RDMA/cxgb4: rmb() after reading valid gen bit

Some HW platforms can reorder read operations, so we must rmb() after
we see a valid gen bit in a CQE but before we read any other fields
from the CQE.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/infiniband/hw/cxgb4/t4.h b/drivers/infiniband/hw/cxgb4/t4.h
index 931bfd105c49..1f329fac9801 100644
--- a/drivers/infiniband/hw/cxgb4/t4.h
+++ b/drivers/infiniband/hw/cxgb4/t4.h
@@ -620,6 +620,9 @@ static inline int t4_next_hw_cqe(struct t4_cq *cq, struct t4_cqe **cqe)
                 printk(KERN_ERR MOD "cq overflow cqid %u\n", cq->cqid);
                 BUG_ON(1);
         } else if (t4_valid_cqe(cq, &cq->queue[cq->cidx])) {
+
+                /* Ensure CQE is flushed to memory */
+                rmb();
                 *cqe = &cq->queue[cq->cidx];
                 ret = 0;
         } else