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

2017-03-17 09:45, Zhang, Helin:

From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com] 

quoted

2017-03-17 03:28, Zhang, Helin:

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From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]

quoted

2017-02-23 13:27, Qi Zhang:

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 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.

What prevent you from submitting your code to the kernel community?
Note that your statement does not respect the agreed policy:
	http://dpdk.org/ml/archives/dev/2017-January/055224.html
	http://dpdk.org/doc/guides/contributing/design.html#pf-and-vf-considerations

quoted

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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.

Yes, I understood that's the reality and the issue. But I don't think we can address it with your suggestion.
Linux is just one of the OS, as you said, FreeBSD, Windows, VMWare,  ...

I am talking about migration from a KVM to another one.
So BSD, Windows and VMware are irrelevant.

I'd suggest to start another discussion on the tech board to solve that problem, but not limit
adding new features. They are different topics and things, based on my understanding.

Helin, you just want to add your new code and hide issues.
You don't even bother to document the limitations or the partial support
as I have suggested earlier.
As a maintainer, I have to check the quality and the usability.
I can tell you that I stack the promises "I will fix it later" and
we are still waiting for a lot of them.
That's why, even if you think it is not related, we need sometimes
to block things until they are properly done and completed.