Author: vmaffione
Date: Wed Jun 10 19:58:03 2020
New Revision: 362020
URL: https://svnweb.freebsd.org/changeset/base/362020
Log:
MFC r361698
netmap: if_vtnet: avoid netmap ring wraparound
netmap assumes the one "slot" is left unused to distinguish
the empty ring and full ring conditions. This assumption was
violated by vtnet_netmap_rxq_populate().
Modified:
stable/12/sys/dev/netmap/if_vtnet_netmap.h
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/dev/netmap/if_vtnet_netmap.h
==============================================================================
--- stable/12/sys/dev/netmap/if_vtnet_netmap.h Wed Jun 10 19:57:10 2020
(r362019)
+++ stable/12/sys/dev/netmap/if_vtnet_netmap.h Wed Jun 10 19:58:03 2020
(r362020)
@@ -275,8 +275,8 @@ vtnet_netmap_rxq_populate(struct vtnet_rxq *rxq)
/* Expose all the RX netmap buffers we can. In case of no indirect
* buffers, the number of netmap slots in the RX ring matches the
* maximum number of 2-elements sglist that the RX virtqueue can
- * accommodate. */
- error = vtnet_netmap_kring_refill(kring, na->num_rx_desc);
+ * accommodate (minus 1 to avoid netmap ring wraparound). */
+ error = vtnet_netmap_kring_refill(kring, na->num_rx_desc - 1);
virtqueue_notify(rxq->vtnrx_vq);
return error < 0 ? ENXIO : 0;
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