drivers/hv/hv.c - LeafOS-Devices/android_kernel_samsung_gta4xl - 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/mm.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/hyperv.h>
 #include <linux/version.h>
 #include <linux/interrupt.h>
 #include <linux/clockchips.h>
 #include <asm/hyperv.h>
 #include <asm/mshyperv.h>
 #include "hyperv_vmbus.h"

 /* The one and only */
 struct hv_context hv_context = {
 	.synic_initialized	= false,
 };

 #define HV_TIMER_FREQUENCY (10 * 1000 * 1000) /* 100ns period */
 #define HV_MAX_MAX_DELTA_TICKS 0xffffffff
 #define HV_MIN_DELTA_TICKS 1

 /*
  * hv_init - Main initialization routine.
  *
  * This routine must be called before any other routines in here are called
  */
 int hv_init(void)
 {
 	if (!hv_is_hypercall_page_setup())
 		return -ENOTSUPP;

 	hv_context.cpu_context = alloc_percpu(struct hv_per_cpu_context);
 	if (!hv_context.cpu_context)
 		return -ENOMEM;

 	return 0;
 }

 /*
  * hv_post_message - Post a message using the hypervisor message IPC.
  *
  * This involves a hypercall.
  */
 int hv_post_message(union hv_connection_id connection_id,
 		  enum hv_message_type message_type,
 		  void *payload, size_t payload_size)
 {
 	struct hv_input_post_message *aligned_msg;
 	struct hv_per_cpu_context *hv_cpu;
 	u64 status;

 	if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
 		return -EMSGSIZE;

 	hv_cpu = get_cpu_ptr(hv_context.cpu_context);
 	aligned_msg = hv_cpu->post_msg_page;
 	aligned_msg->connectionid = connection_id;
 	aligned_msg->reserved = 0;
 	aligned_msg->message_type = message_type;
 	aligned_msg->payload_size = payload_size;
 	memcpy((void *)aligned_msg->payload, payload, payload_size);

 	status = hv_do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL);

 	/* Preemption must remain disabled until after the hypercall
 	 * so some other thread can't get scheduled onto this cpu and
 	 * corrupt the per-cpu post_msg_page
 	 */
 	put_cpu_ptr(hv_cpu);

 	return status & 0xFFFF;
 }

 static int hv_ce_set_next_event(unsigned long delta,
 				struct clock_event_device *evt)
 {
 	u64 current_tick;

 	WARN_ON(!clockevent_state_oneshot(evt));

 	current_tick = hyperv_cs->read(NULL);
 	current_tick += delta;
 	hv_init_timer(HV_X64_MSR_STIMER0_COUNT, current_tick);
 	return 0;
 }

 static int hv_ce_shutdown(struct clock_event_device *evt)
 {
 	hv_init_timer(HV_X64_MSR_STIMER0_COUNT, 0);
 	hv_init_timer_config(HV_X64_MSR_STIMER0_CONFIG, 0);

 	return 0;
 }

 static int hv_ce_set_oneshot(struct clock_event_device *evt)
 {
 	union hv_timer_config timer_cfg;

 	timer_cfg.enable = 1;
 	timer_cfg.auto_enable = 1;
 	timer_cfg.sintx = VMBUS_MESSAGE_SINT;
 	hv_init_timer_config(HV_X64_MSR_STIMER0_CONFIG, timer_cfg.as_uint64);

 	return 0;
 }

 static void hv_init_clockevent_device(struct clock_event_device *dev, int cpu)
 {
 	dev->name = "Hyper-V clockevent";
 	dev->features = CLOCK_EVT_FEAT_ONESHOT;
 	dev->cpumask = cpumask_of(cpu);
 	dev->rating = 1000;
 	/*
 	 * Avoid settint dev->owner = THIS_MODULE deliberately as doing so will
 	 * result in clockevents_config_and_register() taking additional
 	 * references to the hv_vmbus module making it impossible to unload.
 	 */

