Merge branch 'netvsc-NAPI'

Stephen Hemminger says:

====================
NAPI support for Hyper-V

These patches enable NAPI, GRO and napi_alloc_skb for Hyper-V netvsc
driver.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/hv/ring_buffer.c

@@ -32,6 +32,8 @@
 
 #include "hyperv_vmbus.h"
 
+#define VMBUS_PKT_TRAILER	8
+
 /*
  * When we write to the ring buffer, check if the host needs to
  * be signaled. Here is the details of this protocol:
@@ -336,6 +338,12 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
 	return 0;
 }
 
+static inline void
+init_cached_read_index(struct hv_ring_buffer_info *rbi)
+{
+	rbi->cached_read_index = rbi->ring_buffer->read_index;
+}
+
 int hv_ringbuffer_read(struct vmbus_channel *channel,
 		       void *buffer, u32 buflen, u32 *buffer_actual_len,
 		       u64 *requestid, bool raw)
@@ -366,7 +374,8 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
 		return ret;
 	}
 
-	init_cached_read_index(channel);
+	init_cached_read_index(inring_info);
+
 	next_read_location = hv_get_next_read_location(inring_info);
 	next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc,
 						    sizeof(desc),
@@ -410,3 +419,86 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
 
 	return ret;
 }
+
+/*
+ * Determine number of bytes available in ring buffer after
+ * the current iterator (priv_read_index) location.
+ *
+ * This is similar to hv_get_bytes_to_read but with private
+ * read index instead.
+ */
+static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
+{
+	u32 priv_read_loc = rbi->priv_read_index;
+	u32 write_loc = READ_ONCE(rbi->ring_buffer->write_index);
+
+	if (write_loc >= priv_read_loc)
+		return write_loc - priv_read_loc;
+	else
+		return (rbi->ring_datasize - priv_read_loc) + write_loc;
+}
+
+/*
+ * Get first vmbus packet from ring buffer after read_index
+ *
+ * If ring buffer is empty, returns NULL and no other action needed.
+ */
+struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
+{
+	struct hv_ring_buffer_info *rbi = &channel->inbound;
+
+	/* set state for later hv_signal_on_read() */
+	init_cached_read_index(rbi);
+
+	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
+		return NULL;
+
+	return hv_get_ring_buffer(rbi) + rbi->priv_read_index;
+}
+EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
+
+/*
+ * Get next vmbus packet from ring buffer.
+ *
+ * Advances the current location (priv_read_index) and checks for more
+ * data. If the end of the ring buffer is reached, then return NULL.
+ */
+struct vmpacket_descriptor *
+__hv_pkt_iter_next(struct vmbus_channel *channel,
+		   const struct vmpacket_descriptor *desc)
+{
+	struct hv_ring_buffer_info *rbi = &channel->inbound;
+	u32 packetlen = desc->len8 << 3;
+	u32 dsize = rbi->ring_datasize;
+
+	/* bump offset to next potential packet */
+	rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
+	if (rbi->priv_read_index >= dsize)
+		rbi->priv_read_index -= dsize;
+
+	/* more data? */
+	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
+		return NULL;
+	else
+		return hv_get_ring_buffer(rbi) + rbi->priv_read_index;
+}
+EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
+
+/*
+ * Update host ring buffer after iterating over packets.
+ */
+void hv_pkt_iter_close(struct vmbus_channel *channel)
+{
+	struct hv_ring_buffer_info *rbi = &channel->inbound;
+
+	/*
+	 * Make sure all reads are done before we update the read index since
+	 * the writer may start writing to the read area once the read index
+	 * is updated.
+	 */
+	virt_rmb();
+	rbi->ring_buffer->read_index = rbi->priv_read_index;
+
+	hv_signal_on_read(channel);
+}
+EXPORT_SYMBOL_GPL(hv_pkt_iter_close);

drivers/net/hyperv/hyperv_net.h

@@ -196,6 +196,7 @@ int netvsc_recv_callback(struct net_device *net,
 			 const struct ndis_tcp_ip_checksum_info *csum_info,
 			 const struct ndis_pkt_8021q_info *vlan);
 void netvsc_channel_cb(void *context);
+int netvsc_poll(struct napi_struct *napi, int budget);
 int rndis_filter_open(struct netvsc_device *nvdev);
 int rndis_filter_close(struct netvsc_device *nvdev);
 int rndis_filter_device_add(struct hv_device *dev,
@@ -720,6 +721,7 @@ struct net_device_context {
 /* Per channel data */
 struct netvsc_channel {
 	struct vmbus_channel *channel;
+	struct napi_struct napi;
 	struct multi_send_data msd;
 	struct multi_recv_comp mrc;
 	atomic_t queue_sends;

