diff mbox series

[v13,05/10] net/virtio: implement transmit path for packed queues

Message ID 20181214155916.1142-6-jfreimann@redhat.com (mailing list archive)
State Superseded, archived
Delegated to: Maxime Coquelin
Headers
Series implement packed virtqueues |

Checks

Context Check Description
ci/Intel-compilation success Compilation OK

Commit Message

Jens Freimann Dec. 14, 2018, 3:59 p.m. UTC 
  This implements the transmit path for devices with
support for packed virtqueues.

Signed-off-by: Jens Freiman <jfreimann@redhat.com>
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
---
 drivers/net/virtio/virtio_ethdev.c |  57 ++++---
 drivers/net/virtio/virtio_ethdev.h |   2 +
 drivers/net/virtio/virtio_rxtx.c   | 236 ++++++++++++++++++++++++++++-
 drivers/net/virtio/virtqueue.h     |  20 ++-
 4 files changed, 293 insertions(+), 22 deletions(-)

Comments

Maxime Coquelin Dec. 17, 2018, 4:35 p.m. UTC | #1 
On 12/14/18 4:59 PM, Jens Freimann wrote:
> This implements the transmit path for devices with
> support for packed virtqueues.
> 
> Signed-off-by: Jens Freiman <jfreimann@redhat.com>
> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> ---
>   drivers/net/virtio/virtio_ethdev.c |  57 ++++---
>   drivers/net/virtio/virtio_ethdev.h |   2 +
>   drivers/net/virtio/virtio_rxtx.c   | 236 ++++++++++++++++++++++++++++-
>   drivers/net/virtio/virtqueue.h     |  20 ++-
>   4 files changed, 293 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index e6ba1282b..9f1b72e56 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -390,6 +390,9 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t vtpci_queue_idx)
>   	if (vtpci_packed_queue(hw)) {
>   		vq->avail_wrap_counter = 1;
>   		vq->used_wrap_counter = 1;
> +		vq->avail_used_flags =
> +			VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
> +			VRING_DESC_F_USED(!vq->avail_wrap_counter);
>   	}
>   
>   	/*
> @@ -497,17 +500,26 @@ virtio_init_queue(struct rte_eth_dev *dev, uint16_t vtpci_queue_idx)
>   		memset(txr, 0, vq_size * sizeof(*txr));
>   		for (i = 0; i < vq_size; i++) {
>   			struct vring_desc *start_dp = txr[i].tx_indir;
> -
> -			vring_desc_init_split(start_dp,
> -					      RTE_DIM(txr[i].tx_indir));
> +			struct vring_packed_desc *start_dp_packed =
> +				txr[i].tx_indir_pq;
>   
>   			/* first indirect descriptor is always the tx header */
> -			start_dp->addr = txvq->virtio_net_hdr_mem
> -				+ i * sizeof(*txr)
> -				+ offsetof(struct virtio_tx_region, tx_hdr);
> -
> -			start_dp->len = hw->vtnet_hdr_size;
> -			start_dp->flags = VRING_DESC_F_NEXT;
> +			if (vtpci_packed_queue(hw)) {
> +				start_dp_packed->addr = txvq->virtio_net_hdr_mem
> +					+ i * sizeof(*txr)
> +					+ offsetof(struct virtio_tx_region,
> +						   tx_hdr);
> +				start_dp_packed->len = hw->vtnet_hdr_size;
> +			} else {
> +				vring_desc_init_split(start_dp,
> +						      RTE_DIM(txr[i].tx_indir));
> +				start_dp->addr = txvq->virtio_net_hdr_mem
> +					+ i * sizeof(*txr)
> +					+ offsetof(struct virtio_tx_region,
> +						   tx_hdr);
> +				start_dp->len = hw->vtnet_hdr_size;
> +				start_dp->flags = VRING_DESC_F_NEXT;
> +			}
>   		}
>   	}
>   
> @@ -1336,6 +1348,23 @@ set_rxtx_funcs(struct rte_eth_dev *eth_dev)
>   {
>   	struct virtio_hw *hw = eth_dev->data->dev_private;
>   
> +	if (vtpci_packed_queue(hw)) {
> +		PMD_INIT_LOG(INFO,
> +			"virtio: using packed ring standard Tx path on port %u",
> +			eth_dev->data->port_id);
> +		eth_dev->tx_pkt_burst = virtio_xmit_pkts_packed;
> +	} else {
> +		if (hw->use_inorder_tx) {
> +			PMD_INIT_LOG(INFO, "virtio: using inorder Tx path on port %u",
> +				eth_dev->data->port_id);
> +			eth_dev->tx_pkt_burst = virtio_xmit_pkts_inorder;
> +		} else {
> +			PMD_INIT_LOG(INFO, "virtio: using standard Tx path on port %u",
> +				eth_dev->data->port_id);
> +			eth_dev->tx_pkt_burst = virtio_xmit_pkts;
> +		}
> +	}
> +
>   	if (hw->use_simple_rx) {
>   		PMD_INIT_LOG(INFO, "virtio: using simple Rx path on port %u",
>   			eth_dev->data->port_id);
> @@ -1356,15 +1385,7 @@ set_rxtx_funcs(struct rte_eth_dev *eth_dev)
>   		eth_dev->rx_pkt_burst = &virtio_recv_pkts;
>   	}
>   
> -	if (hw->use_inorder_tx) {
> -		PMD_INIT_LOG(INFO, "virtio: using inorder Tx path on port %u",
> -			eth_dev->data->port_id);
> -		eth_dev->tx_pkt_burst = virtio_xmit_pkts_inorder;
> -	} else {
> -		PMD_INIT_LOG(INFO, "virtio: using standard Tx path on port %u",
> -			eth_dev->data->port_id);
> -		eth_dev->tx_pkt_burst = virtio_xmit_pkts;
> -	}
> +

