Re: [dpdk-dev] RFC - vdev_netvsc automatic blacklisting

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 12 Jun 2019 05:15:47 +0000
Matan Azrad <matan@mellanox.com> wrote:

>  From: Stephen Hemminger 
> > > Hi Stephen
> > >
> > > From: Stephen Hemminger  
> > > > When using DPDK on Azure it is common to have one non-DPDK  
> > interface.  
> > > > If that non-DPDK interface is present vdev_netvsc correctly skip it.
> > > > But if the non-DPDK has accelerated networking the Mellanox driver
> > > > will still get associated with DPDK (and break connectivity).
> > > >
> > > > The current process is to tell users to do whitelist or blacklist
> > > > the PCI
> > > > device(s) not used for DPDK. But vdev_netvsc already is doing a lot
> > > > of looking at devices and VF devices.
> > > >
> > > > Could vdev_netvsc just do this automatically by setting devargs for
> > > > the VF to blacklist?  
> > >
> > >
> > > There is way to blacklist a device by setting it a rout\IP\IPv6, from the  
> > VDEV_NETVSC doc:  
> > > "Not specifying either iface or mac makes this driver attach itself to all  
> > unrouted NetVSC interfaces found on the system. Specifying the device
> > makes this driver attach itself to the device regardless the device routes."  
> > >
> > > So, we are expecting that used VFs will be with a rout and DPDK VFs will not  
> > be with a rout.  
> > >
> > > Doesn't it enough?
> > >
> > >
> > > Matan  
> > 
> > I am talking about if eth0 has a route, it gets skipped but the associated MLX
> > SR-IOV device does not. When the MLX device is then configured for DPDK, it
> > breaks it for use by kernel; and therefore connectivity with the VM is lost.  
> 
> Ok, I think I got you.
> You want to blacklist the PCI device which its netvsc net-device is detected as routed. Do you?
> 
> If so,
> 
> I don't think that probing the pci device hurts the connectivity, only the configuration should hurt it.
> 
> It means that the application configures the device and hurt it.
> Doesn't it an application issue? 
> 
> Matan

Actually probing does hurt, it corrupts the MLX driver.
In theory, the driver supports bifurcated but in practice it is greedy and grabs all flows.