Re: [Qemu-devel] Is network backend netmap worth keeping? (was: [PATCH v2 27/29] Include sysemu/sysemu.h a lot less)

[Stefano Garzarella]

On Thu, Aug 08, 2019 at 06:48:25AM +0200, Markus Armbruster wrote:
> Please excuse the attention-grabbing subject.
> 
> Philippe Mathieu-Daudé <address@hidden> writes:
> 
> > On 8/7/19 10:16 PM, Markus Armbruster wrote:
> [...]
> >> Can you tell me offhand what I have to install so configure enables
> >> CONFIG_NETMAP?
> >
> > The steps are listed in tests/docker/dockerfiles/debian-amd64.docker,
> > but you can get to this point running:
> >
> >   $ make docker-image-debian-amd64 V=1 DEBUG=1
> >
> > This will build the docker image with netmap (so you don't have to mess
> > with your workstation setup), then build QEMU within the image.
> 
> So, to make use of QEMU's netmap backend (CONFIG_NETMAP), you have to
> build and install netmap software from sources.  Which pretty much
> ensures nobody uses it.  It was added in commit 58952137b0b (Nov 2013).
> The commit message points to <http://info.iet.unipi.it/~luigi/netmap/>,
> which gives me "connection timed out" right now.
> 
> On the other hand, it's covered in MAINTAINERS, and has seen
> non-janitorial activity as late as Dec 2018 (commit c693fc748a).
> 
> Luigi, Giuseppe, Vincenzo, what's the status of the netmap project?

I think Giuseppe and Vincenzo are currently maintain netmap.
I worked with them on my master's thesis. :) I can give you some information,
but I'm sure they can be more specific.

More info here: https://github.com/luigirizzo/netmap

> 
> Why is the QEMU netmap backend worth keeping?

Netmap provides a virtual switch (VALE) and netmap pipes that can be
useful for VMs and the netmap backend allows us to use them.

> 
> Who is using the netmap backend?
> 
> How do they obtain a netmap-enabled QEMU?  Compile it from sources
> themselves?

Yes, I think so.

> 
> Would it make sense to have netmap packaged in common Linux distros?
> 

Maybe yes, for the virtual switch (VALE) and netmap pipes there shouldn't
be a problem. To use the network cards, however, you would need the modified
drivers.

Cheers,
Stefano