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1/* SPDX-License-Identifier: GPL-2.0 */2 3/*4 * Definitions for the clocksource provided by the Hyper-V5 * hypervisor to guest VMs, as described in the Hyper-V Top6 * 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_H14#define __CLKSOURCE_HYPERV_TIMER_H15 16#include <linux/clocksource.h>17#include <linux/math64.h>18#include <asm/hyperv-tlfs.h>19 20#define HV_MAX_MAX_DELTA_TICKS 0xffffffff21#define HV_MIN_DELTA_TICKS 122 23#ifdef CONFIG_HYPERV_TIMER24 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 41static __always_inline bool42hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,43 u64 *cur_tsc, u64 *time)44{45 u64 scale, offset;46 u32 sequence;47 48 /*49 * The protocol for reading Hyper-V TSC page is specified in Hypervisor50 * Top-Level Functional Specification ver. 3.0 and above. To get the51 * reference time we must do the following:52 * - READ ReferenceTscSequence53 * A special '0' value indicates the time source is unreliable and we54 * need to use something else. The currently published specification55 * versions (up to 4.0b) contain a mistake and wrongly claim '-1'56 * instead of '0' as the special value, see commit c35b82ef0294.57 * - ReferenceTime =58 * ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset59 * - READ ReferenceTscSequence again. In case its value has changed60 * since our first reading we need to discard ReferenceTime and repeat61 * the whole sequence as the hypervisor was updating the page in62 * between.63 */64 do {65 sequence = READ_ONCE(tsc_pg->tsc_sequence);66 if (!sequence)67 return false;68 /*69 * Make sure we read sequence before we read other values from70 * TSC page.71 */72 smp_rmb();73 74 scale = READ_ONCE(tsc_pg->tsc_scale);75 offset = READ_ONCE(tsc_pg->tsc_offset);76 *cur_tsc = hv_get_raw_timer();77 78 /*79 * Make sure we read sequence after we read all other values80 * from TSC page.81 */82 smp_rmb();83 84 } while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);85 86 *time = mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;87 return true;88}89 90#else /* CONFIG_HYPERV_TIMER */91static inline unsigned long hv_get_tsc_pfn(void)92{93 return 0;94}95 96static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)97{98 return NULL;99}100 101static __always_inline bool102hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc, u64 *time)103{104 return false;105}106 107static inline int hv_stimer_cleanup(unsigned int cpu) { return 0; }108static inline void hv_stimer_legacy_init(unsigned int cpu, int sint) {}109static inline void hv_stimer_legacy_cleanup(unsigned int cpu) {}110static inline void hv_stimer_global_cleanup(void) {}111static inline void hv_stimer0_isr(void) {}112 113#endif /* CONFIG_HYPERV_TIMER */114 115#endif116