Trailing new line?


Apart from that, it looks good to me:
Reviewed-by: Maxime coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime
diff mbox series

Patch

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index e6ba1282b..9f1b72e56 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -390,6 +390,9 @@  virtio_init_queue(struct rte_eth_dev *dev, uint16_t vtpci_queue_idx)
 	if (vtpci_packed_queue(hw)) {
 		vq->avail_wrap_counter = 1;
 		vq->used_wrap_counter = 1;
+		vq->avail_used_flags =
+			VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
+			VRING_DESC_F_USED(!vq->avail_wrap_counter);
 	}
 
 	/*
@@ -497,17 +500,26 @@  virtio_init_queue(struct rte_eth_dev *dev, uint16_t vtpci_queue_idx)
 		memset(txr, 0, vq_size * sizeof(*txr));
 		for (i = 0; i < vq_size; i++) {
 			struct vring_desc *start_dp = txr[i].tx_indir;
-
-			vring_desc_init_split(start_dp,
-					      RTE_DIM(txr[i].tx_indir));
+			struct vring_packed_desc *start_dp_packed =
+				txr[i].tx_indir_pq;
 
 			/* first indirect descriptor is always the tx header */
-			start_dp->addr = txvq->virtio_net_hdr_mem
-				+ i * sizeof(*txr)
-				+ offsetof(struct virtio_tx_region, tx_hdr);
-
-			start_dp->len = hw->vtnet_hdr_size;
-			start_dp->flags = VRING_DESC_F_NEXT;
+			if (vtpci_packed_queue(hw)) {
+				start_dp_packed->addr = txvq->virtio_net_hdr_mem
+					+ i * sizeof(*txr)
+					+ offsetof(struct virtio_tx_region,
+						   tx_hdr);
+				start_dp_packed->len = hw->vtnet_hdr_size;
+			} else {
+				vring_desc_init_split(start_dp,
+						      RTE_DIM(txr[i].tx_indir));
+				start_dp->addr = txvq->virtio_net_hdr_mem
+					+ i * sizeof(*txr)
+					+ offsetof(struct virtio_tx_region,
+						   tx_hdr);
+				start_dp->len = hw->vtnet_hdr_size;
+				start_dp->flags = VRING_DESC_F_NEXT;
+			}
 		}
 	}
 
