[Intel-wired-lan] ixgbe: 5.10.0 kernel regression for 2.5Gbps link negotiation?

[Fujinaka, Todd]

Well, actually, we considered defeaturing 2.5G and 5G in hardware. Would that have been better for you?

I am stripping the maintainers because they're on the mailing list already and multiple copies of the same email means they get annoyed and likely ignore the email.

And if you do put it back, we will likely have to disable the feature in hardware and have variants that allow it for the people who need it. You really want that outcome?

Todd Fujinaka
Software Application Engineer
Data Center Group
Intel Corporation
todd.fujinaka at intel.com

-----Original Message-----
From: Paul Menzel <pmenzel at molgen.mpg.de> 
Sent: Friday, December 18, 2020 11:55 PM
To: Fujinaka, Todd <todd.fujinaka at intel.com>; Ben Greear <greearb at candelatech.com>
Cc: Greg KH <gregkh at linuxfoundation.org>; intel-wired-lan at lists.osuosl.org; Brandeburg, Jesse <jesse.brandeburg at intel.com>; Nguyen, Anthony L <anthony.l.nguyen at intel.com>; David S. Miller <davem at davemloft.net>; Linus Torvalds <torvalds at linux-foundation.org>; Tyl, RadoslawX <radoslawx.tyl at intel.com>
Subject: Re: [Intel-wired-lan] ixgbe: 5.10.0 kernel regression for 2.5Gbps link negotiation?

Dear Todd,


Thank you for your reply.

What is the reason you stripped the maintainers from Cc list again?

Also, please adhere to mailing list etiquette, and do not top post, but use interleaved style.

For context: Commit a296d665ea (ixgbe: Add ethtool support to enable 2.5 and 5.0 Gbps support), present since 5.9-rc1, introduced a regression, that link negotiation now defaults to 1 Gbps, and ethtool has to be run to enable higher speeds 2.5.


Am 19.12.20 um 01:09 schrieb Fujinaka, Todd:
> What do you consider a regression? Having to enable 2.5G and 5G using 
> ethtool which can be done at boot time?

Well, Linux’ no regression policy should be well known by Linux kernel developers and maintainers.

People can always update to the mainline Linux kernel, and expect their setup to work as with the old Linux kernel. Even if the behavior before was a bug.

But maybe I am wrong, so Linus is in the Cc list now.

> We had more than a few datacenters with issues because of competing 
> standards. I checked with our marketing people and, on the whole, no 
> one could think of a large number of 2.5G or 5G customers.
> 
> We had several escalations from major OEMs and this was the solution 
> they wanted.
> 
> We consider this necessary for interoperability.

As written, this does not matter, as far as I know. You have to find a way to not regress working setups. It also shows, that your process should be more open.

In this case, I am particularly upset, that the commit changed the defaults without any mentioning in the commit message, and the commit message misses all the information and context, which now took a while to gather from you.

Additionally, in my opinion, additionally, a warning or notice should be printed by Linux about this issue.


Kind regards,

Paul


> -----Original Message-----
> From: Paul Menzel <pmenzel at molgen.mpg.de> Sent: Friday, December 18, 2020 3:19 PM
> To: Ben Greear <greearb at candelatech.com>; Fujinaka, Todd <todd.fujinaka at intel.com>
> Cc: intel-wired-lan at lists.osuosl.org; Greg KH <gregkh at linuxfoundation.org>; Nguyen, Anthony L <anthony.l.nguyen at intel.com>; Brandeburg, Jesse <jesse.brandeburg at intel.com>; Tyl, RadoslawX <radoslawx.tyl at intel.com>; Loktionov, Aleksandr <aleksandr.loktionov at intel.com>; Mclean, Arthur F <arthur.f.mclean at intel.com>; Skajewski, PiotrX <piotrx.skajewski at intel.com>
> Subject: Re: [Intel-wired-lan] 5.10.0 kernel regression for 2.5Gbps link negotiation?
> 
> [+cc Radoslaw, Aleksandr, Piotr]
> 
> Am 19.12.20 um 00:07 schrieb Ben Greear:> On 12/18/20 11:43 AM, Paul Menzel wrote:
> 
>>> Am 18.12.20 um 20:27 schrieb Fujinaka, Todd:
>>>> Yes, and I'm plugging the hole in the README right now. Here's the 
>>>> proposed text:
>>>>
>>>> Advertisements for 2.5G and 5G on the x550 were turned off by 
>>>> default due to interoperability issues with certain switches. To 
>>>> turn them back on, use
>>>>
>>>> ethtool -s <ethX> advertise N
>>>>
>>>> where N is a combination of the following.
>>>>
>>>> 100baseTFull    0x008
>>>> 1000baseTFull   0x020
>>>> 2500baseTFull   0x800000000000
>>>> 5000baseTFull   0x1000000000000
>>>> 10000baseTFull  0x1000
>>>>
>>>> For example, to turn on all modes:
>>>> ethtool -s <ethX> advertise 0x1800000001028
>>>>
>>>> For more details please see the ethtool man page.
>>>
>>> What commit introduced this regression. Please bear in mind, that 
>>> this contradicts Linux’ no-regression policy, and the commit should 
>>> therefore be reverted as soon as possible.
>> 
>> Looks like it is at the end of this patch, though the description 
>> doesn't mention changing defaults:
>> 
>> Commit a296d665eae1e8ec6445683bfb999c884058426a
>> Author: Radoslaw Tyl <radoslawx.tyl at intel.com>
>> Date:   Fri Jun 26 15:28:14 2020 +0200
>> 
>>      ixgbe: Add ethtool support to enable 2.5 and 5.0 Gbps support
>> 
>>      Added full support for new version Ethtool API. New API allow use
>>      2500Gbase-T and 5000base-T supported and advertised link speed modes.
>> 
>>      Signed-off-by: Radoslaw Tyl <radoslawx.tyl at intel.com>
>>      Tested-by: Andrew Bowers <andrewx.bowers at intel.com>
>>      Signed-off-by: Tony Nguyen <anthony.l.nguyen at intel.com>
>> 
>> Thanks,
>> Ben