drivers/clocksource/hyperv_timer.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0

 /*
  * Clocksource driver for the synthetic counter and timers
  * provided by the Hyper-V hypervisor to guest VMs, as described
  * in the Hyper-V Top Level Functional Spec (TLFS). This driver
  * is instruction set architecture independent.
  *
  * Copyright (C) 2019, Microsoft, Inc.
  *
  * Author:  Michael Kelley <mikelley@microsoft.com>
  */

 #include <linux/percpu.h>
 #include <linux/cpumask.h>
 #include <linux/clockchips.h>
 #include <linux/clocksource.h>
 #include <linux/sched_clock.h>
 #include <linux/mm.h>
 #include <linux/cpuhotplug.h>
 #include <clocksource/hyperv_timer.h>
 #include <asm/hyperv-tlfs.h>
 #include <asm/mshyperv.h>

 static struct clock_event_device __percpu *hv_clock_event;
 static u64 hv_sched_clock_offset __ro_after_init;

 /*
  * If false, we're using the old mechanism for stimer0 interrupts
  * where it sends a VMbus message when it expires. The old
  * mechanism is used when running on older versions of Hyper-V
  * that don't support Direct Mode. While Hyper-V provides
  * four stimer's per CPU, Linux uses only stimer0.
  *
  * Because Direct Mode does not require processing a VMbus
  * message, stimer interrupts can be enabled earlier in the
  * process of booting a CPU, and consistent with when timer
  * interrupts are enabled for other clocksource drivers.
  * However, for legacy versions of Hyper-V when Direct Mode
  * is not enabled, setting up stimer interrupts must be
  * delayed until VMbus is initialized and can process the
  * interrupt message.
  */
 static bool direct_mode_enabled;

 static int stimer0_irq;
 static int stimer0_vector;
 static int stimer0_message_sint;

 /*
  * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
  * does not use VMbus or any VMbus messages, so process here and not
  * in the VMbus driver code.
  */
 void hv_stimer0_isr(void)
 {
 	struct clock_event_device *ce;

 	ce = this_cpu_ptr(hv_clock_event);
 	ce->event_handler(ce);
 }
 EXPORT_SYMBOL_GPL(hv_stimer0_isr);

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

 	current_tick = hv_read_reference_counter();
 	current_tick += delta;
 	hv_init_timer(0, current_tick);
 	return 0;
 }

 static int hv_ce_shutdown(struct clock_event_device *evt)
 {
 	hv_init_timer(0, 0);
 	hv_init_timer_config(0, 0);
 	if (direct_mode_enabled)
 		hv_disable_stimer0_percpu_irq(stimer0_irq);

 	return 0;
 }

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

 	timer_cfg.as_uint64 = 0;
 	timer_cfg.enable = 1;
 	timer_cfg.auto_enable = 1;
 	if (direct_mode_enabled) {
 		/*
 		 * When it expires, the timer will directly interrupt
 		 * on the specified hardware vector/IRQ.
 		 */
 		timer_cfg.direct_mode = 1;
 		timer_cfg.apic_vector = stimer0_vector;
 		hv_enable_stimer0_percpu_irq(stimer0_irq);
 	} else {
 		/*
 		 * When it expires, the timer will generate a VMbus message,
 		 * to be handled by the normal VMbus interrupt handler.
 		 */
 		timer_cfg.direct_mode = 0;
 		timer_cfg.sintx = stimer0_message_sint;
 	}
 	hv_init_timer_config(0, timer_cfg.as_uint64);
 	return 0;
 }

 /*
  * hv_stimer_init - Per-cpu initialization of the clockevent
  */
 static int hv_stimer_init(unsigned int cpu)
 {
 	struct clock_event_device *ce;

 	if (!hv_clock_event)
 		return 0;

 	ce = per_cpu_ptr(hv_clock_event, cpu);
 	ce->name = "Hyper-V clockevent";
 	ce->features = CLOCK_EVT_FEAT_ONESHOT;
 	ce->cpumask = cpumask_of(cpu);
 	ce->rating = 1000;
 	ce->set_state_shutdown = hv_ce_shutdown;
 	ce->set_state_oneshot = hv_ce_set_oneshot;
 	ce->set_next_event = hv_ce_set_next_event;

 	clockevents_config_and_register(ce,
 					HV_CLOCK_HZ,
 					HV_MIN_DELTA_TICKS,
 					HV_MAX_MAX_DELTA_TICKS);
 	return 0;
 }

