diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 92e83e53148fe8b1d4848af9a8fd7442cc5624ba..c7c8eca5b2b359f98408acb016788e9005368938 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2467,12 +2467,13 @@ and is between 256 and 4096 characters. It is defined in the file
 			to facilitate early boot debugging.
 			See also Documentation/trace/events.txt
 
-	tsc=		Disable clocksource-must-verify flag for TSC.
+	tsc=		Disable clocksource stability checks for TSC.
 			Format: <string>
 			[x86] reliable: mark tsc clocksource as reliable, this
-			disables clocksource verification at runtime.
-			Used to enable high-resolution timer mode on older
-			hardware, and in virtualized environment.
+			disables clocksource verification at runtime, as well
+			as the stability checks done at bootup.	Used to enable
+			high-resolution timer mode on older hardware, and in
+			virtualized environment.
 			[x86] noirqtime: Do not use TSC to do irq accounting.
 			Used to run time disable IRQ_TIME_ACCOUNTING on any
 			platforms where RDTSC is slow and this accounting
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 0c40d8b72416ba2ef7e86bfd812b7bf6f1db2f8f..bb64beb301d982a7653af75b45c4195d0daecd91 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -872,6 +872,9 @@ __cpuinit int unsynchronized_tsc(void)
 
 	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
 		return 0;
+
+	if (tsc_clocksource_reliable)
+		return 0;
 	/*
 	 * Intel systems are normally all synchronized.
 	 * Exceptions must mark TSC as unstable:
@@ -879,10 +882,10 @@ __cpuinit int unsynchronized_tsc(void)
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
 		/* assume multi socket systems are not synchronized: */
 		if (num_possible_cpus() > 1)
-			tsc_unstable = 1;
+			return 1;
 	}
 
-	return tsc_unstable;
+	return 0;
 }
 
 static void __init init_tsc_clocksource(void)