diff --git a/cpus.c b/cpus.c
index ab8d67b..eb22bd5 100644
--- a/cpus.c
+++ b/cpus.c
@@ -34,6 +34,7 @@
 
 #include "qemu-thread.h"
 #include "cpus.h"
+#include "qtest.h"
 #include "main-loop.h"
 
 #ifndef _WIN32
@@ -238,6 +239,20 @@
     vm_clock_warp_start = -1;
 }
 
+void qtest_clock_warp(int64_t dest)
+{
+    int64_t clock = qemu_get_clock_ns(vm_clock);
+    assert(qtest_enabled());
+    while (clock < dest) {
+        int64_t deadline = qemu_clock_deadline(vm_clock);
+        int64_t warp = MIN(dest - clock, deadline);
+        qemu_icount_bias += warp;
+        qemu_run_timers(vm_clock);
+        clock = qemu_get_clock_ns(vm_clock);
+    }
+    qemu_notify_event();
+}
+
 void qemu_clock_warp(QEMUClock *clock)
 {
     int64_t deadline;
@@ -264,6 +279,11 @@
         return;
     }
 
+    if (qtest_enabled()) {
+        /* When testing, qtest commands advance icount.  */
+	return;
+    }
+
     vm_clock_warp_start = qemu_get_clock_ns(rt_clock);
     deadline = qemu_clock_deadline(vm_clock);
     if (deadline > 0) {
diff --git a/cpus.h b/cpus.h
index 4ea2fe2..81bd817 100644
--- a/cpus.h
+++ b/cpus.h
@@ -11,6 +11,8 @@
 void cpu_synchronize_all_post_reset(void);
 void cpu_synchronize_all_post_init(void);
 
+void qtest_clock_warp(int64_t dest);
+
 /* vl.c */
 extern int smp_cores;
 extern int smp_threads;
diff --git a/qemu-timer.c b/qemu-timer.c
index d7f56e5..80bcc56 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -397,7 +397,7 @@
     return qemu_timer_expired_ns(timer_head, current_time * timer_head->scale);
 }
 
-static void qemu_run_timers(QEMUClock *clock)
+void qemu_run_timers(QEMUClock *clock)
 {
     QEMUTimer **ptimer_head, *ts;
     int64_t current_time;
diff --git a/qemu-timer.h b/qemu-timer.h
index de17f3b..661bbe7 100644
--- a/qemu-timer.h
+++ b/qemu-timer.h
@@ -59,6 +59,7 @@
 int qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time);
 uint64_t qemu_timer_expire_time_ns(QEMUTimer *ts);
 
+void qemu_run_timers(QEMUClock *clock);
 void qemu_run_all_timers(void);
 int qemu_alarm_pending(void);
 void configure_alarms(char const *opt);
diff --git a/qtest.c b/qtest.c
index a1eca49..53e2b79 100644
--- a/qtest.c
+++ b/qtest.c
@@ -18,6 +18,7 @@
 #include "memory.h"
 #include "hw/irq.h"
 #include "sysemu.h"
+#include "cpus.h"
 
 #define MAX_IRQ 256
 
@@ -44,6 +45,30 @@
  *
  * Valid requests
  *
+ * Clock management:
+ *
+ * The qtest client is completely in charge of the vm_clock.  qtest commands
+ * let you adjust the value of the clock (monotonically).  All the commands
+ * return the current value of the clock in nanoseconds.
+ *
+ *  > clock_step
+ *  < OK VALUE
+ *
+ *     Advance the clock to the next deadline.  Useful when waiting for
+ *     asynchronous events.
+ *
+ *  > clock_step NS
+ *  < OK VALUE
+ *
+ *     Advance the clock by NS nanoseconds.
+ *
+ *  > clock_set NS
+ *  < OK VALUE
+ *
+ *     Advance the clock to NS nanoseconds (do nothing if it's already past).
+ *
+ * PIO and memory access:
+ *
  *  > outb ADDR VALUE
  *  < OK
  *
@@ -299,6 +324,25 @@
 
         qtest_send_prefix(chr);
         qtest_send(chr, "OK\n");
+    } else if (strcmp(words[0], "clock_step") == 0) {
+        int64_t ns;
+
+        if (words[1]) {
+            ns = strtoll(words[1], NULL, 0);
+        } else {
+            ns = qemu_clock_deadline(vm_clock);
+        }
+        qtest_clock_warp(qemu_get_clock_ns(vm_clock) + ns);
+        qtest_send_prefix(chr);
+        qtest_send(chr, "OK %"PRIi64"\n", (int64_t)qemu_get_clock_ns(vm_clock));
+    } else if (strcmp(words[0], "clock_set") == 0) {
+        int64_t ns;
+
+        g_assert(words[1]);
+        ns = strtoll(words[1], NULL, 0);
+        qtest_clock_warp(ns);
+        qtest_send_prefix(chr);
+        qtest_send(chr, "OK %"PRIi64"\n", (int64_t)qemu_get_clock_ns(vm_clock));
     } else {
         qtest_send_prefix(chr);
         qtest_send(chr, "FAIL Unknown command `%s'\n", words[0]);
@@ -377,6 +421,7 @@
 
     g_assert(qtest_chrdev != NULL);
 
+    configure_icount("0");
     chr = qemu_chr_new("qtest", qtest_chrdev, NULL);
 
     qemu_chr_add_handlers(chr, qtest_can_read, qtest_read, qtest_event, chr);