 /*
  * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
  */
 int hv_stimer_cleanup(unsigned int cpu)
 {
 	struct clock_event_device *ce;

 	if (!hv_clock_event)
 		return 0;

 	/*
 	 * In the legacy case where Direct Mode is not enabled
 	 * (which can only be on x86/64), stimer cleanup happens
 	 * relatively early in the CPU offlining process. We
 	 * must unbind the stimer-based clockevent device so
 	 * that the LAPIC timer can take over until clockevents
 	 * are no longer needed in the offlining process. Note
 	 * that clockevents_unbind_device() eventually calls
 	 * hv_ce_shutdown().
 	 *
 	 * The unbind should not be done when Direct Mode is
 	 * enabled because we may be on an architecture where
 	 * there are no other clockevent devices to fallback to.
 	 */
 	ce = per_cpu_ptr(hv_clock_event, cpu);
 	if (direct_mode_enabled)
 		hv_ce_shutdown(ce);
 	else
 		clockevents_unbind_device(ce, cpu);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(hv_stimer_cleanup);

 /* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
 int hv_stimer_alloc(void)
 {
 	int ret = 0;

 	/*
 	 * Synthetic timers are always available except on old versions of
 	 * Hyper-V on x86.  In that case, return as error as Linux will use a
 	 * clockevent based on emulated LAPIC timer hardware.
 	 */
 	if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
 		return -EINVAL;

 	hv_clock_event = alloc_percpu(struct clock_event_device);
 	if (!hv_clock_event)
 		return -ENOMEM;

 	direct_mode_enabled = ms_hyperv.misc_features &
 			HV_STIMER_DIRECT_MODE_AVAILABLE;
 	if (direct_mode_enabled) {
 		ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
 				hv_stimer0_isr);
 		if (ret)
 			goto free_percpu;

 		/*
 		 * Since we are in Direct Mode, stimer initialization
 		 * can be done now with a CPUHP value in the same range
 		 * as other clockevent devices.
 		 */
 		ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING,
 				"clockevents/hyperv/stimer:starting",
 				hv_stimer_init, hv_stimer_cleanup);
 		if (ret < 0)
 			goto free_stimer0_irq;
 	}
 	return ret;

 free_stimer0_irq:
 	hv_remove_stimer0_irq(stimer0_irq);
 	stimer0_irq = 0;
 free_percpu:
 	free_percpu(hv_clock_event);
 	hv_clock_event = NULL;
 	return ret;
 }
 EXPORT_SYMBOL_GPL(hv_stimer_alloc);

 /*
  * hv_stimer_legacy_init -- Called from the VMbus driver to handle
  * the case when Direct Mode is not enabled, and the stimer
  * must be initialized late in the CPU onlining process.
  *
  */
 void hv_stimer_legacy_init(unsigned int cpu, int sint)
 {
 	if (direct_mode_enabled)
 		return;

 	/*
 	 * This function gets called by each vCPU, so setting the
 	 * global stimer_message_sint value each time is conceptually
 	 * not ideal, but the value passed in is always the same and
 	 * it avoids introducing yet another interface into this
 	 * clocksource driver just to set the sint in the legacy case.
 	 */
 	stimer0_message_sint = sint;
 	(void)hv_stimer_init(cpu);
 }
 EXPORT_SYMBOL_GPL(hv_stimer_legacy_init);

 /*
  * hv_stimer_legacy_cleanup -- Called from the VMbus driver to
  * handle the case when Direct Mode is not enabled, and the
  * stimer must be cleaned up early in the CPU offlining
  * process.
  */
 void hv_stimer_legacy_cleanup(unsigned int cpu)
 {
 	if (direct_mode_enabled)
 		return;
 	(void)hv_stimer_cleanup(cpu);
 }
 EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup);


 /* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
 void hv_stimer_free(void)
 {
 	if (!hv_clock_event)
 		return;

 	if (direct_mode_enabled) {
 		cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING);
 		hv_remove_stimer0_irq(stimer0_irq);
 		stimer0_irq = 0;
 	}
 	free_percpu(hv_clock_event);
 	hv_clock_event = NULL;
 }
 EXPORT_SYMBOL_GPL(hv_stimer_free);

