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

Ferruh Yigit ferruh.yigit at intel.com
Tue Apr 17 21:25:59 CEST 2018


On 4/5/2018 4:01 PM, Chas Williams wrote:
> On Thu, Apr 5, 2018 at 6:03 AM, Thomas Monjalon <thomas at monjalon.net> wrote:
>> 20/03/2018 15:12, Ferruh Yigit:
>>> On 3/18/2018 1:45 AM, Chas Williams wrote:
>>>> From: Chas Williams <chas3 at 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


> 
>>
>>
>>>> Author: Thomas Monjalon <thomas at monjalon.net>
>>>> Date:   Fri Jan 5 18:38:55 2018 +0100
>>>>
>>>> Fixes: 1e3a958f40b3 ("ethdev: fix link autonegotiation value")
>>>> Cc: stable at 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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