drivers/hv/connection.c - kernel/msm-5.4 - Gitiles

 /*
  *
  * 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/delay.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/hyperv.h>
 #include <linux/export.h>
 #include <asm/hyperv.h>
 #include <asm/mshyperv.h>

 #include "hyperv_vmbus.h"


 struct vmbus_connection vmbus_connection = {
 	.conn_state		= DISCONNECTED,
 	.next_gpadl_handle	= ATOMIC_INIT(0xE1E10),
 };
 EXPORT_SYMBOL_GPL(vmbus_connection);

 /*
  * Negotiated protocol version with the host.
  */
 __u32 vmbus_proto_version;
 EXPORT_SYMBOL_GPL(vmbus_proto_version);

 static __u32 vmbus_get_next_version(__u32 current_version)
 {
 	switch (current_version) {
 	case (VERSION_WIN7):
 		return VERSION_WS2008;

 	case (VERSION_WIN8):
 		return VERSION_WIN7;

 	case (VERSION_WIN8_1):
 		return VERSION_WIN8;

 	case (VERSION_WIN10):
 		return VERSION_WIN8_1;

 	case (VERSION_WS2008):
 	default:
 		return VERSION_INVAL;
 	}
 }

 static int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo,
 					__u32 version)
 {
 	int ret = 0;
 	struct vmbus_channel_initiate_contact *msg;
 	unsigned long flags;

 	init_completion(&msginfo->waitevent);

 	msg = (struct vmbus_channel_initiate_contact *)msginfo->msg;

 	msg->header.msgtype = CHANNELMSG_INITIATE_CONTACT;
 	msg->vmbus_version_requested = version;
 	msg->interrupt_page = virt_to_phys(vmbus_connection.int_page);
 	msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages[0]);
 	msg->monitor_page2 = virt_to_phys(vmbus_connection.monitor_pages[1]);
 	/*
 	 * We want all channel messages to be delivered on CPU 0.
 	 * This has been the behavior pre-win8. This is not
 	 * perf issue and having all channel messages delivered on CPU 0
 	 * would be ok.
 	 * For post win8 hosts, we support receiving channel messagges on
 	 * all the CPUs. This is needed for kexec to work correctly where
 	 * the CPU attempting to connect may not be CPU 0.
 	 */
 	if (version >= VERSION_WIN8_1) {
 		msg->target_vcpu =
 			hv_cpu_number_to_vp_number(smp_processor_id());
 		vmbus_connection.connect_cpu = smp_processor_id();
 	} else {
 		msg->target_vcpu = 0;
 		vmbus_connection.connect_cpu = 0;
 	}

 	/*
 	 * Add to list before we send the request since we may
 	 * receive the response before returning from this routine
 	 */
 	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 	list_add_tail(&msginfo->msglistentry,
 		      &vmbus_connection.chn_msg_list);

 	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

 	ret = vmbus_post_msg(msg,
 			     sizeof(struct vmbus_channel_initiate_contact),
 			     true);

 	trace_vmbus_negotiate_version(msg, ret);

 	if (ret != 0) {
 		spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 		list_del(&msginfo->msglistentry);
 		spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock,
 					flags);
 		return ret;
 	}

 	/* Wait for the connection response */
 	wait_for_completion(&msginfo->waitevent);

 	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 	list_del(&msginfo->msglistentry);
 	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

 	/* Check if successful */
 	if (msginfo->response.version_response.version_supported) {
 		vmbus_connection.conn_state = CONNECTED;
 	} else {
 		return -ECONNREFUSED;
 	}

 	return ret;
 }

 /*
  * vmbus_connect - Sends a connect request on the partition service connection
  */
 int vmbus_connect(void)
 {
 	int ret = 0;
 	struct vmbus_channel_msginfo *msginfo = NULL;
 	__u32 version;

 	/* Initialize the vmbus connection */
 	vmbus_connection.conn_state = CONNECTING;
 	vmbus_connection.work_queue = create_workqueue("hv_vmbus_con");
 	if (!vmbus_connection.work_queue) {
 		ret = -ENOMEM;
 		goto cleanup;
 	}

