Kernel: Reorganize Arch/x86 directory to Arch/x86_64 after i686 removal

No functional change.

Kernel/Arch/x86_64/MSR.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+
+#include <Kernel/Arch/x86_64/CPUID.h>
+
+#include <AK/Platform.h>
+VALIDATE_IS_X86()
+
+namespace Kernel {
+
+class MSR {
+    uint32_t m_msr;
+
+public:
+    static bool have()
+    {
+        CPUID id(1);
+        return (id.edx() & (1 << 5)) != 0;
+    }
+
+    MSR(const MSR&) = delete;
+    MSR& operator=(const MSR&) = delete;
+
+    MSR(uint32_t msr)
+        : m_msr(msr)
+    {
+    }
+
+    [[nodiscard]] u64 get()
+    {
+        u32 low, high;
+        asm volatile("rdmsr"
+                     : "=a"(low), "=d"(high)
+                     : "c"(m_msr));
+        return ((u64)high << 32) | low;
+    }
+
+    void set(u64 value)
+    {
+        u32 low = value & 0xffffffff;
+        u32 high = value >> 32;
+        asm volatile("wrmsr" ::"a"(low), "d"(high), "c"(m_msr));
+    }
+};
+
+}