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-rw-r--r--arch/x86/kernel/tsc.c59
1 files changed, 59 insertions, 0 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 5a6cb46..5638044 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -43,6 +43,11 @@ static DEFINE_STATIC_KEY_FALSE(__use_tsc);
int tsc_clocksource_reliable;
+static u32 art_to_tsc_numerator;
+static u32 art_to_tsc_denominator;
+static u64 art_to_tsc_offset;
+struct clocksource *art_related_clocksource;
+
/*
* Use a ring-buffer like data structure, where a writer advances the head by
* writing a new data entry and a reader advances the tail when it observes a
@@ -964,6 +969,37 @@ core_initcall(cpufreq_tsc);
#endif /* CONFIG_CPU_FREQ */
+#define ART_CPUID_LEAF (0x15)
+#define ART_MIN_DENOMINATOR (1)
+
+
+/*
+ * If ART is present detect the numerator:denominator to convert to TSC
+ */
+static void detect_art(void)
+{
+ unsigned int unused[2];
+
+ if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF)
+ return;
+
+ cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator,
+ &art_to_tsc_numerator, unused, unused+1);
+
+ /* Don't enable ART in a VM, non-stop TSC required */
+ if (boot_cpu_has(X86_FEATURE_HYPERVISOR) ||
+ !boot_cpu_has(X86_FEATURE_NONSTOP_TSC) ||
+ art_to_tsc_denominator < ART_MIN_DENOMINATOR)
+ return;
+
+ if (rdmsrl_safe(MSR_IA32_TSC_ADJUST, &art_to_tsc_offset))
+ return;
+
+ /* Make this sticky over multiple CPU init calls */
+ setup_force_cpu_cap(X86_FEATURE_ART);
+}
+
+
/* clocksource code */
static struct clocksource clocksource_tsc;
@@ -1071,6 +1107,25 @@ int unsynchronized_tsc(void)
return 0;
}
+/*
+ * Convert ART to TSC given numerator/denominator found in detect_art()
+ */
+struct system_counterval_t convert_art_to_tsc(cycle_t art)
+{
+ u64 tmp, res, rem;
+
+ rem = do_div(art, art_to_tsc_denominator);
+
+ res = art * art_to_tsc_numerator;
+ tmp = rem * art_to_tsc_numerator;
+
+ do_div(tmp, art_to_tsc_denominator);
+ res += tmp + art_to_tsc_offset;
+
+ return (struct system_counterval_t) {.cs = art_related_clocksource,
+ .cycles = res};
+}
+EXPORT_SYMBOL(convert_art_to_tsc);
static void tsc_refine_calibration_work(struct work_struct *work);
static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
@@ -1142,6 +1197,8 @@ static void tsc_refine_calibration_work(struct work_struct *work)
(unsigned long)tsc_khz % 1000);
out:
+ if (boot_cpu_has(X86_FEATURE_ART))
+ art_related_clocksource = &clocksource_tsc;
clocksource_register_khz(&clocksource_tsc, tsc_khz);
}
@@ -1235,6 +1292,8 @@ void __init tsc_init(void)
mark_tsc_unstable("TSCs unsynchronized");
check_system_tsc_reliable();
+
+ detect_art();
}
#ifdef CONFIG_SMP
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