drivers/net/hyperv/netvsc.c

@@ -556,6 +556,7 @@ void netvsc_device_remove(struct hv_device *device)
 	struct net_device *ndev = hv_get_drvdata(device);
 	struct net_device_context *net_device_ctx = netdev_priv(ndev);
 	struct netvsc_device *net_device = net_device_ctx->nvdev;
+	int i;
 
 	netvsc_disconnect_vsp(device);
 
@@ -570,6 +571,9 @@ void netvsc_device_remove(struct hv_device *device)
 	/* Now, we can close the channel safely */
 	vmbus_close(device->channel);
 
+	for (i = 0; i < VRSS_CHANNEL_MAX; i++)
+		napi_disable(&net_device->chan_table[0].napi);
+
 	/* Release all resources */
 	free_netvsc_device(net_device);
 }
@@ -600,9 +604,9 @@ static inline void netvsc_free_send_slot(struct netvsc_device *net_device,
 static void netvsc_send_tx_complete(struct netvsc_device *net_device,
 				    struct vmbus_channel *incoming_channel,
 				    struct hv_device *device,
-				    struct vmpacket_descriptor *packet)
+				    const struct vmpacket_descriptor *desc)
 {
-	struct sk_buff *skb = (struct sk_buff *)(unsigned long)packet->trans_id;
+	struct sk_buff *skb = (struct sk_buff *)(unsigned long)desc->trans_id;
 	struct net_device *ndev = hv_get_drvdata(device);
 	struct net_device_context *net_device_ctx = netdev_priv(ndev);
 	struct vmbus_channel *channel = device->channel;
@@ -647,14 +651,11 @@ static void netvsc_send_tx_complete(struct netvsc_device *net_device,
 static void netvsc_send_completion(struct netvsc_device *net_device,
 				   struct vmbus_channel *incoming_channel,
 				   struct hv_device *device,
-				   struct vmpacket_descriptor *packet)
+				   const struct vmpacket_descriptor *desc)
 {
-	struct nvsp_message *nvsp_packet;
+	struct nvsp_message *nvsp_packet = hv_pkt_data(desc);
 	struct net_device *ndev = hv_get_drvdata(device);
 
-	nvsp_packet = (struct nvsp_message *)((unsigned long)packet +
-					      (packet->offset8 << 3));
-
 	switch (nvsp_packet->hdr.msg_type) {
 	case NVSP_MSG_TYPE_INIT_COMPLETE:
 	case NVSP_MSG1_TYPE_SEND_RECV_BUF_COMPLETE:
@@ -668,7 +669,7 @@ static void netvsc_send_completion(struct netvsc_device *net_device,
 
 	case NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE:
 		netvsc_send_tx_complete(net_device, incoming_channel,
-					device, packet);
+					device, desc);
 		break;
 
 	default:
@@ -1066,28 +1067,29 @@ static inline struct recv_comp_data *get_recv_comp_slot(
 	return rcd;
 }
 
-static void netvsc_receive(struct net_device *ndev,
+static int netvsc_receive(struct net_device *ndev,
 		   struct netvsc_device *net_device,
 		   struct net_device_context *net_device_ctx,
 		   struct hv_device *device,
 		   struct vmbus_channel *channel,
-		   struct vmtransfer_page_packet_header *vmxferpage_packet,
+		   const struct vmpacket_descriptor *desc,
 		   struct nvsp_message *nvsp)
 {
+	const struct vmtransfer_page_packet_header *vmxferpage_packet
+		= container_of(desc, const struct vmtransfer_page_packet_header, d);
+	u16 q_idx = channel->offermsg.offer.sub_channel_index;
 	char *recv_buf = net_device->recv_buf;
 	u32 status = NVSP_STAT_SUCCESS;
 	int i;
 	int count = 0;
 	int ret;
-	struct recv_comp_data *rcd;
-	u16 q_idx = channel->offermsg.offer.sub_channel_index;
 