 /*
  * Do a global cleanup of clockevents for the cases of kexec and
  * vmbus exit
  */
 void hv_stimer_global_cleanup(void)
 {
 	int	cpu;

 	/*
 	 * hv_stime_legacy_cleanup() will stop the stimer if Direct
 	 * Mode is not enabled, and fallback to the LAPIC timer.
 	 */
 	for_each_present_cpu(cpu) {
 		hv_stimer_legacy_cleanup(cpu);
 	}

 	/*
 	 * If Direct Mode is enabled, the cpuhp teardown callback
 	 * (hv_stimer_cleanup) will be run on all CPUs to stop the
 	 * stimers.
 	 */
 	hv_stimer_free();
 }
 EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);

 /*
  * Code and definitions for the Hyper-V clocksources.  Two
  * clocksources are defined: one that reads the Hyper-V defined MSR, and
  * the other that uses the TSC reference page feature as defined in the
  * TLFS.  The MSR version is for compatibility with old versions of
  * Hyper-V and 32-bit x86.  The TSC reference page version is preferred.
  *
  * The Hyper-V clocksource ratings of 250 are chosen to be below the
  * TSC clocksource rating of 300.  In configurations where Hyper-V offers
  * an InvariantTSC, the TSC is not marked "unstable", so the TSC clocksource
  * is available and preferred.  With the higher rating, it will be the
  * default.  On older hardware and Hyper-V versions, the TSC is marked
  * "unstable", so no TSC clocksource is created and the selected Hyper-V
  * clocksource will be the default.
  */

 u64 (*hv_read_reference_counter)(void);
 EXPORT_SYMBOL_GPL(hv_read_reference_counter);

 static union {
 	struct ms_hyperv_tsc_page page;
 	u8 reserved[PAGE_SIZE];
 } tsc_pg __aligned(PAGE_SIZE);

 struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 {
 	return &tsc_pg.page;
 }
 EXPORT_SYMBOL_GPL(hv_get_tsc_page);

 static u64 notrace read_hv_clock_tsc(void)
 {
 	u64 current_tick = hv_read_tsc_page(hv_get_tsc_page());

 	if (current_tick == U64_MAX)
 		hv_get_time_ref_count(current_tick);

 	return current_tick;
 }

 static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
 {
 	return read_hv_clock_tsc();
 }

 static u64 notrace read_hv_sched_clock_tsc(void)
 {
 	return (read_hv_clock_tsc() - hv_sched_clock_offset) *
 		(NSEC_PER_SEC / HV_CLOCK_HZ);
 }

 static void suspend_hv_clock_tsc(struct clocksource *arg)
 {
 	u64 tsc_msr;

 	/* Disable the TSC page */
 	hv_get_reference_tsc(tsc_msr);
 	tsc_msr &= ~BIT_ULL(0);
 	hv_set_reference_tsc(tsc_msr);
 }


 static void resume_hv_clock_tsc(struct clocksource *arg)
 {
 	phys_addr_t phys_addr = virt_to_phys(&tsc_pg);
 	u64 tsc_msr;

 	/* Re-enable the TSC page */
 	hv_get_reference_tsc(tsc_msr);
 	tsc_msr &= GENMASK_ULL(11, 0);
 	tsc_msr |= BIT_ULL(0) | (u64)phys_addr;
 	hv_set_reference_tsc(tsc_msr);
 }

 static int hv_cs_enable(struct clocksource *cs)
 {
 	hv_enable_vdso_clocksource();
 	return 0;
 }

 static struct clocksource hyperv_cs_tsc = {
 	.name	= "hyperv_clocksource_tsc_page",
 	.rating	= 250,
 	.read	= read_hv_clock_tsc_cs,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 	.suspend= suspend_hv_clock_tsc,
 	.resume	= resume_hv_clock_tsc,
 	.enable = hv_cs_enable,
 };

 static u64 notrace read_hv_clock_msr(void)
 {
 	u64 current_tick;
 	/*
 	 * Read the partition counter to get the current tick count. This count
 	 * is set to 0 when the partition is created and is incremented in
 	 * 100 nanosecond units.
 	 */
 	hv_get_time_ref_count(current_tick);
 	return current_tick;
 }

 static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
 {
 	return read_hv_clock_msr();
 }

 static u64 notrace read_hv_sched_clock_msr(void)
 {
 	return (read_hv_clock_msr() - hv_sched_clock_offset) *
 		(NSEC_PER_SEC / HV_CLOCK_HZ);
 }

 static struct clocksource hyperv_cs_msr = {
 	.name	= "hyperv_clocksource_msr",
 	.rating	= 250,
 	.read	= read_hv_clock_msr_cs,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 };

 static bool __init hv_init_tsc_clocksource(void)
 {
 	u64		tsc_msr;
 	phys_addr_t	phys_addr;

