x86, tsc: Skip TSC synchronization checks for tsc=reliable (28a00184) · Commits · 戴 / test

tsc=reliable boot parameter is supposed to skip all the TSC stablility checks during boot time. On a 8-socket system where we want to run an experiment with the "tsc=reliable" boot option, TSC synchronization checks are not getting skipped and marking the TSC as not stable. Check for tsc_clocksource_reliable (which is set via tsc=reliable or for platforms supporting synthetic TSC_RELIABLE feature bit etc) and when set, skip the TSC synchronization tests during boot. Signed-off-by:

Suresh Siddha <suresh.b.siddha@intel.com> Acked-by:

John Stultz <johnstul@us.ibm.com> Tested-by:

Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/1320446537.15071.14.camel@sbsiddha-desk.sc.intel.com Signed-off-by:

Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/tsc.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -51,6 +51,8 @@ extern int unsynchronized_tsc(void);
		extern int check_tsc_unstable(void);
		extern unsigned long native_calibrate_tsc(void);

		extern int tsc_clocksource_reliable;

		/*
		* Boot-time check whether the TSCs are synchronized across
		* all CPUs/cores:

arch/x86/kernel/tsc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -35,7 +35,7 @@ static int __read_mostly tsc_unstable;
		erroneous rdtsc usage on !cpu_has_tsc processors */
		static int __read_mostly tsc_disabled = -1;

		static int tsc_clocksource_reliable;
		int tsc_clocksource_reliable;
		/*
		* Scheduler clock - returns current time in nanosec units.
		*/

arch/x86/kernel/tsc_sync.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -113,7 +113,7 @@ void __cpuinit check_tsc_sync_source(int cpu)
		if (unsynchronized_tsc())
		return;

		if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) {
		if (tsc_clocksource_reliable) {
		if (cpu == (nr_cpu_ids-1) \|\| system_state != SYSTEM_BOOTING)
		pr_info(
		"Skipped synchronization checks as TSC is reliable.\n");
		@@ -172,7 +172,7 @@ void __cpuinit check_tsc_sync_target(void)
		{
		int cpus = 2;

		if (unsynchronized_tsc() \|\| boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
		if (unsynchronized_tsc() \|\| tsc_clocksource_reliable)
		return;

		/*

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