Re: [dpdk-dev] [PATCH v3 1/2] common/mlx5: add provider query port support to glue library

01/07/2021 09:15, Viacheslav Ovsiienko:

In order to get E-Switch vport identifiers the mlx5 PMD relies
on two approaches:
  - use port query API if it is provided by rdma-core library
  - otherwise, deduce vport ids from the related VF index
The latter is not reliable and may not work with newer kernel
driver versions and in some configurations (LAG), causing
the E-Switch malfunction. Hence, engaging the port query API
is highly desirable.

The port attributes query API was supported by vendor rdma-core
versions only (in OFED). In Upstream, the rdma-core mlx5 provider
introduced the port attributes query API since version v35.0 - the
mlx5dv_query_port routine, that differs from vendor API. 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 is still
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

"this version" of what?

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.

With this patch applied the mlx5 PMD can be compiled and operates
over all rdma-core versions:
  - Upstream rdma-core before v35 (deduces vport id from VF name)
                           (* E-Switch may not operate correctly)
  - Upstream rdma-core v35 and above (uses common port query API)
  - rdma-core OFED before 5.5 (uses proprietary port query API)
  - rdma-core OFED 5.5 and above (uses common port query API)

This is the kind of explanation which should come first,
with exact function and flag names, before and after.

Despite this patch is not a bugfix (it follows the introduced API
variation in underlying library), it covers the major compatibility
issue and is highly desired to be ported to DPDK LTS.

Cc: stable@dpdk.org

Signed-off-by: Viacheslav Ovsiienko <redacted>
Acked-by: Matan Azrad <redacted>

[...]

It seems there is an indentation issue.

         [ 'HAVE_IBV_DEVX_OBJ', 'infiniband/mlx5dv.h',
             'mlx5dv_devx_obj_create' ],
         [ 'HAVE_IBV_FLOW_DEVX_COUNTERS', 'infiniband/mlx5dv.h',

[...]

+		 * pf0vf2, we can deduce the VF number as 2, and set vport index
+		 * as 3 (2+1). This assigning schema should be changed if the
+		 * multiple E-Switch instances per PF configurations or/and PCI
+		 * subfunctions are added.

I don't understand this last sentence.