Re: [dpdk-dev] [RFC] eal: provide option to set vhost_user socket owner/permissions

[Christian Ehrhardt <christian.ehrhardt@canonical.com>]

Thanks,
great that you added more on CC for a wider discussion - I think that is
the only right way to go.

Just to "defend" a bit - solution a) was created under the special
circumstance that I wanted a workaround that would work today.
But that is/was special to what I package with DPDK 2.2 + OVS 2.5 as of
today - and therefore was the right place for a fast interim fix for me.
I totally agree that the A in EAL was meant for abstraction and we might
want to avoid vhost specific things in there that in the long run.

I like your suggestion of a new API as a proper long term solution, but I
don't feel deeply enough involved yet on the API level to give it any
judgement.
So I look forward for more opinions on it.

P.S. the patch bot hit me hard with 2 pages of space/bracket issues, sorry
for that - but it was only meant as RFC after all :-)


Christian Ehrhardt
Software Engineer, Ubuntu Server
Canonical Ltd

On Tue, Apr 26, 2016 at 6:16 AM, Yuanhan Liu <yuanhan.liu@linux.intel.com>
wrote:

> On Mon, Apr 25, 2016 at 11:18:16AM +0200, Christian Ehrhardt wrote:
> > The API doesn't hold a way to specify a owner/permission set for
> vhost_user
> > created sockets.
>
> Yes, it's kind of like a known issue. So, thanks for bringing it, with
> a solution, for dicussion (cc'ed more people).
>
> > I don't even think an API change would make that much sense.
> >
> > Projects consuming DPDK start to do 'their own workarounds' like
> openvswitch
> > https://patchwork.ozlabs.org/patch/559043/
> > https://patchwork.ozlabs.org/patch/559045/
> > But for this specific example they are blocked/stalled behind a bigger
> > rework (https://patchwork.ozlabs.org/patch/604898/).
> > Also one could ask why each project would need their own workaround.
> >
> > At the same time - as I want it for existing code linking against DPDK I
> > wanted to avoid changing API/ABI. That way I want to provide something
> existing
> > users could utilize. So I created a DPDK EAL commandline option based
> ideas in
> > the former patches.
> >
> > For myself I consider this a nice interim solution for existing released
> > Openvswitch+DPDK solution. And I intend to put it as delta into the DPDK
> 2.2
> > currently packaged in Ubuntu to get it working more smoothly with
> > openvswitch 2.5.
> >
> > But I'd be interested if DPDK in general would be interested in:
> > a) an approach like this?
>
> You were trying to add a vhost specific stuff as EAL command option,
> which is something we might should try to avoid.
>
> > b) would prefer a change of the API?
>
> Adding a new option to the current register API might will not work well,
> either. It gives you no ability to do a dynamic change later. I mean,
> taking OVS as an example, OVS provides you the flexible ability to do all
> kinds of configuration in a dynamic way, say number of rx queues. If we
> do the permissions setup in the register time, there would be no way to
> change it later, right?
>
> So, I'm thinking that we may could add a new API for that? It then would
> allow applications to change it at anytime.
>
> > c) consider it an issue of consuming projects and let them take care?
>
> It's not exactly an issue of consuming projects; we created the socket
> file after all.
>
> And I'd like to hear what others would say.
>
> Thanks.
>
>         --yliu
>