1 files changed, 156 insertions, 0 deletions
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
new file mode 100644
index 000000000..eda37df01
--- /dev/null
+++ b/arch/x86/kernel/pvclock.c
@@ -0,0 +1,156 @@
+// 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);