 	INIT_LIST_HEAD(&vmbus_connection.chn_msg_list);
 	spin_lock_init(&vmbus_connection.channelmsg_lock);

 	INIT_LIST_HEAD(&vmbus_connection.chn_list);
 	mutex_init(&vmbus_connection.channel_mutex);

 	/*
 	 * Setup the vmbus event connection for channel interrupt
 	 * abstraction stuff
 	 */
 	vmbus_connection.int_page =
 	(void *)__get_free_pages(GFP_KERNEL|__GFP_ZERO, 0);
 	if (vmbus_connection.int_page == NULL) {
 		ret = -ENOMEM;
 		goto cleanup;
 	}

 	vmbus_connection.recv_int_page = vmbus_connection.int_page;
 	vmbus_connection.send_int_page =
 		(void *)((unsigned long)vmbus_connection.int_page +
 			(PAGE_SIZE >> 1));

 	/*
 	 * Setup the monitor notification facility. The 1st page for
 	 * parent->child and the 2nd page for child->parent
 	 */
 	vmbus_connection.monitor_pages[0] = (void *)__get_free_pages((GFP_KERNEL|__GFP_ZERO), 0);
 	vmbus_connection.monitor_pages[1] = (void *)__get_free_pages((GFP_KERNEL|__GFP_ZERO), 0);
 	if ((vmbus_connection.monitor_pages[0] == NULL) ||
 	    (vmbus_connection.monitor_pages[1] == NULL)) {
 		ret = -ENOMEM;
 		goto cleanup;
 	}

 	msginfo = kzalloc(sizeof(*msginfo) +
 			  sizeof(struct vmbus_channel_initiate_contact),
 			  GFP_KERNEL);
 	if (msginfo == NULL) {
 		ret = -ENOMEM;
 		goto cleanup;
 	}

 	/*
 	 * Negotiate a compatible VMBUS version number with the
 	 * host. We start with the highest number we can support
 	 * and work our way down until we negotiate a compatible
 	 * version.
 	 */

 	version = VERSION_CURRENT;

 	do {
 		ret = vmbus_negotiate_version(msginfo, version);
 		if (ret == -ETIMEDOUT)
 			goto cleanup;

 		if (vmbus_connection.conn_state == CONNECTED)
 			break;

 		version = vmbus_get_next_version(version);
 	} while (version != VERSION_INVAL);

 	if (version == VERSION_INVAL)
 		goto cleanup;

 	vmbus_proto_version = version;
 	pr_info("Vmbus version:%d.%d\n",
 		version >> 16, version & 0xFFFF);

 	kfree(msginfo);
 	return 0;

 cleanup:
 	pr_err("Unable to connect to host\n");

 	vmbus_connection.conn_state = DISCONNECTED;
 	vmbus_disconnect();

 	kfree(msginfo);

 	return ret;
 }

 void vmbus_disconnect(void)
 {
 	/*
 	 * First send the unload request to the host.
 	 */
 	vmbus_initiate_unload(false);

 	if (vmbus_connection.work_queue) {
 		drain_workqueue(vmbus_connection.work_queue);
 		destroy_workqueue(vmbus_connection.work_queue);
 	}

 	if (vmbus_connection.int_page) {
 		free_pages((unsigned long)vmbus_connection.int_page, 0);
 		vmbus_connection.int_page = NULL;
 	}

 	free_pages((unsigned long)vmbus_connection.monitor_pages[0], 0);
 	free_pages((unsigned long)vmbus_connection.monitor_pages[1], 0);
 	vmbus_connection.monitor_pages[0] = NULL;
 	vmbus_connection.monitor_pages[1] = NULL;
 }

 /*
  * relid2channel - Get the channel object given its
  * child relative id (ie channel id)
  */
 struct vmbus_channel *relid2channel(u32 relid)
 {
 	struct vmbus_channel *channel;
 	struct vmbus_channel *found_channel  = NULL;
 	struct list_head *cur, *tmp;
 	struct vmbus_channel *cur_sc;

