[linux-block.git] / include / clocksource / hyperv_timer.h

/* SPDX-License-Identifier: GPL-2.0 */

/*
 * Definitions for the clocksource provided by the Hyper-V
 * hypervisor to guest VMs, as described in the Hyper-V Top
 * Level Functional Spec (TLFS).
 *
 * Copyright (C) 2019, Microsoft, Inc.
 *
 * Author:  Michael Kelley <mikelley@microsoft.com>
 */

#ifndef __CLKSOURCE_HYPERV_TIMER_H
#define __CLKSOURCE_HYPERV_TIMER_H

#include <linux/clocksource.h>
#include <linux/math64.h>
#include <asm/hyperv-tlfs.h>

#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
#define HV_MIN_DELTA_TICKS 1

#ifdef CONFIG_HYPERV_TIMER

#include <asm/hyperv_timer.h>

/* Routines called by the VMbus driver */
extern int hv_stimer_alloc(bool have_percpu_irqs);
extern int hv_stimer_cleanup(unsigned int cpu);
extern void hv_stimer_legacy_init(unsigned int cpu, int sint);
extern void hv_stimer_legacy_cleanup(unsigned int cpu);
extern void hv_stimer_global_cleanup(void);
extern void hv_stimer0_isr(void);

extern void hv_init_clocksource(void);
extern void hv_remap_tsc_clocksource(void);

extern unsigned long hv_get_tsc_pfn(void);
extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);

static inline notrace u64
hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc)
{
	u64 scale, offset;
	u32 sequence;

	/*
	 * The protocol for reading Hyper-V TSC page is specified in Hypervisor
	 * Top-Level Functional Specification ver. 3.0 and above. To get the
	 * reference time we must do the following:
	 * - READ ReferenceTscSequence
	 *   A special '0' value indicates the time source is unreliable and we
	 *   need to use something else. The currently published specification
	 *   versions (up to 4.0b) contain a mistake and wrongly claim '-1'
	 *   instead of '0' as the special value, see commit c35b82ef0294.
	 * - ReferenceTime =
	 *        ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
	 * - READ ReferenceTscSequence again. In case its value has changed
	 *   since our first reading we need to discard ReferenceTime and repeat
	 *   the whole sequence as the hypervisor was updating the page in
	 *   between.
	 */
	do {
		sequence = READ_ONCE(tsc_pg->tsc_sequence);
		if (!sequence)
			return U64_MAX;
		/*
		 * Make sure we read sequence before we read other values from
		 * TSC page.
		 */
		smp_rmb();

		scale = READ_ONCE(tsc_pg->tsc_scale);
		offset = READ_ONCE(tsc_pg->tsc_offset);
		*cur_tsc = hv_get_raw_timer();

		/*
		 * Make sure we read sequence after we read all other values
		 * from TSC page.
		 */
		smp_rmb();

	} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);

	return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
}

static inline notrace u64
hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
{
	u64 cur_tsc;

	return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
}

#else /* CONFIG_HYPERV_TIMER */
static inline unsigned long hv_get_tsc_pfn(void)
{
	return 0;
}

static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
{
	return NULL;
}

static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
				       u64 *cur_tsc)
{
	return U64_MAX;
}

static inline int hv_stimer_cleanup(unsigned int cpu) { return 0; }
static inline void hv_stimer_legacy_init(unsigned int cpu, int sint) {}
static inline void hv_stimer_legacy_cleanup(unsigned int cpu) {}
static inline void hv_stimer_global_cleanup(void) {}
static inline void hv_stimer0_isr(void) {}

