diff -Npru kexec-kernel-only/arch/x86_64/kernel/machine_kexec.c kexec-kernel-only_20121203/arch/x86_64/kernel/machine_kexec.c
--- kexec-kernel-only/arch/x86_64/kernel/machine_kexec.c	2012-11-07 13:09:47.000000000 +0100
+++ kexec-kernel-only_20121203/arch/x86_64/kernel/machine_kexec.c	2012-12-03 10:48:06.000000000 +0100
@@ -813,9 +813,18 @@ NORET_TYPE void xen_pv_machine_kexec(str
 	atomic_inc(&control_page_ready);
 #endif
 
+#if 0
+	/*
+	 * Disabled due to some Amazon EC2 machines are not able
+	 * to restart timer properly in crash kernel. If this happens
+	 * then it hangs in loop in calibrate_delay_direct() because
+	 * jiffies are not incremented.
+	 */
+
 	/* Stop singleshot timer. */
 	if (HYPERVISOR_set_timer_op(0))
 		BUG();
+#endif
 
 #ifdef CONFIG_SMP
 	for_each_present_cpu(i)
diff -Npru kexec-kernel-only/init/calibrate.c kexec-kernel-only_20121203/init/calibrate.c
--- kexec-kernel-only/init/calibrate.c	2012-09-17 11:56:40.000000000 +0200
+++ kexec-kernel-only_20121203/init/calibrate.c	2012-12-03 10:34:02.000000000 +0100
@@ -67,7 +67,7 @@ static unsigned long __devinit calibrate
 		pre_start = 0;
 		read_current_timer(&start);
 		start_jiffies = jiffies;
-		while (jiffies <= (start_jiffies + tick_divider)) {
+		while (time_before_eq(jiffies, start_jiffies + tick_divider)) {
 			pre_start = start;
 			read_current_timer(&start);
 		}
@@ -75,8 +75,8 @@ static unsigned long __devinit calibrate
 
 		pre_end = 0;
 		end = post_start;
-		while (jiffies <=
-		       (start_jiffies + tick_divider * (1 + delay_calibration_ticks))) {
+		while (time_before_eq(jiffies,
+		       start_jiffies + tick_divider * (1 + delay_calibration_ticks))) {
 			pre_end = end;
 			read_current_timer(&end);
 		}