 	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
 		return false;

 	hv_read_reference_counter = read_hv_clock_tsc;
 	phys_addr = virt_to_phys(hv_get_tsc_page());

 	/*
 	 * The Hyper-V TLFS specifies to preserve the value of reserved
 	 * bits in registers. So read the existing value, preserve the
 	 * low order 12 bits, and add in the guest physical address
 	 * (which already has at least the low 12 bits set to zero since
 	 * it is page aligned). Also set the "enable" bit, which is bit 0.
 	 */
 	hv_get_reference_tsc(tsc_msr);
 	tsc_msr &= GENMASK_ULL(11, 0);
 	tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
 	hv_set_reference_tsc(tsc_msr);

 	hv_set_clocksource_vdso(hyperv_cs_tsc);
 	clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);

 	hv_sched_clock_offset = hv_read_reference_counter();
 	hv_setup_sched_clock(read_hv_sched_clock_tsc);

 	return true;
 }

 void __init hv_init_clocksource(void)
 {
 	/*
 	 * Try to set up the TSC page clocksource. If it succeeds, we're
 	 * done. Otherwise, set up the MSR clocksoruce.  At least one of
 	 * these will always be available except on very old versions of
 	 * Hyper-V on x86.  In that case we won't have a Hyper-V
 	 * clocksource, but Linux will still run with a clocksource based
 	 * on the emulated PIT or LAPIC timer.
 	 */
 	if (hv_init_tsc_clocksource())
 		return;

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

 	hv_read_reference_counter = read_hv_clock_msr;
 	clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);

 	hv_sched_clock_offset = hv_read_reference_counter();
 	hv_setup_sched_clock(read_hv_sched_clock_msr);
 }
	// SPDX-License-Identifier: GPL-2.0

	/*
	* Clocksource driver for the synthetic counter and timers
	* provided by the Hyper-V hypervisor to guest VMs, as described
	* in the Hyper-V Top Level Functional Spec (TLFS). This driver
	* is instruction set architecture independent.
	*
	* Copyright (C) 2019, Microsoft, Inc.
	*
	* Author: Michael Kelley <mikelley@microsoft.com>
	*/

	#include <linux/percpu.h>
	#include <linux/cpumask.h>
	#include <linux/clockchips.h>
	#include <linux/clocksource.h>
	#include <linux/sched_clock.h>
	#include <linux/mm.h>
	#include <linux/cpuhotplug.h>
	#include <clocksource/hyperv_timer.h>
	#include <asm/hyperv-tlfs.h>
	#include <asm/mshyperv.h>

	static struct clock_event_device __percpu *hv_clock_event;
	static u64 hv_sched_clock_offset __ro_after_init;

	/*
	* If false, we're using the old mechanism for stimer0 interrupts
	* where it sends a VMbus message when it expires. The old
	* mechanism is used when running on older versions of Hyper-V
	* that don't support Direct Mode. While Hyper-V provides
	* four stimer's per CPU, Linux uses only stimer0.
	*
	* Because Direct Mode does not require processing a VMbus
	* message, stimer interrupts can be enabled earlier in the
	* process of booting a CPU, and consistent with when timer
	* interrupts are enabled for other clocksource drivers.
	* However, for legacy versions of Hyper-V when Direct Mode
	* is not enabled, setting up stimer interrupts must be
	* delayed until VMbus is initialized and can process the
	* interrupt message.
	*/
	static bool direct_mode_enabled;

	static int stimer0_irq;
	static int stimer0_vector;
	static int stimer0_message_sint;

