IB/mlx4: Fix data corruption triggered by wrong headroom marking order

[linux-block.git] / drivers / infiniband / hw / mlx4 / qp.c

diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
index ba0428d872aa4bc0a6cc2993049c6f60f2eba25e..85c51bdc36f1d403130fdf81655c51c7eca6e817 100644 (file)
--- a/drivers/infiniband/hw/mlx4/qp.c
+++ b/drivers/infiniband/hw/mlx4/qp.c
@@ -1211,12 +1211,42 @@ static void set_datagram_seg(struct mlx4_wqe_datagram_seg *dseg,
        dseg->qkey = cpu_to_be32(wr->wr.ud.remote_qkey);
 }
 
-static void set_data_seg(struct mlx4_wqe_data_seg *dseg,
-                        struct ib_sge *sg)
+static void set_mlx_icrc_seg(void *dseg)
+{
+       u32 *t = dseg;
+       struct mlx4_wqe_inline_seg *iseg = dseg;
+
+       t[1] = 0;
+
+       /*
+        * Need a barrier here before writing the byte_count field to
+        * make sure that all the data is visible before the
+        * byte_count field is set.  Otherwise, if the segment begins
+        * a new cacheline, the HCA prefetcher could grab the 64-byte
+        * chunk and get a valid (!= * 0xffffffff) byte count but
+        * stale data, and end up sending the wrong data.
+        */
+       wmb();
+
+       iseg->byte_count = cpu_to_be32((1 << 31) | 4);
+}
+
+static void set_data_seg(struct mlx4_wqe_data_seg *dseg, struct ib_sge *sg)
 {
-       dseg->byte_count = cpu_to_be32(sg->length);
        dseg->lkey       = cpu_to_be32(sg->lkey);
        dseg->addr       = cpu_to_be64(sg->addr);
+
+       /*
+        * Need a barrier here before writing the byte_count field to
+        * make sure that all the data is visible before the
+        * byte_count field is set.  Otherwise, if the segment begins
+        * a new cacheline, the HCA prefetcher could grab the 64-byte
+        * chunk and get a valid (!= * 0xffffffff) byte count but
+        * stale data, and end up sending the wrong data.
+        */
+       wmb();
+
+       dseg->byte_count = cpu_to_be32(sg->length);
 }
 
 int mlx4_ib_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
@@ -1225,6 +1255,7 @@ int mlx4_ib_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
        struct mlx4_ib_qp *qp = to_mqp(ibqp);
        void *wqe;
        struct mlx4_wqe_ctrl_seg *ctrl;
+       struct mlx4_wqe_data_seg *dseg;
        unsigned long flags;
        int nreq;
        int err = 0;
@@ -1324,22 +1355,27 @@ int mlx4_ib_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
                        break;
                }
 
-               for (i = 0; i < wr->num_sge; ++i) {
-                       set_data_seg(wqe, wr->sg_list + i);
+               /*
+                * Write data segments in reverse order, so as to
+                * overwrite cacheline stamp last within each
+                * cacheline.  This avoids issues with WQE
+                * prefetching.
+                */
 
-                       wqe  += sizeof (struct mlx4_wqe_data_seg);
-                       size += sizeof (struct mlx4_wqe_data_seg) / 16;
-               }
+               dseg = wqe;
+               dseg += wr->num_sge - 1;
+               size += wr->num_sge * (sizeof (struct mlx4_wqe_data_seg) / 16);
 
                /* Add one more inline data segment for ICRC for MLX sends */
-               if (qp->ibqp.qp_type == IB_QPT_SMI || qp->ibqp.qp_type == IB_QPT_GSI) {
-                       ((struct mlx4_wqe_inline_seg *) wqe)->byte_count =
-                               cpu_to_be32((1 << 31) | 4);
-                       ((u32 *) wqe)[1] = 0;
-                       wqe  += sizeof (struct mlx4_wqe_data_seg);
+               if (unlikely(qp->ibqp.qp_type == IB_QPT_SMI ||
+                            qp->ibqp.qp_type == IB_QPT_GSI)) {
+                       set_mlx_icrc_seg(dseg + 1);
                        size += sizeof (struct mlx4_wqe_data_seg) / 16;
                }
 
+               for (i = wr->num_sge - 1; i >= 0; --i, --dseg)
+                       set_data_seg(dseg, wr->sg_list + i);
+
                ctrl->fence_size = (wr->send_flags & IB_SEND_FENCE ?
                                    MLX4_WQE_CTRL_FENCE : 0) | size;