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>

diff --git a/drivers/infiniband/hw/cxgb4/t4.h b/drivers/infiniband/hw/cxgb4/t4.h
index 931bfd105c49549a1530f4e19266d4954e1abc3d..1f329fac980198df953a58f03db3fef2567ff72e 100644 (file)
--- 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