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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
16#include <linux/clocksource.h>
17#include <linux/math64.h>
18#include <asm/hyperv-tlfs.h>
19
20#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
21#define HV_MIN_DELTA_TICKS 1
22
23#ifdef CONFIG_HYPERV_TIMER
24
25#include <asm/hyperv_timer.h>
26
27/* Routines called by the VMbus driver */
28extern int hv_stimer_alloc(bool have_percpu_irqs);
29extern int hv_stimer_cleanup(unsigned int cpu);
30extern void hv_stimer_legacy_init(unsigned int cpu, int sint);
31extern void hv_stimer_legacy_cleanup(unsigned int cpu);
32extern void hv_stimer_global_cleanup(void);
33extern void hv_stimer0_isr(void);
34
35extern void hv_init_clocksource(void);
36extern void hv_remap_tsc_clocksource(void);
37
38extern unsigned long hv_get_tsc_pfn(void);
39extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
40
41extern void hv_adj_sched_clock_offset(u64 offset);
42
43static __always_inline bool
44hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
45 u64 *cur_tsc, u64 *time)
46{
47 u64 scale, offset;
48 u32 sequence;
49
50 /*
51 * The protocol for reading Hyper-V TSC page is specified in Hypervisor
52 * Top-Level Functional Specification ver. 3.0 and above. To get the
53 * reference time we must do the following:
54 * - READ ReferenceTscSequence
55 * A special '0' value indicates the time source is unreliable and we
56 * need to use something else. The currently published specification
57 * versions (up to 4.0b) contain a mistake and wrongly claim '-1'
58 * instead of '0' as the special value, see commit c35b82ef0294.
59 * - ReferenceTime =
60 * ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
61 * - READ ReferenceTscSequence again. In case its value has changed
62 * since our first reading we need to discard ReferenceTime and repeat
63 * the whole sequence as the hypervisor was updating the page in
64 * between.
65 */
66 do {
67 sequence = READ_ONCE(tsc_pg->tsc_sequence);
68 if (!sequence)
69 return false;
70 /*
71 * Make sure we read sequence before we read other values from
72 * TSC page.
73 */
74 smp_rmb();
75
76 scale = READ_ONCE(tsc_pg->tsc_scale);
77 offset = READ_ONCE(tsc_pg->tsc_offset);
78 *cur_tsc = hv_get_raw_timer();
79
80 /*
81 * Make sure we read sequence after we read all other values
82 * from TSC page.
83 */
84 smp_rmb();
85
86 } while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
87
88 *time = mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
89 return true;
90}
91
92#else /* CONFIG_HYPERV_TIMER */
93static inline unsigned long hv_get_tsc_pfn(void)
94{
95 return 0;
96}
97
98static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
99{
100 return NULL;
101}
102
103static __always_inline bool
104hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc, u64 *time)
105{
106 return false;
107}
108
109static inline int hv_stimer_cleanup(unsigned int cpu) { return 0; }
110static inline void hv_stimer_legacy_init(unsigned int cpu, int sint) {}
111static inline void hv_stimer_legacy_cleanup(unsigned int cpu) {}
112static inline void hv_stimer_global_cleanup(void) {}
113static inline void hv_stimer0_isr(void) {}
114
115#endif /* CONFIG_HYPERV_TIMER */
116
117#endif