diff --git a/xen/common/domain.c b/xen/common/domain.c
index 64ee29d..ac59452 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -937,18 +937,27 @@ long do_vcpu_op(int cmd, int vcpuid, XEN_GUEST_HANDLE_PARAM(void) arg)
     {
         struct vcpu_set_singleshot_timer set;
 
-        if ( v != current )
+        if ( v != current ) {
+            TRACE_1D(TRC_PV_TIMER_FAIL, 1);
             return -EINVAL;
+        }
 
-        if ( copy_from_guest(&set, arg, 1) )
+        if ( copy_from_guest(&set, arg, 1) ) {
+            TRACE_1D(TRC_PV_TIMER_FAIL, 2);
             return -EFAULT;
+        }
 
         if ( (set.flags & VCPU_SSHOTTMR_future) &&
-             (set.timeout_abs_ns < NOW()) )
+             (set.timeout_abs_ns < NOW()) ) {
+            TRACE_1D(TRC_PV_TIMER_FAIL, 3);
             return -ETIME;
+        }
 
         migrate_timer(&v->singleshot_timer, smp_processor_id());
+        v->singleshot_timer.debug = 1;
         set_timer(&v->singleshot_timer, set.timeout_abs_ns);
+        TRACE_2D(TRC_PV_SET_TIMER, (uint32_t)set.timeout_abs_ns,
+            (uint32_t)(set.timeout_abs_ns >> 32));
 
         break;
     }
@@ -958,6 +967,8 @@ long do_vcpu_op(int cmd, int vcpuid, XEN_GUEST_HANDLE_PARAM(void) arg)
             return -EINVAL;
 
         stop_timer(&v->singleshot_timer);
+        TRACE_2D(TRC_PV_STOP_TIMER, (uint32_t)v->singleshot_timer.expires,
+            (uint32_t)(v->singleshot_timer.expires >> 32));
 
         break;
 
diff --git a/xen/common/timer.c b/xen/common/timer.c
index 9ed74e9..61e4383 100644
--- a/xen/common/timer.c
+++ b/xen/common/timer.c
@@ -21,6 +21,7 @@
 #include <xen/cpu.h>
 #include <xen/rcupdate.h>
 #include <xen/symbols.h>
+#include <xen/trace.h>
 #include <asm/system.h>
 #include <asm/desc.h>
 #include <asm/atomic.h>
@@ -421,6 +422,9 @@ static void execute_timer(struct timers *ts, struct timer *t)
     list_add(&t->inactive, &ts->inactive);
 
     ts->running = t;
+    if (t->debug)
+        TRACE_2D(TRC_PV_FIRE_TIMER, (uint32_t)t->expires,
+                (uint32_t)(t->expires >> 32));
     spin_unlock_irq(&ts->lock);
     (*fn)(data);
     spin_lock_irq(&ts->lock);
diff --git a/xen/include/public/trace.h b/xen/include/public/trace.h
index e2f60a6..4571d74 100644
--- a/xen/include/public/trace.h
+++ b/xen/include/public/trace.h
@@ -122,6 +122,7 @@
 
 #define TRC_PV_ENTRY   0x00201000 /* Hypervisor entry points for PV guests. */
 #define TRC_PV_SUBCALL 0x00202000 /* Sub-call in a multicall hypercall */
+#define TRC_PV_TIMER   0x00208000 /* PV timer */
 
 #define TRC_PV_HYPERCALL             (TRC_PV_ENTRY +  1)
 #define TRC_PV_TRAP                  (TRC_PV_ENTRY +  3)
@@ -136,6 +137,10 @@
 #define TRC_PV_PTWR_EMULATION_PAE    (TRC_PV_ENTRY + 12)
 #define TRC_PV_HYPERCALL_V2          (TRC_PV_ENTRY + 13)
 #define TRC_PV_HYPERCALL_SUBCALL     (TRC_PV_SUBCALL + 14)
+#define TRC_PV_SET_TIMER             (TRC_PV_TIMER + 15)
+#define TRC_PV_FIRE_TIMER            (TRC_PV_TIMER + 16)
+#define TRC_PV_TIMER_FAIL            (TRC_PV_TIMER + 17)
+#define TRC_PV_STOP_TIMER            (TRC_PV_TIMER + 18)
 
 /*
  * TRC_PV_HYPERCALL_V2 format
diff --git a/xen/include/xen/timer.h b/xen/include/xen/timer.h
index 9531800..b69ae20 100644
--- a/xen/include/xen/timer.h
+++ b/xen/include/xen/timer.h
@@ -43,6 +43,7 @@ struct timer {
 #define TIMER_STATUS_in_heap  3 /* In use; on timer heap.           */
 #define TIMER_STATUS_in_list  4 /* In use; on overflow linked list. */
     uint8_t status;
+    uint8_t debug;
 };
 
 /*