 	BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));

 	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
 		if (channel->offermsg.child_relid == relid) {
 			found_channel = channel;
 			break;
 		} else if (!list_empty(&channel->sc_list)) {
 			/*
 			 * Deal with sub-channels.
 			 */
 			list_for_each_safe(cur, tmp, &channel->sc_list) {
 				cur_sc = list_entry(cur, struct vmbus_channel,
 							sc_list);
 				if (cur_sc->offermsg.child_relid == relid) {
 					found_channel = cur_sc;
 					break;
 				}
 			}
 		}
 	}

 	return found_channel;
 }

 /*
  * vmbus_on_event - Process a channel event notification
  *
  * For batched channels (default) optimize host to guest signaling
  * by ensuring:
  * 1. While reading the channel, we disable interrupts from host.
  * 2. Ensure that we process all posted messages from the host
  *    before returning from this callback.
  * 3. Once we return, enable signaling from the host. Once this
  *    state is set we check to see if additional packets are
  *    available to read. In this case we repeat the process.
  *    If this tasklet has been running for a long time
  *    then reschedule ourselves.
  */
 void vmbus_on_event(unsigned long data)
 {
 	struct vmbus_channel *channel = (void *) data;
 	unsigned long time_limit = jiffies + 2;

 	trace_vmbus_on_event(channel);

 	do {
 		void (*callback_fn)(void *);

 		/* A channel once created is persistent even when
 		 * there is no driver handling the device. An
 		 * unloading driver sets the onchannel_callback to NULL.
 		 */
 		callback_fn = READ_ONCE(channel->onchannel_callback);
 		if (unlikely(callback_fn == NULL))
 			return;

 		(*callback_fn)(channel->channel_callback_context);

 		if (channel->callback_mode != HV_CALL_BATCHED)
 			return;

 		if (likely(hv_end_read(&channel->inbound) == 0))
 			return;

 		hv_begin_read(&channel->inbound);
 	} while (likely(time_before(jiffies, time_limit)));

 	/* The time limit (2 jiffies) has been reached */
 	tasklet_schedule(&channel->callback_event);
 }

 /*
  * vmbus_post_msg - Send a msg on the vmbus's message connection
  */
 int vmbus_post_msg(void *buffer, size_t buflen, bool can_sleep)
 {
 	union hv_connection_id conn_id;
 	int ret = 0;
 	int retries = 0;
 	u32 usec = 1;

 	conn_id.asu32 = 0;
 	conn_id.u.id = VMBUS_MESSAGE_CONNECTION_ID;

 	/*
 	 * hv_post_message() can have transient failures because of
 	 * insufficient resources. Retry the operation a couple of
 	 * times before giving up.
 	 */
 	while (retries < 100) {
 		ret = hv_post_message(conn_id, 1, buffer, buflen);

 		switch (ret) {
 		case HV_STATUS_INVALID_CONNECTION_ID:
 			/*
 			 * We could get this if we send messages too
 			 * frequently.
 			 */
 			ret = -EAGAIN;
 			break;
 		case HV_STATUS_INSUFFICIENT_MEMORY:
 		case HV_STATUS_INSUFFICIENT_BUFFERS:
 			ret = -ENOBUFS;
 			break;
 		case HV_STATUS_SUCCESS:
 			return ret;
 		default:
 			pr_err("hv_post_msg() failed; error code:%d\n", ret);
 			return -EINVAL;
 		}

 		retries++;
 		if (can_sleep && usec > 1000)
 			msleep(usec / 1000);
 		else if (usec < MAX_UDELAY_MS * 1000)
 			udelay(usec);
 		else
 			mdelay(usec / 1000);

 		if (retries < 22)
 			usec *= 2;
 	}
 	return ret;
 }

 /*
  * vmbus_set_event - Send an event notification to the parent
  */
 void vmbus_set_event(struct vmbus_channel *channel)
 {
 	u32 child_relid = channel->offermsg.child_relid;

 	if (!channel->is_dedicated_interrupt)
 		vmbus_send_interrupt(child_relid);