 	dev->set_state_shutdown = hv_ce_shutdown;
 	dev->set_state_oneshot = hv_ce_set_oneshot;
 	dev->set_next_event = hv_ce_set_next_event;
 }


 int hv_synic_alloc(void)
 {
 	int cpu;

 	hv_context.hv_numa_map = kzalloc(sizeof(struct cpumask) * nr_node_ids,
 					 GFP_ATOMIC);
 	if (hv_context.hv_numa_map == NULL) {
 		pr_err("Unable to allocate NUMA map\n");
 		goto err;
 	}

 	for_each_present_cpu(cpu) {
 		struct hv_per_cpu_context *hv_cpu
 			= per_cpu_ptr(hv_context.cpu_context, cpu);

 		memset(hv_cpu, 0, sizeof(*hv_cpu));
 		tasklet_init(&hv_cpu->msg_dpc,
 			     vmbus_on_msg_dpc, (unsigned long) hv_cpu);

 		hv_cpu->clk_evt = kzalloc(sizeof(struct clock_event_device),
 					  GFP_KERNEL);
 		if (hv_cpu->clk_evt == NULL) {
 			pr_err("Unable to allocate clock event device\n");
 			goto err;
 		}
 		hv_init_clockevent_device(hv_cpu->clk_evt, cpu);

 		hv_cpu->synic_message_page =
 			(void *)get_zeroed_page(GFP_ATOMIC);
 		if (hv_cpu->synic_message_page == NULL) {
 			pr_err("Unable to allocate SYNIC message page\n");
 			goto err;
 		}

 		hv_cpu->synic_event_page = (void *)get_zeroed_page(GFP_ATOMIC);
 		if (hv_cpu->synic_event_page == NULL) {
 			pr_err("Unable to allocate SYNIC event page\n");
 			goto err;
 		}

 		hv_cpu->post_msg_page = (void *)get_zeroed_page(GFP_ATOMIC);
 		if (hv_cpu->post_msg_page == NULL) {
 			pr_err("Unable to allocate post msg page\n");
 			goto err;
 		}

 		INIT_LIST_HEAD(&hv_cpu->chan_list);
 	}

 	return 0;
 err:
 	/*
 	 * Any memory allocations that succeeded will be freed when
 	 * the caller cleans up by calling hv_synic_free()
 	 */
 	return -ENOMEM;
 }


 void hv_synic_free(void)
 {
 	int cpu;

 	for_each_present_cpu(cpu) {
 		struct hv_per_cpu_context *hv_cpu
 			= per_cpu_ptr(hv_context.cpu_context, cpu);

 		kfree(hv_cpu->clk_evt);
 		free_page((unsigned long)hv_cpu->synic_event_page);
 		free_page((unsigned long)hv_cpu->synic_message_page);
 		free_page((unsigned long)hv_cpu->post_msg_page);
 	}

 	kfree(hv_context.hv_numa_map);
 }

 /*
  * hv_synic_init - Initialize the Synthethic Interrupt Controller.
  *
  * If it is already initialized by another entity (ie x2v shim), we need to
  * retrieve the initialized message and event pages.  Otherwise, we create and
  * initialize the message and event pages.
  */
 int hv_synic_init(unsigned int cpu)
 {
 	struct hv_per_cpu_context *hv_cpu
 		= per_cpu_ptr(hv_context.cpu_context, cpu);
 	union hv_synic_simp simp;
 	union hv_synic_siefp siefp;
 	union hv_synic_sint shared_sint;
 	union hv_synic_scontrol sctrl;

 	/* Setup the Synic's message page */
 	hv_get_simp(simp.as_uint64);
 	simp.simp_enabled = 1;
 	simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
 		>> PAGE_SHIFT;

 	hv_set_simp(simp.as_uint64);

 	/* Setup the Synic's event page */
 	hv_get_siefp(siefp.as_uint64);
 	siefp.siefp_enabled = 1;
 	siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
 		>> PAGE_SHIFT;

 	hv_set_siefp(siefp.as_uint64);

