svn commit: r289156 - head/sys/dev/ntb/if_ntb

[Conrad E. Meyer]

Author: cem
Date: Sun Oct 11 21:00:19 2015
New Revision: 289156
URL: https://svnweb.freebsd.org/changeset/base/289156

Log:
  NTB: MFV c9d534c8: Correctly handle receive buffers of the minimal size
  
  The ring logic of the NTB receive buffer/transmit memory window requires
  there to be at least 2 payload sized allotments.  For the minimal size
  case, split the buffer into two and set the transport_mtu to the
  appropriate size.
  
  Authored by:	Jon Mason
  Obtained from:	Linux
  Sponsored by:	EMC / Isilon Storage Division

Modified:
  head/sys/dev/ntb/if_ntb/if_ntb.c

Modified: head/sys/dev/ntb/if_ntb/if_ntb.c
==============================================================================
--- head/sys/dev/ntb/if_ntb/if_ntb.c	Sun Oct 11 20:59:40 2015	(r289155)
+++ head/sys/dev/ntb/if_ntb/if_ntb.c	Sun Oct 11 21:00:19 2015	(r289156)
@@ -559,8 +559,9 @@ ntb_transport_init_queue(struct ntb_netd
 	tx_size -= sizeof(struct ntb_rx_info);
 
 	qp->tx_mw = qp->rx_info + 1;
+	/* Due to house-keeping, there must be at least 2 buffs */
 	qp->tx_max_frame = min(transport_mtu + sizeof(struct ntb_payload_header),
-	    tx_size);
+	    tx_size / 2);
 	qp->tx_max_entry = tx_size / qp->tx_max_frame;
 
 	callout_init(&qp->link_work, 0);
@@ -1187,12 +1188,13 @@ ntb_transport_setup_qp_mw(struct ntb_net
 	rx_size -= sizeof(struct ntb_rx_info);
 
 	qp->rx_buff = qp->remote_rx_info + 1;
+	/* Due to house-keeping, there must be at least 2 buffs */
 	qp->rx_max_frame = min(transport_mtu + sizeof(struct ntb_payload_header),
-	    rx_size);
+	    rx_size / 2);
 	qp->rx_max_entry = rx_size / qp->rx_max_frame;
 	qp->rx_index = 0;
 
-	qp->remote_rx_info->entry = qp->rx_max_entry;
+	qp->remote_rx_info->entry = qp->rx_max_entry - 1;
 
 	/* setup the hdr offsets with 0's */
 	for (i = 0; i < qp->rx_max_entry; i++) {