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Subject[PATCH v10 1/7] x86/tsc: remove tsc_disabled flag
Date
tsc_disabled is set when notsc is passed as kernel parameter. The reason we
have notsc is to avoid timing problems on multi-socket systems. We already
have a mechanism, however, to detect and resolve these issues by invoking
tsc unstable path. Thus, make notsc to behave the same as tsc=unstable.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
---
arch/x86/kernel/tsc.c | 19 +++----------------
1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index fb4302738410..700a61cbafa5 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -38,11 +38,6 @@ EXPORT_SYMBOL(tsc_khz);
*/
static int __read_mostly tsc_unstable;

-/* native_sched_clock() is called before tsc_init(), so
- we must start with the TSC soft disabled to prevent
- erroneous rdtsc usage on !boot_cpu_has(X86_FEATURE_TSC) processors */
-static int __read_mostly tsc_disabled = -1;
-
static DEFINE_STATIC_KEY_FALSE(__use_tsc);

int tsc_clocksource_reliable;
@@ -248,8 +243,7 @@ EXPORT_SYMBOL_GPL(check_tsc_unstable);
#ifdef CONFIG_X86_TSC
int __init notsc_setup(char *str)
{
- pr_warn("Kernel compiled with CONFIG_X86_TSC, cannot disable TSC completely\n");
- tsc_disabled = 1;
+ mark_tsc_unstable("boot parameter notsc");
return 1;
}
#else
@@ -1269,7 +1263,7 @@ static void tsc_refine_calibration_work(struct work_struct *work)

static int __init init_tsc_clocksource(void)
{
- if (!boot_cpu_has(X86_FEATURE_TSC) || tsc_disabled > 0 || !tsc_khz)
+ if (!boot_cpu_has(X86_FEATURE_TSC) || !tsc_khz)
return 0;

if (check_tsc_unstable())
@@ -1375,12 +1369,6 @@ void __init tsc_init(void)
set_cyc2ns_scale(tsc_khz, cpu, cyc);
}

- if (tsc_disabled > 0)
- return;
-
- /* now allow native_sched_clock() to use rdtsc */
-
- tsc_disabled = 0;
static_branch_enable(&__use_tsc);

if (!no_sched_irq_time)
@@ -1413,10 +1401,9 @@ void __init tsc_init(void)
unsigned long calibrate_delay_is_known(void)
{
int sibling, cpu = smp_processor_id();
- int constant_tsc = cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC);
const struct cpumask *mask = topology_core_cpumask(cpu);

- if (tsc_disabled || !constant_tsc || !mask)
+ if (!cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC) || !mask)
return 0;

sibling = cpumask_any_but(mask, cpu);
--
2.16.1
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