 	/* Setup the shared SINT. */
 	hv_get_synint_state(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT,
 			    shared_sint.as_uint64);

 	shared_sint.as_uint64 = 0;
 	shared_sint.vector = HYPERVISOR_CALLBACK_VECTOR;
 	shared_sint.masked = false;
 	if (ms_hyperv.hints & HV_X64_DEPRECATING_AEOI_RECOMMENDED)
 		shared_sint.auto_eoi = false;
 	else
 		shared_sint.auto_eoi = true;

 	hv_set_synint_state(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT,
 			    shared_sint.as_uint64);

 	/* Enable the global synic bit */
 	hv_get_synic_state(sctrl.as_uint64);
 	sctrl.enable = 1;

 	hv_set_synic_state(sctrl.as_uint64);

 	hv_context.synic_initialized = true;

 	/*
 	 * Register the per-cpu clockevent source.
 	 */
 	if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE)
 		clockevents_config_and_register(hv_cpu->clk_evt,
 						HV_TIMER_FREQUENCY,
 						HV_MIN_DELTA_TICKS,
 						HV_MAX_MAX_DELTA_TICKS);
 	return 0;
 }

 /*
  * hv_synic_clockevents_cleanup - Cleanup clockevent devices
  */
 void hv_synic_clockevents_cleanup(void)
 {
 	int cpu;

 	if (!(ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE))
 		return;

 	for_each_present_cpu(cpu) {
 		struct hv_per_cpu_context *hv_cpu
 			= per_cpu_ptr(hv_context.cpu_context, cpu);

 		clockevents_unbind_device(hv_cpu->clk_evt, cpu);
 	}
 }

 /*
  * hv_synic_cleanup - Cleanup routine for hv_synic_init().
  */
 int hv_synic_cleanup(unsigned int cpu)
 {
 	union hv_synic_sint shared_sint;
 	union hv_synic_simp simp;
 	union hv_synic_siefp siefp;
 	union hv_synic_scontrol sctrl;
 	struct vmbus_channel *channel, *sc;
 	bool channel_found = false;
 	unsigned long flags;

 	if (!hv_context.synic_initialized)
 		return -EFAULT;

 	/*
 	 * Search for channels which are bound to the CPU we're about to
 	 * cleanup. In case we find one and vmbus is still connected we need to
 	 * fail, this will effectively prevent CPU offlining. There is no way
 	 * we can re-bind channels to different CPUs for now.
 	 */
 	mutex_lock(&vmbus_connection.channel_mutex);
 	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
 		if (channel->target_cpu == cpu) {
 			channel_found = true;
 			break;
 		}
 		spin_lock_irqsave(&channel->lock, flags);
 		list_for_each_entry(sc, &channel->sc_list, sc_list) {
 			if (sc->target_cpu == cpu) {
 				channel_found = true;
 				break;
 			}
 		}
 		spin_unlock_irqrestore(&channel->lock, flags);
 		if (channel_found)
 			break;
 	}
 	mutex_unlock(&vmbus_connection.channel_mutex);

 	if (channel_found && vmbus_connection.conn_state == CONNECTED)
 		return -EBUSY;

 	/* Turn off clockevent device */
 	if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE) {
 		struct hv_per_cpu_context *hv_cpu
 			= this_cpu_ptr(hv_context.cpu_context);

 		clockevents_unbind_device(hv_cpu->clk_evt, cpu);
 		hv_ce_shutdown(hv_cpu->clk_evt);
 	}

 	hv_get_synint_state(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT,
 			    shared_sint.as_uint64);

 	shared_sint.masked = 1;

 	/* Need to correctly cleanup in the case of SMP!!! */
 	/* Disable the interrupt */
 	hv_set_synint_state(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT,
 			    shared_sint.as_uint64);

 	hv_get_simp(simp.as_uint64);
 	simp.simp_enabled = 0;
 	simp.base_simp_gpa = 0;

 	hv_set_simp(simp.as_uint64);

 	hv_get_siefp(siefp.as_uint64);
 	siefp.siefp_enabled = 0;
 	siefp.base_siefp_gpa = 0;

 	hv_set_siefp(siefp.as_uint64);