 	++channel->sig_events;

 	hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, channel->sig_event);
 }
 EXPORT_SYMBOL_GPL(vmbus_set_event);
	/*
	*
	* 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/delay.h>
	#include <linux/mm.h>
	#include <linux/slab.h>
	#include <linux/vmalloc.h>
	#include <linux/hyperv.h>
	#include <linux/export.h>
	#include <asm/hyperv.h>
	#include <asm/mshyperv.h>

	#include "hyperv_vmbus.h"


	struct vmbus_connection vmbus_connection = {
	.conn_state = DISCONNECTED,
	.next_gpadl_handle = ATOMIC_INIT(0xE1E10),
	};
	EXPORT_SYMBOL_GPL(vmbus_connection);

	/*
	* Negotiated protocol version with the host.
	*/
	__u32 vmbus_proto_version;
	EXPORT_SYMBOL_GPL(vmbus_proto_version);

	static __u32 vmbus_get_next_version(__u32 current_version)
	{
	switch (current_version) {
	case (VERSION_WIN7):
	return VERSION_WS2008;

	case (VERSION_WIN8):
	return VERSION_WIN7;

	case (VERSION_WIN8_1):
	return VERSION_WIN8;

	case (VERSION_WIN10):
	return VERSION_WIN8_1;

	case (VERSION_WS2008):
	default:
	return VERSION_INVAL;
	}
	}

	static int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo,
	__u32 version)
	{
	int ret = 0;
	struct vmbus_channel_initiate_contact *msg;
	unsigned long flags;

	init_completion(&msginfo->waitevent);

	msg = (struct vmbus_channel_initiate_contact *)msginfo->msg;

	msg->header.msgtype = CHANNELMSG_INITIATE_CONTACT;
	msg->vmbus_version_requested = version;
	msg->interrupt_page = virt_to_phys(vmbus_connection.int_page);
	msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages[0]);
	msg->monitor_page2 = virt_to_phys(vmbus_connection.monitor_pages[1]);
	/*
	* We want all channel messages to be delivered on CPU 0.
	* This has been the behavior pre-win8. This is not
	* perf issue and having all channel messages delivered on CPU 0
	* would be ok.
	* For post win8 hosts, we support receiving channel messagges on
	* all the CPUs. This is needed for kexec to work correctly where
	* the CPU attempting to connect may not be CPU 0.
	*/
	if (version >= VERSION_WIN8_1) {
	msg->target_vcpu =
	hv_cpu_number_to_vp_number(smp_processor_id());
	vmbus_connection.connect_cpu = smp_processor_id();
	} else {
	msg->target_vcpu = 0;
	vmbus_connection.connect_cpu = 0;
	}

	/*
	* Add to list before we send the request since we may
	* receive the response before returning from this routine
	*/
	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
	list_add_tail(&msginfo->msglistentry,
	&vmbus_connection.chn_msg_list);

	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

	ret = vmbus_post_msg(msg,
	sizeof(struct vmbus_channel_initiate_contact),
	true);

	trace_vmbus_negotiate_version(msg, ret);

	if (ret != 0) {
	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
	list_del(&msginfo->msglistentry);
	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock,
	flags);
	return ret;
	}

	/* Wait for the connection response */
	wait_for_completion(&msginfo->waitevent);

	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
	list_del(&msginfo->msglistentry);
	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);

	/* Check if successful */
	if (msginfo->response.version_response.version_supported) {
	vmbus_connection.conn_state = CONNECTED;
	} else {
	return -ECONNREFUSED;
	}

	return ret;
	}

	/*
	* vmbus_connect - Sends a connect request on the partition service connection
	*/
	int vmbus_connect(void)
	{
	int ret = 0;
	struct vmbus_channel_msginfo *msginfo = NULL;
	__u32 version;

