Re: [dpdk-dev] [dpdk-dev, 5/7] net/mlx5: add port representor awareness

["Xueming(Steven) Li" <xuemingl@mellanox.com>]

> -----Original Message-----
> From: Adrien Mazarguil <adrien.mazarguil@6wind.com>
> Sent: Tuesday, June 12, 2018 9:20 PM
> To: Xueming(Steven) Li <xuemingl@mellanox.com>
> Cc: Shahaf Shuler <shahafs@mellanox.com>; dev@dpdk.org
> Subject: Re: [dpdk-dev,5/7] net/mlx5: add port representor awareness
> 
> On Mon, Jun 11, 2018 at 01:05:55PM +0000, Xueming(Steven) Li wrote:
> > Hi Adrien,
> >
> > Couldn't find your original email from inbox anyway, have to start a new thread here.
> <snip>
> > > +static int
> > > +mlx5_cmp_ibv_name(const void *a, const void *b) {
> > > +	const char *name_a = (*(const struct ibv_device *const *)a)->name;
> > > +	const char *name_b = (*(const struct ibv_device *const *)b)->name;
> > > +	size_t i = 0;
> > > +
> > > +	while (name_a[i] && name_a[i] == name_b[i])
> > > +		++i;
> > > +	return atoi(name_a + i) - atoi(name_b + i);
> >
> > Comparing "1" and "10" here will return 0, does this matter?
> 
> Sure it does! The whole point of this function is precisely to avoid this kind of issues. I'll fix it
> for v2, thanks.
> 
> <snip>
> > > +	if (n > 1) {
> > > +		/*
> > > +		 * The existence of several matching entries means port
> > > +		 * representors have been instantiated. No existing Verbs
> > > +		 * call nor /sys entries can tell them apart at this point.
> > > +		 *
> > > +		 * While definitely hackish, assume their names are numbered
> > > +		 * based on order of creation with master device first,
> > > +		 * followed by first port representor, followed by the
> > > +		 * second one and so on.
> > > +		 */
> > > +		DRV_LOG(WARNING,
> > > +			"probing device with port representors involves"
> > > +			" heuristics with uncertain outcome");
> > > +		qsort(ibv_match, n, sizeof(*ibv_match), mlx5_cmp_ibv_name);
> > > +		DRV_LOG(WARNING, "assuming \"%s\" is the master device",
> > > +			ibv_match[0]->name);
> > > +		for (ret = 1; ret < n; ++ret)
> > > +			DRV_LOG(WARNING,
> > > +				"assuming \"%s\" is port representor #%d",
> > > +				ibv_match[ret]->name, ret - 1);
> >
> > Such dump will appear when attaching each rep port, how about just do
> > it for PF in DEBUG level?
> 
> It occurs only once when probing the master device and detecting the presence of representors, not for
> each of them.
> 
> I prefer to leave it as a warning because this detection approach, while an undeniable improvement
> over not checking anything and ending up configuring the wrong netdevice, is unfortunately not 100%
> accurate. This will be improved, however users must be warned of possible issues in the meantime.

Yes, the list is different when VF number changed outside, a full dump should be helpful, how about set it to DEBUG or INFO level?
Users don't need to know this, just for debug purpose.

> 
> --
> Adrien Mazarguil
> 6WIND