drivers/clocksource/hyperv_timer.c - 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 <clocksource/hyperv_timer.h>
 #include <asm/hyperv-tlfs.h>
 #include <asm/mshyperv.h>

 static struct clock_event_device __percpu *hv_clock_event;

 /*
  * 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.
  */
 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 = hyperv_cs->read(NULL);
 	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
  */
 void hv_stimer_init(unsigned int cpu)
 {
 	struct clock_event_device *ce;

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

 	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);
 }
 EXPORT_SYMBOL_GPL(hv_stimer_init);

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

 	/* Turn off clockevent device */
 	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
 		ce = per_cpu_ptr(hv_clock_event, cpu);
 		hv_ce_shutdown(ce);
 	}
 }
 EXPORT_SYMBOL_GPL(hv_stimer_cleanup);

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

 	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) {
 			free_percpu(hv_clock_event);
 			hv_clock_event = NULL;
 			return ret;
 		}
 	}

 	stimer0_message_sint = sint;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(hv_stimer_alloc);

 /* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
 void hv_stimer_free(void)
 {
 	if (direct_mode_enabled && (stimer0_irq != 0)) {
 		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;
 	struct clock_event_device *ce;

 	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
 		for_each_present_cpu(cpu) {
 			ce = per_cpu_ptr(hv_clock_event, cpu);
 			clockevents_unbind_device(ce, cpu);
 		}
 	}
 	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.
  */

 struct clocksource *hyperv_cs;
 EXPORT_SYMBOL_GPL(hyperv_cs);

 #ifdef CONFIG_HYPERV_TSCPAGE

 static struct ms_hyperv_tsc_page *tsc_pg;

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

 static u64 notrace read_hv_sched_clock_tsc(void)
 {
 	u64 current_tick = hv_read_tsc_page(tsc_pg);

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

 	return current_tick;
 }

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

 static struct clocksource hyperv_cs_tsc = {
 	.name	= "hyperv_clocksource_tsc_page",
 	.rating	= 400,
 	.read	= read_hv_clock_tsc,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 #endif

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

 static struct clocksource hyperv_cs_msr = {
 	.name	= "hyperv_clocksource_msr",
 	.rating	= 400,
 	.read	= read_hv_clock_msr,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 };

 #ifdef CONFIG_HYPERV_TSCPAGE
 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;

 	tsc_pg = vmalloc(PAGE_SIZE);
 	if (!tsc_pg)
 		return false;

 	hyperv_cs = &hyperv_cs_tsc;
 	phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));

 	/*
 	 * 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);

 	/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
 	sched_clock_register(read_hv_sched_clock_tsc, 64, HV_CLOCK_HZ);
 	return true;
 }
 #else
 static bool __init hv_init_tsc_clocksource(void)
 {
 	return false;
 }
 #endif


 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;

 	hyperv_cs = &hyperv_cs_msr;
 	clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);

 	/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
 	sched_clock_register(read_hv_sched_clock_msr, 64, HV_CLOCK_HZ);
 }
 EXPORT_SYMBOL_GPL(hv_init_clocksource);
	// 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 <clocksource/hyperv_timer.h>
	#include <asm/hyperv-tlfs.h>
	#include <asm/mshyperv.h>

	static struct clock_event_device __percpu *hv_clock_event;

	/*
	* 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.
	*/
	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 = hyperv_cs->read(NULL);
	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
	*/
	void hv_stimer_init(unsigned int cpu)
	{
	struct clock_event_device *ce;

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

	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);
	}
	EXPORT_SYMBOL_GPL(hv_stimer_init);

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

	/* Turn off clockevent device */
	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
	ce = per_cpu_ptr(hv_clock_event, cpu);
	hv_ce_shutdown(ce);
	}
	}
	EXPORT_SYMBOL_GPL(hv_stimer_cleanup);

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

	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) {
	free_percpu(hv_clock_event);
	hv_clock_event = NULL;
	return ret;
	}
	}

	stimer0_message_sint = sint;
	return 0;
	}
	EXPORT_SYMBOL_GPL(hv_stimer_alloc);

	/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
	void hv_stimer_free(void)
	{
	if (direct_mode_enabled && (stimer0_irq != 0)) {
	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;
	struct clock_event_device *ce;

	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
	for_each_present_cpu(cpu) {
	ce = per_cpu_ptr(hv_clock_event, cpu);
	clockevents_unbind_device(ce, cpu);
	}
	}
	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.
	*/

	struct clocksource *hyperv_cs;
	EXPORT_SYMBOL_GPL(hyperv_cs);

	#ifdef CONFIG_HYPERV_TSCPAGE

	static struct ms_hyperv_tsc_page *tsc_pg;

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

	static u64 notrace read_hv_sched_clock_tsc(void)
	{
	u64 current_tick = hv_read_tsc_page(tsc_pg);

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

	return current_tick;
	}

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

	static struct clocksource hyperv_cs_tsc = {
	.name = "hyperv_clocksource_tsc_page",
	.rating = 400,
	.read = read_hv_clock_tsc,
	.mask = CLOCKSOURCE_MASK(64),
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
	};
	#endif

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

	static struct clocksource hyperv_cs_msr = {
	.name = "hyperv_clocksource_msr",
	.rating = 400,
	.read = read_hv_clock_msr,
	.mask = CLOCKSOURCE_MASK(64),
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
	};

	#ifdef CONFIG_HYPERV_TSCPAGE
	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;

	tsc_pg = vmalloc(PAGE_SIZE);
	if (!tsc_pg)
	return false;

	hyperv_cs = &hyperv_cs_tsc;
	phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));

	/*
	* 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);

	/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
	sched_clock_register(read_hv_sched_clock_tsc, 64, HV_CLOCK_HZ);
	return true;
	}
	#else
	static bool __init hv_init_tsc_clocksource(void)
	{
	return false;
	}
	#endif


	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;

	hyperv_cs = &hyperv_cs_msr;
	clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);

	/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
	sched_clock_register(read_hv_sched_clock_msr, 64, HV_CLOCK_HZ);
	}
	EXPORT_SYMBOL_GPL(hv_init_clocksource);