// SPDX-License-Identifier: GPL-2.0-or-later/*  paravirtual clock -- common code used by kvm/xen */ #include <linux/clocksource.h>#include <linux/kernel.h>#include <linux/percpu.h>#include <linux/notifier.h>#include <linux/sched.h>#include <linux/gfp.h>#include <linux/memblock.h>#include <linux/nmi.h> #include <asm/fixmap.h>#include <asm/pvclock.h>#include <asm/vgtod.h> static u8 valid_flags __read_mostly = 0;static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly; void pvclock_set_flags(u8 flags){	valid_flags = flags;} unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src){	u64 pv_tsc_khz = 1000000ULL << 32; 	do_div(pv_tsc_khz, src->tsc_to_system_mul);	if (src->tsc_shift < 0)		pv_tsc_khz <<= -src->tsc_shift;	else		pv_tsc_khz >>= src->tsc_shift;	return pv_tsc_khz;} void pvclock_touch_watchdogs(void){	touch_softlockup_watchdog_sync();	clocksource_touch_watchdog();	rcu_cpu_stall_reset();	reset_hung_task_detector();} static atomic64_t last_value = ATOMIC64_INIT(0); void pvclock_resume(void){	atomic64_set(&last_value, 0);} u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src){	unsigned version;	u8 flags; 	do {		version = pvclock_read_begin(src);		flags = src->flags;	} while (pvclock_read_retry(src, version)); 	return flags & valid_flags;} static __always_inlineu64 __pvclock_clocksource_read(struct pvclock_vcpu_time_info *src, bool dowd){	unsigned version;	u64 ret;	u64 last;	u8 flags; 	do {		version = pvclock_read_begin(src);		ret = __pvclock_read_cycles(src, rdtsc_ordered());		flags = src->flags;	} while (pvclock_read_retry(src, version)); 	if (dowd && unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {		src->flags &= ~PVCLOCK_GUEST_STOPPED;		pvclock_touch_watchdogs();	} 	if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&		(flags & PVCLOCK_TSC_STABLE_BIT))		return ret; 	/*	 * Assumption here is that last_value, a global accumulator, always goes	 * forward. If we are less than that, we should not be much smaller.	 * We assume there is an error margin we're inside, and then the correction	 * does not sacrifice accuracy.	 *	 * For reads: global may have changed between test and return,	 * but this means someone else updated poked the clock at a later time.	 * We just need to make sure we are not seeing a backwards event.	 *	 * For updates: last_value = ret is not enough, since two vcpus could be	 * updating at the same time, and one of them could be slightly behind,	 * making the assumption that last_value always go forward fail to hold.	 */	last = raw_atomic64_read(&last_value);	do {		if (ret <= last)			return last;	} while (!raw_atomic64_try_cmpxchg(&last_value, &last, ret)); 	return ret;} u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src){	return __pvclock_clocksource_read(src, true);} noinstr u64 pvclock_clocksource_read_nowd(struct pvclock_vcpu_time_info *src){	return __pvclock_clocksource_read(src, false);} void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,			    struct pvclock_vcpu_time_info *vcpu_time,			    struct timespec64 *ts){	u32 version;	u64 delta;	struct timespec64 now; 	/* get wallclock at system boot */	do {		version = wall_clock->version;		rmb();		/* fetch version before time */		/*		 * Note: wall_clock->sec is a u32 value, so it can		 * only store dates between 1970 and 2106. To allow		 * times beyond that, we need to create a new hypercall		 * interface with an extended pvclock_wall_clock structure		 * like ARM has.		 */		now.tv_sec  = wall_clock->sec;		now.tv_nsec = wall_clock->nsec;		rmb();		/* fetch time before checking version */	} while ((wall_clock->version & 1) || (version != wall_clock->version)); 	delta = pvclock_clocksource_read(vcpu_time);	/* time since system boot */	delta += now.tv_sec * NSEC_PER_SEC + now.tv_nsec; 	now.tv_nsec = do_div(delta, NSEC_PER_SEC);	now.tv_sec = delta; 	set_normalized_timespec64(ts, now.tv_sec, now.tv_nsec);} void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti){	WARN_ON(vclock_was_used(VDSO_CLOCKMODE_PVCLOCK));	pvti_cpu0_va = pvti;} struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void){	return pvti_cpu0_va;}EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va);