Re: [dpdk-dev] [PATCH v2] common/mlx5: add provider query port support to glue library

[Slava Ovsiienko <viacheslavo@nvidia.com>]

Hi David,

> -----Original Message-----
> From: David Marchand <david.marchand@redhat.com>
> Sent: Wednesday, June 23, 2021 13:43
> To: Slava Ovsiienko <viacheslavo@nvidia.com>
> Cc: dev <dev@dpdk.org>; Raslan Darawsheh <rasland@nvidia.com>; Matan
> Azrad <matan@nvidia.com>; NBU-Contact-Thomas Monjalon
> <thomas@monjalon.net>; dpdk stable <stable@dpdk.org>
> Subject: Re: [dpdk-dev] [PATCH v2] common/mlx5: add provider query port
> support to glue library
> 
> On Sat, Jun 19, 2021 at 2:49 PM Viacheslav Ovsiienko
> <viacheslavo@nvidia.com> wrote:
> >
> > The rdma-core mlx5 provider introduced the port attributes query API
> > since version v35.0 - the mlx5dv_query_port routine. In order to
> > support this change in the rdma-core the conditional compilation flag
> > HAVE_MLX5DV_DR_DEVX_PORT_V35 is introduced by the this patch.
> >
> > In the OFED rdma-core version the new compatible mlx5dv_query_port
> > routine was introduced as well, replacing the existing proprietary
> > mlx5dv_query_devx_port routine. The proprietary routine was controlled
> > in PMD code with HAVE_MLX5DV_DR_DEVX_PORT conditional flag.
> >
> > Currently, the OFED rdma-core library contains both versions of port
> > query API. And this version is a transitional one, there are the plans
> > to remove the proprietary mlx5dv_query_devx_port routine and the
> > HAVE_MLX5DV_DR_DEVX_PORT flag in PMD will not work anymore.
> >
> > We had one more dependency on this flag in the code (for the
> > mlx5dv_dr_action_create_dest_ib_port routine) and the patch fixes
> > mentioned dependency also, by introducing the new dedicated
> > conditional flag - HAVE_MLX5DV_DR_CREATE_DEST_IB_PORT.
> >
> > This patch is highly desirable to be provided in DPDK LTS releases due
> > to it covers the major compatibility issue.
> 
> This patch is a fix, yet nothing tells this story in the title.

This patch is not a fix. Actually it covers the compatibility issue, not a bug.
The Upstream rdma-core was evolved, its community adopted a
slightly different API version than was presented in the vendor version.
Our PMD should conform both versions and we provided this patch for DPDK.

> And the title does not reflect that it is a fix wrt versions of rdma-core.
> Is this a build issue? or a runtime compat issue?

It is not a build because we have conditional compilation and we can
build PMD, but functionality is affected in severe way.

> 
> A good title makes life easier for users and people maintaining stable versions
> of DPDK.
I'm in contact with LTS maintainers about the patch,
the title should not be a problem.

Anyway, if you prefer the title be changed to one with "fix" word -
please, let me know, I'll provide the update. 

With best regards,
Slava