x86, tsc: Skip TSC synchronization checks for tsc=reliable
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>
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@ -51,6 +51,8 @@ extern int unsynchronized_tsc(void);
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extern int check_tsc_unstable(void);
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extern int check_tsc_unstable(void);
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extern unsigned long native_calibrate_tsc(void);
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extern unsigned long native_calibrate_tsc(void);
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extern int tsc_clocksource_reliable;
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/*
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/*
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* Boot-time check whether the TSCs are synchronized across
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* Boot-time check whether the TSCs are synchronized across
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* all CPUs/cores:
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* all CPUs/cores:
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@ -35,7 +35,7 @@ static int __read_mostly tsc_unstable;
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erroneous rdtsc usage on !cpu_has_tsc processors */
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erroneous rdtsc usage on !cpu_has_tsc processors */
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static int __read_mostly tsc_disabled = -1;
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static int __read_mostly tsc_disabled = -1;
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static int tsc_clocksource_reliable;
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int tsc_clocksource_reliable;
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/*
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/*
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* Scheduler clock - returns current time in nanosec units.
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* Scheduler clock - returns current time in nanosec units.
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*/
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*/
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@ -113,7 +113,7 @@ void __cpuinit check_tsc_sync_source(int cpu)
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if (unsynchronized_tsc())
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if (unsynchronized_tsc())
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return;
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return;
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if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) {
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if (tsc_clocksource_reliable) {
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if (cpu == (nr_cpu_ids-1) || system_state != SYSTEM_BOOTING)
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if (cpu == (nr_cpu_ids-1) || system_state != SYSTEM_BOOTING)
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pr_info(
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pr_info(
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"Skipped synchronization checks as TSC is reliable.\n");
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"Skipped synchronization checks as TSC is reliable.\n");
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@ -172,7 +172,7 @@ void __cpuinit check_tsc_sync_target(void)
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{
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{
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int cpus = 2;
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int cpus = 2;
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if (unsynchronized_tsc() || boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
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if (unsynchronized_tsc() || tsc_clocksource_reliable)
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return;
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return;
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/*
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/*
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