	/*
	* ISR for when stimer0 is operating in Direct Mode. Direct Mode
	* does not use VMbus or any VMbus messages, so process here and not
	* in the VMbus driver code.
	*/
	void hv_stimer0_isr(void)
	{
	struct clock_event_device *ce;

	ce = this_cpu_ptr(hv_clock_event);
	ce->event_handler(ce);
	}
	EXPORT_SYMBOL_GPL(hv_stimer0_isr);

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

	current_tick = hv_read_reference_counter();
	current_tick += delta;
	hv_init_timer(0, current_tick);
	return 0;
	}

	static int hv_ce_shutdown(struct clock_event_device *evt)
	{
	hv_init_timer(0, 0);
	hv_init_timer_config(0, 0);
	if (direct_mode_enabled)
	hv_disable_stimer0_percpu_irq(stimer0_irq);

	return 0;
	}

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

	timer_cfg.as_uint64 = 0;
	timer_cfg.enable = 1;
	timer_cfg.auto_enable = 1;
	if (direct_mode_enabled) {
	/*
	* When it expires, the timer will directly interrupt
	* on the specified hardware vector/IRQ.
	*/
	timer_cfg.direct_mode = 1;
	timer_cfg.apic_vector = stimer0_vector;
	hv_enable_stimer0_percpu_irq(stimer0_irq);
	} else {
	/*
	* When it expires, the timer will generate a VMbus message,
	* to be handled by the normal VMbus interrupt handler.
	*/
	timer_cfg.direct_mode = 0;
	timer_cfg.sintx = stimer0_message_sint;
	}
	hv_init_timer_config(0, timer_cfg.as_uint64);
	return 0;
	}

	/*
	* hv_stimer_init - Per-cpu initialization of the clockevent
	*/
	static int hv_stimer_init(unsigned int cpu)
	{
	struct clock_event_device *ce;

	if (!hv_clock_event)
	return 0;

	ce = per_cpu_ptr(hv_clock_event, cpu);
	ce->name = "Hyper-V clockevent";
	ce->features = CLOCK_EVT_FEAT_ONESHOT;
	ce->cpumask = cpumask_of(cpu);
	ce->rating = 1000;
	ce->set_state_shutdown = hv_ce_shutdown;
	ce->set_state_oneshot = hv_ce_set_oneshot;
	ce->set_next_event = hv_ce_set_next_event;

	clockevents_config_and_register(ce,
	HV_CLOCK_HZ,
	HV_MIN_DELTA_TICKS,
	HV_MAX_MAX_DELTA_TICKS);
	return 0;
	}

	/*
	* hv_stimer_cleanup - Per-cpu cleanup of the clockevent
	*/
	int hv_stimer_cleanup(unsigned int cpu)
	{
	struct clock_event_device *ce;

	if (!hv_clock_event)
	return 0;

	/*
	* In the legacy case where Direct Mode is not enabled
	* (which can only be on x86/64), stimer cleanup happens
	* relatively early in the CPU offlining process. We
	* must unbind the stimer-based clockevent device so
	* that the LAPIC timer can take over until clockevents
	* are no longer needed in the offlining process. Note
	* that clockevents_unbind_device() eventually calls
	* hv_ce_shutdown().
	*
	* The unbind should not be done when Direct Mode is
	* enabled because we may be on an architecture where
	* there are no other clockevent devices to fallback to.
	*/
	ce = per_cpu_ptr(hv_clock_event, cpu);
	if (direct_mode_enabled)
	hv_ce_shutdown(ce);
	else
	clockevents_unbind_device(ce, cpu);

	return 0;
	}
	EXPORT_SYMBOL_GPL(hv_stimer_cleanup);

	/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
	int hv_stimer_alloc(void)
	{
	int ret = 0;

	/*
	* Synthetic timers are always available except on old versions of
	* Hyper-V on x86. In that case, return as error as Linux will use a
	* clockevent based on emulated LAPIC timer hardware.
	*/
	if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
	return -EINVAL;

	hv_clock_event = alloc_percpu(struct clock_event_device);
	if (!hv_clock_event)
	return -ENOMEM;

	direct_mode_enabled = ms_hyperv.misc_features &
	HV_STIMER_DIRECT_MODE_AVAILABLE;
	if (direct_mode_enabled) {
	ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
	hv_stimer0_isr);
	if (ret)
	goto free_percpu;

