[dpdk-dev] [PATCH v2] net/virtio: fix an incorrect behavior of device stop/start

[Tiwei Bie <tiwei.bie@intel.com>]

After starting a device, the driver shouldn't deliver the
packets that already existed before the device is started
to applications. Otherwise it will lead to incorrect packet
collection for port state. This patch fixes this issue by
flushing the Rx queues when starting the device.

Fixes: a85786dc816f ("virtio: fix states handling during initialization")
Cc: stable@dpdk.org

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Jens Freimann <jfreimann@redhat.com>
---
v2:
- Use the existing `for` loop
- Improve the commit log

 drivers/net/virtio/virtio_ethdev.c |  2 ++
 drivers/net/virtio/virtio_rxtx.c   |  2 +-
 drivers/net/virtio/virtqueue.c     | 25 +++++++++++++++++++++++++
 drivers/net/virtio/virtqueue.h     |  5 +++++
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index 42c2836..9ccb0f4 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -1819,6 +1819,8 @@ virtio_dev_start(struct rte_eth_dev *dev)
 
 	for (i = 0; i < dev->data->nb_rx_queues; i++) {
 		rxvq = dev->data->rx_queues[i];
+		/* Flush the old packets */
+		virtqueue_flush(rxvq->vq);
 		virtqueue_notify(rxvq->vq);
 	}
 
diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 609b413..f5b6f94 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -80,7 +80,7 @@ virtio_dev_rx_queue_done(void *rxq, uint16_t offset)
 	return VIRTQUEUE_NUSED(vq) >= offset;
 }
 
-static void
+void
 vq_ring_free_chain(struct virtqueue *vq, uint16_t desc_idx)
 {
 	struct vring_desc *dp, *dp_tail;
diff --git a/drivers/net/virtio/virtqueue.c b/drivers/net/virtio/virtqueue.c
index 9ad77b8..c3a536f 100644
--- a/drivers/net/virtio/virtqueue.c
+++ b/drivers/net/virtio/virtqueue.c
@@ -59,3 +59,28 @@ virtqueue_detatch_unused(struct virtqueue *vq)
 		}
 	return NULL;
 }
+
+/* Flush the elements in the used ring. */
+void
+virtqueue_flush(struct virtqueue *vq)
+{
+	struct vring_used_elem *uep;
+	struct vq_desc_extra *dxp;
+	uint16_t used_idx, desc_idx;
+	uint16_t nb_used, i;
+
+	nb_used = VIRTQUEUE_NUSED(vq);
+
+	for (i = 0; i < nb_used; i++) {
+		used_idx = vq->vq_used_cons_idx & (vq->vq_nentries - 1);
+		uep = &vq->vq_ring.used->ring[used_idx];
+		desc_idx = (uint16_t)uep->id;
+		dxp = &vq->vq_descx[desc_idx];
+		if (dxp->cookie != NULL) {
+			rte_pktmbuf_free(dxp->cookie);
+			dxp->cookie = NULL;
+		}
+		vq->vq_used_cons_idx++;
+		vq_ring_free_chain(vq, desc_idx);
+	}
+}
diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 9c4f96d..11059fb 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -304,6 +304,9 @@ void virtqueue_dump(struct virtqueue *vq);
  */
 struct rte_mbuf *virtqueue_detatch_unused(struct virtqueue *vq);
 
+/* Flush the elements in the used ring. */
+void virtqueue_flush(struct virtqueue *vq);
+
 static inline int
 virtqueue_full(const struct virtqueue *vq)
 {
@@ -312,6 +315,8 @@ virtqueue_full(const struct virtqueue *vq)
 
 #define VIRTQUEUE_NUSED(vq) ((uint16_t)((vq)->vq_ring.used->idx - (vq)->vq_used_cons_idx))
 
+void vq_ring_free_chain(struct virtqueue *vq, uint16_t desc_idx);
+
 static inline void
 vq_update_avail_idx(struct virtqueue *vq)
 {
-- 
2.7.4