 	/* Make sure this is a valid nvsp packet */
 	if (unlikely(nvsp->hdr.msg_type != NVSP_MSG1_TYPE_SEND_RNDIS_PKT)) {
 		netif_err(net_device_ctx, rx_err, ndev,
 			  "Unknown nvsp packet type received %u\n",
 			  nvsp->hdr.msg_type);
-		return;
+		return 0;
 	}
 
 	if (unlikely(vmxferpage_packet->xfer_pageset_id != NETVSC_RECEIVE_BUFFER_ID)) {
@@ -1095,7 +1097,7 @@ static void netvsc_receive(struct net_device *ndev,
 			  "Invalid xfer page set id - expecting %x got %x\n",
 			  NETVSC_RECEIVE_BUFFER_ID,
 			  vmxferpage_packet->xfer_pageset_id);
-		return;
+		return 0;
 	}
 
 	count = vmxferpage_packet->range_cnt;
@@ -1111,26 +1113,26 @@ static void netvsc_receive(struct net_device *ndev,
 					      channel, data, buflen);
 	}
 
-	if (!net_device->chan_table[q_idx].mrc.buf) {
+	if (net_device->chan_table[q_idx].mrc.buf) {
+		struct recv_comp_data *rcd;
+
+		rcd = get_recv_comp_slot(net_device, channel, q_idx);
+		if (rcd) {
+			rcd->tid = vmxferpage_packet->d.trans_id;
+			rcd->status = status;
+		} else {
+			netdev_err(ndev, "Recv_comp full buf q:%hd, tid:%llx\n",
+				   q_idx, vmxferpage_packet->d.trans_id);
+		}
+	} else {
 		ret = netvsc_send_recv_completion(channel,
 						  vmxferpage_packet->d.trans_id,
 						  status);
 		if (ret)
 			netdev_err(ndev, "Recv_comp q:%hd, tid:%llx, err:%d\n",
 				   q_idx, vmxferpage_packet->d.trans_id, ret);
-		return;
-	}
-
-	rcd = get_recv_comp_slot(net_device, channel, q_idx);
-
-	if (!rcd) {
-		netdev_err(ndev, "Recv_comp full buf q:%hd, tid:%llx\n",
-			   q_idx, vmxferpage_packet->d.trans_id);
-		return;
 	}
-
-	rcd->tid = vmxferpage_packet->d.trans_id;
-	rcd->status = status;
+	return count;
 }
 
 static void netvsc_send_table(struct hv_device *hdev,
@@ -1180,17 +1182,15 @@ static inline void netvsc_receive_inband(struct hv_device *hdev,
 	}
 }
 
-static void netvsc_process_raw_pkt(struct hv_device *device,
+static int netvsc_process_raw_pkt(struct hv_device *device,
 				  struct vmbus_channel *channel,
 				  struct netvsc_device *net_device,
 				  struct net_device *ndev,
 				  u64 request_id,
-				   struct vmpacket_descriptor *desc)
+				  const struct vmpacket_descriptor *desc)
 {
 	struct net_device_context *net_device_ctx = netdev_priv(ndev);
-	struct nvsp_message *nvmsg
-		= (struct nvsp_message *)((unsigned long)desc
-					  + (desc->offset8 << 3));
+	struct nvsp_message *nvmsg = hv_pkt_data(desc);
 
 	switch (desc->type) {
 	case VM_PKT_COMP:
@@ -1198,10 +1198,8 @@ static void netvsc_process_raw_pkt(struct hv_device *device,
 		break;
 
 	case VM_PKT_DATA_USING_XFER_PAGES:
-		netvsc_receive(ndev, net_device, net_device_ctx,
-			       device, channel,
-			       (struct vmtransfer_page_packet_header *)desc,
-			       nvmsg);
+		return netvsc_receive(ndev, net_device, net_device_ctx,
+				      device, channel, desc, nvmsg);
 		break;
 
