Index: head/sys/amd64/vmm/io/vatpit.c
===================================================================
--- head/sys/amd64/vmm/io/vatpit.c
+++ head/sys/amd64/vmm/io/vatpit.c
@@ -2,6 +2,7 @@
  * Copyright (c) 2014 Tycho Nightingale <tycho.nightingale@pluribusnetworks.com>
  * Copyright (c) 2011 NetApp, Inc.
  * All rights reserved.
+ * Copyright (c) 2018 Joyent, Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -78,7 +79,7 @@
 struct channel {
 	int		mode;
 	uint16_t	initial;	/* initial counter value */
-	sbintime_t	now_sbt;	/* uptime when counter was loaded */
+	struct bintime	now_bt;		/* uptime when counter was loaded */
 	uint8_t		cr[2];
 	uint8_t		ol[2];
 	bool		slatched;	/* status latched */
@@ -87,7 +88,7 @@
 	int		olbyte;
 	int		frbyte;
 	struct callout	callout;
-	sbintime_t	callout_sbt;	/* target time */
+	struct bintime	callout_bt;	/* target time */
 	struct vatpit_callout_arg callout_arg;
 };
 
@@ -95,26 +96,41 @@
 	struct vm	*vm;
 	struct mtx	mtx;
 
-	sbintime_t	freq_sbt;
+	struct bintime	freq_bt;
 
 	struct channel	channel[3];
 };
 
 static void pit_timer_start_cntr0(struct vatpit *vatpit);
 
+static uint64_t
+vatpit_delta_ticks(struct vatpit *vatpit, struct channel *c)
+{
+	struct bintime delta;
+	uint64_t result;
+
+	binuptime(&delta);
+	bintime_sub(&delta, &c->now_bt);
+
+	result = delta.sec * PIT_8254_FREQ;
+	result += delta.frac / vatpit->freq_bt.frac;
+
+	return (result);
+}
+
 static int
 vatpit_get_out(struct vatpit *vatpit, int channel)
 {
 	struct channel *c;
-	sbintime_t delta_ticks;
+	uint64_t delta_ticks;
 	int out;
 
 	c = &vatpit->channel[channel];
 
 	switch (c->mode) {
 	case TIMER_INTTC:
-		delta_ticks = (sbinuptime() - c->now_sbt) / vatpit->freq_sbt;
-		out = ((c->initial - delta_ticks) <= 0);
+		delta_ticks = vatpit_delta_ticks(vatpit, c);
+		out = (delta_ticks >= c->initial);
 		break;
 	default:
 		out = 0;
@@ -164,24 +180,28 @@
 pit_timer_start_cntr0(struct vatpit *vatpit)
 {
 	struct channel *c;
-	sbintime_t now, delta, precision;
+	struct bintime now, delta;
+	sbintime_t precision;
 
 	c = &vatpit->channel[0];
 	if (c->initial != 0) {
-		delta = c->initial * vatpit->freq_sbt;
-		precision = delta >> tc_precexp;
-		c->callout_sbt = c->callout_sbt + delta;
+		delta.sec = 0;
+		delta.frac = vatpit->freq_bt.frac * c->initial;
+		bintime_add(&c->callout_bt, &delta);
+		precision = bttosbt(delta) >> tc_precexp;
 
 		/*
-		 * Reset 'callout_sbt' if the time that the callout
+		 * Reset 'callout_bt' if the time that the callout
 		 * was supposed to fire is more than 'c->initial'
 		 * ticks in the past.
 		 */
-		now = sbinuptime();
-		if (c->callout_sbt < now)
-			c->callout_sbt = now + delta;
+		binuptime(&now);
+		if (bintime_cmp(&c->callout_bt, &now, <)) {
+			c->callout_bt = now;
+			bintime_add(&c->callout_bt, &delta);
+		}
 
-		callout_reset_sbt(&c->callout, c->callout_sbt,
+		callout_reset_sbt(&c->callout, bttosbt(c->callout_bt),
 		    precision, vatpit_callout_handler, &c->callout_arg,
 		    C_ABSOLUTE);
 	}
@@ -191,7 +211,7 @@
 pit_update_counter(struct vatpit *vatpit, struct channel *c, bool latch)
 {
 	uint16_t lval;
-	sbintime_t delta_ticks;
+	uint64_t delta_ticks;
 
 	/* cannot latch a new value until the old one has been consumed */
 	if (latch && c->olbyte != 0)
@@ -207,12 +227,11 @@
 		 * here.
 		 */
 		c->initial = TIMER_DIV(PIT_8254_FREQ, 100);
-		c->now_sbt = sbinuptime();
+		binuptime(&c->now_bt);
 		c->status &= ~TIMER_STS_NULLCNT;
 	}
 
-	delta_ticks = (sbinuptime() - c->now_sbt) / vatpit->freq_sbt;
-
+	delta_ticks = vatpit_delta_ticks(vatpit, c);
 	lval = c->initial - delta_ticks % c->initial;
 
 	if (latch) {
@@ -383,10 +402,10 @@
 			c->frbyte = 0;
 			c->crbyte = 0;
 			c->initial = c->cr[0] | (uint16_t)c->cr[1] << 8;
-			c->now_sbt = sbinuptime();
+			binuptime(&c->now_bt);
 			/* Start an interval timer for channel 0 */
 			if (port == TIMER_CNTR0) {
-				c->callout_sbt = c->now_sbt;
+				c->callout_bt = c->now_bt;
 				pit_timer_start_cntr0(vatpit);
 			}
 			if (c->initial == 0)
@@ -423,7 +442,6 @@
 vatpit_init(struct vm *vm)
 {
 	struct vatpit *vatpit;
-	struct bintime bt;
 	struct vatpit_callout_arg *arg;
 	int i;
 
@@ -432,8 +450,7 @@
 
 	mtx_init(&vatpit->mtx, "vatpit lock", NULL, MTX_SPIN);
 
-	FREQ2BT(PIT_8254_FREQ, &bt);
-	vatpit->freq_sbt = bttosbt(bt);
+	FREQ2BT(PIT_8254_FREQ, &vatpit->freq_bt);
 
 	for (i = 0; i < 3; i++) {
 		callout_init(&vatpit->channel[i].callout, 1);