Initial import

1 files changed, 862 insertions, 0 deletions

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
new file mode 100644
index 000000000..0eeb1b3bc
--- /dev/null
+++ b/drivers/hv/channel_mgmt.c
@@ -0,0 +1,862 @@
+/*
+ * Copyright (c) 2009, Microsoft Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+ * Place - Suite 330, Boston, MA 02111-1307 USA.
+ *
+ * Authors:
+ *   Haiyang Zhang <haiyangz@microsoft.com>
+ *   Hank Janssen  <hjanssen@microsoft.com>
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/hyperv.h>
+
+#include "hyperv_vmbus.h"
+
+/**
+ * vmbus_prep_negotiate_resp() - Create default response for Hyper-V Negotiate message
+ * @icmsghdrp: Pointer to msg header structure
+ * @icmsg_negotiate: Pointer to negotiate message structure
+ * @buf: Raw buffer channel data
+ *
+ * @icmsghdrp is of type &struct icmsg_hdr.
+ * @negop is of type &struct icmsg_negotiate.
+ * Set up and fill in default negotiate response message.
+ *
+ * The fw_version specifies the  framework version that
+ * we can support and srv_version specifies the service
+ * version we can support.
+ *
+ * Mainly used by Hyper-V drivers.
+ */
+bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
+				struct icmsg_negotiate *negop, u8 *buf,
+				int fw_version, int srv_version)
+{
+	int icframe_major, icframe_minor;
+	int icmsg_major, icmsg_minor;
+	int fw_major, fw_minor;
+	int srv_major, srv_minor;
+	int i;
+	bool found_match = false;
+
+	icmsghdrp->icmsgsize = 0x10;
+	fw_major = (fw_version >> 16);
+	fw_minor = (fw_version & 0xFFFF);
+
+	srv_major = (srv_version >> 16);
+	srv_minor = (srv_version & 0xFFFF);
+
+	negop = (struct icmsg_negotiate *)&buf[
+		sizeof(struct vmbuspipe_hdr) +
+		sizeof(struct icmsg_hdr)];
+
+	icframe_major = negop->icframe_vercnt;
+	icframe_minor = 0;
+
+	icmsg_major = negop->icmsg_vercnt;
+	icmsg_minor = 0;
+
+	/*
+	 * Select the framework version number we will
+	 * support.
+	 */
+
+	for (i = 0; i < negop->icframe_vercnt; i++) {
+		if ((negop->icversion_data[i].major == fw_major) &&
+		   (negop->icversion_data[i].minor == fw_minor)) {
+			icframe_major = negop->icversion_data[i].major;
+			icframe_minor = negop->icversion_data[i].minor;
+			found_match = true;
+		}
+	}
+
+	if (!found_match)
+		goto fw_error;
+
+	found_match = false;
+
+	for (i = negop->icframe_vercnt;
+		 (i < negop->icframe_vercnt + negop->icmsg_vercnt); i++) {
+		if ((negop->icversion_data[i].major == srv_major) &&
+		   (negop->icversion_data[i].minor == srv_minor)) {
+			icmsg_major = negop->icversion_data[i].major;
+			icmsg_minor = negop->icversion_data[i].minor;
+			found_match = true;
+		}
+	}
+
+	/*
+	 * Respond with the framework and service
+	 * version numbers we can support.
