vhost: replace SMP with thread fence for packed vring

Simply replace smp barriers with atomic thread fence for
virtio packed vring.

Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index b779034..e145fcb 100644 (file)
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -171,7 +171,8 @@ vhost_flush_enqueue_shadow_packed(struct virtio_net *dev,
                        used_idx -= vq->size;
        }
 
-       rte_smp_wmb();
+       /* The ordering for storing desc flags needs to be enforced. */
+       rte_atomic_thread_fence(__ATOMIC_RELEASE);
 
        for (i = 0; i < vq->shadow_used_idx; i++) {
                uint16_t flags;
@@ -254,7 +255,7 @@ vhost_flush_enqueue_batch_packed(struct virtio_net *dev,
                vq->desc_packed[vq->last_used_idx + i].len = lens[i];
        }
 
-       rte_smp_wmb();
+       rte_atomic_thread_fence(__ATOMIC_RELEASE);
 
        vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE)
                vq->desc_packed[vq->last_used_idx + i].flags = flags;
@@ -313,7 +314,7 @@ vhost_shadow_dequeue_batch_packed(struct virtio_net *dev,
                vq->desc_packed[vq->last_used_idx + i].len = 0;
        }
 
-       rte_smp_wmb();
+       rte_atomic_thread_fence(__ATOMIC_RELEASE);
        vhost_for_each_try_unroll(i, begin, PACKED_BATCH_SIZE)
                vq->desc_packed[vq->last_used_idx + i].flags = flags;
 
@@ -2246,7 +2247,7 @@ vhost_reserve_avail_batch_packed(struct virtio_net *dev,
                        return -1;
        }
 
-       rte_smp_rmb();
+       rte_atomic_thread_fence(__ATOMIC_ACQUIRE);
 
        vhost_for_each_try_unroll(i, 0, PACKED_BATCH_SIZE)
                lens[i] = descs[avail_idx + i].len;