Re: [Qemu-devel] Is network backend netmap worth keeping?

[Vincenzo Maffione]

Yes, indeed.
Netmap is actively maintained on FreeBSD, and QEMU is packaged on FreeBSD
with netmap support enabled.
Also keep in mind that, differently from Linux, the (current) tap driver on
FreeBSD does not support offloads (e.g. IFF_VNET_HDR, TUNSETVNETHDRSIZE and
so on). On the contrary, netmap (VALE) supports the same offloads as tap
does on Linux. This makes inter-VM networking with VALE more appealing on
FreeBSD.

Cheers,
  Vincenzo

Il giorno gio 8 ago 2019 alle ore 15:36 Philippe Mathieu-Daudé <
address@hidden> ha scritto:

> On 8/8/19 7:38 AM, Jason Wang wrote:
> >
> > On 2019/8/8 下午12:48, 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?
> >>
> >> Why is the QEMU netmap backend worth keeping?
> >>
> >> Who is using the netmap backend?
> >
> >
> > Netmap was supported by freebsd:
> > https://www.freebsd.org/cgi/man.cgi?query=netmap&sektion=4. So I guess
> > there should be real users.
> >
> >
> >>
> >> How do they obtain a netmap-enabled QEMU?  Compile it from sources
> >> themselves?
> >
> >
> > Yes.
>
> Hmm at least on the FreeBSD setup by vmtest (12.0-RELEASE r341666) we
> don't need to build it from source:
>
> $ make vm-build-freebsd V=1 DEBUG=1
> [...]
> netmap support    yes
> [...]
>
> $ fgrep -r CONFIG_NETMAP .
> ./config-host.mak:CONFIG_NETMAP=y
>