IB/mthca: memfree completion with error FW bug workaround

Memfree firmware is in rare cases reporting WQE index == base - 1 in
receive completion with error, instead of (rq size - 1); base is 0 in
mthca.  Here is a patch to avoid kernel crash and report a correct WR
id in this case.

Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/infiniband/hw/mthca/mthca_cq.c b/drivers/infiniband/hw/mthca/mthca_cq.c
index 205854e9c662..87a8f1166a3b 100644
--- a/drivers/infiniband/hw/mthca/mthca_cq.c
+++ b/drivers/infiniband/hw/mthca/mthca_cq.c
@@ -540,8 +540,17 @@ static inline int mthca_poll_one(struct mthca_dev *dev,
                 entry->wr_id = srq->wrid[wqe_index];
                 mthca_free_srq_wqe(srq, wqe);
         } else {
+                s32 wqe;
                 wq = &(*cur_qp)->rq;
-                wqe_index = be32_to_cpu(cqe->wqe) >> wq->wqe_shift;
+                wqe = be32_to_cpu(cqe->wqe);
+                wqe_index = wqe >> wq->wqe_shift;
+               /*
+                * WQE addr == base - 1 might be reported in receive completion
+                * with error instead of (rq size - 1) by Sinai FW 1.0.800 and
+                * Arbel FW 5.1.400.  This bug should be fixed in later FW revs.
+                */
+                if (unlikely(wqe_index < 0))
+                        wqe_index = wq->max - 1;
                 entry->wr_id = (*cur_qp)->wrid[wqe_index];
         }