// SPDX-License-Identifier: GPL-2.0 /* * Clocksource driver for the synthetic counter and timers * provided by the Hyper-V hypervisor to guest VMs, as described * in the Hyper-V Top Level Functional Spec (TLFS). This driver * is instruction set architecture independent. * * Copyright (C) 2019, Microsoft, Inc. * * Author:  Michael Kelley <mikelley@microsoft.com> */ #include <linux/percpu.h>#include <linux/cpumask.h>#include <linux/clockchips.h>#include <linux/clocksource.h>#include <linux/sched_clock.h>#include <linux/mm.h>#include <linux/cpuhotplug.h>#include <clocksource/hyperv_timer.h>#include <asm/hyperv-tlfs.h>#include <asm/mshyperv.h> static struct clock_event_device __percpu *hv_clock_event;static u64 hv_sched_clock_offset __ro_after_init; /* * If false, we're using the old mechanism for stimer0 interrupts * where it sends a VMbus message when it expires. The old * mechanism is used when running on older versions of Hyper-V * that don't support Direct Mode. While Hyper-V provides * four stimer's per CPU, Linux uses only stimer0. * * Because Direct Mode does not require processing a VMbus * message, stimer interrupts can be enabled earlier in the * process of booting a CPU, and consistent with when timer * interrupts are enabled for other clocksource drivers. * However, for legacy versions of Hyper-V when Direct Mode * is not enabled, setting up stimer interrupts must be * delayed until VMbus is initialized and can process the * interrupt message. */static bool direct_mode_enabled; static int stimer0_irq;static int stimer0_vector;static int stimer0_message_sint; /* * ISR for when stimer0 is operating in Direct Mode.  Direct Mode * does not use VMbus or any VMbus messages, so process here and not * in the VMbus driver code. */void hv_stimer0_isr(void){	struct clock_event_device *ce; 	ce = this_cpu_ptr(hv_clock_event);	ce->event_handler(ce);}EXPORT_SYMBOL_GPL(hv_stimer0_isr); static int hv_ce_set_next_event(unsigned long delta,				struct clock_event_device *evt){	u64 current_tick; 	current_tick = hv_read_reference_counter();	current_tick += delta;	hv_init_timer(0, current_tick);	return 0;} static int hv_ce_shutdown(struct clock_event_device *evt){	hv_init_timer(0, 0);	hv_init_timer_config(0, 0);	if (direct_mode_enabled)		hv_disable_stimer0_percpu_irq(stimer0_irq); 	return 0;} static int hv_ce_set_oneshot(struct clock_event_device *evt){	union hv_stimer_config timer_cfg; 	timer_cfg.as_uint64 = 0;	timer_cfg.enable = 1;	timer_cfg.auto_enable = 1;	if (direct_mode_enabled) {		/*		 * When it expires, the timer will directly interrupt		 * on the specified hardware vector/IRQ.		 */		timer_cfg.direct_mode = 1;		timer_cfg.apic_vector = stimer0_vector;		hv_enable_stimer0_percpu_irq(stimer0_irq);	} else {		/*		 * When it expires, the timer will generate a VMbus message,		 * to be handled by the normal VMbus interrupt handler.		 */		timer_cfg.direct_mode = 0;		timer_cfg.sintx = stimer0_message_sint;	}	hv_init_timer_config(0, timer_cfg.as_uint64);	return 0;} /* * hv_stimer_init - Per-cpu initialization of the clockevent */static int hv_stimer_init(unsigned int cpu){	struct clock_event_device *ce; 	if (!hv_clock_event)		return 0; 	ce = per_cpu_ptr(hv_clock_event, cpu);	ce->name = "Hyper-V clockevent";	ce->features = CLOCK_EVT_FEAT_ONESHOT;	ce->cpumask = cpumask_of(cpu);	ce->rating = 1000;	ce->set_state_shutdown = hv_ce_shutdown;	ce->set_state_oneshot = hv_ce_set_oneshot;	ce->set_next_event = hv_ce_set_next_event; 	clockevents_config_and_register(ce,					HV_CLOCK_HZ,					HV_MIN_DELTA_TICKS,					HV_MAX_MAX_DELTA_TICKS);	return 0;} /* * hv_stimer_cleanup - Per-cpu cleanup of the clockevent */int hv_stimer_cleanup(unsigned int cpu){	struct clock_event_device *ce; 	if (!hv_clock_event)		return 0; 	/*	 * In the legacy case where Direct Mode is not enabled	 * (which can only be on x86/64), stimer cleanup happens	 * relatively early in the CPU offlining process. We	 * must unbind the stimer-based clockevent device so	 * that the LAPIC timer can take over until clockevents	 * are no longer needed in the offlining process. Note	 * that clockevents_unbind_device() eventually calls	 * hv_ce_shutdown().	 *	 * The unbind should not be done when Direct Mode is	 * enabled because we may be on an architecture where	 * there are no other clockevent devices to fallback to.	 */	ce = per_cpu_ptr(hv_clock_event, cpu);	if (direct_mode_enabled)		hv_ce_shutdown(ce);	else		clockevents_unbind_device(ce, cpu); 	return 0;}EXPORT_SYMBOL_GPL(hv_stimer_cleanup); /* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */int hv_stimer_alloc(void){	int ret = 0; 	/*	 * Synthetic timers are always available except on old versions of	 * Hyper-V on x86.  In that case, return as error as Linux will use a	 * clockevent based on emulated LAPIC timer hardware.	 */	if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))		return -EINVAL; 	hv_clock_event = alloc_percpu(struct clock_event_device);	if (!hv_clock_event)		return -ENOMEM; 	direct_mode_enabled = ms_hyperv.misc_features &			HV_STIMER_DIRECT_MODE_AVAILABLE;	if (direct_mode_enabled) {		ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,				hv_stimer0_isr);		if (ret)			goto free_percpu; 		/*		 * Since we are in Direct Mode, stimer initialization		 * can be done now with a CPUHP value in the same range		 * as other clockevent devices.		 */		ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING,				"clockevents/hyperv/stimer:starting",				hv_stimer_init, hv_stimer_cleanup);		if (ret < 0)			goto free_stimer0_irq;	}	return ret; free_stimer0_irq:	hv_remove_stimer0_irq(stimer0_irq);	stimer0_irq = 0;free_percpu:	free_percpu(hv_clock_event);	hv_clock_event = NULL;	return ret;}EXPORT_SYMBOL_GPL(hv_stimer_alloc); /* * hv_stimer_legacy_init -- Called from the VMbus driver to handle * the case when Direct Mode is not enabled, and the stimer * must be initialized late in the CPU onlining process. * */void hv_stimer_legacy_init(unsigned int cpu, int sint){	if (direct_mode_enabled)		return; 	/*	 * This function gets called by each vCPU, so setting the	 * global stimer_message_sint value each time is conceptually	 * not ideal, but the value passed in is always the same and	 * it avoids introducing yet another interface into this	 * clocksource driver just to set the sint in the legacy case.	 */	stimer0_message_sint = sint;	(void)hv_stimer_init(cpu);}EXPORT_SYMBOL_GPL(hv_stimer_legacy_init); /* * hv_stimer_legacy_cleanup -- Called from the VMbus driver to * handle the case when Direct Mode is not enabled, and the * stimer must be cleaned up early in the CPU offlining * process. */void hv_stimer_legacy_cleanup(unsigned int cpu){	if (direct_mode_enabled)		return;	(void)hv_stimer_cleanup(cpu);}EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup);  /* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */void hv_stimer_free(void){	if (!hv_clock_event)		return; 	if (direct_mode_enabled) {		cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING);		hv_remove_stimer0_irq(stimer0_irq);		stimer0_irq = 0;	}	free_percpu(hv_clock_event);	hv_clock_event = NULL;}EXPORT_SYMBOL_GPL(hv_stimer_free); /* * Do a global cleanup of clockevents for the cases of kexec and * vmbus exit */void hv_stimer_global_cleanup(void){	int	cpu; 	/*	 * hv_stime_legacy_cleanup() will stop the stimer if Direct	 * Mode is not enabled, and fallback to the LAPIC timer.	 */	for_each_present_cpu(cpu) {		hv_stimer_legacy_cleanup(cpu);	} 	/*	 * If Direct Mode is enabled, the cpuhp teardown callback	 * (hv_stimer_cleanup) will be run on all CPUs to stop the	 * stimers.	 */	hv_stimer_free();}EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup); /* * Code and definitions for the Hyper-V clocksources.  Two * clocksources are defined: one that reads the Hyper-V defined MSR, and * the other that uses the TSC reference page feature as defined in the * TLFS.  The MSR version is for compatibility with old versions of * Hyper-V and 32-bit x86.  The TSC reference page version is preferred. * * The Hyper-V clocksource ratings of 250 are chosen to be below the * TSC clocksource rating of 300.  In configurations where Hyper-V offers * an InvariantTSC, the TSC is not marked "unstable", so the TSC clocksource * is available and preferred.  With the higher rating, it will be the * default.  