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>

3 files changed, 16 insertions, 6 deletions

diff --git a/drivers/net/enic/enic_res.h b/drivers/net/enic/enic_res.h
index 68534a29b7ac..7bf272fa859b 100644
--- a/drivers/net/enic/enic_res.h
+++ b/drivers/net/enic/enic_res.h
@@ -58,8 +58,6 @@ static inline void enic_queue_wq_desc_ex(struct vnic_wq *wq,
                 (u16)vlan_tag,
                 0 /* loopback */);
 
-        wmb();
-
         vnic_wq_post(wq, os_buf, dma_addr, len, sop, eop);
 }
 
@@ -127,8 +125,6 @@ static inline void enic_queue_rq_desc(struct vnic_rq *rq,
                 (u64)dma_addr | VNIC_PADDR_TARGET,
                 type, (u16)len);
 
-        wmb();
-
         vnic_rq_post(rq, os_buf, os_buf_index, dma_addr, len);
 }
 
diff --git a/drivers/net/enic/vnic_rq.h b/drivers/net/enic/vnic_rq.h
index 82bfca67cc4d..fd0ef66d2e9f 100644
--- a/drivers/net/enic/vnic_rq.h
+++ b/drivers/net/enic/vnic_rq.h
@@ -132,8 +132,15 @@ static inline void vnic_rq_post(struct vnic_rq *rq,
 #define VNIC_RQ_RETURN_RATE             0xf     /* keep 2^n - 1 */
 #endif
 
-        if ((buf->index & VNIC_RQ_RETURN_RATE) == 0)
+        if ((buf->index & VNIC_RQ_RETURN_RATE) == 0) {
+                /* 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, &rq->ctrl->posted_index);
+        }
 }
 
 static inline void vnic_rq_return_descs(struct vnic_rq *rq, unsigned int count)
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--;