 @@ -1,14 +1,14 @@
-/*	$NetBSD: xen_clock.c,v 1.14 2023/07/28 10:39:01 riastradh Exp $	*/
+/*	$NetBSD: xen_clock.c,v 1.15 2023/07/28 10:39:14 riastradh Exp $	*/
 /*-
  * Copyright (c) 2017, 2018 The NetBSD Foundation, Inc.
  * All rights reserved.
+ *
  * This code is derived from software contributed to The NetBSD Foundation
  * by Taylor R. Campbell.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
 @@ -26,27 +26,27 @@
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */
 #include "opt_xen.h"
 #ifndef XEN_CLOCK_DEBUG
 #define	XEN_CLOCK_DEBUG	0
 #endif
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xen_clock.c,v 1.14 2023/07/28 10:39:01 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xen_clock.c,v 1.15 2023/07/28 10:39:14 riastradh Exp $");
 #include <sys/param.h>
 #include <sys/types.h>
 #include <sys/atomic.h>
 #include <sys/callout.h>
 #include <sys/cpu.h>
 #include <sys/device.h>
 #include <sys/evcnt.h>
 #include <sys/intr.h>
 #include <sys/kernel.h>
 #include <sys/lwp.h>
 #include <sys/proc.h>
 #include <sys/sdt.h>
 @@ -110,26 +110,33 @@ SDT_PROBE_DEFINE7(sdt, xen, clock, systi
     "int"/*tsc_shift*/,
     "uint64_t"/*delta_ns*/,
     "uint64_t"/*tsc*/,
     "uint64_t"/*systime_ns*/);
 SDT_PROBE_DEFINE3(sdt, xen, timecounter, backward,
     "uint64_t"/*local*/,
     "uint64_t"/*skew*/,
     "uint64_t"/*global*/);
 SDT_PROBE_DEFINE2(sdt, xen, hardclock, systime__backward,
     "uint64_t"/*last_systime_ns*/,
     "uint64_t"/*this_systime_ns*/);
 SDT_PROBE_DEFINE2(sdt, xen, hardclock, tick,
     "uint64_t"/*last_systime_ns*/,
     "uint64_t"/*this_systime_ns*/);
 SDT_PROBE_DEFINE3(sdt, xen, hardclock, jump,
     "uint64_t"/*last_systime_ns*/,
     "uint64_t"/*this_systime_ns*/,
     "uint64_t"/*nticks*/);
 SDT_PROBE_DEFINE3(sdt, xen, hardclock, missed,
     "uint64_t"/*last_systime_ns*/,
     "uint64_t"/*this_systime_ns*/,
     "uint64_t"/*remaining_ns*/);
 /*
  * xen timecounter:
+ *
  *	Xen vCPU system time, plus an adjustment with rdtsc.
  */
 static struct timecounter xen_timecounter = {
 	.tc_get_timecount = xen_get_timecount,
 	.tc_poll_pps = NULL,
 @@ -790,44 +797,49 @@ xen_timer_handler(void *cookie, struct c
 	KASSERT(cpu_intr_p());
 	KASSERT(cookie == ci);
 #if defined(XENPV)
 	frame = NULL; /* We use values cached in curcpu()  */
 #endif
 again:
 	/*
 	 * Find how many nanoseconds of Xen system time has elapsed
 	 * since the last hardclock tick.
 	 */
 	last = ci->ci_xen_hardclock_systime_ns;
 	now = xen_vcputime_systime_ns();
-	if (now < last) {
+	SDT_PROBE2(sdt, xen, hardclock, tick,  last, now);
 	if (__predict_false(now < last)) {
 		SDT_PROBE2(sdt, xen, hardclock, systime__backward,
 		    last, now);
 #if XEN_CLOCK_DEBUG
 		device_printf(ci->ci_dev, "xen systime ran backwards"
 		    " in hardclock %"PRIu64"ns\n",
 		    last - now);
 #endif
 		ci->ci_xen_systime_backwards_hardclock_evcnt.ev_count++;
 		now = last;
+	}
 	delta = now - last;
 	/*
 	 * Play hardclock catchup: run the hardclock timer as many
 	 * times as appears necessary based on how much time has
 	 * passed.
 	 */
 	if (__predict_false(delta >= 2*ns_per_tick)) {
 		SDT_PROBE3(sdt, xen, hardclock, jump,
 		    last, now, delta/ns_per_tick);
+	}
 	while (delta >= ns_per_tick) {
 		ci->ci_xen_hardclock_systime_ns += ns_per_tick;
 		delta -= ns_per_tick;
 		hardclock(frame);
 		if (__predict_false(delta >= ns_per_tick)) {
 			SDT_PROBE3(sdt, xen, hardclock, missed,
 			    last, now, delta);
 			ci->ci_xen_missed_hardclock_evcnt.ev_count++;
+		}
+	}
 	/*
 	 * Re-arm the timer.  If it fails, it's probably because the