On older hardware and Hyper-V versions, the TSC is marked * "unstable", so no TSC clocksource is created and the selected Hyper-V * clocksource will be the default. */ u64 (*hv_read_reference_counter)(void);EXPORT_SYMBOL_GPL(hv_read_reference_counter); static union {	struct ms_hyperv_tsc_page page;	u8 reserved[PAGE_SIZE];} tsc_pg __aligned(PAGE_SIZE); struct ms_hyperv_tsc_page *hv_get_tsc_page(void){	return &tsc_pg.page;}EXPORT_SYMBOL_GPL(hv_get_tsc_page); static u64 notrace read_hv_clock_tsc(void){	u64 current_tick = hv_read_tsc_page(hv_get_tsc_page()); 	if (current_tick == U64_MAX)		hv_get_time_ref_count(current_tick); 	return current_tick;} static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg){	return read_hv_clock_tsc();} static u64 read_hv_sched_clock_tsc(void){	return (read_hv_clock_tsc() - hv_sched_clock_offset) *		(NSEC_PER_SEC / HV_CLOCK_HZ);} static void suspend_hv_clock_tsc(struct clocksource *arg){	u64 tsc_msr; 	/* Disable the TSC page */	hv_get_reference_tsc(tsc_msr);	tsc_msr &= ~BIT_ULL(0);	hv_set_reference_tsc(tsc_msr);}  static void resume_hv_clock_tsc(struct clocksource *arg){	phys_addr_t phys_addr = virt_to_phys(&tsc_pg);	u64 tsc_msr; 	/* Re-enable the TSC page */	hv_get_reference_tsc(tsc_msr);	tsc_msr &= GENMASK_ULL(11, 0);	tsc_msr |= BIT_ULL(0) | (u64)phys_addr;	hv_set_reference_tsc(tsc_msr);} static int hv_cs_enable(struct clocksource *cs){	hv_enable_vdso_clocksource();	return 0;} static struct clocksource hyperv_cs_tsc = {	.name	= "hyperv_clocksource_tsc_page",	.rating	= 250,	.read	= read_hv_clock_tsc_cs,	.mask	= CLOCKSOURCE_MASK(64),	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,	.suspend= suspend_hv_clock_tsc,	.resume	= resume_hv_clock_tsc,	.enable = hv_cs_enable,}; static u64 notrace read_hv_clock_msr(void){	u64 current_tick;	/*	 * Read the partition counter to get the current tick count. This count	 * is set to 0 when the partition is created and is incremented in	 * 100 nanosecond units.	 */	hv_get_time_ref_count(current_tick);	return current_tick;} static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg){	return read_hv_clock_msr();} static u64 read_hv_sched_clock_msr(void){	return (read_hv_clock_msr() - hv_sched_clock_offset) *		(NSEC_PER_SEC / HV_CLOCK_HZ);} static struct clocksource hyperv_cs_msr = {	.name	= "hyperv_clocksource_msr",	.rating	= 250,	.read	= read_hv_clock_msr_cs,	.mask	= CLOCKSOURCE_MASK(64),	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,}; static bool __init hv_init_tsc_clocksource(void){	u64		tsc_msr;	phys_addr_t	phys_addr; 	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))		return false; 	hv_read_reference_counter = read_hv_clock_tsc;	phys_addr = virt_to_phys(hv_get_tsc_page()); 	/*	 * The Hyper-V TLFS specifies to preserve the value of reserved	 * bits in registers. So read the existing value, preserve the	 * low order 12 bits, and add in the guest physical address	 * (which already has at least the low 12 bits set to zero since	 * it is page aligned). Also set the "enable" bit, which is bit 0.	 */	hv_get_reference_tsc(tsc_msr);	tsc_msr &= GENMASK_ULL(11, 0);	tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;	hv_set_reference_tsc(tsc_msr); 	hv_set_clocksource_vdso(hyperv_cs_tsc);	clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100); 	hv_sched_clock_offset = hv_read_reference_counter();	hv_setup_sched_clock(read_hv_sched_clock_tsc); 	return true;} void __init hv_init_clocksource(void){	/*	 * Try to set up the TSC page clocksource. If it succeeds, we're	 * done. Otherwise, set up the MSR clocksoruce.  At least one of	 * these will always be available except on very old versions of	 * Hyper-V on x86.  In that case we won't have a Hyper-V	 * clocksource, but Linux will still run with a clocksource based	 * on the emulated PIT or LAPIC timer.	 */	if (hv_init_tsc_clocksource())		return; 	if (!(ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE))		return; 	hv_read_reference_counter = read_hv_clock_msr;	clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100); 	hv_sched_clock_offset = hv_read_reference_counter();	hv_setup_sched_clock(read_hv_sched_clock_msr);}EXPORT_SYMBOL_GPL(hv_init_clocksource);