Kernel: Rename Kernel/VM/ to Kernel/Memory/

This directory isn't just about virtual memory, it's about all kinds
of memory management.

Kernel/Memory/ProcessPagingScope.cpp

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Arch/x86/InterruptDisabler.h>
+#include <Kernel/Memory/MemoryManager.h>
+#include <Kernel/Memory/ProcessPagingScope.h>
+
+namespace Kernel {
+
+ProcessPagingScope::ProcessPagingScope(Process& process)
+{
+    VERIFY(Thread::current() != nullptr);
+    m_previous_cr3 = read_cr3();
+    MM.enter_process_paging_scope(process);
+}
+
+ProcessPagingScope::~ProcessPagingScope()
+{
+    InterruptDisabler disabler;
+    Thread::current()->regs().cr3 = m_previous_cr3;
+    write_cr3(m_previous_cr3);
+}
+
+}