@@ -1336,6 +1348,23 @@  set_rxtx_funcs(struct rte_eth_dev *eth_dev)
 {
 	struct virtio_hw *hw = eth_dev->data->dev_private;
 
+	if (vtpci_packed_queue(hw)) {
+		PMD_INIT_LOG(INFO,
+			"virtio: using packed ring standard Tx path on port %u",
+			eth_dev->data->port_id);
+		eth_dev->tx_pkt_burst = virtio_xmit_pkts_packed;
+	} else {
+		if (hw->use_inorder_tx) {
+			PMD_INIT_LOG(INFO, "virtio: using inorder Tx path on port %u",
+				eth_dev->data->port_id);
+			eth_dev->tx_pkt_burst = virtio_xmit_pkts_inorder;
+		} else {
+			PMD_INIT_LOG(INFO, "virtio: using standard Tx path on port %u",
+				eth_dev->data->port_id);
+			eth_dev->tx_pkt_burst = virtio_xmit_pkts;
+		}
+	}
+
 	if (hw->use_simple_rx) {
 		PMD_INIT_LOG(INFO, "virtio: using simple Rx path on port %u",
 			eth_dev->data->port_id);
@@ -1356,15 +1385,7 @@  set_rxtx_funcs(struct rte_eth_dev *eth_dev)
 		eth_dev->rx_pkt_burst = &virtio_recv_pkts;
 	}
 
-	if (hw->use_inorder_tx) {
-		PMD_INIT_LOG(INFO, "virtio: using inorder Tx path on port %u",
-			eth_dev->data->port_id);
-		eth_dev->tx_pkt_burst = virtio_xmit_pkts_inorder;
-	} else {
-		PMD_INIT_LOG(INFO, "virtio: using standard Tx path on port %u",
-			eth_dev->data->port_id);
-		eth_dev->tx_pkt_burst = virtio_xmit_pkts;
-	}
+
 }
 
 /* Only support 1:1 queue/interrupt mapping so far.
diff --git a/drivers/net/virtio/virtio_ethdev.h b/drivers/net/virtio/virtio_ethdev.h
index e0f80e5a4..05d355180 100644
--- a/drivers/net/virtio/virtio_ethdev.h
+++ b/drivers/net/virtio/virtio_ethdev.h
@@ -82,6 +82,8 @@  uint16_t virtio_recv_mergeable_pkts_inorder(void *rx_queue,
 
 uint16_t virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 		uint16_t nb_pkts);
+uint16_t virtio_xmit_pkts_packed(void *tx_queue, struct rte_mbuf **tx_pkts,
+		uint16_t nb_pkts);
 
 uint16_t virtio_xmit_pkts_inorder(void *tx_queue, struct rte_mbuf **tx_pkts,
 		uint16_t nb_pkts);
diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index cb8f89f18..9cc7ad2d0 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -88,6 +88,23 @@  vq_ring_free_chain(struct virtqueue *vq, uint16_t desc_idx)
 	dp->next = VQ_RING_DESC_CHAIN_END;
 }
 
+static void
+vq_ring_free_id_packed(struct virtqueue *vq, uint16_t id)
+{
+	struct vq_desc_extra *dxp;
+
+	dxp = &vq->vq_descx[id];
+	vq->vq_free_cnt += dxp->ndescs;
+
+	if (vq->vq_desc_tail_idx == VQ_RING_DESC_CHAIN_END)
+		vq->vq_desc_head_idx = id;
+	else
+		vq->vq_descx[vq->vq_desc_tail_idx].next = id;
+
+	vq->vq_desc_tail_idx = id;
+	dxp->next = VQ_RING_DESC_CHAIN_END;
+}
+
 static uint16_t
 virtqueue_dequeue_burst_rx(struct virtqueue *vq, struct rte_mbuf **rx_pkts,
 			   uint32_t *len, uint16_t num)
@@ -165,6 +182,33 @@  virtqueue_dequeue_rx_inorder(struct virtqueue *vq,
 #endif
 
