RDMA/nes: Check for zero STag

STags are generated randomly but the driver does not correctly prevent
a zero STag.  Using STag zero is privileged and causes a user space
application to fail.  This change prevents the driver from trying to
allocate a zero STag.
Signed-off-by: Faisal Latif <faisal.latif@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/nes/nes_hw.c

@@ -437,11 +437,12 @@ struct nes_adapter *nes_init_adapter(struct nes_device *nesdev, u8 hw_rev) {
 	nesadapter->qp_table = (struct nes_qp **)(&nesadapter->allocated_arps[BITS_TO_LONGS(arp_table_size)]);
 
 
-	/* mark the usual suspect QPs and CQs as in use */
+	/* mark the usual suspect QPs, MR and CQs as in use */
 	for (u32temp = 0; u32temp < NES_FIRST_QPN; u32temp++) {
 		set_bit(u32temp, nesadapter->allocated_qps);
 		set_bit(u32temp, nesadapter->allocated_cqs);
 	}
+	set_bit(0, nesadapter->allocated_mrs);
 
 	for (u32temp = 0; u32temp < 20; u32temp++)
 		set_bit(u32temp, nesadapter->allocated_pds);

drivers/infiniband/hw/nes/nes_verbs.c

@@ -2503,9 +2503,6 @@ static struct ib_mr *nes_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 			stag = stag_index << 8;
 			stag |= driver_key;
 			stag += (u32)stag_key;
-			if (stag == 0) {
-				stag = 1;
-			}
 
 			iova_start = virt;
 			/* Make the leaf PBL the root if only one PBL */