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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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3.0 kB · 111 lines
C
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112/* 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 <hyperv/hvhdk.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_global_cleanup(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);
extern void hv_adj_sched_clock_offset(u64 offset);
static __always_inline boolhv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc, u64 *time){ 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 false; /* * 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);
*time = mul_u64_u64_shr(*cur_tsc, scale, 64) + offset; return true;}
#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 __always_inline boolhv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc, u64 *time){ return false;}
static inline int hv_stimer_cleanup(unsigned int cpu) { return 0; }static inline void hv_stimer_global_cleanup(void) {}
#endif /* CONFIG_HYPERV_TIMER */
#endif