 /* Cleanup from completed transmits. */
+static void
+virtio_xmit_cleanup_packed(struct virtqueue *vq, int num)
+{
+	uint16_t used_idx, id;
+	uint16_t size = vq->vq_nentries;
+	struct vring_packed_desc *desc = vq->ring_packed.desc_packed;
+	struct vq_desc_extra *dxp;
+
+	used_idx = vq->vq_used_cons_idx;
+	while (num-- && desc_is_used(&desc[used_idx], vq)) {
+		used_idx = vq->vq_used_cons_idx;
+		id = desc[used_idx].id;
+		dxp = &vq->vq_descx[id];
+		vq->vq_used_cons_idx += dxp->ndescs;
+		if (vq->vq_used_cons_idx >= size) {
+			vq->vq_used_cons_idx -= size;
+			vq->used_wrap_counter ^= 1;
+		}
+		vq_ring_free_id_packed(vq, id);
+		if (dxp->cookie != NULL) {
+			rte_pktmbuf_free(dxp->cookie);
+			dxp->cookie = NULL;
+		}
+		used_idx = vq->vq_used_cons_idx;
+	}
+}
+
 static void
 virtio_xmit_cleanup(struct virtqueue *vq, uint16_t num)
 {
@@ -456,6 +500,107 @@  virtqueue_enqueue_xmit_inorder(struct virtnet_tx *txvq,
 	vq->vq_desc_head_idx = idx & (vq->vq_nentries - 1);
 }
 
+static inline void
+virtqueue_enqueue_xmit_packed(struct virtnet_tx *txvq, struct rte_mbuf *cookie,
+			      uint16_t needed, int can_push)
+{
+	struct virtio_tx_region *txr = txvq->virtio_net_hdr_mz->addr;
+	struct vq_desc_extra *dxp;
+	struct virtqueue *vq = txvq->vq;
+	struct vring_packed_desc *start_dp, *head_dp;
+	uint16_t idx, id, head_idx, head_flags;
+	uint16_t head_size = vq->hw->vtnet_hdr_size;
+	struct virtio_net_hdr *hdr;
+	uint16_t prev;
+
+	id = vq->vq_desc_head_idx;
+
+	dxp = &vq->vq_descx[id];
+	dxp->ndescs = needed;
+	dxp->cookie = cookie;
+
+	head_idx = vq->vq_avail_idx;
+	idx = head_idx;
+	prev = head_idx;
+	start_dp = vq->ring_packed.desc_packed;
+
+	head_dp = &vq->ring_packed.desc_packed[idx];
+	head_flags = cookie->next ? VRING_DESC_F_NEXT : 0;
+	head_flags |= vq->avail_used_flags;
+
+	if (can_push) {
+		/* prepend cannot fail, checked by caller */
+		hdr = (struct virtio_net_hdr *)
+			rte_pktmbuf_prepend(cookie, head_size);
+		/* rte_pktmbuf_prepend() counts the hdr size to the pkt length,
+		 * which is wrong. Below subtract restores correct pkt size.
+		 */
+		cookie->pkt_len -= head_size;