+	 */
+
+fw_error:
+	if (!found_match) {
+		negop->icframe_vercnt = 0;
+		negop->icmsg_vercnt = 0;
+	} else {
+		negop->icframe_vercnt = 1;
+		negop->icmsg_vercnt = 1;
+	}
+
+	negop->icversion_data[0].major = icframe_major;
+	negop->icversion_data[0].minor = icframe_minor;
+	negop->icversion_data[1].major = icmsg_major;
+	negop->icversion_data[1].minor = icmsg_minor;
+	return found_match;
+}
+
+EXPORT_SYMBOL_GPL(vmbus_prep_negotiate_resp);
+
+/*
+ * alloc_channel - Allocate and initialize a vmbus channel object
+ */
+static struct vmbus_channel *alloc_channel(void)
+{
+	static atomic_t chan_num = ATOMIC_INIT(0);
+	struct vmbus_channel *channel;
+
+	channel = kzalloc(sizeof(*channel), GFP_ATOMIC);
+	if (!channel)
+		return NULL;
+
+	channel->id = atomic_inc_return(&chan_num);
+	spin_lock_init(&channel->inbound_lock);
+	spin_lock_init(&channel->lock);
+
+	INIT_LIST_HEAD(&channel->sc_list);
+	INIT_LIST_HEAD(&channel->percpu_list);
+
+	return channel;
+}
+
+/*
+ * free_channel - Release the resources used by the vmbus channel object
+ */
+static void free_channel(struct vmbus_channel *channel)
+{
+	kfree(channel);
+}
+
+static void percpu_channel_enq(void *arg)
+{
+	struct vmbus_channel *channel = arg;
+	int cpu = smp_processor_id();
+
+	list_add_tail(&channel->percpu_list, &hv_context.percpu_list[cpu]);
+}
+
+static void percpu_channel_deq(void *arg)
+{
+	struct vmbus_channel *channel = arg;
+
+	list_del(&channel->percpu_list);
+}
+
+
+void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
+{
+	struct vmbus_channel_relid_released msg;
+	unsigned long flags;
+	struct vmbus_channel *primary_channel;
+
+	memset(&msg, 0, sizeof(struct vmbus_channel_relid_released));
+	msg.child_relid = relid;
+	msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
+	vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released));
+
+	if (channel == NULL)
+		return;
+
+	if (channel->target_cpu != get_cpu()) {
+		put_cpu();
+		smp_call_function_single(channel->target_cpu,
+					 percpu_channel_deq, channel, true);
+	} else {
+		percpu_channel_deq(channel);
+		put_cpu();
+	}
+
+	if (channel->primary_channel == NULL) {
+		spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
+		list_del(&channel->listentry);
+		spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
+	} else {
+		primary_channel = channel->primary_channel;
+		spin_lock_irqsave(&primary_channel->lock, flags);
+		list_del(&channel->sc_list);
+		spin_unlock_irqrestore(&primary_channel->lock, flags);
+	}
+	free_channel(channel);
+}
+
+void vmbus_free_channels(void)
+{
+	struct vmbus_channel *channel;
+
+	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
+		vmbus_device_unregister(channel->device_obj);
+		free_channel(channel);
+	}
+}
+
+/*
+ * vmbus_process_offer - Process the offer by creating a channel/device
+ * associated with this offer
+ */
+static void vmbus_process_offer(struct vmbus_channel *newchannel)
+{
+	struct vmbus_channel *channel;
+	bool fnew = true;
+	bool enq = false;
+	unsigned long flags;
+
+	/* Make sure this is a new offer */
+	spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
+
+	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
+		if (!uuid_le_cmp(channel->offermsg.offer.if_type,
+			newchannel->offermsg.offer.if_type) &&
+			!uuid_le_cmp(channel->offermsg.offer.if_instance,
+				newchannel->offermsg.offer.if_instance)) {
+			fnew = false;
+			break;
+		}
+	}
+
+	if (fnew) {
+		list_add_tail(&newchannel->listentry,
+			      &vmbus_connection.chn_list);
+		enq = true;
+	}
+
+	spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
+
+	if (enq) {
+		if (newchannel->target_cpu != get_cpu()) {
+			put_cpu();
+			smp_call_function_single(newchannel->target_cpu,
+						 percpu_channel_enq,
+						 newchannel, true);
+		} else {
+			percpu_channel_enq(newchannel);
+			put_cpu();
+		}
+	}
+	if (!fnew) {
+		/*
+		 * Check to see if this is a sub-channel.
+		 */
+		if (newchannel->offermsg.offer.sub_channel_index != 0) {
+			/*
+			 * Process the sub-channel.
