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/PhysicalRegion.h

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/OwnPtr.h>
+#include <Kernel/Memory/PhysicalPage.h>
+#include <Kernel/Memory/PhysicalZone.h>
+
+namespace Kernel {
+
+class PhysicalRegion {
+    AK_MAKE_ETERNAL;
+    AK_MAKE_NONCOPYABLE(PhysicalRegion);
+    AK_MAKE_NONMOVABLE(PhysicalRegion);
+
+public:
+    static OwnPtr<PhysicalRegion> try_create(PhysicalAddress lower, PhysicalAddress upper)
+    {
+        return adopt_own_if_nonnull(new PhysicalRegion { lower, upper });
+    }
+
+    ~PhysicalRegion();
+
+    void initialize_zones();
+
+    PhysicalAddress lower() const { return m_lower; }
+    PhysicalAddress upper() const { return m_upper; }
+    unsigned size() const { return m_pages; }
+    bool contains(PhysicalAddress paddr) const { return paddr >= m_lower && paddr < m_upper; }
+
+    OwnPtr<PhysicalRegion> try_take_pages_from_beginning(unsigned);
+
+    RefPtr<PhysicalPage> take_free_page();
+    NonnullRefPtrVector<PhysicalPage> take_contiguous_free_pages(size_t count);
+    void return_page(PhysicalAddress);
+
+private:
+    PhysicalRegion(PhysicalAddress lower, PhysicalAddress upper);
+
+    NonnullOwnPtrVector<PhysicalZone> m_zones;
+
+    PhysicalZone::List m_usable_zones;
+    PhysicalZone::List m_full_zones;
+
+    PhysicalAddress m_lower;
+    PhysicalAddress m_upper;
+    unsigned m_pages { 0 };
+};
+
+}