+
+		/* if offload disabled, it is not zeroed below, do it now */
+		if (!vq->hw->has_tx_offload) {
+			ASSIGN_UNLESS_EQUAL(hdr->csum_start, 0);
+			ASSIGN_UNLESS_EQUAL(hdr->csum_offset, 0);
+			ASSIGN_UNLESS_EQUAL(hdr->flags, 0);
+			ASSIGN_UNLESS_EQUAL(hdr->gso_type, 0);
+			ASSIGN_UNLESS_EQUAL(hdr->gso_size, 0);
+			ASSIGN_UNLESS_EQUAL(hdr->hdr_len, 0);
+		}
+	} else {
+		/* setup first tx ring slot to point to header
+		 * stored in reserved region.
+		 */
+		start_dp[idx].addr  = txvq->virtio_net_hdr_mem +
+			RTE_PTR_DIFF(&txr[idx].tx_hdr, txr);
+		start_dp[idx].len   = vq->hw->vtnet_hdr_size;
+		hdr = (struct virtio_net_hdr *)&txr[idx].tx_hdr;
+		idx++;
+		if (idx >= vq->vq_nentries) {
+			idx -= vq->vq_nentries;
+			vq->avail_wrap_counter ^= 1;
+			vq->avail_used_flags =
+				VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
+				VRING_DESC_F_USED(!vq->avail_wrap_counter);
+		}
+	}
+
+	virtqueue_xmit_offload(hdr, cookie, vq->hw->has_tx_offload);
+
+	do {
+		uint16_t flags;
+
+		start_dp[idx].addr = VIRTIO_MBUF_DATA_DMA_ADDR(cookie, vq);
+		start_dp[idx].len  = cookie->data_len;
+		if (likely(idx != head_idx)) {
+			flags = cookie->next ? VRING_DESC_F_NEXT : 0;
+			flags |= vq->avail_used_flags;
+			start_dp[idx].flags = flags;
+		}
+		prev = idx;
+		idx++;
+		if (idx >= vq->vq_nentries) {
+			idx -= vq->vq_nentries;
+			vq->avail_wrap_counter ^= 1;
+			vq->avail_used_flags =
+				VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
+				VRING_DESC_F_USED(!vq->avail_wrap_counter);
+		}
+	} while ((cookie = cookie->next) != NULL);
+
+	start_dp[prev].id = id;
+
+	vq->vq_free_cnt = (uint16_t)(vq->vq_free_cnt - needed);
+
+	vq->vq_desc_head_idx = dxp->next;
+	if (vq->vq_desc_head_idx == VQ_RING_DESC_CHAIN_END)
+		vq->vq_desc_tail_idx = VQ_RING_DESC_CHAIN_END;
+
+	vq->vq_avail_idx = idx;
+
+	rte_smp_wmb();
+	head_dp->flags = head_flags;
+}
+
 static inline void
 virtqueue_enqueue_xmit(struct virtnet_tx *txvq, struct rte_mbuf *cookie,
 			uint16_t needed, int use_indirect, int can_push,
@@ -733,8 +878,10 @@  virtio_dev_tx_queue_setup_finish(struct rte_eth_dev *dev,
 
