Re: [dpdk-dev] [PATCH] net/vdev_netvsc: print warning if Mellanox devices are not configured

[Thomas Monjalon <thomas@monjalon.net>]

24/05/2019 18:07, Stephen Hemminger:
> On Fri, 24 May 2019 14:26:40 +0100
> Ferruh Yigit <ferruh.yigit@intel.com> wrote:
> 
> > On 5/23/2019 11:01 PM, Stephen Hemminger wrote:
> > > Several users have run into problems where the MLX drivers were not
> > > enabled in their build. And then trying to run their DPDK
> > > application on Azure. What happens is that all packets
> > > go over the slow path, and failsafe repeatedly probes for never
> > > existing sub-device.
> > > 
> > > Both Mellanox drivers should be checked. MLX4 for current versions,
> > > and MLX5 for future upgrades. This code is only called if Hyper-V/Azure
> > > is detected.
> > > 
> > > Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
> > > ---
> > >  drivers/net/vdev_netvsc/vdev_netvsc.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/drivers/net/vdev_netvsc/vdev_netvsc.c b/drivers/net/vdev_netvsc/vdev_netvsc.c
> > > index 801f54c96e01..64f9dbf66e18 100644
> > > --- a/drivers/net/vdev_netvsc/vdev_netvsc.c
> > > +++ b/drivers/net/vdev_netvsc/vdev_netvsc.c
> > > @@ -812,6 +812,13 @@ vdev_netvsc_scan_callback(__rte_unused void *arg)
> > >  	struct rte_devargs *devargs;
> > >  	struct rte_bus *vbus = rte_bus_find_by_name("vdev");
> > >  
> > > +#ifndef RTE_LIBRTE_MLX4_PMD
> > > +	DRV_LOG(WARNING, "Mellanox MLX4 not configured.");
> > > +#endif
> > > +#ifndef RTE_LIBRTE_MLX5_PMD
> > > +	DRV_LOG(WARNING, "Mellanox MLX5 not configured.");
> > > +#endif  
> > 
> > Is it OK a virtual PMD being this much aware of another PMD?
> > Can it be an option to add this check into build system? And if there is direct
> > dependency perhaps even don't compile the 'vdev_netvsc' when none mlx PMD is
> > enabled.
> 
> vdev_netvsc is not a device, it is really just a hack to start other
> device drivers on Hyper-V/Azure.  If the build system supported dependencies
> (like Linux kbuild) this would not be necessary. Meson only does dynamic dependencies
> so that doesn't help.
> 
> This is a warning and not fatal only because application will still at
> least run, and somebody may want to run with SR-IOV with Intel NIC's on Hyper-V.
> 
> 
> The warning is just to give users better immediate feedback rather than
> trying to diagnose poor performance or mystery device not found messages.


It really looks strange to me.
What you need is to fail at compilation if requested PMD is not built.
I would advise to work on a script to configure meson.