On Mon, Nov 4, 2013 at 12:54 PM, Anthony Liguori <anth...@codemonkey.ws>wrote:
> On Mon, Nov 4, 2013 at 11:51 AM, Luigi Rizzo <ri...@iet.unipi.it> wrote: > > On Mon, Nov 04, 2013 at 10:20:12AM -0800, Anthony Liguori wrote: > >> On Mon, Nov 4, 2013 at 10:08 AM, Luigi Rizzo <ri...@iet.unipi.it> > wrote: > > ... > >> >> On Tue, Oct 29, 2013 at 3:12 AM, Vincenzo Maffione < > v.maffi...@gmail.com> > >> >> 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. > >> > >> Without being in upstream Linux, we have no guarantee that the API/ABI > >> will be stable over time. I suspect it's also very unlikely that any > >> many stream distro will include these patches meaning that the number > >> of users that will test this is very low. > >> > >> I don't think just adding another backend because we can helps us out > >> in the long term. Either this is the Right Approach to networking and > >> we should focus on getting proper kernel support or if that's not > >> worth it, then there's no reason to include this in QEMU either. > > > > anthony, > > i'd still like you to answer the question that i asked before: > > > > are you opposed to netmap support just for linux, or you > > oppose to it in general (despite netmap being already > > upstream in FreeBSD) ? > > > > Your reasoning seems along the lines "if feature X is not upstream > > in linux we do not want to support it". > > Yes. This is the historic policy we have taken for any feature. I > have no problem with netmap being used on FreeBSD hosts but I think it > should not be enabled on Linux hosts. > ok thanks for the clarification. S o I misunderstood , the policy is "if not upstream in linux, we do not want to support it _on linux_". A fundamental difference :) So in ./configure we must change to 'netmap="no"' in the initial section to disable it by default, and add a line 'netmap=""' in the FreeBSD section to enable autodetect there. cheers luigi
