enic: move wmb closer to where needed: before writing posted_index to hw

Signed-off-by: Scott Feldman <scofeldm@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/net/enic/vnic_wq.h b/drivers/net/enic/vnic_wq.h
index 7081828d8a42..c826137dc651 100644
--- a/drivers/net/enic/vnic_wq.h
+++ b/drivers/net/enic/vnic_wq.h
@@ -108,8 +108,15 @@ static inline void vnic_wq_post(struct vnic_wq *wq,
         buf->len = len;
 
         buf = buf->next;
-        if (eop)
+        if (eop) {
+                /* Adding write memory barrier prevents compiler and/or CPU
+                 * reordering, thus avoiding descriptor posting before
+                 * descriptor is initialized. Otherwise, hardware can read
+                 * stale descriptor fields.
+                 */
+                wmb();
                 iowrite32(buf->index, &wq->ctrl->posted_index);
+        }
         wq->to_use = buf;
 
         wq->ring.desc_avail--;