/* 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