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- // 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;
- }
- u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
- {
- 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 (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 = atomic64_read(&last_value);
- do {
- if (ret < last)
- return last;
- last = atomic64_cmpxchg(&last_value, last, ret);
- } while (unlikely(last != ret));
- return ret;
- }
- 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);
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