 	case VM_PKT_DATA_INBAND:
@@ -1213,22 +1211,63 @@ static void netvsc_process_raw_pkt(struct hv_device *device,
 			   desc->type, request_id);
 		break;
 	}
+
+	return 0;
+}
+
+static struct hv_device *netvsc_channel_to_device(struct vmbus_channel *channel)
+{
+	struct vmbus_channel *primary = channel->primary_channel;
+
+	return primary ? primary->device_obj : channel->device_obj;
+}
+
+int netvsc_poll(struct napi_struct *napi, int budget)
+{
+	struct netvsc_channel *nvchan
+		= container_of(napi, struct netvsc_channel, napi);
+	struct vmbus_channel *channel = nvchan->channel;
+	struct hv_device *device = netvsc_channel_to_device(channel);
+	u16 q_idx = channel->offermsg.offer.sub_channel_index;
+	struct net_device *ndev = hv_get_drvdata(device);
+	struct netvsc_device *net_device = net_device_to_netvsc_device(ndev);
+	const struct vmpacket_descriptor *desc;
+	int work_done = 0;
+
+	desc = hv_pkt_iter_first(channel);
+	while (desc) {
+		int count;
+
+		count = netvsc_process_raw_pkt(device, channel, net_device,
+					       ndev, desc->trans_id, desc);
+		work_done += count;
+		desc = __hv_pkt_iter_next(channel, desc);
+
+		/* If receive packet budget is exhausted, reschedule */
+		if (work_done >= budget) {
+			work_done = budget;
+			break;
+		}
+	}
+	hv_pkt_iter_close(channel);
+
+	/* If ring is empty and NAPI is not doing polling */
+	if (work_done < budget &&
+	    napi_complete_done(napi, work_done) &&
+	    hv_end_read(&channel->inbound) != 0)
+		napi_reschedule(napi);
+
+	netvsc_chk_recv_comp(net_device, channel, q_idx);
+	return work_done;
 }
 
 void netvsc_channel_cb(void *context)
 {
 	struct vmbus_channel *channel = context;
+	struct hv_device *device = netvsc_channel_to_device(channel);
 	u16 q_idx = channel->offermsg.offer.sub_channel_index;
-	struct hv_device *device;
 	struct netvsc_device *net_device;
-	struct vmpacket_descriptor *desc;
 	struct net_device *ndev;
-	bool need_to_commit = false;
-
-	if (channel->primary_channel != NULL)
-		device = channel->primary_channel->device_obj;
-	else
-		device = channel->device_obj;
 
 	ndev = hv_get_drvdata(device);
 	if (unlikely(!ndev))
@@ -1239,21 +1278,9 @@ void netvsc_channel_cb(void *context)
 	    netvsc_channel_idle(net_device, q_idx))
 		return;
 
-	/* commit_rd_index() -> hv_signal_on_read() needs this. */
-	init_cached_read_index(channel);
-
-	while ((desc = get_next_pkt_raw(channel)) != NULL) {
-		netvsc_process_raw_pkt(device, channel, net_device,
-				       ndev, desc->trans_id, desc);
-
-		put_pkt_raw(channel, desc);
-		need_to_commit = true;
-	}
-
-	if (need_to_commit)
-		commit_rd_index(channel);
-
-	netvsc_chk_recv_comp(net_device, channel, q_idx);
+	/* disable interupts from host */
+	hv_begin_read(&channel->inbound);
+	napi_schedule(&net_device->chan_table[q_idx].napi);
 }
 
 /*
@@ -1275,6 +1302,11 @@ int netvsc_device_add(struct hv_device *device,
 
 	net_device->ring_size = ring_size;
 
+	/* Because the device uses NAPI, all the interrupt batching and
+	 * control is done via Net softirq, not the channel handling
+	 */
+	set_channel_read_mode(device->channel, HV_CALL_ISR);
+
 	/* Open the channel */
 	ret = vmbus_open(device->channel, ring_size * PAGE_SIZE,
 			 ring_size * PAGE_SIZE, NULL, 0,
@@ -1292,8 +1324,16 @@ int netvsc_device_add(struct hv_device *device,
 	 * chn_table with the default channel to use it before subchannels are
 	 * opened.
 	 */
-	for (i = 0; i < VRSS_CHANNEL_MAX; i++)
-		net_device->chan_table[i].channel = device->channel;
+	for (i = 0; i < VRSS_CHANNEL_MAX; i++) {
+		struct netvsc_channel *nvchan = &net_device->chan_table[i];
+
+		nvchan->channel = device->channel;
+		netif_napi_add(ndev, &nvchan->napi,
+			       netvsc_poll, NAPI_POLL_WEIGHT);
+	}
+
+	/* Enable NAPI handler for init callbacks */
+	napi_enable(&net_device->chan_table[0].napi);
 
