/* 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 /* Routines called by the VMbus driver */extern int hv_stimer_alloc(int sint);extern void hv_stimer_free(void);extern void hv_stimer_init(unsigned int cpu);extern void hv_stimer_cleanup(unsigned int cpu);extern void hv_stimer_global_cleanup(void);extern void hv_stimer0_isr(void); #if IS_ENABLED(CONFIG_HYPERV)extern struct clocksource *hyperv_cs;extern void hv_init_clocksource(void);#endif /* CONFIG_HYPERV */ #ifdef CONFIG_HYPERV_TSCPAGEextern struct ms_hyperv_tsc_page *hv_get_tsc_page(void); static inline notrace u64hv_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 u64hv_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_TSC_PAGE */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;}#endif /* CONFIG_HYPERV_TSCPAGE */ #endif