doc: add mlx5 note for Bluefield build configuration

Fixes: d14e4e976f65 ("config: add Mellanox BlueField armv8 SoC")
Cc: stable@dpdk.org
Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Acked-by: Shahaf Shuler <shahafs@mellanox.com>

diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index 3f168b1..62de860 100644 (file)
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -221,6 +221,13 @@ These options can be modified in the ``.config`` file.
   adds additional run-time checks and debugging messages at the cost of
   lower performance.
 
+.. note::
+
+   For Bluefield, target should be set to ``arm64-bluefield-linuxapp-gcc``. This
+   will enable ``CONFIG_RTE_LIBRTE_MLX5_PMD`` and set ``RTE_CACHE_LINE_SIZE`` to
+   64. Default armv8a configuration of make build and meson build set it to 128
+   then brings performance degradation.
+
 Environment variables
 ~~~~~~~~~~~~~~~~~~~~~