+			 */
+			newchannel->primary_channel = channel;
+			spin_lock_irqsave(&channel->lock, flags);
+			list_add_tail(&newchannel->sc_list, &channel->sc_list);
+			spin_unlock_irqrestore(&channel->lock, flags);
+
+			if (newchannel->target_cpu != get_cpu()) {
+				put_cpu();
+				smp_call_function_single(newchannel->target_cpu,
+							 percpu_channel_enq,
+							 newchannel, true);
+			} else {
+				percpu_channel_enq(newchannel);
+				put_cpu();
+			}
+
+			newchannel->state = CHANNEL_OPEN_STATE;
+			channel->num_sc++;
+			if (channel->sc_creation_callback != NULL)
+				channel->sc_creation_callback(newchannel);
+
+			return;
+		}
+
+		goto err_free_chan;
+	}
+
+	/*
+	 * This state is used to indicate a successful open
+	 * so that when we do close the channel normally, we
+	 * can cleanup properly
+	 */
+	newchannel->state = CHANNEL_OPEN_STATE;
+
+	/*
+	 * Start the process of binding this offer to the driver
+	 * We need to set the DeviceObject field before calling
+	 * vmbus_child_dev_add()
+	 */
+	newchannel->device_obj = vmbus_device_create(
+		&newchannel->offermsg.offer.if_type,
+		&newchannel->offermsg.offer.if_instance,
+		newchannel);
+	if (!newchannel->device_obj)
+		goto err_deq_chan;
+
+	/*
+	 * Add the new device to the bus. This will kick off device-driver
+	 * binding which eventually invokes the device driver's AddDevice()
+	 * method.
+	 */
+	if (vmbus_device_register(newchannel->device_obj) != 0) {
+		pr_err("unable to add child device object (relid %d)\n",
+			newchannel->offermsg.child_relid);
+		kfree(newchannel->device_obj);
+		goto err_deq_chan;
+	}
+	return;
+
+err_deq_chan:
+	spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
+	list_del(&newchannel->listentry);
+	spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
+
+	if (newchannel->target_cpu != get_cpu()) {
+		put_cpu();
+		smp_call_function_single(newchannel->target_cpu,
+					 percpu_channel_deq, newchannel, true);
+	} else {
+		percpu_channel_deq(newchannel);
+		put_cpu();
+	}
+
+err_free_chan:
+	free_channel(newchannel);
+}
+
+enum {
+	IDE = 0,
+	SCSI,
+	NIC,
+	MAX_PERF_CHN,
+};
+
+/*
+ * This is an array of device_ids (device types) that are performance critical.
+ * We attempt to distribute the interrupt load for these devices across
+ * all available CPUs.
+ */
+static const struct hv_vmbus_device_id hp_devs[] = {
+	/* IDE */
+	{ HV_IDE_GUID, },
+	/* Storage - SCSI */
+	{ HV_SCSI_GUID, },
+	/* Network */
+	{ HV_NIC_GUID, },
+	/* NetworkDirect Guest RDMA */
+	{ HV_ND_GUID, },
+};
+
+
+/*
+ * We use this state to statically distribute the channel interrupt load.
+ */
+static u32  next_vp;
+
+/*
+ * Starting with Win8, we can statically distribute the incoming
+ * channel interrupt load by binding a channel to VCPU. We
+ * implement here a simple round robin scheme for distributing
+ * the interrupt load.
+ * We will bind channels that are not performance critical to cpu 0 and
+ * performance critical channels (IDE, SCSI and Network) will be uniformly
+ * distributed across all available CPUs.
