Use APIC for interrupts rather than PIC.

Still rely on the PIT for now rather than the local APIC timer.

zion/common/msr.cpp

@@ -0,0 +1,13 @@
+#include "common/msr.h"
+
+uint64_t GetMSR(uint32_t msr) {
+  uint32_t lo, hi;
+  asm("rdmsr" : "=a"(lo), "=d"(hi) : "c"(msr));
+  return (static_cast<uint64_t>(hi) << 32) | lo;
+}
+
+void SetMSR(uint32_t msr, uint64_t val) {
+  uint32_t lo = static_cast<uint32_t>(val);
+  uint32_t hi = val >> 32;
+  asm("wrmsr" ::"a"(lo), "d"(hi), "c"(msr));
+}

zion/common/msr.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include <stdint.h>
+
+uint64_t GetMSR(uint32_t msr);
+void SetMSR(uint32_t msr, uint64_t val);