Re: [Qemu-devel] [PATCH v3] net: Adding netmap network backend

[Luigi Rizzo]

On Mon, Nov 4, 2013 at 9:41 AM, Anthony Liguori <address@hidden> wrote:

On Tue, Oct 29, 2013 at 3:12 AM, Vincenzo Maffione <address@hidden> wrote:
> This patch adds support for a network backend based on netmap.
> netmap is a framework for high speed packet I/O. You can use it
> to build extremely fast traffic generators, monitors, software
> switches or network middleboxes. Its companion software switch
> VALE lets you interconnect virtual machines.
> netmap and VALE are implemented as a non intrusive kernel module,
> support NICs from multiple vendors, are part of standard FreeBSD
> distributions and available in source format for Linux too.

I don't think it's a good idea to support this on Linux hosts.  This
is an out of tree module that most likely will never go upstream.

I don't want to live through another kqemu with this if it eventually
starts to bit-rot.

I believe this is very different from kqemu.

For first, it is just a one-file backend (the patches

to other files are just because there is not yet a way

to automatically generate them; but i am sure qemu

will get there). Getting rid of it, should the code

bit-rot, is completely trivial.

Second, there is nothing linux specific here. Unless configure

determines that the (possibly out of tree, as in Linux,

or in-tree, as in FreeBSD) netmap headers are

installed, it just won't build the backend.

I am not sure if you do not want to support netmap _in general_

(despite it is already upstream in FreeBSD),

or you'd like to put extra checks in ./configure to actually

prevent its use on linux hosts.

Both cases it seems to me a loss of a useful feature with no

real return

>

configure         |  31 ++++

>

 hmp-commands.hx   |   4 +-

>

 net/Makefile.objs |   1 +

>

 net/clients.h     |   5 +

>

 net/net.c         |   6 +

>

 net/netmap.c      | 423 ++++++++++++++++++++++++++++++++++++++++++++++++++++++

>

 qapi-schema.json  |  19 ++-

>

 qemu-options.hx   |   8 ++

>

 8 files changed, 494 insertions(+), 3 deletions(-)

>

 create mode 100644 net/netmap.c

cheers

luigi