+ */
+static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_guid)
+{
+	u32 cur_cpu;
+	int i;
+	bool perf_chn = false;
+	u32 max_cpus = num_online_cpus();
+
+	for (i = IDE; i < MAX_PERF_CHN; i++) {
+		if (!memcmp(type_guid->b, hp_devs[i].guid,
+				 sizeof(uuid_le))) {
+			perf_chn = true;
+			break;
+		}
+	}
+	if ((vmbus_proto_version == VERSION_WS2008) ||
+	    (vmbus_proto_version == VERSION_WIN7) || (!perf_chn)) {
+		/*
+		 * Prior to win8, all channel interrupts are
+		 * delivered on cpu 0.
+		 * Also if the channel is not a performance critical
+		 * channel, bind it to cpu 0.
+		 */
+		channel->target_cpu = 0;
+		channel->target_vp = 0;
+		return;
+	}
+	cur_cpu = (++next_vp % max_cpus);
+	channel->target_cpu = cur_cpu;
+	channel->target_vp = hv_context.vp_index[cur_cpu];
+}
+
+/*
+ * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
+ *
+ */
+static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
+{
+	struct vmbus_channel_offer_channel *offer;
+	struct vmbus_channel *newchannel;
+
+	offer = (struct vmbus_channel_offer_channel *)hdr;
+
+	/* Allocate the channel object and save this offer. */
+	newchannel = alloc_channel();
+	if (!newchannel) {
+		pr_err("Unable to allocate channel object\n");
+		return;
+	}
+
+	/*
+	 * By default we setup state to enable batched
+	 * reading. A specific service can choose to
+	 * disable this prior to opening the channel.
+	 */
+	newchannel->batched_reading = true;
+
+	/*
+	 * Setup state for signalling the host.
+	 */
+	newchannel->sig_event = (struct hv_input_signal_event *)
+				(ALIGN((unsigned long)
+				&newchannel->sig_buf,
+				HV_HYPERCALL_PARAM_ALIGN));
+
+	newchannel->sig_event->connectionid.asu32 = 0;
+	newchannel->sig_event->connectionid.u.id = VMBUS_EVENT_CONNECTION_ID;
+	newchannel->sig_event->flag_number = 0;
+	newchannel->sig_event->rsvdz = 0;
+
+	if (vmbus_proto_version != VERSION_WS2008) {
+		newchannel->is_dedicated_interrupt =
+				(offer->is_dedicated_interrupt != 0);
+		newchannel->sig_event->connectionid.u.id =
+				offer->connection_id;
+	}
+
+	init_vp_index(newchannel, &offer->offer.if_type);
+
+	memcpy(&newchannel->offermsg, offer,
+	       sizeof(struct vmbus_channel_offer_channel));
+	newchannel->monitor_grp = (u8)offer->monitorid / 32;
+	newchannel->monitor_bit = (u8)offer->monitorid % 32;
+
+	vmbus_process_offer(newchannel);
+}
+
+/*
+ * vmbus_onoffer_rescind - Rescind offer handler.
+ *
+ * We queue a work item to process this offer synchronously
+ */
+static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
+{
+	struct vmbus_channel_rescind_offer *rescind;
+	struct vmbus_channel *channel;
+	unsigned long flags;
+	struct device *dev;
+
+	rescind = (struct vmbus_channel_rescind_offer *)hdr;
+	channel = relid2channel(rescind->child_relid);
+
+	if (channel == NULL) {
+		hv_process_channel_removal(NULL, rescind->child_relid);
+		return;
+	}
+
+	spin_lock_irqsave(&channel->lock, flags);
+	channel->rescind = true;
+	spin_unlock_irqrestore(&channel->lock, flags);
+
+	if (channel->device_obj) {
+		/*
+		 * We will have to unregister this device from the
+		 * driver core.
+		 */
+		dev = get_device(&channel->device_obj->device);
+		if (dev) {
+			vmbus_device_unregister(channel->device_obj);
+			put_device(dev);
+		}
+	} else {
+		hv_process_channel_removal(channel,
+			channel->offermsg.child_relid);
+	}
+}
+
+/*
+ * vmbus_onoffers_delivered -
+ * This is invoked when all offers have been delivered.
+ *
+ * Nothing to do here.