 	/* Disable the global synic bit */
 	hv_get_synic_state(sctrl.as_uint64);
 	sctrl.enable = 0;
 	hv_set_synic_state(sctrl.as_uint64);

 	return 0;
 }
	/*
	* 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/mm.h>
	#include <linux/slab.h>
	#include <linux/vmalloc.h>
	#include <linux/hyperv.h>
	#include <linux/version.h>
	#include <linux/interrupt.h>
	#include <linux/clockchips.h>
	#include <asm/hyperv.h>
	#include <asm/mshyperv.h>
	#include "hyperv_vmbus.h"

	/* The one and only */
	struct hv_context hv_context = {
	.synic_initialized = false,
	};

	#define HV_TIMER_FREQUENCY (10 * 1000 * 1000) /* 100ns period */
	#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
	#define HV_MIN_DELTA_TICKS 1

	/*
	* hv_init - Main initialization routine.
	*
	* This routine must be called before any other routines in here are called
	*/
	int hv_init(void)
	{
	if (!hv_is_hypercall_page_setup())
	return -ENOTSUPP;

	hv_context.cpu_context = alloc_percpu(struct hv_per_cpu_context);
	if (!hv_context.cpu_context)
	return -ENOMEM;

	return 0;
	}

	/*
	* hv_post_message - Post a message using the hypervisor message IPC.
	*
	* This involves a hypercall.
	*/
	int hv_post_message(union hv_connection_id connection_id,
	enum hv_message_type message_type,
	void *payload, size_t payload_size)
	{
	struct hv_input_post_message *aligned_msg;
	struct hv_per_cpu_context *hv_cpu;
	u64 status;

	if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
	return -EMSGSIZE;

	hv_cpu = get_cpu_ptr(hv_context.cpu_context);
	aligned_msg = hv_cpu->post_msg_page;
	aligned_msg->connectionid = connection_id;
	aligned_msg->reserved = 0;
	aligned_msg->message_type = message_type;
	aligned_msg->payload_size = payload_size;
	memcpy((void *)aligned_msg->payload, payload, payload_size);

	status = hv_do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL);

	/* Preemption must remain disabled until after the hypercall
	* so some other thread can't get scheduled onto this cpu and
	* corrupt the per-cpu post_msg_page
	*/
	put_cpu_ptr(hv_cpu);

	return status & 0xFFFF;
	}

	static int hv_ce_set_next_event(unsigned long delta,
	struct clock_event_device *evt)
	{
	u64 current_tick;

	WARN_ON(!clockevent_state_oneshot(evt));

	current_tick = hyperv_cs->read(NULL);
	current_tick += delta;
	hv_init_timer(HV_X64_MSR_STIMER0_COUNT, current_tick);
	return 0;
	}

	static int hv_ce_shutdown(struct clock_event_device *evt)
	{
	hv_init_timer(HV_X64_MSR_STIMER0_COUNT, 0);
	hv_init_timer_config(HV_X64_MSR_STIMER0_CONFIG, 0);

	return 0;
	}

	static int hv_ce_set_oneshot(struct clock_event_device *evt)
	{
	union hv_timer_config timer_cfg;

	timer_cfg.enable = 1;
	timer_cfg.auto_enable = 1;
	timer_cfg.sintx = VMBUS_MESSAGE_SINT;
	hv_init_timer_config(HV_X64_MSR_STIMER0_CONFIG, timer_cfg.as_uint64);

	return 0;
	}

	static void hv_init_clockevent_device(struct clock_event_device *dev, int cpu)
	{
	dev->name = "Hyper-V clockevent";
	dev->features = CLOCK_EVT_FEAT_ONESHOT;
	dev->cpumask = cpumask_of(cpu);
	dev->rating = 1000;
	/*
	* Avoid settint dev->owner = THIS_MODULE deliberately as doing so will
	* result in clockevents_config_and_register() taking additional
	* references to the hv_vmbus module making it impossible to unload.
	*/

