[dpdk-stable] patch 'net/mlx5: disable ConnectX-4 Lx Multi Packet Send by default' has been queued to stable release 18.08.1

[Kevin Traynor]

Hi,

FYI, your patch has been queued to stable release 18.08.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 11/23/18. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the patch applied
to the branch. If the code is different (ie: not only metadata diffs), due for example to
a change in context or macro names, please double check it.

Thanks.

Kevin Traynor

---
>From 6ffff221711e179459a9b1e2549d2e1d29d35d8f Mon Sep 17 00:00:00 2001
From: Shahaf Shuler <shahafs at mellanox.com>
Date: Mon, 13 Aug 2018 09:47:57 +0300
Subject: [PATCH] net/mlx5: disable ConnectX-4 Lx Multi Packet Send by default

[ upstream commit f9de87187b7f233cc5b1ea964c05311dfeed951a ]

On ConnectX-4 Lx the Multi Packet Send (MPW) feature is considered
un-secure, as on some cases were the application provides incorrect mbufs
on the Tx burst the host or NIC can get stuck.

Hence, disabling the feature by default for this specific NIC.
Users can still enable this feature and enjoy the performance gain
(mostly for low number of cores) by using the txq_mpw_en devarg.

This patch will impact the out of the box performance of some application
using ConnectX-4 Lx for the sack of security and robustness.

Since we need different defaults based on the underlying device the mpw
field in the configuration struct was extended to contain also the
MLX5_ARG_UNSET option.

Signed-off-by: Shahaf Shuler <shahafs at mellanox.com>
Acked-by: Yongseok Koh <yskoh at mellanox.com>
---
 doc/guides/nics/mlx5.rst |  7 ++++++-
 drivers/net/mlx5/mlx5.c  | 20 +++++++++++---------
 drivers/net/mlx5/mlx5.h  |  2 +-
 3 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index 52e1213cf..dbdb90b59 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -340,5 +340,10 @@ Run-time configuration
 
   It is currently only supported on the ConnectX-4 Lx, ConnectX-5 and Bluefield
-  families of adapters. Enabled by default.
+  families of adapters.
+  On ConnectX-4 Lx the MPW is considered un-secure hence disabled by default.
+  Users which enable the MPW should be aware that application which provides incorrect
+  mbuf descriptors in the Tx burst can lead to serious errors in the host including, on some cases,
+  NIC to get stuck.
+  On ConnectX-5 and Bluefield the MPW is secure and enabled by default.
 
 - ``txq_mpw_hdr_dseg_en`` parameter [int]
diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
index ec63bc6e2..30d4e70a7 100644
--- a/drivers/net/mlx5/mlx5.c
+++ b/drivers/net/mlx5/mlx5.c
@@ -478,5 +478,5 @@ mlx5_args_check(const char *key, const char *val, void *opaque)
 		config->txqs_inline = tmp;
 	} else if (strcmp(MLX5_TXQ_MPW_EN, key) == 0) {
-		config->mps = !!tmp ? config->mps : 0;
+		config->mps = !!tmp;
 	} else if (strcmp(MLX5_TXQ_MPW_HDR_DSEG_EN, key) == 0) {
 		config->mpw_hdr_dseg = !!tmp;
@@ -703,4 +703,5 @@ mlx5_dev_spawn(struct rte_device *dpdk_dev,
 	struct mlx5_dev_config config = {
 		.vf = !!vf,
+		.mps = MLX5_ARG_UNSET,
 		.tx_vec_en = 1,
 		.rx_vec_en = 1,
@@ -792,5 +793,4 @@ mlx5_dev_spawn(struct rte_device *dpdk_dev,
 		mps = MLX5_MPW_DISABLED;
 	}
-	config.mps = mps;
 #ifdef HAVE_IBV_MLX5_MOD_SWP
 	if (dv_attr.comp_mask & MLX5DV_CONTEXT_MASK_SWP)
@@ -1036,11 +1036,13 @@ mlx5_dev_spawn(struct rte_device *dpdk_dev,
 	if (config.tso)
 		config.tso_max_payload_sz = attr.tso_caps.max_tso;
-	if (config.mps && !mps) {
-		DRV_LOG(ERR,
-			"multi-packet send not supported on this device"
-			" (" MLX5_TXQ_MPW_EN ")");
-		err = ENOTSUP;
-		goto error;
-	}
+	/*
+	 * MPW is disabled by default, while the Enhanced MPW is enabled
+	 * by default.
+	 */
+	if (config.mps == MLX5_ARG_UNSET)
+		config.mps = (mps == MLX5_MPW_ENHANCED) ? MLX5_MPW_ENHANCED :
+							  MLX5_MPW_DISABLED;
+	else
+		config.mps = config.mps ? mps : MLX5_MPW_DISABLED;
 	DRV_LOG(INFO, "%sMPS is %s",
 		config.mps == MLX5_MPW_ENHANCED ? "enhanced " : "",
diff --git a/drivers/net/mlx5/mlx5.h b/drivers/net/mlx5/mlx5.h
index a3a34cffd..35a196e76 100644
--- a/drivers/net/mlx5/mlx5.h
+++ b/drivers/net/mlx5/mlx5.h
@@ -100,5 +100,4 @@ struct mlx5_dev_config {
 	unsigned int hw_padding:1; /* End alignment padding is supported. */
 	unsigned int vf:1; /* This is a VF. */
-	unsigned int mps:2; /* Multi-packet send supported mode. */
 	unsigned int tunnel_en:1;
 	/* Whether tunnel stateless offloads are supported. */
@@ -123,4 +122,5 @@ struct mlx5_dev_config {
 		/* Rx queue count threshold to enable MPRQ. */
 	} mprq; /* Configurations for Multi-Packet RQ. */
+	int mps; /* Multi-packet send supported mode. */
 	unsigned int flow_prio; /* Number of flow priorities. */
 	unsigned int tso_max_payload_sz; /* Maximum TCP payload for TSO. */
-- 
2.19.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2018-11-20 17:53:07.775337119 +0000
+++ 0013-net-mlx5-disable-ConnectX-4-Lx-Multi-Packet-Send-by-.patch	2018-11-20 17:53:07.000000000 +0000
@@ -1,8 +1,10 @@
-From f9de87187b7f233cc5b1ea964c05311dfeed951a Mon Sep 17 00:00:00 2001
+From 6ffff221711e179459a9b1e2549d2e1d29d35d8f Mon Sep 17 00:00:00 2001
 From: Shahaf Shuler <shahafs at mellanox.com>
 Date: Mon, 13 Aug 2018 09:47:57 +0300
 Subject: [PATCH] net/mlx5: disable ConnectX-4 Lx Multi Packet Send by default
 
+[ upstream commit f9de87187b7f233cc5b1ea964c05311dfeed951a ]
+
 On ConnectX-4 Lx the Multi Packet Send (MPW) feature is considered
 un-secure, as on some cases were the application provides incorrect mbufs
 on the Tx burst the host or NIC can get stuck.
@@ -18,8 +20,6 @@
 field in the configuration struct was extended to contain also the
 MLX5_ARG_UNSET option.
 
-Cc: stable at dpdk.org
-
 Signed-off-by: Shahaf Shuler <shahafs at mellanox.com>
 Acked-by: Yongseok Koh <yskoh at mellanox.com>
 ---