 	PMD_INIT_FUNC_TRACE();
 
-	if (hw->use_inorder_tx)
-		vq->vq_ring.desc[vq->vq_nentries - 1].next = 0;
+	if (!vtpci_packed_queue(hw)) {
+		if (hw->use_inorder_tx)
+			vq->vq_ring.desc[vq->vq_nentries - 1].next = 0;
+	}
 
 	VIRTQUEUE_DUMP(vq);
 
@@ -1346,6 +1493,91 @@  virtio_recv_mergeable_pkts(void *rx_queue,
 	return nb_rx;
 }
 
+uint16_t
+virtio_xmit_pkts_packed(void *tx_queue, struct rte_mbuf **tx_pkts,
+			uint16_t nb_pkts)
+{
+	struct virtnet_tx *txvq = tx_queue;
+	struct virtqueue *vq = txvq->vq;
+	struct virtio_hw *hw = vq->hw;
+	uint16_t hdr_size = hw->vtnet_hdr_size;
+	uint16_t nb_tx = 0;
+	int error;
+
+	if (unlikely(hw->started == 0 && tx_pkts != hw->inject_pkts))
+		return nb_tx;
+
+	if (unlikely(nb_pkts < 1))
+		return nb_pkts;
+
+	PMD_TX_LOG(DEBUG, "%d packets to xmit", nb_pkts);
+
+	if (nb_pkts > vq->vq_free_cnt)
+		virtio_xmit_cleanup_packed(vq, nb_pkts - vq->vq_free_cnt);
+
+	for (nb_tx = 0; nb_tx < nb_pkts; nb_tx++) {
+		struct rte_mbuf *txm = tx_pkts[nb_tx];
+		int can_push = 0, slots, need;
+
+		/* Do VLAN tag insertion */
+		if (unlikely(txm->ol_flags & PKT_TX_VLAN_PKT)) {
+			error = rte_vlan_insert(&txm);
+			if (unlikely(error)) {
+				rte_pktmbuf_free(txm);
+				continue;
+			}
+		}
+
+		/* optimize ring usage */
+		if ((vtpci_with_feature(hw, VIRTIO_F_ANY_LAYOUT) ||
+		      vtpci_with_feature(hw, VIRTIO_F_VERSION_1)) &&
+		    rte_mbuf_refcnt_read(txm) == 1 &&
+		    RTE_MBUF_DIRECT(txm) &&
+		    txm->nb_segs == 1 &&
+		    rte_pktmbuf_headroom(txm) >= hdr_size &&
+		    rte_is_aligned(rte_pktmbuf_mtod(txm, char *),
+			   __alignof__(struct virtio_net_hdr_mrg_rxbuf)))
+			can_push = 1;
+
+		/* How many main ring entries are needed to this Tx?
+		 * any_layout => number of segments
+		 * default    => number of segments + 1
+		 */
+		slots = txm->nb_segs + !can_push;
+		need = slots - vq->vq_free_cnt;
+
+		/* Positive value indicates it need free vring descriptors */
+		if (unlikely(need > 0)) {
+			virtio_rmb();
+			need = RTE_MIN(need, (int)nb_pkts);
+			virtio_xmit_cleanup_packed(vq, need);
+			need = slots - vq->vq_free_cnt;
+			if (unlikely(need > 0)) {
+				PMD_TX_LOG(ERR,
+					   "No free tx descriptors to transmit");
+				break;
+			}
+		}
+
+		/* Enqueue Packet buffers */
+		virtqueue_enqueue_xmit_packed(txvq, txm, slots, can_push);
+
+		txvq->stats.bytes += txm->pkt_len;
+		virtio_update_packet_stats(&txvq->stats, txm);
+	}
+
+	txvq->stats.packets += nb_tx;
+
+	if (likely(nb_tx)) {
+		if (unlikely(virtqueue_kick_prepare_packed(vq))) {
+			virtqueue_notify(vq);
+			PMD_TX_LOG(DEBUG, "Notified backend after xmit");
+		}
+	}
+
+	return nb_tx;
+}
+
 uint16_t
 virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 {
diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
index 9c65ad54f..3cd7d6cf9 100644
--- a/drivers/net/virtio/virtqueue.h
+++ b/drivers/net/virtio/virtqueue.h
@@ -247,8 +247,12 @@  struct virtio_net_hdr_mrg_rxbuf {
 #define VIRTIO_MAX_TX_INDIRECT 8
 struct virtio_tx_region {
 	struct virtio_net_hdr_mrg_rxbuf tx_hdr;
-	struct vring_desc tx_indir[VIRTIO_MAX_TX_INDIRECT]
-			   __attribute__((__aligned__(16)));
+	union {
+		struct vring_desc tx_indir[VIRTIO_MAX_TX_INDIRECT]
+			__attribute__((__aligned__(16)));
+		struct vring_packed_desc tx_indir_pq[VIRTIO_MAX_TX_INDIRECT]
+			__attribute__((__aligned__(16)));
+	};
 };
 
 static inline void
@@ -399,6 +403,7 @@  virtio_get_queue_type(struct virtio_hw *hw, uint16_t vtpci_queue_idx)
 #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);
+void vq_ring_free_chain_packed(struct virtqueue *vq, uint16_t used_idx);
 void vq_ring_free_inorder(struct virtqueue *vq, uint16_t desc_idx,
 			  uint16_t num);
 
@@ -432,6 +437,17 @@  virtqueue_kick_prepare(struct virtqueue *vq)
 	return !(vq->vq_ring.used->flags & VRING_USED_F_NO_NOTIFY);
 }
 
+static inline int
+virtqueue_kick_prepare_packed(struct virtqueue *vq)
+{
+	uint16_t flags;
+
+	virtio_mb();
+	flags = vq->ring_packed.device_event->desc_event_flags;
+
+	return flags != RING_EVENT_FLAGS_DISABLE;
+}
+
 static inline void
 virtqueue_notify(struct virtqueue *vq)
 {