[dpdk-stable] [PATCH 20.11 v2 00/18] Backport the new VLAN design for Intel ice PMD

[Wang, Haiyue]

> -----Original Message-----
> From: Thomas Monjalon <thomas at monjalon.net>
> Sent: Monday, June 21, 2021 16:29
> To: Kevin Traynor <ktraynor at redhat.com>; Xueming(Steven) Li <xuemingl at nvidia.com>; Luca Boccassi
> <bluca at debian.org>; Wang, Haiyue <haiyue.wang at intel.com>; christian.ehrhardt at canonical.com
> Cc: stable at dpdk.org; Zhang, Qi Z <qi.z.zhang at intel.com>; Fu, Qi <qi.fu at intel.com>; techboard at dpdk.org
> Subject: Re: [dpdk-stable] [PATCH 20.11 v2 00/18] Backport the new VLAN design for Intel ice PMD
> 
> 18/06/2021 05:22, Wang, Haiyue:
> > From: Kevin Traynor <ktraynor at redhat.com>
> > > On 17/06/2021 09:53, Xueming(Steven) Li wrote:
> > > > From: Wang, Haiyue <haiyue.wang at intel.com>
> > > >> From: Luca Boccassi <bluca at debian.org>
> > > >>> On Fri, 2021-06-11 at 15:15 +0800, Haiyue Wang wrote:
> > > >>>> When LTS 20.11 was released, the Intel ice PMD has a basic VLAN
> > > >>>> offload, which can only handle single VLAN mode for firmware
> > > >>>> limitation. Now the firmware is updated to support double VLAN mode
> > > >>>> and single VLAN mode at the same time.
> > > >>>> It depends on the driver to do selection at the boot time.
> > > >>>>
> > > >>>> As VLAN protocol handling like strip, filter, flow is very common
> > > >>>> use, we request to support the ice PMD can run on the latest
> > > >>>> firmware for enabling the new design. This is compatible backport as the main tree.
> [...]
> > > >>>>  19 files changed, 1545 insertions(+), 363 deletions(-)  create mode
> [...]
> > > >>> At 1.9k diffstat, this series is quite large. Given it's a new
> > > >>> feature, rather than a series of bug fixes, this would seem a bit risky to me.
> > > >>> Final word of course belongs to Xueming, since he's managing this one.
> 
> [...]
> > > >> 06. Is it obvious that the feature will not impact existing functionality?
> > > >>
> > > >> Yes.
> > >
> > > No. It is 1.9KLOC change. The key part of the question is "obvious". It
> > > was meant so the maintainer could use their judgement and review that
> > > for example, a few lines of code adding a PCI ID or adding a case in a
> > > switch statement, is obviously not going to impact existing functionality.
> > > On the other hand, for a more complex code change to existing code, it
> > > is not immediately obvious that there would be no risk to existing
> > > functionality.
> 
> [...]
> > > >> 11. Is there a community consensus about the backport?
> > > >>
> > > >> ...
> > > >
> > > > Kevin happens to updated the documents on new feature backport 4 months ago, thanks for checking
> > > them
> > > > one by one. Luca's only concern is size of the series, driver vendor is on it's own risk to
> backport
> > > a big patch set.
> > > > The series supports new fw and QinQ, is it easy to split?
> > > >
> > > > Kevin, is this the first case of feature backport? How do you think?
> > > >
> > >
> > > Like Luca, main concern would be the size and intrusiveness of the
> > > changes, and if it's ok to change 1.9KLOC in this driver now, then why
> > > not 20KLOC in next release to multiple drivers. I had pushed against a
> >
> > TBH, we won't want to change the stable i40e, ixgbe PMDs, but ice is a fresh
> > one, current VLAN has a limited usage, customer is hard to use. That's why we
> > try to request to backport the new VLAN design.
> 
> Yes ice is quite recent.
> If a required feature is not working, it should motivate to upgrade.
> Because ice is "fresh", I don't understand why sticking to 20.11.
> My concern is that backporting this big feature would create a precedent,
> so all users will require to stick on the last LTS when getting
> all the new reworked features.

"Performance improvements are generally not considered to be fixes, but may be
 considered in some cases where:

It is fixing a performance regression that occurred previously.
An existing feature in LTS is not usable as intended without it."

I think "An existing feature in LTS is not usable as intended without it " can
be one reason, since the old design is out of date in two year of LTS lifetime.

> I think it would be a bad situation for all of us.
> 
>