[dpdk-dev] [PATCH v5] net/virtio-user: fix packed ring server mode

[Xuan Ding <xuan.ding@intel.com>]

This patch fixes the situation where data path does not work properly when
vhost reconnects to virtio in server mode with packed ring.

Currently, virtio and vhost share memory of vring. For split ring, vhost
can read the status of descriptors directly from the available ring and
the used ring during reconnection. Therefore, the data path can continue.

But for packed ring, when reconnecting to virtio, vhost cannot get the
status of descriptors via the descriptor ring. By resetting Tx
and Rx queues, the data path can restart from the beginning.

Fixes: 4c3f5822eb214 ("net/virtio: add packed virtqueue defines")
Cc: stable@dpdk.org

Signed-off-by: Xuan Ding <xuan.ding@intel.com>
---

v5:
* Fixed two spelling mistakes in the commit log.
* Added notice message when resetting vring.

v4:
* Moved change log below '---' marker.

v3:
* Removed an extra asterisk from a comment.
* Renamed device reset function and moved it to virtio_user_ethdev.c.

v2:
* Renamed queue reset functions and moved them to virtqueue.c.
---
 drivers/net/virtio/virtio_ethdev.c      |  4 +-
 drivers/net/virtio/virtio_user_ethdev.c | 42 +++++++++++++++
 drivers/net/virtio/virtqueue.c          | 71 +++++++++++++++++++++++++
 drivers/net/virtio/virtqueue.h          |  4 ++
 4 files changed, 119 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index 044eb10a7..f9d0ea70d 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -1913,6 +1913,8 @@ eth_virtio_dev_init(struct rte_eth_dev *eth_dev)
 			goto err_vtpci_init;
 	}
 
+	rte_spinlock_init(&hw->state_lock);
+
 	/* reset device and negotiate default features */
 	ret = virtio_init_device(eth_dev, VIRTIO_PMD_DEFAULT_GUEST_FEATURES);
 	if (ret < 0)
@@ -2155,8 +2157,6 @@ virtio_dev_configure(struct rte_eth_dev *dev)
 			return -EBUSY;
 		}
 
-	rte_spinlock_init(&hw->state_lock);
-
 	hw->use_simple_rx = 1;
 
 	if (vtpci_with_feature(hw, VIRTIO_F_IN_ORDER)) {
diff --git a/drivers/net/virtio/virtio_user_ethdev.c b/drivers/net/virtio/virtio_user_ethdev.c
index 3fc172573..9c9d3407f 100644
--- a/drivers/net/virtio/virtio_user_ethdev.c
+++ b/drivers/net/virtio/virtio_user_ethdev.c
@@ -25,12 +25,48 @@
 #define virtio_user_get_dev(hw) \
 	((struct virtio_user_dev *)(hw)->virtio_user_dev)
 
+static void
+virtio_user_reset_queues_packed(struct rte_eth_dev *dev)
+{
+	struct virtio_hw *hw = dev->data->dev_private;
+	struct virtnet_rx *rxvq;
+	struct virtnet_tx *txvq;
+	uint16_t i;
+
+	/* Add lock to avoid queue contention. */
+	rte_spinlock_lock(&hw->state_lock);
+	hw->started = 0;
+
+	/*
+	 * Waitting for datapath to complete before resetting queues.
+	 * 1 ms should be enough for the ongoing Tx/Rx function to finish.
+	 */
+	rte_delay_ms(1);
+
+	/* Vring reset for each Tx queue and Rx queue. */
+	for (i = 0; i < dev->data->nb_rx_queues; i++) {
+		rxvq = dev->data->rx_queues[i];
+		virtqueue_rxvq_reset_packed(rxvq->vq);
+		virtio_dev_rx_queue_setup_finish(dev, i);
+	}
+
+	for (i = 0; i < dev->data->nb_tx_queues; i++) {
+		txvq = dev->data->tx_queues[i];
+		virtqueue_txvq_reset_packed(txvq->vq);
+	}
+
+	hw->started = 1;
+	rte_spinlock_unlock(&hw->state_lock);
+}
+
+
 static int
 virtio_user_server_reconnect(struct virtio_user_dev *dev)
 {
 	int ret;
 	int connectfd;
 	struct rte_eth_dev *eth_dev = &rte_eth_devices[dev->port_id];
+	struct virtio_hw *hw = eth_dev->data->dev_private;
 
 	connectfd = accept(dev->listenfd, NULL, NULL);
 	if (connectfd < 0)
@@ -51,6 +87,12 @@ virtio_user_server_reconnect(struct virtio_user_dev *dev)
 
 	dev->features &= dev->device_features;
 