	/* Initialize the vmbus connection */
	vmbus_connection.conn_state = CONNECTING;
	vmbus_connection.work_queue = create_workqueue("hv_vmbus_con");
	if (!vmbus_connection.work_queue) {
	ret = -ENOMEM;
	goto cleanup;
	}

	INIT_LIST_HEAD(&vmbus_connection.chn_msg_list);
	spin_lock_init(&vmbus_connection.channelmsg_lock);

	INIT_LIST_HEAD(&vmbus_connection.chn_list);
	mutex_init(&vmbus_connection.channel_mutex);

	/*
	* Setup the vmbus event connection for channel interrupt
	* abstraction stuff
	*/
	vmbus_connection.int_page =
	(void *)__get_free_pages(GFP_KERNEL\|__GFP_ZERO, 0);
	if (vmbus_connection.int_page == NULL) {
	ret = -ENOMEM;
	goto cleanup;
	}

	vmbus_connection.recv_int_page = vmbus_connection.int_page;
	vmbus_connection.send_int_page =
	(void *)((unsigned long)vmbus_connection.int_page +
	(PAGE_SIZE >> 1));

	/*
	* Setup the monitor notification facility. The 1st page for
	* parent->child and the 2nd page for child->parent
	*/
	vmbus_connection.monitor_pages[0] = (void *)__get_free_pages((GFP_KERNEL\|__GFP_ZERO), 0);
	vmbus_connection.monitor_pages[1] = (void *)__get_free_pages((GFP_KERNEL\|__GFP_ZERO), 0);
	if ((vmbus_connection.monitor_pages[0] == NULL) \|\|
	(vmbus_connection.monitor_pages[1] == NULL)) {
	ret = -ENOMEM;
	goto cleanup;
	}

	msginfo = kzalloc(sizeof(*msginfo) +
	sizeof(struct vmbus_channel_initiate_contact),
	GFP_KERNEL);
	if (msginfo == NULL) {
	ret = -ENOMEM;
	goto cleanup;
	}

	/*
	* Negotiate a compatible VMBUS version number with the
	* host. We start with the highest number we can support
	* and work our way down until we negotiate a compatible
	* version.
	*/

	version = VERSION_CURRENT;

	do {
	ret = vmbus_negotiate_version(msginfo, version);
	if (ret == -ETIMEDOUT)
	goto cleanup;

	if (vmbus_connection.conn_state == CONNECTED)
	break;

	version = vmbus_get_next_version(version);
	} while (version != VERSION_INVAL);

	if (version == VERSION_INVAL)
	goto cleanup;

	vmbus_proto_version = version;
	pr_info("Vmbus version:%d.%d\n",
	version >> 16, version & 0xFFFF);

	kfree(msginfo);
	return 0;

	cleanup:
	pr_err("Unable to connect to host\n");

	vmbus_connection.conn_state = DISCONNECTED;
	vmbus_disconnect();

	kfree(msginfo);

	return ret;
	}

	void vmbus_disconnect(void)
	{
	/*
	* First send the unload request to the host.
	*/
	vmbus_initiate_unload(false);

	if (vmbus_connection.work_queue) {
	drain_workqueue(vmbus_connection.work_queue);
	destroy_workqueue(vmbus_connection.work_queue);
	}

	if (vmbus_connection.int_page) {
	free_pages((unsigned long)vmbus_connection.int_page, 0);
	vmbus_connection.int_page = NULL;
	}

	free_pages((unsigned long)vmbus_connection.monitor_pages[0], 0);
	free_pages((unsigned long)vmbus_connection.monitor_pages[1], 0);
	vmbus_connection.monitor_pages[0] = NULL;
	vmbus_connection.monitor_pages[1] = NULL;
	}

	/*
	* relid2channel - Get the channel object given its
	* child relative id (ie channel id)
	*/
	struct vmbus_channel *relid2channel(u32 relid)
	{
	struct vmbus_channel *channel;
	struct vmbus_channel *found_channel = NULL;
	struct list_head cur, tmp;
	struct vmbus_channel *cur_sc;

	BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));

	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
	if (channel->offermsg.child_relid == relid) {
	found_channel = channel;
	break;
	} else if (!list_empty(&channel->sc_list)) {
	/*
	* Deal with sub-channels.
	*/
	list_for_each_safe(cur, tmp, &channel->sc_list) {
	cur_sc = list_entry(cur, struct vmbus_channel,
	sc_list);
	if (cur_sc->offermsg.child_relid == relid) {
	found_channel = cur_sc;
	break;
	}
	}
	}
	}

	return found_channel;
	}

	/*
	* vmbus_on_event - Process a channel event notification
	*
	* For batched channels (default) optimize host to guest signaling
	* by ensuring:
	* 1. While reading the channel, we disable interrupts from host.
	* 2. Ensure that we process all posted messages from the host
	* before returning from this callback.
	* 3. Once we return, enable signaling from the host. Once this
	* state is set we check to see if additional packets are
	* available to read. In this case we repeat the process.
	* If this tasklet has been running for a long time
	* then reschedule ourselves.
	*/
	void vmbus_on_event(unsigned long data)
	{
	struct vmbus_channel channel = (void ) data;
	unsigned long time_limit = jiffies + 2;

	trace_vmbus_on_event(channel);

	do {
	void (callback_fn)(void );

	/* A channel once created is persistent even when
	* there is no driver handling the device. An
	* unloading driver sets the onchannel_callback to NULL.
	*/
	callback_fn = READ_ONCE(channel->onchannel_callback);
	if (unlikely(callback_fn == NULL))
	return;

	(*callback_fn)(channel->channel_callback_context);

	if (channel->callback_mode != HV_CALL_BATCHED)
	return;

	if (likely(hv_end_read(&channel->inbound) == 0))
	return;

	hv_begin_read(&channel->inbound);
	} while (likely(time_before(jiffies, time_limit)));

	/* The time limit (2 jiffies) has been reached */
	tasklet_schedule(&channel->callback_event);
	}

	/*
	* vmbus_post_msg - Send a msg on the vmbus's message connection
	*/
	int vmbus_post_msg(void *buffer, size_t buflen, bool can_sleep)
	{
	union hv_connection_id conn_id;
	int ret = 0;
	int retries = 0;
	u32 usec = 1;

	conn_id.asu32 = 0;
	conn_id.u.id = VMBUS_MESSAGE_CONNECTION_ID;

	/*
	* hv_post_message() can have transient failures because of
	* insufficient resources. Retry the operation a couple of
	* times before giving up.
	*/
	while (retries < 100) {
	ret = hv_post_message(conn_id, 1, buffer, buflen);

	switch (ret) {
	case HV_STATUS_INVALID_CONNECTION_ID:
	/*
	* We could get this if we send messages too
	* frequently.
	*/
	ret = -EAGAIN;
	break;
	case HV_STATUS_INSUFFICIENT_MEMORY:
	case HV_STATUS_INSUFFICIENT_BUFFERS:
	ret = -ENOBUFS;
	break;
	case HV_STATUS_SUCCESS:
	return ret;
	default:
	pr_err("hv_post_msg() failed; error code:%d\n", ret);
	return -EINVAL;
	}

	retries++;
	if (can_sleep && usec > 1000)
	msleep(usec / 1000);
	else if (usec < MAX_UDELAY_MS * 1000)
	udelay(usec);
	else
	mdelay(usec / 1000);

	if (retries < 22)
	usec *= 2;
	}
	return ret;
	}

	/*
	* vmbus_set_event - Send an event notification to the parent
	*/
	void vmbus_set_event(struct vmbus_channel *channel)
	{
	u32 child_relid = channel->offermsg.child_relid;

	if (!channel->is_dedicated_interrupt)
	vmbus_send_interrupt(child_relid);

	++channel->sig_events;

	hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, channel->sig_event);
	}
	EXPORT_SYMBOL_GPL(vmbus_set_event);