Re: [dpdk-dev] [dpdk-stable] [PATCH] net/vmxnet3: keep link state consistent

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 4/17/2018 9:24 PM, Thomas Monjalon wrote:
> 17/04/2018 21:25, Ferruh Yigit:
>> On 4/5/2018 4:01 PM, Chas Williams wrote:
>>> On Thu, Apr 5, 2018 at 6:03 AM, Thomas Monjalon <thomas@monjalon.net> wrote:
>>>> 20/03/2018 15:12, Ferruh Yigit:
>>>>> On 3/18/2018 1:45 AM, Chas Williams wrote:
>>>>>> From: Chas Williams <chas3@att.com>
>>>>>>
>>>>>> The vmxnet3 never attempts link speed negotiation.  As a virtual device
>>>>>> the link speed is vague at best.  However, it is important for certain
>>>>>> applications, like bonding, to see a consistent link_status.  802.3ad
>>>>>> requires that only links of the same cost (link speed) be enslaved.
>>>>>> Keeping the link status consistent in vmxnet3 avoids races with bonding
>>>>>> enslavement.
>>>>
>>>> I don't understand the issue.
>>>> Are you sure it is not an issue in bonding?
>>>
>>> 802.3ad "requires" you to bond together links of the same speed and duplex.  The
>>> primary reason for this (or so I gather) is to ensure that the
>>> spanning-tree cost for
>>> each port is the same.  If you fail from one link to another, you
>>> don't want a spanning
>>> tree reconfiguration.
>>>
>>> The problem exists in general for most of the PMDs -- see
>>> https://dpdk.org/ml/archives/dev/2018-April/094696.html
>>>
>>> The problem is more vexing for AUTONEG and bonding.  I am still thinking about
>>> that.  You don't know until you go to activate the slave and bonding
>>> only makes its
>>> check during the setup phase.  So for virtual adapters and bonding, not using
>>> AUTONEG makes more sense because it is just easier to handle.
>>>
>>>>
>>>> About the right value to set for virtual PMDs, I don't know, both are fakes.
>>>> I thought that AUTONEG better convey the vague link speed you describe.
>>>
>>> It's not vague.  There is no negotiation of any sort.  The link speed
>>> (and therefore cost)
>>> of the link is fixed.  While the particular rate you get from the
>>> adapter depends
>>> on a number of factors, the link speed isn't going to change.  The
>>> adapter is not
>>> going to change the link speed from 10G to 1G or change from full duplex to half
>>> duplex.
>>
>> Hi Chas, Thomas,
>>
>> What is the latest status of this patch? Is it agreed to convert link_autoneg to
>> ETH_LINK_FIXED for following PMDs [1]?
>>
>> [1]
>> pcap
>> softnic
>> vmxnet3
> 
> Yes, OK for ETH_LINK_FIXED.

Thanks for clarification.


Hi Chas,

Do you prefer to re-make the patch to cover them all, or should I get this one
as start, which one do you prefer?

Thanks,
ferruh

> 
> 
>>>>>> Author: Thomas Monjalon <thomas@monjalon.net>
>>>>>> Date:   Fri Jan 5 18:38:55 2018 +0100
>>>>>>
>>>>>> Fixes: 1e3a958f40b3 ("ethdev: fix link autonegotiation value")
>>>>>> Cc: stable@dpdk.org
>>>>>
>>>>> There were a few more PMDs [1] they have been updated from FIXED to AUTONEG with
>>>>> above commit, do you think should we update them back to FIXED as well?
>>>>>
>>>>> [1]
>>>>> pcap
>>>>> softnic
>>>>> vmxnet3
>>>>
>>>> Yes, they all can be fixed/LINK_FIXED :) I guess
>>>>
>>>>
>>>>
>>
>>
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