Patch "IB/mlx4: Fix WQE LSO segment calculation" has been added to the 3.10-stable tree

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

IB/mlx4: Fix WQE LSO segment calculation

to the 3.10-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-fix-wqe-lso-segment-calculation.patch
and it can be found in the queue-3.10 subdirectory.

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

From: Erez Shitrit <[email protected]>
Date: Thu, 2 Apr 2015 13:39:05 +0300
Subject: IB/mlx4: Fix WQE LSO segment calculation

From: Erez Shitrit <[email protected]>

commit ca9b590caa17bcbbea119594992666e96cde9c2f upstream.

The current code decreases from the mss size (which is the gso_size from the kernel skb) the size of the packet headers.

It shouldn't do that because the mss that comes from the stack (e.g IPoIB) includes only the tcp payload without the headers.

The result is indication to the HW that each packet that the HW sends is smaller than what it could be, and too many packets will be sent for big messages.

An easy way to demonstrate one more aspect of the problem is by configuring the ipoib mtu to be less than 2*hlen (2*56) and then run app sending big TCP messages. This will tell the HW to send packets with giant (negative value which under unsigned arithmetics becomes a huge positive one) length and the QP moves to SQE state.

---
 drivers/infiniband/hw/mlx4/qp.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

@@ -2174,8 +2174,7 @@ static int build_lso_seg(struct mlx4_wqe
 
 	memcpy(wqe->header, wr->wr.ud.header, wr->wr.ud.hlen);
 
-	*lso_hdr_sz  = cpu_to_be32((wr->wr.ud.mss - wr->wr.ud.hlen) << 16 |
-				   wr->wr.ud.hlen);
+	*lso_hdr_sz  = cpu_to_be32(wr->wr.ud.mss << 16 | wr->wr.ud.hlen);
 	*lso_seg_len = halign;
 	return 0;
 }

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

queue-3.10/ib-mlx4-fix-wqe-lso-segment-calculation.patch