I think we just got too clever.

Regards,

Anthony Liguori