[dpdk-dev] [PATCH] vhost: call write barrier before used index update

[Nikita Kalyazin]

Descriptors that have been put into the used vring must be observable by
guest earlier than the new used index value.
Although compiler barrier serves well for Intel architectue here, the
proper cross-platform solution is to use write barrier before the used
index is updated.

Signed-off-by: Nikita Kalyazin <n.kalyazin at samsung.com>
---
 lib/librte_vhost/vhost_rxtx.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 7026bfa..d955287 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -216,7 +216,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 		}
 	}
 
-	rte_compiler_barrier();
+	rte_wmb();
 
 	/* Wait until it's our turn to add our buffer to the used ring. */
 	while (unlikely(vq->last_used_idx != res_base_idx))
@@ -512,7 +512,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 		entry_success = copy_from_mbuf_to_vring(dev, res_base_idx,
 			res_cur_idx, pkts[pkt_idx]);
 
-		rte_compiler_barrier();
+		rte_wmb();
 
 		/*
 		 * Wait until it's our turn to add our buffer
@@ -751,7 +751,7 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
 		entry_success++;
 	}
 
-	rte_compiler_barrier();
+	rte_wmb();
 	vq->used->idx += entry_success;
 	/* Kick guest if required. */
 	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
-- 
2.5.3