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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>
This commit is contained in:
Suresh Siddha 2011-11-04 15:42:17 -07:00 committed by Ingo Molnar
parent 8e8da023f5
commit 28a00184be
3 changed files with 5 additions and 3 deletions
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2
arch/x86/include/asm/tsc.h
View File

@ -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:

2
arch/x86/kernel/tsc.c
View File

@ -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.
*/

4
arch/x86/kernel/tsc_sync.c
View File

@ -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;
/*