Calling rte_vhost_enqueue_burst() simultaneously from different threads
for the same queue_id requires additional SMP memory barrier to avoid
reordering of used->idx and last_used_idx updates.
In case of virtio_dev_rx() memory barrier rte_mb() simply moved one
instruction higher.
Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
---
lib/librte_vhost/vhost_rxtx.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index a8e2582..4d37aa3 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -323,13 +323,16 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
rte_pause();
*(volatile uint16_t *)&vq->used->idx += count;
- vq->last_used_idx = res_end_idx;
vhost_log_used_vring(dev, vq,
offsetof(struct vring_used, idx),
sizeof(vq->used->idx));
- /* flush used->idx update before we read avail->flags. */
+ /*
+ * Flush used->idx update to make it visible to virtio and all other
+ * threads before allowing to modify it.
+ */
rte_mb();
+ vq->last_used_idx = res_end_idx;
/* Kick the guest if necessary. */
if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
@@ -645,19 +648,24 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t
queue_id,
rte_pause();
*(volatile uint16_t *)&vq->used->idx += entry_success;
+ /*
+ * Flush used->idx update to make it visible to all
+ * other threads before allowing to modify it.
+ */
+ rte_smp_wmb();
+
vq->last_used_idx = res_cur_idx;
}
merge_rx_exit:
if (likely(pkt_idx)) {
- /* flush used->idx update before we read avail->flags. */
+ /* Flush used->idx update to make it visible to virtio. */
rte_mb();
/* Kick the guest if necessary. */
if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
eventfd_write(vq->callfd, (eventfd_t)1);
}
-
return pkt_idx;
}
--
2.5.0