 	/* Writing nvdev pointer unlocks netvsc_send(), make sure chn_table is
 	 * populated.
@@ -1313,6 +1353,8 @@ int netvsc_device_add(struct hv_device *device,
 	return ret;
 
 close:
+	napi_disable(&net_device->chan_table[0].napi);
+
 	/* Now, we can close the channel safely */
 	vmbus_close(device->channel);
 

drivers/net/hyperv/netvsc_drv.c

@@ -589,13 +589,14 @@ void netvsc_linkstatus_callback(struct hv_device *device_obj,
 }
 
 static struct sk_buff *netvsc_alloc_recv_skb(struct net_device *net,
+					     struct napi_struct *napi,
 					     const struct ndis_tcp_ip_checksum_info *csum_info,
 					     const struct ndis_pkt_8021q_info *vlan,
 					     void *data, u32 buflen)
 {
 	struct sk_buff *skb;
 
-	skb = netdev_alloc_skb_ip_align(net, buflen);
+	skb = napi_alloc_skb(napi, buflen);
 	if (!skb)
 		return skb;
 
@@ -642,11 +643,11 @@ int netvsc_recv_callback(struct net_device *net,
 {
 	struct net_device_context *net_device_ctx = netdev_priv(net);
 	struct netvsc_device *net_device = net_device_ctx->nvdev;
+	u16 q_idx = channel->offermsg.offer.sub_channel_index;
+	struct netvsc_channel *nvchan = &net_device->chan_table[q_idx];
 	struct net_device *vf_netdev;
 	struct sk_buff *skb;
 	struct netvsc_stats *rx_stats;
-	u16 q_idx = channel->offermsg.offer.sub_channel_index;
-
 
 	if (net->reg_state != NETREG_REGISTERED)
 		return NVSP_STAT_FAIL;
@@ -664,7 +665,8 @@ int netvsc_recv_callback(struct net_device *net,
 		net = vf_netdev;
 
 	/* Allocate a skb - TODO direct I/O to pages? */
-	skb = netvsc_alloc_recv_skb(net, csum_info, vlan, data, len);
+	skb = netvsc_alloc_recv_skb(net, &nvchan->napi,
+				    csum_info, vlan, data, len);
 	if (unlikely(!skb)) {
 		++net->stats.rx_dropped;
 		rcu_read_unlock();
@@ -679,7 +681,7 @@ int netvsc_recv_callback(struct net_device *net,
 	 * on the synthetic device because modifying the VF device
 	 * statistics will not work correctly.
 	 */
-	rx_stats = &net_device->chan_table[q_idx].rx_stats;
+	rx_stats = &nvchan->rx_stats;
 	u64_stats_update_begin(&rx_stats->syncp);
 	rx_stats->packets++;
 	rx_stats->bytes += len;
@@ -690,12 +692,7 @@ int netvsc_recv_callback(struct net_device *net,
 		++rx_stats->multicast;
 	u64_stats_update_end(&rx_stats->syncp);
 
-	/*
-	 * Pass the skb back up. Network stack will deallocate the skb when it
-	 * is done.
-	 * TODO - use NAPI?
-	 */
-	netif_receive_skb(skb);
+	napi_gro_receive(&nvchan->napi, skb);
 	rcu_read_unlock();
 
 	return 0;

drivers/net/hyperv/rndis_filter.c

@@ -1012,6 +1012,8 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc)
 	if (ret == 0)
 		nvscdev->chan_table[chn_index].channel = new_sc;
 
+	napi_enable(&nvscdev->chan_table[chn_index].napi);
+
 	spin_lock_irqsave(&nvscdev->sc_lock, flags);
 	nvscdev->num_sc_offered--;
 	spin_unlock_irqrestore(&nvscdev->sc_lock, flags);

include/linux/hyperv.h

@@ -1504,14 +1504,6 @@ static inline  void hv_signal_on_read(struct vmbus_channel *channel)
 	return;
 }
 
