[dpdk-stable] [PATCH] net/mlx5: document workaround for ConnectX-4 with L2 encap

[dpdk-stable] [PATCH] net/mlx5: document workaround for ConnectX-4 with L2 encap

[Dmitry Kozlyuk]

ConnectX-4 and ConnectX-4 Lx NICs require all L2 headers of transmitted
packets to be inlined. By default only first 18 bytes are inlined,
which is insufficient if additional encapsulation is used, like Q-in-Q.
Thus, default settings caused such traffic to be dropepd on Tx.
Document a workaround to increase inlined data size in such cases.

Fixes: 505f1fe426d3 ("net/mlx5: add Tx devargs")
Cc: stable@dpdk.org

Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
Reviewed-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
---
 doc/guides/nics/mlx5.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index ebefbe607e..05a89d08f2 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -705,6 +705,13 @@ Driver options
   it is not recommended and may prevent NIC from sending packets over
   some configurations.
 
+  For ConnectX-4 and ConnectX-4 Lx NICs, automatically configured value
+  is insufficient for some traffic, because they require at least all L2 headers
+  to be inlined. For example, Q-in-Q adds 4 bytes to default 18 bytes
+  of Ethernet and VLAN, thus ``txq_inline_min`` must be set to 22.
+  MPLS would add 4 bytes per label. Final value must account for all possible
+  L2 encapsulation headers used in particular environment.
+
   Please, note, this minimal data inlining disengages eMPW feature (Enhanced
   Multi-Packet Write), because last one does not support partial packet inlining.
   This is not very critical due to minimal data inlining is mostly required
-- 
2.25.1

Re: [dpdk-stable] [dpdk-dev] [PATCH] net/mlx5: document workaround for ConnectX-4 with L2 encap

[Raslan Darawsheh]

Hi,

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Dmitry Kozlyuk
> Sent: Wednesday, June 30, 2021 10:01 AM
> To: dev@dpdk.org
> Cc: stable@dpdk.org; Slava Ovsiienko <viacheslavo@nvidia.com>; Matan
> Azrad <matan@nvidia.com>; Shahaf Shuler <shahafs@nvidia.com>
> Subject: [dpdk-dev] [PATCH] net/mlx5: document workaround for
> ConnectX-4 with L2 encap
> 
> ConnectX-4 and ConnectX-4 Lx NICs require all L2 headers of transmitted
> packets to be inlined. By default only first 18 bytes are inlined,
> which is insufficient if additional encapsulation is used, like Q-in-Q.
> Thus, default settings caused such traffic to be dropepd on Tx.
> Document a workaround to increase inlined data size in such cases.
> 
> Fixes: 505f1fe426d3 ("net/mlx5: add Tx devargs")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
> Reviewed-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

Patch applied to next-net-mlx,

Kindest regards,
Raslan Darawsheh