+ */
+static void vmbus_onoffers_delivered(
+			struct vmbus_channel_message_header *hdr)
+{
+}
+
+/*
+ * vmbus_onopen_result - Open result handler.
+ *
+ * This is invoked when we received a response to our channel open request.
+ * Find the matching request, copy the response and signal the requesting
+ * thread.
+ */
+static void vmbus_onopen_result(struct vmbus_channel_message_header *hdr)
+{
+	struct vmbus_channel_open_result *result;
+	struct vmbus_channel_msginfo *msginfo;
+	struct vmbus_channel_message_header *requestheader;
+	struct vmbus_channel_open_channel *openmsg;
+	unsigned long flags;
+
+	result = (struct vmbus_channel_open_result *)hdr;
+
+	/*
+	 * Find the open msg, copy the result and signal/unblock the wait event
+	 */
+	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
+
+	list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
+				msglistentry) {
+		requestheader =
+			(struct vmbus_channel_message_header *)msginfo->msg;
+
+		if (requestheader->msgtype == CHANNELMSG_OPENCHANNEL) {
+			openmsg =
+			(struct vmbus_channel_open_channel *)msginfo->msg;
+			if (openmsg->child_relid == result->child_relid &&
+			    openmsg->openid == result->openid) {
+				memcpy(&msginfo->response.open_result,
+				       result,
+				       sizeof(
+					struct vmbus_channel_open_result));
+				complete(&msginfo->waitevent);
+				break;
+			}
+		}
+	}
+	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
+}
+
+/*
+ * vmbus_ongpadl_created - GPADL created handler.
+ *
+ * This is invoked when we received a response to our gpadl create request.
+ * Find the matching request, copy the response and signal the requesting
+ * thread.
+ */
+static void vmbus_ongpadl_created(struct vmbus_channel_message_header *hdr)
+{
+	struct vmbus_channel_gpadl_created *gpadlcreated;
+	struct vmbus_channel_msginfo *msginfo;
+	struct vmbus_channel_message_header *requestheader;
+	struct vmbus_channel_gpadl_header *gpadlheader;
+	unsigned long flags;
+
+	gpadlcreated = (struct vmbus_channel_gpadl_created *)hdr;
+
+	/*
+	 * Find the establish msg, copy the result and signal/unblock the wait
+	 * event
+	 */
+	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
+
+	list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
+				msglistentry) {
+		requestheader =
+			(struct vmbus_channel_message_header *)msginfo->msg;
+
+		if (requestheader->msgtype == CHANNELMSG_GPADL_HEADER) {
+			gpadlheader =
+			(struct vmbus_channel_gpadl_header *)requestheader;
+
+			if ((gpadlcreated->child_relid ==
+			     gpadlheader->child_relid) &&
+			    (gpadlcreated->gpadl == gpadlheader->gpadl)) {
+				memcpy(&msginfo->response.gpadl_created,
+				       gpadlcreated,
+				       sizeof(
+					struct vmbus_channel_gpadl_created));
+				complete(&msginfo->waitevent);
+				break;
+			}
+		}
+	}
+	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
+}
+
+/*
+ * vmbus_ongpadl_torndown - GPADL torndown handler.
+ *
+ * This is invoked when we received a response to our gpadl teardown request.
+ * Find the matching request, copy the response and signal the requesting
+ * thread.