+	/* For packed ring, resetting queues is required in reconnection. */
+	if (vtpci_packed_queue(hw))
+		PMD_INIT_LOG(NOTICE, "Packets on the fly will be dropped"
+				" when packed ring reconnecting.");
+		virtio_user_reset_queues_packed(eth_dev);
+
 	ret = virtio_user_start_device(dev);
 	if (ret < 0)
 		return -1;
diff --git a/drivers/net/virtio/virtqueue.c b/drivers/net/virtio/virtqueue.c
index 5ff1e3587..0b4e3bf3e 100644
--- a/drivers/net/virtio/virtqueue.c
+++ b/drivers/net/virtio/virtqueue.c
@@ -141,3 +141,74 @@ virtqueue_rxvq_flush(struct virtqueue *vq)
 	else
 		virtqueue_rxvq_flush_split(vq);
 }
+
+int
+virtqueue_rxvq_reset_packed(struct virtqueue *vq)
+{
+	int size = vq->vq_nentries;
+	struct vq_desc_extra *dxp;
+	struct virtnet_rx *rxvq;
+	uint16_t desc_idx;
+
+	vq->vq_used_cons_idx = 0;
+	vq->vq_desc_head_idx = 0;
+	vq->vq_avail_idx = 0;
+	vq->vq_desc_tail_idx = (uint16_t)(vq->vq_nentries - 1);
+	vq->vq_free_cnt = vq->vq_nentries;
+
+	vq->vq_packed.used_wrap_counter = 1;
+	vq->vq_packed.cached_flags = VRING_PACKED_DESC_F_AVAIL;
+	vq->vq_packed.event_flags_shadow = 0;
+	vq->vq_packed.cached_flags |= VRING_DESC_F_WRITE;
+
+	rxvq = &vq->rxq;
+	memset(rxvq->mz->addr, 0, rxvq->mz->len);
+
+	for (desc_idx = 0; desc_idx < vq->vq_nentries; desc_idx++) {
+		dxp = &vq->vq_descx[desc_idx];
+		if (dxp->cookie != NULL) {
+			rte_pktmbuf_free(dxp->cookie);
+			dxp->cookie = NULL;
+		}
+	}
+
+	vring_desc_init_packed(vq, size);
+
+	return 0;
+}
+
+int
+virtqueue_txvq_reset_packed(struct virtqueue *vq)
+{
+	int size = vq->vq_nentries;
+	struct vq_desc_extra *dxp;
+	struct virtnet_tx *txvq;
+	uint16_t desc_idx;
+
+	vq->vq_used_cons_idx = 0;
+	vq->vq_desc_head_idx = 0;
+	vq->vq_avail_idx = 0;
+	vq->vq_desc_tail_idx = (uint16_t)(vq->vq_nentries - 1);
+	vq->vq_free_cnt = vq->vq_nentries;
+
+	vq->vq_packed.used_wrap_counter = 1;
+	vq->vq_packed.cached_flags = VRING_PACKED_DESC_F_AVAIL;
+	vq->vq_packed.event_flags_shadow = 0;
+
+	txvq = &vq->txq;
+	memset(txvq->mz->addr, 0, txvq->mz->len);
+	memset(txvq->virtio_net_hdr_mz->addr, 0,
+		txvq->virtio_net_hdr_mz->len);
+
+	for (desc_idx = 0; desc_idx < vq->vq_nentries; desc_idx++) {
+		dxp = &vq->vq_descx[desc_idx];
+		if (dxp->cookie != NULL) {
+			rte_pktmbuf_free(dxp->cookie);
+			dxp->cookie = NULL;
+		}
+	}
+
+	vring_desc_init_packed(vq, size);
+
+	return 0;
+}
diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 8d7f197b1..58ad7309a 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -443,6 +443,10 @@ struct rte_mbuf *virtqueue_detach_unused(struct virtqueue *vq);
 /* Flush the elements in the used ring. */
 void virtqueue_rxvq_flush(struct virtqueue *vq);
 
+int virtqueue_rxvq_reset_packed(struct virtqueue *vq);
+
+int virtqueue_txvq_reset_packed(struct virtqueue *vq);
+
 static inline int
 virtqueue_full(const struct virtqueue *vq)
 {
-- 
2.17.1