Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 | /* 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/mshyperv.h> #define HV_MAX_MAX_DELTA_TICKS 0xffffffff #define HV_MIN_DELTA_TICKS 1 #ifdef CONFIG_HYPERV_TIMER /* 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 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 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 |