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

-----Original Message-----
From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
Sent: Friday, March 17, 2017 6:15 PM
To: Zhang, Helin
Cc: Zhang, Qi Z; techboard@dpdk.org; dev@dpdk.org; Wu, Jingjing; Yigit,
Ferruh; Liang, Cunming; Fastabend, John R
Subject: Re: [dpdk-dev] [PATCH] net/i40e: enable statistic reset for VF

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

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

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

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

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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

There might be some confusing or misunderstanding.
I didn't say we will not submit any patches to kernel community.
We will try to send a few first, and then see what will happen. If it will be
rejected, or take too much time to be accepted. Then we may give up.
If it can be accepted by kernel community, then we may continue.
That's the reality, we will try, but we cannot make any commitment
on having anything in kernel side.

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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!

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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?

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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.

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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.

But as a guest user, he may want to his application running well in all the VMs
without modifying anything, no matter in KVM, Windows, or VMWare.
Do you want to address that issue too?

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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.

There is no doubt, I appreciate your great job!
As I said before, we will try to submit a few first, and see what will happen.
For your doc requests, I think somebody else already replied you.

Sorry, I don't know that you are thinking about KVM migration. I was informed by
Vincent that all DPDK PF host features should be consistent with kernel host driver,
though I am not sure if I missed anything.
OK. Let's focus on the issue. What's the problem statement? What's the solution
well discussed and accepted widely by the community?
BTW, do we need to think about that a bit more? For example, do we need to
think about the similar policy on rte_flow API, ACL and possibly other features?

Thanks,
Helin