[dpdk-dev] [PATCH] vhost: don't stall if guest is slow

[Stephen Hemminger <stephen@networkplumber.org>]

When guest is booting (or any othertime guest is busy) it is possible
for the small receive ring (256) to get full. If this happens the
vhost library should just return normally. It's current behavior
of logging just creates massive log spew/overflow which could even
act as a DoS attack against host.

Reported-by: Nathan Law <nlaw@brocade.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/librte_vhost/vhost_rxtx.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 9322ce6..bbf3fac 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -510,17 +510,12 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 
 			do {
 				avail_idx = *((volatile uint16_t *)&vq->avail->idx);
-				if (unlikely(res_cur_idx == avail_idx)) {
-					LOG_DEBUG(VHOST_DATA,
-						"(%"PRIu64") Failed "
-						"to get enough desc from "
-						"vring\n",
-						dev->device_fh);
+				if (unlikely(res_cur_idx == avail_idx))
 					goto merge_rx_exit;
-				} else {
-					update_secure_len(vq, res_cur_idx, &secure_len, &vec_idx);
-					res_cur_idx++;
-				}
+
+				update_secure_len(vq, res_cur_idx,
+						  &secure_len, &vec_idx);
+				res_cur_idx++;
 			} while (pkt_len > secure_len);
 
 			/* vq->last_used_idx_res is atomically updated. */
-- 
2.1.4