Patch "IB/mlx4: Increase maximal message size under UD QP" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

IB/mlx4: Increase maximal message size under UD QP

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ib-mlx4-increase-maximal-message-size-under-ud-qp.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mark Bloch <[email protected]>
Date: Thu, 2 Nov 2017 15:22:26 +0200
Subject: IB/mlx4: Increase maximal message size under UD QP

From: Mark Bloch <[email protected]>

[ Upstream commit 5f22a1d87c5315a98981ecf93cd8de226cffe6ca ]

Maximal message should be used as a limit to the max message payload allowed, without the headers. The ConnectX-3 check is done against this value includes the headers. When the payload is 4K this will cause the NIC to drop packets.

Increase maximal message to 8K as workaround, this shouldn't change current behaviour because we continue to set the MTU to 4k.

To reproduce;
set MTU to 4296 on the corresponding interface, for example:
ifconfig eth0 mtu 4296 (both server and client)

On server:
ib_send_bw -c UD -d mlx4_0 -s 4096 -n 1000000 -i1 -m 4096

On client:
ib_send_bw -d mlx4_0 -c UD <server_ip> -s 4096 -n 1000000 -i 1 -m 4096

---
 drivers/infiniband/hw/mlx4/qp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -2216,7 +2216,7 @@ static int __mlx4_ib_modify_qp(void *src
 			context->mtu_msgmax = (IB_MTU_4096 << 5) |
 					      ilog2(dev->dev->caps.max_gso_sz);
 		else
-			context->mtu_msgmax = (IB_MTU_4096 << 5) | 12;
+			context->mtu_msgmax = (IB_MTU_4096 << 5) | 13;
 	} else if (attr_mask & IB_QP_PATH_MTU) {
 		if (attr->path_mtu < IB_MTU_256 || attr->path_mtu > IB_MTU_4096) {
 			pr_err("path MTU (%u) is invalid\n",

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/ib-mlx4-increase-maximal-message-size-under-ud-qp.patch