	/*
	* Since we are in Direct Mode, stimer initialization
	* can be done now with a CPUHP value in the same range
	* as other clockevent devices.
	*/
	ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING,
	"clockevents/hyperv/stimer:starting",
	hv_stimer_init, hv_stimer_cleanup);
	if (ret < 0)
	goto free_stimer0_irq;
	}
	return ret;

	free_stimer0_irq:
	hv_remove_stimer0_irq(stimer0_irq);
	stimer0_irq = 0;
	free_percpu:
	free_percpu(hv_clock_event);
	hv_clock_event = NULL;
	return ret;
	}
	EXPORT_SYMBOL_GPL(hv_stimer_alloc);

	/*
	* hv_stimer_legacy_init -- Called from the VMbus driver to handle
	* the case when Direct Mode is not enabled, and the stimer
	* must be initialized late in the CPU onlining process.
	*
	*/
	void hv_stimer_legacy_init(unsigned int cpu, int sint)
	{
	if (direct_mode_enabled)
	return;

	/*
	* This function gets called by each vCPU, so setting the
	* global stimer_message_sint value each time is conceptually
	* not ideal, but the value passed in is always the same and
	* it avoids introducing yet another interface into this
	* clocksource driver just to set the sint in the legacy case.
	*/
	stimer0_message_sint = sint;
	(void)hv_stimer_init(cpu);
	}
	EXPORT_SYMBOL_GPL(hv_stimer_legacy_init);

	/*
	* hv_stimer_legacy_cleanup -- Called from the VMbus driver to
	* handle the case when Direct Mode is not enabled, and the
	* stimer must be cleaned up early in the CPU offlining
	* process.
	*/
	void hv_stimer_legacy_cleanup(unsigned int cpu)
	{
	if (direct_mode_enabled)
	return;
	(void)hv_stimer_cleanup(cpu);
	}
	EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup);


	/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
	void hv_stimer_free(void)
	{
	if (!hv_clock_event)
	return;

	if (direct_mode_enabled) {
	cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING);
	hv_remove_stimer0_irq(stimer0_irq);
	stimer0_irq = 0;
	}
	free_percpu(hv_clock_event);
	hv_clock_event = NULL;
	}
	EXPORT_SYMBOL_GPL(hv_stimer_free);

	/*
	* Do a global cleanup of clockevents for the cases of kexec and
	* vmbus exit
	*/
	void hv_stimer_global_cleanup(void)
	{
	int cpu;

	/*
	* hv_stime_legacy_cleanup() will stop the stimer if Direct
	* Mode is not enabled, and fallback to the LAPIC timer.
	*/
	for_each_present_cpu(cpu) {
	hv_stimer_legacy_cleanup(cpu);
	}

	/*
	* If Direct Mode is enabled, the cpuhp teardown callback
	* (hv_stimer_cleanup) will be run on all CPUs to stop the
	* stimers.
	*/
	hv_stimer_free();
	}
	EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);

	/*
	* Code and definitions for the Hyper-V clocksources. Two
	* clocksources are defined: one that reads the Hyper-V defined MSR, and
	* the other that uses the TSC reference page feature as defined in the
	* TLFS. The MSR version is for compatibility with old versions of
	* Hyper-V and 32-bit x86. The TSC reference page version is preferred.
	*
	* The Hyper-V clocksource ratings of 250 are chosen to be below the
	* TSC clocksource rating of 300. In configurations where Hyper-V offers
	* an InvariantTSC, the TSC is not marked "unstable", so the TSC clocksource
	* is available and preferred. With the higher rating, it will be the
	* default. On older hardware and Hyper-V versions, the TSC is marked
	* "unstable", so no TSC clocksource is created and the selected Hyper-V
	* clocksource will be the default.
	*/

	u64 (*hv_read_reference_counter)(void);
	EXPORT_SYMBOL_GPL(hv_read_reference_counter);

	static union {
	struct ms_hyperv_tsc_page page;
	u8 reserved[PAGE_SIZE];
	} tsc_pg __aligned(PAGE_SIZE);

	struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
	{
	return &tsc_pg.page;
	}
	EXPORT_SYMBOL_GPL(hv_get_tsc_page);

	static u64 notrace read_hv_clock_tsc(void)
	{
	u64 current_tick = hv_read_tsc_page(hv_get_tsc_page());

	if (current_tick == U64_MAX)
	hv_get_time_ref_count(current_tick);

	return current_tick;
	}

	static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
	{
	return read_hv_clock_tsc();
	}

	static u64 notrace read_hv_sched_clock_tsc(void)
	{
	return (read_hv_clock_tsc() - hv_sched_clock_offset) *
	(NSEC_PER_SEC / HV_CLOCK_HZ);
	}

	static void suspend_hv_clock_tsc(struct clocksource *arg)
	{
	u64 tsc_msr;