+ */
+static void vmbus_ongpadl_torndown(
+			struct vmbus_channel_message_header *hdr)
+{
+	struct vmbus_channel_gpadl_torndown *gpadl_torndown;
+	struct vmbus_channel_msginfo *msginfo;
+	struct vmbus_channel_message_header *requestheader;
+	struct vmbus_channel_gpadl_teardown *gpadl_teardown;
+	unsigned long flags;
+
+	gpadl_torndown = (struct vmbus_channel_gpadl_torndown *)hdr;
+
+	/*
+	 * Find the open msg, copy the result and signal/unblock the wait event
+	 */
+	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
+
+	list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
+				msglistentry) {
+		requestheader =
+			(struct vmbus_channel_message_header *)msginfo->msg;
+
+		if (requestheader->msgtype == CHANNELMSG_GPADL_TEARDOWN) {
+			gpadl_teardown =
+			(struct vmbus_channel_gpadl_teardown *)requestheader;
+
+			if (gpadl_torndown->gpadl == gpadl_teardown->gpadl) {
+				memcpy(&msginfo->response.gpadl_torndown,
+				       gpadl_torndown,
+				       sizeof(
+					struct vmbus_channel_gpadl_torndown));
+				complete(&msginfo->waitevent);
+				break;
+			}
+		}
+	}
+	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
+}
+
+/*
+ * vmbus_onversion_response - Version response handler
+ *
+ * This is invoked when we received a response to our initiate contact request.
+ * Find the matching request, copy the response and signal the requesting
+ * thread.
+ */
+static void vmbus_onversion_response(
+		struct vmbus_channel_message_header *hdr)
+{
+	struct vmbus_channel_msginfo *msginfo;
+	struct vmbus_channel_message_header *requestheader;
+	struct vmbus_channel_version_response *version_response;
+	unsigned long flags;
+
+	version_response = (struct vmbus_channel_version_response *)hdr;
+	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
+
+	list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
+				msglistentry) {
+		requestheader =
+			(struct vmbus_channel_message_header *)msginfo->msg;
+
+		if (requestheader->msgtype ==
+		    CHANNELMSG_INITIATE_CONTACT) {
+			memcpy(&msginfo->response.version_response,
+			      version_response,
+			      sizeof(struct vmbus_channel_version_response));
+			complete(&msginfo->waitevent);
+		}
+	}
+	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
+}
+
+/* Channel message dispatch table */
+struct vmbus_channel_message_table_entry
+	channel_message_table[CHANNELMSG_COUNT] = {
+	{CHANNELMSG_INVALID,			0, NULL},
+	{CHANNELMSG_OFFERCHANNEL,		0, vmbus_onoffer},
+	{CHANNELMSG_RESCIND_CHANNELOFFER,	0, vmbus_onoffer_rescind},
+	{CHANNELMSG_REQUESTOFFERS,		0, NULL},
+	{CHANNELMSG_ALLOFFERS_DELIVERED,	1, vmbus_onoffers_delivered},
+	{CHANNELMSG_OPENCHANNEL,		0, NULL},
+	{CHANNELMSG_OPENCHANNEL_RESULT,		1, vmbus_onopen_result},
+	{CHANNELMSG_CLOSECHANNEL,		0, NULL},
+	{CHANNELMSG_GPADL_HEADER,		0, NULL},
+	{CHANNELMSG_GPADL_BODY,			0, NULL},
+	{CHANNELMSG_GPADL_CREATED,		1, vmbus_ongpadl_created},
+	{CHANNELMSG_GPADL_TEARDOWN,		0, NULL},
+	{CHANNELMSG_GPADL_TORNDOWN,		1, vmbus_ongpadl_torndown},
+	{CHANNELMSG_RELID_RELEASED,		0, NULL},
+	{CHANNELMSG_INITIATE_CONTACT,		0, NULL},
+	{CHANNELMSG_VERSION_RESPONSE,		1, vmbus_onversion_response},
+	{CHANNELMSG_UNLOAD,			0, NULL},
+};
+
+/*
+ * vmbus_onmessage - Handler for channel protocol messages.
+ *
+ * This is invoked in the vmbus worker thread context.
