[arbel] Randomise the high-order bits of queue pair numbers

This is a backport of commit 0b1222f ("[hermon] Randomise the
high-order bits of queue pair numbers") to the Arbel driver.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/infiniband/arbel.c

 			       arbel );
 			return qpn_offset;
 		}
-		qp->qpn = ( arbel->qpn_base + qpn_offset );
+		qp->qpn = ( ( random() & ARBEL_QPN_RANDOM_MASK ) |
+			    ( arbel->qpn_base + qpn_offset ) );
 		return 0;
 	default:
 		DBGC ( arbel, "Arbel %p unsupported QP type %d\n",
 	struct arbel *arbel = ib_get_drvdata ( ibdev );
 	int qpn_offset;
 
-	qpn_offset = ( qp->qpn - arbel->qpn_base );
+	qpn_offset = ( ( qp->qpn & ~ARBEL_QPN_RANDOM_MASK ) - arbel->qpn_base );
 	if ( qpn_offset >= 0 )
 		arbel_bitmask_free ( arbel->qp_inuse, qpn_offset );
 }

src/drivers/infiniband/arbel.h

  */
 #define ARBEL_MAX_QPS		8
 
-/** Base queue pair number */
-#define ARBEL_QPN_BASE 0x550000
+/** Queue pair number randomisation mask */
+#define ARBEL_QPN_RANDOM_MASK 0xfff000
 
 /** An Arbel queue pair */
 struct arbel_queue_pair {
  */
 static inline unsigned int
 arbel_send_doorbell_idx ( struct arbel *arbel, struct ib_queue_pair *qp ) {
-	return ( ARBEL_MAX_CQS + ( qp->qpn - arbel->special_qpn_base ) );
+	return ( ARBEL_MAX_CQS +
+		 ( ( qp->qpn & ~ARBEL_QPN_RANDOM_MASK ) -
+		   arbel->special_qpn_base ) );
 }
 
 /**
 static inline unsigned int
 arbel_recv_doorbell_idx ( struct arbel *arbel, struct ib_queue_pair *qp ) {
 	return ( ARBEL_MAX_DOORBELL_RECORDS - ARBEL_MAX_CQS -
-		 ( qp->qpn - arbel->special_qpn_base ) - 1 );
+		 ( ( qp->qpn & ~ARBEL_QPN_RANDOM_MASK ) -
+		   arbel->special_qpn_base ) - 1 );
 }
 
 /**