-static inline void
-init_cached_read_index(struct vmbus_channel *channel)
-{
-	struct hv_ring_buffer_info *rbi = &channel->inbound;
-
-	rbi->cached_read_index = rbi->ring_buffer->read_index;
-}
-
 /*
  * Mask off host interrupt callback notifications
  */
@@ -1545,76 +1537,48 @@ static inline u32 hv_end_read(struct hv_ring_buffer_info *rbi)
 /*
  * An API to support in-place processing of incoming VMBUS packets.
  */
-#define VMBUS_PKT_TRAILER	8
 
-static inline struct vmpacket_descriptor *
-get_next_pkt_raw(struct vmbus_channel *channel)
+/* Get data payload associated with descriptor */
+static inline void *hv_pkt_data(const struct vmpacket_descriptor *desc)
 {
-	struct hv_ring_buffer_info *ring_info = &channel->inbound;
-	u32 priv_read_loc = ring_info->priv_read_index;
-	void *ring_buffer = hv_get_ring_buffer(ring_info);
-	u32 dsize = ring_info->ring_datasize;
-	/*
-	 * delta is the difference between what is available to read and
-	 * what was already consumed in place. We commit read index after
-	 * the whole batch is processed.
-	 */
-	u32 delta = priv_read_loc >= ring_info->ring_buffer->read_index ?
-		priv_read_loc - ring_info->ring_buffer->read_index :
-		(dsize - ring_info->ring_buffer->read_index) + priv_read_loc;
-	u32 bytes_avail_toread = (hv_get_bytes_to_read(ring_info) - delta);
-
-	if (bytes_avail_toread < sizeof(struct vmpacket_descriptor))
-		return NULL;
-
-	return ring_buffer + priv_read_loc;
+	return (void *)((unsigned long)desc + (desc->offset8 << 3));
 }
 
-/*
- * A helper function to step through packets "in-place"
- * This API is to be called after each successful call
- * get_next_pkt_raw().
- */
-static inline void put_pkt_raw(struct vmbus_channel *channel,
-				struct vmpacket_descriptor *desc)
+/* Get data size associated with descriptor */
+static inline u32 hv_pkt_datalen(const struct vmpacket_descriptor *desc)
 {
-	struct hv_ring_buffer_info *ring_info = &channel->inbound;
-	u32 packetlen = desc->len8 << 3;
-	u32 dsize = ring_info->ring_datasize;
-
-	/*
-	 * Include the packet trailer.
-	 */
-	ring_info->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
-	ring_info->priv_read_index %= dsize;
+	return (desc->len8 << 3) - (desc->offset8 << 3);
 }
 
+
+struct vmpacket_descriptor *
+hv_pkt_iter_first(struct vmbus_channel *channel);
+
+struct vmpacket_descriptor *
+__hv_pkt_iter_next(struct vmbus_channel *channel,
+		   const struct vmpacket_descriptor *pkt);
+
+void hv_pkt_iter_close(struct vmbus_channel *channel);
+
 /*
- * This call commits the read index and potentially signals the host.
- * Here is the pattern for using the "in-place" consumption APIs:
- *
- * init_cached_read_index();
- *
- * while (get_next_pkt_raw() {
- *	process the packet "in-place";
- *	put_pkt_raw();
- * }
- * if (packets processed in place)
- *	commit_rd_index();
- */
-static inline void commit_rd_index(struct vmbus_channel *channel)
-{
-	struct hv_ring_buffer_info *ring_info = &channel->inbound;
-	/*
-	 * Make sure all reads are done before we update the read index since
-	 * the writer may start writing to the read area once the read index
-	 * is updated.
+ * Get next packet descriptor from iterator
+ * If at end of list, return NULL and update host.
  */
-	virt_rmb();
-	ring_info->ring_buffer->read_index = ring_info->priv_read_index;
+static inline struct vmpacket_descriptor *
+hv_pkt_iter_next(struct vmbus_channel *channel,
+		 const struct vmpacket_descriptor *pkt)
+{
+	struct vmpacket_descriptor *nxt;
+
+	nxt = __hv_pkt_iter_next(channel, pkt);
+	if (!nxt)
+		hv_pkt_iter_close(channel);
 
-	hv_signal_on_read(channel);
+	return nxt;
 }
 
+#define foreach_vmbus_pkt(pkt, channel) \
+	for (pkt = hv_pkt_iter_first(channel); pkt; \
+	    pkt = hv_pkt_iter_next(channel, pkt))
 
 #endif /* _HYPERV_H */