+ */
+void vmbus_onmessage(void *context)
+{
+	struct hv_message *msg = context;
+	struct vmbus_channel_message_header *hdr;
+	int size;
+
+	hdr = (struct vmbus_channel_message_header *)msg->u.payload;
+	size = msg->header.payload_size;
+
+	if (hdr->msgtype >= CHANNELMSG_COUNT) {
+		pr_err("Received invalid channel message type %d size %d\n",
+			   hdr->msgtype, size);
+		print_hex_dump_bytes("", DUMP_PREFIX_NONE,
+				     (unsigned char *)msg->u.payload, size);
+		return;
+	}
+
+	if (channel_message_table[hdr->msgtype].message_handler)
+		channel_message_table[hdr->msgtype].message_handler(hdr);
+	else
+		pr_err("Unhandled channel message type %d\n", hdr->msgtype);
+}
+
+/*
+ * vmbus_request_offers - Send a request to get all our pending offers.
+ */
+int vmbus_request_offers(void)
+{
+	struct vmbus_channel_message_header *msg;
+	struct vmbus_channel_msginfo *msginfo;
+	int ret;
+
+	msginfo = kmalloc(sizeof(*msginfo) +
+			  sizeof(struct vmbus_channel_message_header),
+			  GFP_KERNEL);
+	if (!msginfo)
+		return -ENOMEM;
+
+	msg = (struct vmbus_channel_message_header *)msginfo->msg;
+
+	msg->msgtype = CHANNELMSG_REQUESTOFFERS;
+
+
+	ret = vmbus_post_msg(msg,
+			       sizeof(struct vmbus_channel_message_header));
+	if (ret != 0) {
+		pr_err("Unable to request offers - %d\n", ret);
+
+		goto cleanup;
+	}
+
+cleanup:
+	kfree(msginfo);
+
+	return ret;
+}
+
+/*
+ * Retrieve the (sub) channel on which to send an outgoing request.
+ * When a primary channel has multiple sub-channels, we try to
+ * distribute the load equally amongst all available channels.
+ */
+struct vmbus_channel *vmbus_get_outgoing_channel(struct vmbus_channel *primary)
+{
+	struct list_head *cur, *tmp;
+	int cur_cpu;
+	struct vmbus_channel *cur_channel;
+	struct vmbus_channel *outgoing_channel = primary;
+	int next_channel;
+	int i = 1;
+
+	if (list_empty(&primary->sc_list))
+		return outgoing_channel;
+
+	next_channel = primary->next_oc++;
+
+	if (next_channel > (primary->num_sc)) {
+		primary->next_oc = 0;
+		return outgoing_channel;
+	}
+
+	cur_cpu = hv_context.vp_index[get_cpu()];
+	put_cpu();
+	list_for_each_safe(cur, tmp, &primary->sc_list) {
+		cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
+		if (cur_channel->state != CHANNEL_OPENED_STATE)
+			continue;
+
+		if (cur_channel->target_vp == cur_cpu)
+			return cur_channel;
+
+		if (i == next_channel)
+			return cur_channel;
+
+		i++;
+	}
+
+	return outgoing_channel;
+}
+EXPORT_SYMBOL_GPL(vmbus_get_outgoing_channel);
+
+static void invoke_sc_cb(struct vmbus_channel *primary_channel)
+{
+	struct list_head *cur, *tmp;
+	struct vmbus_channel *cur_channel;
+
+	if (primary_channel->sc_creation_callback == NULL)
+		return;
+
+	list_for_each_safe(cur, tmp, &primary_channel->sc_list) {
+		cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
+
+		primary_channel->sc_creation_callback(cur_channel);
+	}
+}
+
+void vmbus_set_sc_create_callback(struct vmbus_channel *primary_channel,
+				void (*sc_cr_cb)(struct vmbus_channel *new_sc))
+{
+	primary_channel->sc_creation_callback = sc_cr_cb;
+}
+EXPORT_SYMBOL_GPL(vmbus_set_sc_create_callback);
+
+bool vmbus_are_subchannels_present(struct vmbus_channel *primary)
+{
+	bool ret;
+
+	ret = !list_empty(&primary->sc_list);
+
+	if (ret) {
+		/*
+		 * Invoke the callback on sub-channel creation.
+		 * This will present a uniform interface to the
+		 * clients.
+		 */
+		invoke_sc_cb(primary);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vmbus_are_subchannels_present);