#endif /* CONFIG_HYPERV_TIMER */

#endif
Commit	Line	Data
fd1fea68 MK	1	/* SPDX-License-Identifier: GPL-2.0 */
	2
	3	/*
	4	* Definitions for the clocksource provided by the Hyper-V
	5	* hypervisor to guest VMs, as described in the Hyper-V Top
	6	* Level Functional Spec (TLFS).
	7	*
	8	* Copyright (C) 2019, Microsoft, Inc.
	9	*
	10	* Author: Michael Kelley <mikelley@microsoft.com>
	11	*/
	12
	13	#ifndef __CLKSOURCE_HYPERV_TIMER_H
	14	#define __CLKSOURCE_HYPERV_TIMER_H
	15
dd2cb348 MK	16	#include <linux/clocksource.h>
dd2cb348 MK	17	#include <linux/math64.h>
e5dfd093	18	#include <asm/hyperv-tlfs.h>
dd2cb348	19
fd1fea68 MK	20	#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
	21	#define HV_MIN_DELTA_TICKS 1
	22
31e5e646 MK	23	#ifdef CONFIG_HYPERV_TIMER
31e5e646 MK	24
e5dfd093 TG	25	#include <asm/hyperv_timer.h>
e5dfd093 TG	26
fd1fea68	27	/* Routines called by the VMbus driver */
ec866be6	28	extern int hv_stimer_alloc(bool have_percpu_irqs);
4df4cb9e MK	29	extern int hv_stimer_cleanup(unsigned int cpu);
	30	extern void hv_stimer_legacy_init(unsigned int cpu, int sint);
	31	extern void hv_stimer_legacy_cleanup(unsigned int cpu);
fd1fea68 MK	32	extern void hv_stimer_global_cleanup(void);
	33	extern void hv_stimer0_isr(void);
	34
dd2cb348	35	extern void hv_init_clocksource(void);
0408f16b	36	extern void hv_remap_tsc_clocksource(void);
dd2cb348	37
364adc45	38	extern unsigned long hv_get_tsc_pfn(void);
dd2cb348 MK	39	extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
	40
	41	static inline notrace u64
	42	hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page tsc_pg, u64 cur_tsc)
	43	{
	44	u64 scale, offset;
	45	u32 sequence;
	46
	47	/*
	48	* The protocol for reading Hyper-V TSC page is specified in Hypervisor
	49	* Top-Level Functional Specification ver. 3.0 and above. To get the
	50	* reference time we must do the following:
	51	* - READ ReferenceTscSequence
	52	* A special '0' value indicates the time source is unreliable and we
	53	* need to use something else. The currently published specification
	54	* versions (up to 4.0b) contain a mistake and wrongly claim '-1'
	55	* instead of '0' as the special value, see commit c35b82ef0294.
	56	* - ReferenceTime =
	57	* ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
	58	* - READ ReferenceTscSequence again. In case its value has changed
	59	* since our first reading we need to discard ReferenceTime and repeat
	60	* the whole sequence as the hypervisor was updating the page in
	61	* between.
	62	*/
	63	do {
	64	sequence = READ_ONCE(tsc_pg->tsc_sequence);
	65	if (!sequence)
	66	return U64_MAX;
	67	/*
	68	* Make sure we read sequence before we read other values from
	69	* TSC page.
	70	*/
	71	smp_rmb();
	72
	73	scale = READ_ONCE(tsc_pg->tsc_scale);
	74	offset = READ_ONCE(tsc_pg->tsc_offset);
	75	*cur_tsc = hv_get_raw_timer();
	76
	77	/*
	78	* Make sure we read sequence after we read all other values
	79	* from TSC page.
	80	*/
	81	smp_rmb();
	82
	83	} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
	84
	85	return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
	86	}
	87
	88	static inline notrace u64
	89	hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
	90	{
	91	u64 cur_tsc;
	92
	93	return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
	94	}
	95
3e2d9453	96	#else /* CONFIG_HYPERV_TIMER */
364adc45 SK	97	static inline unsigned long hv_get_tsc_pfn(void)
	98	{
	99	return 0;
	100	}
	101
dd2cb348 MK	102	static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
	103	{
	104	return NULL;
	105	}
	106
	107	static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
	108	u64 *cur_tsc)
	109	{
	110	return U64_MAX;
	111	}
31e5e646 MK	112
	113	static inline int hv_stimer_cleanup(unsigned int cpu) { return 0; }
	114	static inline void hv_stimer_legacy_init(unsigned int cpu, int sint) {}
	115	static inline void hv_stimer_legacy_cleanup(unsigned int cpu) {}
	116	static inline void hv_stimer_global_cleanup(void) {}
	117	static inline void hv_stimer0_isr(void) {}
	118
3e2d9453	119	#endif /* CONFIG_HYPERV_TIMER */
dd2cb348	120
fd1fea68	121	#endif