2 files changed, 10 insertions, 6 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7936b801fe6a..4c6b4150266d 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2484,12 +2484,13 @@ and is between 256 and 4096 characters. It is defined in the file
                         Format:
                         <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
 
-        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.
 
         turbografx.map[2|3]=    [HW,JOY]
                         TurboGraFX parallel port interface
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 71f4368b357e..648fb269e5d1 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -825,6 +825,9 @@ __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:
@@ -832,10 +835,10 @@ __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)