[PATCH] doc: update flow engine availability in mlx5 guide

[Thomas Monjalon <thomas@monjalon.net>]

Starting with NVIDIA ConnectX-9, the future devices will support
only hardware steering (HWS) flow engine.
The software steering options (legacy Verbs and Direct Verbs)
have lower performances, and won't be available for new devices.

Fixes: 1b55eeb7b76f ("common/mlx5: add ConnectX-9 SuperNIC")

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
---
 doc/guides/nics/mlx5.rst | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index 8481cc974a..904a0ac358 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -689,9 +689,11 @@ for an additional list of options shared with other mlx5 drivers.
 - ``dv_flow_en`` parameter [int]
 
   Value 0 means legacy Verbs flow offloading.
+  It is available for devices older than ConnectX-9.
 
-  Value 1 enables the DV flow steering assuming it is supported by the
-  driver (requires rdma-core 24 or higher).
+  Value 1 enables the Direct Verbs flow steering.
+  It is available for devices older than ConnectX-9,
+  and requires rdma-core 24 or later.
 
   Value 2 enables the WQE based hardware steering.
   In this mode, only queue-based flow management is supported.
@@ -1338,7 +1340,8 @@ Hardware Steering
 ~~~~~~~~~~~~~~~~~
 
 Faster than software steering (SWS),
-hardware steering (HWS) is the only mode supporting the flow template async API.
+hardware steering (HWS) is the only mode supporting the flow template async API,
+and the only mode supported on device ConnectX-9 and later.
 
 Flow rules are managed by the hardware,
 with a WQE-based high scaling and safer flow insertion/destruction.
-- 
2.51.0