	dev->set_state_shutdown = hv_ce_shutdown;
	dev->set_state_oneshot = hv_ce_set_oneshot;
	dev->set_next_event = hv_ce_set_next_event;
	}


	int hv_synic_alloc(void)
	{
	int cpu;

	hv_context.hv_numa_map = kzalloc(sizeof(struct cpumask) * nr_node_ids,
	GFP_ATOMIC);
	if (hv_context.hv_numa_map == NULL) {
	pr_err("Unable to allocate NUMA map\n");
	goto err;
	}

	for_each_present_cpu(cpu) {
	struct hv_per_cpu_context *hv_cpu
	= per_cpu_ptr(hv_context.cpu_context, cpu);

	memset(hv_cpu, 0, sizeof(*hv_cpu));
	tasklet_init(&hv_cpu->msg_dpc,
	vmbus_on_msg_dpc, (unsigned long) hv_cpu);

	hv_cpu->clk_evt = kzalloc(sizeof(struct clock_event_device),
	GFP_KERNEL);
	if (hv_cpu->clk_evt == NULL) {
	pr_err("Unable to allocate clock event device\n");
	goto err;
	}
	hv_init_clockevent_device(hv_cpu->clk_evt, cpu);

	hv_cpu->synic_message_page =
	(void *)get_zeroed_page(GFP_ATOMIC);
	if (hv_cpu->synic_message_page == NULL) {
	pr_err("Unable to allocate SYNIC message page\n");
	goto err;
	}

	hv_cpu->synic_event_page = (void *)get_zeroed_page(GFP_ATOMIC);
	if (hv_cpu->synic_event_page == NULL) {
	pr_err("Unable to allocate SYNIC event page\n");
	goto err;
	}

	hv_cpu->post_msg_page = (void *)get_zeroed_page(GFP_ATOMIC);
	if (hv_cpu->post_msg_page == NULL) {
	pr_err("Unable to allocate post msg page\n");
	goto err;
	}

	INIT_LIST_HEAD(&hv_cpu->chan_list);
	}

	return 0;
	err:
	/*
	* Any memory allocations that succeeded will be freed when
	* the caller cleans up by calling hv_synic_free()
	*/
	return -ENOMEM;
	}


	void hv_synic_free(void)
	{
	int cpu;

	for_each_present_cpu(cpu) {
	struct hv_per_cpu_context *hv_cpu
	= per_cpu_ptr(hv_context.cpu_context, cpu);

	kfree(hv_cpu->clk_evt);
	free_page((unsigned long)hv_cpu->synic_event_page);
	free_page((unsigned long)hv_cpu->synic_message_page);
	free_page((unsigned long)hv_cpu->post_msg_page);
	}

	kfree(hv_context.hv_numa_map);
	}

	/*
	* hv_synic_init - Initialize the Synthethic Interrupt Controller.
	*
	* If it is already initialized by another entity (ie x2v shim), we need to
	* retrieve the initialized message and event pages. Otherwise, we create and
	* initialize the message and event pages.
	*/
	int hv_synic_init(unsigned int cpu)
	{
	struct hv_per_cpu_context *hv_cpu
	= per_cpu_ptr(hv_context.cpu_context, cpu);
	union hv_synic_simp simp;
	union hv_synic_siefp siefp;
	union hv_synic_sint shared_sint;
	union hv_synic_scontrol sctrl;

	/* Setup the Synic's message page */
	hv_get_simp(simp.as_uint64);
	simp.simp_enabled = 1;
	simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
	>> PAGE_SHIFT;

	hv_set_simp(simp.as_uint64);

	/* Setup the Synic's event page */
	hv_get_siefp(siefp.as_uint64);
	siefp.siefp_enabled = 1;
	siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
	>> PAGE_SHIFT;

	hv_set_siefp(siefp.as_uint64);

