tsc: initial implementation of timekeeper source

kernel-src/arch/x86-64/hpet.c

@@ -152,6 +152,7 @@ static timekeeper_source_info_t *hpet_init(void) {
 
 }
 
+// ran in at least IPL_DPC
 time_t hpet_ticks(timekeeper_source_info_t *) {
 	if (hpet_private.type == TYPE_64BIT) {
 		return read64(HPET_REG_COUNTER);

kernel-src/arch/x86-64/kvmclock.c

@@ -60,6 +60,7 @@ static timekeeper_source_info_t *kvm_timer_init(void) {
 	return timekeeper_source_info;
 }
 
+// ran in at least IPL_DPC
 static time_t kvm_timer_ticks(timekeeper_source_info_t *timekeeper_source_info) {
 	volatile kvm_timer_info_t *kvm_timer_info = MAKE_HHDM(timekeeper_source_info->private);
 

kernel-src/arch/x86-64/tsc.c

@@ -0,0 +1,76 @@
+#include <kernel/timekeeper.h>
+#include <arch/tsc.h>
+#include <arch/cpuid.h>
+#include <logging.h>
+#include <kernel/alloc.h>
+
+static bool tsc_probe(void) {
+	cpuid_results_t cpuid_results;
+
+	uint32_t max_extended_leaf = cpuid_extended_max_leaf();
+	if (max_extended_leaf < 0x80000007)
+		return false;
+
+	cpuid(0x80000007, &cpuid_results);
+	return cpuid_results.edx & (1 << 8);
+}
+
+static timekeeper_source_info_t *tsc_init(void) {
+	__assert(tsc_probe());
+
+	timekeeper_source_info_t *timekeeper_source_info = alloc(sizeof(timekeeper_source_info_t));
+	__assert(timekeeper_source_info);
+
+	timekeeper_source_info->private = current_cpu();
+
+	bool need_calibration = false;
+	if (cpuid_base_max_leaf() >= 0x15) {
+		cpuid_results_t cpuid_results;
+		cpuid(0x15, &cpuid_results);
+
+		if (cpuid_results.eax == 0 || cpuid_results.ebx == 0 || cpuid_results.ecx == 0) {
+			need_calibration = true;
+			goto calibrate;
+		}
+
+		uint64_t core_frequency = cpuid_results.ecx;
+		uint64_t core_numerator = cpuid_results.ebx;
+		uint64_t core_denominator = cpuid_results.eax;
+
+		uint64_t tsc_frequency = core_frequency * core_numerator / core_denominator;
+		timekeeper_source_info->ticks_per_us = tsc_frequency / 1000000;
+	}
+
+	calibrate:
+	if (need_calibration) {
+		for (int i = 0; i < 10; ++i) {
+			long old_ipl = interrupt_raiseipl(IPL_TIMER - 1);
+			time_t ticks_start = rdtsc_serialized();
+
+			timekeeper_wait_us(50000);
+			time_t ticks_end = rdtsc_serialized();
+
+			interrupt_loweripl(old_ipl);
+
+			timekeeper_source_info->ticks_per_us = (ticks_end - ticks_start) / 50000;
+		}
+	}
+
+	return timekeeper_source_info;
+}
+
+// ran in at least IPL_DPC
+static time_t tsc_ticks(timekeeper_source_info_t *timekeeper_source_info) {
+	__assert(timekeeper_source_info->private == current_cpu());
+
+	return rdtsc_serialized();
+}
+
+TIMEKEEPER_SOURCE(kvmtimer_source,
+	.name = "Invariant TSC",
+	.priority = 990,
+	.probe = tsc_probe,
+	.init = tsc_init,
+	.ticks = tsc_ticks,
+	.flags = 0
+);