1 files changed, 13 insertions, 1 deletions

diff --git a/drivers/infiniband/hw/mthca/mthca_main.c b/drivers/infiniband/hw/mthca/mthca_main.c
index 9ebadd6e0cfb..200cf13fc9bb 100644
--- a/drivers/infiniband/hw/mthca/mthca_main.c
+++ b/drivers/infiniband/hw/mthca/mthca_main.c
@@ -45,6 +45,7 @@
 #include "mthca_cmd.h"
 #include "mthca_profile.h"
 #include "mthca_memfree.h"
+#include "mthca_wqe.h"
 
 MODULE_AUTHOR("Roland Dreier");
 MODULE_DESCRIPTION("Mellanox InfiniBand HCA low-level driver");
@@ -200,7 +201,18 @@ static int mthca_dev_lim(struct mthca_dev *mdev, struct mthca_dev_lim *dev_lim)
         mdev->limits.gid_table_len      = dev_lim->max_gids;
         mdev->limits.pkey_table_len     = dev_lim->max_pkeys;
         mdev->limits.local_ca_ack_delay = dev_lim->local_ca_ack_delay;
-        mdev->limits.max_sg             = dev_lim->max_sg;
+        /*
+         * Need to allow for worst case send WQE overhead and check
+         * whether max_desc_sz imposes a lower limit than max_sg; UD
+         * send has the biggest overhead.
+         */
+        mdev->limits.max_sg             = min_t(int, dev_lim->max_sg,
+                                              (dev_lim->max_desc_sz -
+                                               sizeof (struct mthca_next_seg) -
+                                               (mthca_is_memfree(mdev) ?
+                                                sizeof (struct mthca_arbel_ud_seg) :
+                                                sizeof (struct mthca_tavor_ud_seg))) /
+                                                sizeof (struct mthca_data_seg));
         mdev->limits.max_wqes           = dev_lim->max_qp_sz;
         mdev->limits.max_qp_init_rdma   = dev_lim->max_requester_per_qp;
         mdev->limits.reserved_qps       = dev_lim->reserved_qps;