MLX5 VF stops transmitting when the Physical Function is added to a Linux bridge

[Antonio Di Bacco]

Hi Stephen,

I know that the mlx5_core is bifurcated, I did another test,  I just
added one of the VF to the bridge but I see that testpmd using other
VFs suffer the same problem.
When I add to the bridge another interface (not the one with VF but a
simple 1Gbps named ens5f0) I see that VFs used by testpmd stop
working.

If I give the command ifconfig ens5f0 down, then, the testpmd VF
resumes transmission.

Best regards,
Antonio.


On Mon, Mar 25, 2024 at 6:14 PM Stephen Hemminger
<stephen at networkplumber.org> wrote:
>
> On Mon, 25 Mar 2024 15:59:36 +0100
> Antonio Di Bacco <a.dibacco.ks at gmail.com> wrote:
>
> > I have a Connect X5 card (PF ens1f0np0) directly connected to another server:
> >
> > 1) create VF on PF on both servers
> > 2) change mac address of VFs to my own addressing
> > 3) start testpmd on server 1 in txonly mode to transmit to server 0
> > 4) start testpmd on server 0 in rxonly mode to receive
> > 5) everything is fine, I keep receiving packets on node-0
> >
> > Now, on server 1 I add the PF to a linux bridge, and everything's still fine.
> >
> > If I add another interface (a simple 1Gbps with no VF, ens5f0)  to the
> > linux bridge, then, I don't receive anymore packets on node-0
> >
> > If I remove the ens5f0 from the bridge or I put down the ens5f0 the
> > traffic flow restarts.
> >
> > I understand that DPDK uses the VF directly with no dependencies on
> > the kernel. How can operations on the kernel side (like adding an
> > interface to bridge) can affect the VF?
> >
> >
> > Best regards,
> > Antonio.
>
> Mellanox is bifurcated driver, so kernel and DPDK interact.
> Adding device to bridge will change MAC address.