Re: [dpdk-dev] [PATCH] net/i40e: enable statistic reset for VF

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2017-03-17 03:28, Zhang, Helin:
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > 2017-02-23 13:27, Qi Zhang:
> > >  static void
> > > +i40evf_dev_stats_reset(struct rte_eth_dev *dev) {
> > > +	struct i40e_vf *vf = I40EVF_DEV_PRIVATE_TO_VF(dev->data-
> > >dev_private);
> > > +	/* only DPDK PF support this */
> > > +	if (vf->version_major == I40E_DPDK_VERSION_MAJOR) {
> > > +		if (i40evf_reset_statistics(dev))
> > > +			PMD_DRV_LOG(ERR, "Reset statistics failed");
> > > +	}
> > > +}
> > 
> > One more SR-IOV feature not supported with a Linux PF.
> > The basic stats feature must be marked as partially supported in
> > 	doc/guides/nics/features/i40e_vf.ini
> > See also this email:
> > 	http://dpdk.org/ml/archives/dev/2017-March/060063.html
> > 
> > I wonder whether we should allow such divergence between PF
> > implementations. Intel committed to avoid such fragmentation and keep the
> > SR-IOV messaging standard but it does not happen.
> > It is said that we must allow fast innovation in DPDK space.
> > I agree but we should also target a good usability of the VF drivers, allowing to
> > replace the PF implementations as needed.
> 
> Hi Thomas
> 
> I think I need to clarify a little bit here.
> I think we will try our best, but I don't think we can commit. As they are on
> totally different community, and of cause code repositories.
> 
> > 
> > Here is my suggestion: let's accept a VF feature only if the PF support is
> > submitted to both dpdk.org and kernel.org mailing lists.
> > I ask to add this topic to the next techboard meeting.
> 
> Sorry, technically I disagree with this suggestion, as I don't understand why!
> I was told DPDK is not Linux, and Linux is not DPDK. Why we want to add this
> dependency on Linux PF host driver? And why just on PF/VF driver feature only?
> I think if we can have any good innovative idea on DPDK first, why not just
> have it on DPDK? Then Linux or even other OS/community/Company can learn
> from DPDK and develop their own.

It is really a general problem.
Here you are adding a feature in a VF driver. But it does not work with
some PF drivers. We have the same problem when adding a feature which
does not work on BSD or on a CPU architecture.
Generally speaking, we have a usability issue when a feature works only
with a given environment.
And it is worst in the SR-IOV case because a VM can migrate from an
hypervisor (with a given PF) to another (and different) one.