	/* Setup the shared SINT. */
	hv_get_synint_state(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT,
	shared_sint.as_uint64);

	shared_sint.as_uint64 = 0;
	shared_sint.vector = HYPERVISOR_CALLBACK_VECTOR;
	shared_sint.masked = false;
	if (ms_hyperv.hints & HV_X64_DEPRECATING_AEOI_RECOMMENDED)
	shared_sint.auto_eoi = false;
	else
	shared_sint.auto_eoi = true;

	hv_set_synint_state(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT,
	shared_sint.as_uint64);

	/* Enable the global synic bit */
	hv_get_synic_state(sctrl.as_uint64);
	sctrl.enable = 1;

	hv_set_synic_state(sctrl.as_uint64);

	hv_context.synic_initialized = true;

	/*
	* Register the per-cpu clockevent source.
	*/
	if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE)
	clockevents_config_and_register(hv_cpu->clk_evt,
	HV_TIMER_FREQUENCY,
	HV_MIN_DELTA_TICKS,
	HV_MAX_MAX_DELTA_TICKS);
	return 0;
	}

	/*
	* hv_synic_clockevents_cleanup - Cleanup clockevent devices
	*/
	void hv_synic_clockevents_cleanup(void)
	{
	int cpu;

	if (!(ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE))
	return;

	for_each_present_cpu(cpu) {
	struct hv_per_cpu_context *hv_cpu
	= per_cpu_ptr(hv_context.cpu_context, cpu);

	clockevents_unbind_device(hv_cpu->clk_evt, cpu);
	}
	}

	/*
	* hv_synic_cleanup - Cleanup routine for hv_synic_init().
	*/
	int hv_synic_cleanup(unsigned int cpu)
	{
	union hv_synic_sint shared_sint;
	union hv_synic_simp simp;
	union hv_synic_siefp siefp;
	union hv_synic_scontrol sctrl;
	struct vmbus_channel channel, sc;
	bool channel_found = false;
	unsigned long flags;

	if (!hv_context.synic_initialized)
	return -EFAULT;

	/*
	* Search for channels which are bound to the CPU we're about to
	* cleanup. In case we find one and vmbus is still connected we need to
	* fail, this will effectively prevent CPU offlining. There is no way
	* we can re-bind channels to different CPUs for now.
	*/
	mutex_lock(&vmbus_connection.channel_mutex);
	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
	if (channel->target_cpu == cpu) {
	channel_found = true;
	break;
	}
	spin_lock_irqsave(&channel->lock, flags);
	list_for_each_entry(sc, &channel->sc_list, sc_list) {
	if (sc->target_cpu == cpu) {
	channel_found = true;
	break;
	}
	}
	spin_unlock_irqrestore(&channel->lock, flags);
	if (channel_found)
	break;
	}
	mutex_unlock(&vmbus_connection.channel_mutex);

	if (channel_found && vmbus_connection.conn_state == CONNECTED)
	return -EBUSY;

	/* Turn off clockevent device */
	if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE) {
	struct hv_per_cpu_context *hv_cpu
	= this_cpu_ptr(hv_context.cpu_context);

	clockevents_unbind_device(hv_cpu->clk_evt, cpu);
	hv_ce_shutdown(hv_cpu->clk_evt);
	}

	hv_get_synint_state(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT,
	shared_sint.as_uint64);

	shared_sint.masked = 1;

	/* Need to correctly cleanup in the case of SMP!!! */
	/* Disable the interrupt */
	hv_set_synint_state(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT,
	shared_sint.as_uint64);

	hv_get_simp(simp.as_uint64);
	simp.simp_enabled = 0;
	simp.base_simp_gpa = 0;

	hv_set_simp(simp.as_uint64);

	hv_get_siefp(siefp.as_uint64);
	siefp.siefp_enabled = 0;
	siefp.base_siefp_gpa = 0;

	hv_set_siefp(siefp.as_uint64);

	/* Disable the global synic bit */
	hv_get_synic_state(sctrl.as_uint64);
	sctrl.enable = 0;
	hv_set_synic_state(sctrl.as_uint64);

	return 0;
	}