[ovs-dev] [PATCH 2/2] dpdk docs: Drop file share in libvirt config.

[Stephen Finucane]

On Thu, 2018-04-12 at 08:24 +0100, Lam, Tiago wrote:
> On 11/04/2018 15:03, Stephen Finucane wrote:
> > On Wed, 2018-04-11 at 09:54 -0400, Aaron Conole wrote:
> > > Tiago Lam <tiago.lam at intel.com> writes:
> > > 
> > > > When explaining on how to add vhost-user ports to a guest, using
> > > > libvirt, the following piece of configuration is used:
> > > >      <disk type='dir' device='disk'>
> > > >        <driver name='qemu' type='fat'/>
> > > >        <source dir='/usr/src/dpdk-stable-17.11.1'/>
> > > >        <target dev='vdb' bus='virtio'/>
> > > >        <readonly/>
> > > >      </disk>
> > > > 
> > > > This is used to facilitate sharing of a DPDK directory between the host
> > > > and the guest. However, for this to work selinux also needs to be
> > > > configured (or disabled).  Furthermore, if one is using Ubuntu, libvirtd
> > > > would need to be added to complain only in AppArmor. Instead, in [1] it
> > > > is advised to use wget to get the DPDK sources over the internet, which
> > > > avoids this differentiation. Thus, we drop this piece of configuration
> > > > here as well and keep the example configuration as simple as possible.
> > > > 
> > > > This has been verified on both a Fedora 27 image and a Ubuntu 16.04 LTS
> > > > image.
> > > > 
> > > > [1] http://docs.openvswitch.org/en/latest/topics/dpdk/vhost-user/#dpdk-in-the-guest
> > > > 
> > > > Signed-off-by: Tiago Lam <tiago.lam at intel.com>
> > > > ---
> > > > 
> > > > CC'ed Stephen,
> > > > 
> > > > I took the liberty of removing your TODO from here, as I read it to be related
> > > > to the (now removed) SELinux instruction below. If you think it should still be
> > > > there let me know and I'll gladly send a v2.
> > > 
> > > I think it should remain until the selinux issues have been addressed.
> > > 
> > > Is there a list somewhere of the AVC denials?  Maybe it makes sense to
> > > allow them.
> > 
> > If I'm reading this correctly, Tiago is saying these exceptions only
> > happen because we're sharing an arbitrary directory with the guest to
> > avoid downloading the DPDK sources twice. Given that there's a valid
> > workaround (just fetching sources twice), simply removing that section
> > of the XML removes the need to disable SELinux. If so, dropping the
> > warning does make sense in my mind.
> > 
> > Stephen
> > 
> 
> Thanks, Stephen. Yeah, that's what I was aiming at. In order to get the 
> file sharing working properly, one must fiddle around with either 
> SELinux or AppArmor, and that seems to be the sole reason why 
> `setenforce 0` is there. Losing the dependency on the file sharing means 
> we can lose any instructions that tell the user how to fiddle with 
> either of those systems.
> 
> Just a note though, in that the user won't have to download the DPDK 
> sources twice, only once. Following the guide, the user first sets up 
> the vhost-user ports using libvirt, and once inside the VM he should 
> follow up on running `testpmd` inside the guest [1], where he will be 
> instructed to download the DPDK sources. This makes this piece of the 
> docs a bit more consistent, I think.
> 
> [1] 
> http://docs.openvswitch.org/en/latest/topics/dpdk/vhost-user/#dpdk-in-the-guest

That all sounds fair to me.

Acked-by: Stephen Finucane <stephen at that.guru>