Re: [PATCH v4] doc: announce KNI deprecation

[Thomas Monjalon <thomas@monjalon.net>]

14/07/2022 17:03, Ferruh Yigit:
> On 7/14/2022 3:50 PM, Ferruh Yigit wrote:
> > On 7/14/2022 10:20 AM, Bruce Richardson wrote:
> >> On Wed, Jul 13, 2022 at 06:10:47PM +0200, Thomas Monjalon wrote:
> >>> From: Ferruh Yigit <ferruh.yigit@intel.com>
> >>>
> >>> Announce the deprecation plan for KNI kernel module, library and 
> >>> example.
> >>>
> >>> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> >>> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> >>> ---
> >>> Squashed and updated 2 deprecations:
> >>> https://patches.dpdk.org/project/dpdk/patch/20211124171609.3101896-2-ferruh.yigit@intel.com/
> >>> https://patches.dpdk.org/project/dpdk/patch/20211124171609.3101896-2-ferruh.yigit@intel.com/
> >>> ---
> >>
> >> One suggestion below.
> >> With corrected link and with/without suggested change:
> >>
> >> Acked-by: Bruce Richardson <bruce.richardson@intel.com>
> >>
> >>>   doc/guides/prog_guide/kernel_nic_interface.rst | 3 +++
> >>>   doc/guides/rel_notes/deprecation.rst           | 9 +++++++++
> >>>   2 files changed, 12 insertions(+)
> >>>
> >>> diff --git a/doc/guides/prog_guide/kernel_nic_interface.rst 
> >>> b/doc/guides/prog_guide/kernel_nic_interface.rst
> >>> index e021cc69b6..03b5bca958 100644
> >>> --- a/doc/guides/prog_guide/kernel_nic_interface.rst
> >>> +++ b/doc/guides/prog_guide/kernel_nic_interface.rst
> >>> @@ -8,6 +8,9 @@ Kernel NIC Interface
> >>>   .. note::
> >>> +   KNI is deprecated and will be removed in future.
> >>> +   See :doc:`../rel_notes/deprecation`.
> >>> +
> >>>      For an alternative to KNI, that does not require any out-of-tree 
> >>> Linux kernel modules,
> >>>      or a custom library, see :ref:`virtio_user_as_exception_path`.
> >>> diff --git a/doc/guides/rel_notes/deprecation.rst 
> >>> b/doc/guides/rel_notes/deprecation.rst
> >>> index 4e5b23c53d..e54597c591 100644
> >>> --- a/doc/guides/rel_notes/deprecation.rst
> >>> +++ b/doc/guides/rel_notes/deprecation.rst
> >>> @@ -48,6 +48,15 @@ Deprecation Notices
> >>>     in the header will not be considered as ABI anymore. This change 
> >>> is inspired
> >>>     by the RFC 
> >>> https://patchwork.dpdk.org/project/dpdk/list/?series=17176.
> >>> +* kni: The KNI kernel module and library are not recommended for use 
> >>> by new
> >>> +  applications - other technologies such as virtio-user are 
> >>> recommended instead.
> >>> +  The KNI kernel module and library will be removed from DPDK 23.11,
> >>> +  following the DPDK technical board
> >>> +  `decision 
> >>> <https://mails.dpdk.org/archives/dev/2021-January/197077.html>`_
> >>> +  and `refinement 
> >>> <http://mails.dpdk.org/archives/dev/2022-June/243596.html>`_.
> >>> +  The first steps are to add deprecation warnings
> >>> +  and to remove the example application from 22.11.
> >>> +
> >>
> >> I wonder whether having this done as bullet points in chronological order
> >> might be clearer. Something like:
> >>
> >> * kni: The KNI kernel module and library are not recommended for use 
> >> by new
> >>    applications - other technologies such as virtio-user are 
> >> recommended instead.
> >>    Following the DPDK technical board
> >>    `decision 
> >> <https://mails.dpdk.org/archives/dev/2021-January/197077.html>`_
> >>    and `refinement 
> >> <http://mails.dpdk.org/archives/dev/2022-June/243596.html>`_:
> >>    * The KNI example application will be removed from DPDK 22.11 release
> >>    * The KNI kernel module and library will be removed from the DPDK 
> >> 23.11
> >>      release
> > 
> > +1 to list actions in chronological order
> > 
> > I have a concern with removing sample application without replacing one 
> > with alternate methods: virtio-user and tun/tap.
> > 
> > It is easy to create a virtio-user PMD by testpmd or any sample 
> > application, and as far as I understand Bruce already documented this. 
> > But for many KNI users they are not using KNI PMD, so replacing KNI with 
> > this new method may require some hand holding.
> 
> As mentioned KNI PMD, it also should be removed when library and module 
> are removed, may be good to list above to be explicit.

Yes I'm adding the PMD in removal list.

> > One option can be hotplug the virtio-user PMD and use the port_id for 
> > packet forwarding, and I don't know if the PMD has APIs that 
> > applications can use directly, as done in KNI, @Maxime & @Chenbo can 
> > answer this better.
> > 
> > It can be good to have a sample application for above before deprecating 
> > the KNI sample application.
> > And same sample can use tun/tap PMD with a runtime parameter, to show 
> > how other example can be used, again tap can be used as tap PMD or Linux 
> > tun/tap APIs.
> > 
> > Question is who can work on such a sample, but if we can find some 
> > resource I am for having a replacement exception path sample app before 
> > deprecating KNI.

We are not sure we'll have time and resource,
and it has not been discussed earlier.
Thus I'll consider having a replacement example as a nice-to-have.
I have to be a bit conservative with techboard decisions.