---

yaml
---
r: 120823
b: refs/heads/master
c: 395628e
h: refs/heads/master
i:
  120821: 09aa04b
  120819: ee29244
  120815: dfee799
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: eca0cd028bdf0f6aaceb0d023e9c7501079a7dda
+refs/heads/master: 395628ef4ea12ff0748099f145363b5e33c69acb

trunk/Documentation/kernel-parameters.txt

@@ -2267,6 +2267,13 @@ 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.
+			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.
+
 	turbografx.map[2|3]=	[HW,JOY]
 			TurboGraFX parallel port interface
 			Format:

trunk/arch/x86/kernel/tsc.c

@@ -32,6 +32,7 @@ static int tsc_unstable;
    erroneous rdtsc usage on !cpu_has_tsc processors */
 static int tsc_disabled = -1;
 
+static int tsc_clocksource_reliable;
 /*
  * Scheduler clock - returns current time in nanosec units.
  */
@@ -99,6 +100,15 @@ int __init notsc_setup(char *str)
 
 __setup("notsc", notsc_setup);
 
+static int __init tsc_setup(char *str)
+{
+	if (!strcmp(str, "reliable"))
+		tsc_clocksource_reliable = 1;
+	return 1;
+}
+
+__setup("tsc=", tsc_setup);
+
 #define MAX_RETRIES     5
 #define SMI_TRESHOLD    50000
 
@@ -738,24 +748,21 @@ static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
 	{}
 };
 
-/*
- * Geode_LX - the OLPC CPU has a possibly a very reliable TSC
- */
+static void __init check_system_tsc_reliable(void)
+{
 #ifdef CONFIG_MGEODE_LX
-/* RTSC counts during suspend */
+	/* RTSC counts during suspend */
 #define RTSC_SUSP 0x100
-
-static void __init check_geode_tsc_reliable(void)
-{
 	unsigned long res_low, res_high;
 
 	rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
+	/* Geode_LX - the OLPC CPU has a possibly a very reliable TSC */
 	if (res_low & RTSC_SUSP)
-		clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
-}
-#else
-static inline void check_geode_tsc_reliable(void) { }
+		tsc_clocksource_reliable = 1;
 #endif
+	if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
+		tsc_clocksource_reliable = 1;
+}
 
 /*
  * Make an educated guess if the TSC is trustworthy and synchronized
@@ -790,6 +797,8 @@ static void __init init_tsc_clocksource(void)
 {
 	clocksource_tsc.mult = clocksource_khz2mult(tsc_khz,
 			clocksource_tsc.shift);
+	if (tsc_clocksource_reliable)
+		clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
 	/* lower the rating if we already know its unstable: */
 	if (check_tsc_unstable()) {
 		clocksource_tsc.rating = 0;
@@ -850,7 +859,7 @@ void __init tsc_init(void)
 	if (unsynchronized_tsc())
 		mark_tsc_unstable("TSCs unsynchronized");
 
-	check_geode_tsc_reliable();
+	check_system_tsc_reliable();
 	init_tsc_clocksource();
 }