	/* Disable the TSC page */
	hv_get_reference_tsc(tsc_msr);
	tsc_msr &= ~BIT_ULL(0);
	hv_set_reference_tsc(tsc_msr);
	}


	static void resume_hv_clock_tsc(struct clocksource *arg)
	{
	phys_addr_t phys_addr = virt_to_phys(&tsc_pg);
	u64 tsc_msr;

	/* Re-enable the TSC page */
	hv_get_reference_tsc(tsc_msr);
	tsc_msr &= GENMASK_ULL(11, 0);
	tsc_msr \|= BIT_ULL(0) \| (u64)phys_addr;
	hv_set_reference_tsc(tsc_msr);
	}

	static int hv_cs_enable(struct clocksource *cs)
	{
	hv_enable_vdso_clocksource();
	return 0;
	}

	static struct clocksource hyperv_cs_tsc = {
	.name = "hyperv_clocksource_tsc_page",
	.rating = 250,
	.read = read_hv_clock_tsc_cs,
	.mask = CLOCKSOURCE_MASK(64),
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
	.suspend= suspend_hv_clock_tsc,
	.resume = resume_hv_clock_tsc,
	.enable = hv_cs_enable,
	};

	static u64 notrace read_hv_clock_msr(void)
	{
	u64 current_tick;
	/*
	* Read the partition counter to get the current tick count. This count
	* is set to 0 when the partition is created and is incremented in
	* 100 nanosecond units.
	*/
	hv_get_time_ref_count(current_tick);
	return current_tick;
	}

	static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
	{
	return read_hv_clock_msr();
	}

	static u64 notrace read_hv_sched_clock_msr(void)
	{
	return (read_hv_clock_msr() - hv_sched_clock_offset) *
	(NSEC_PER_SEC / HV_CLOCK_HZ);
	}

	static struct clocksource hyperv_cs_msr = {
	.name = "hyperv_clocksource_msr",
	.rating = 250,
	.read = read_hv_clock_msr_cs,
	.mask = CLOCKSOURCE_MASK(64),
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
	};

	static bool __init hv_init_tsc_clocksource(void)
	{
	u64 tsc_msr;
	phys_addr_t phys_addr;

	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
	return false;

	hv_read_reference_counter = read_hv_clock_tsc;
	phys_addr = virt_to_phys(hv_get_tsc_page());

	/*
	* The Hyper-V TLFS specifies to preserve the value of reserved
	* bits in registers. So read the existing value, preserve the
	* low order 12 bits, and add in the guest physical address
	* (which already has at least the low 12 bits set to zero since
	* it is page aligned). Also set the "enable" bit, which is bit 0.
	*/
	hv_get_reference_tsc(tsc_msr);
	tsc_msr &= GENMASK_ULL(11, 0);
	tsc_msr = tsc_msr \| 0x1 \| (u64)phys_addr;
	hv_set_reference_tsc(tsc_msr);

	hv_set_clocksource_vdso(hyperv_cs_tsc);
	clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);

	hv_sched_clock_offset = hv_read_reference_counter();
	hv_setup_sched_clock(read_hv_sched_clock_tsc);

	return true;
	}

	void __init hv_init_clocksource(void)
	{
	/*
	* Try to set up the TSC page clocksource. If it succeeds, we're
	* done. Otherwise, set up the MSR clocksoruce. At least one of
	* these will always be available except on very old versions of
	* Hyper-V on x86. In that case we won't have a Hyper-V
	* clocksource, but Linux will still run with a clocksource based
	* on the emulated PIT or LAPIC timer.
	*/
	if (hv_init_tsc_clocksource())
	return;

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

	hv_read_reference_counter = read_hv_clock_msr;
	clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);

	hv_sched_clock_offset = hv_read_reference_counter();
	hv_setup_sched_clock(read_hv_sched_clock_msr);
	}