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.tatas...@oracle.com>
Reviewed-by: Dou Liyang <douly.f...@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

Reply via email to