From 4c1812ae37bef16ff9031e603bec66b31ac60692 Mon Sep 17 00:00:00 2001
From: bunnei <bunneidev@gmail.com>
Date: Wed, 8 Apr 2020 22:49:51 -0400
Subject: [PATCH] common: page_table: Update to use VirtualBuffer and simplify.

---
 src/common/page_table.cpp | 34 +++++++++-------------------------
 src/common/page_table.h   | 37 +++++++++----------------------------
 2 files changed, 18 insertions(+), 53 deletions(-)

diff --git a/src/common/page_table.cpp b/src/common/page_table.cpp
index 566b57b62..e5d3090d5 100644
--- a/src/common/page_table.cpp
+++ b/src/common/page_table.cpp
@@ -6,36 +6,20 @@
 
 namespace Common {
 
-PageTable::PageTable(std::size_t page_size_in_bits) : page_size_in_bits{page_size_in_bits} {}
+PageTable::PageTable() = default;
 
 PageTable::~PageTable() = default;
 
-void PageTable::Resize(std::size_t address_space_width_in_bits) {
-    const std::size_t num_page_table_entries = 1ULL
-                                               << (address_space_width_in_bits - page_size_in_bits);
-
+void PageTable::Resize(std::size_t address_space_width_in_bits, std::size_t page_size_in_bits,
+                       bool has_attribute) {
+    const std::size_t num_page_table_entries{1ULL
+                                             << (address_space_width_in_bits - page_size_in_bits)};
     pointers.resize(num_page_table_entries);
-    attributes.resize(num_page_table_entries);
-
-    // The default is a 39-bit address space, which causes an initial 1GB allocation size. If the
-    // vector size is subsequently decreased (via resize), the vector might not automatically
-    // actually reallocate/resize its underlying allocation, which wastes up to ~800 MB for
-    // 36-bit titles. Call shrink_to_fit to reduce capacity to what's actually in use.
-
-    pointers.shrink_to_fit();
-    attributes.shrink_to_fit();
-}
-
-BackingPageTable::BackingPageTable(std::size_t page_size_in_bits) : PageTable{page_size_in_bits} {}
-
-BackingPageTable::~BackingPageTable() = default;
-
-void BackingPageTable::Resize(std::size_t address_space_width_in_bits) {
-    PageTable::Resize(address_space_width_in_bits);
-    const std::size_t num_page_table_entries = 1ULL
-                                               << (address_space_width_in_bits - page_size_in_bits);
     backing_addr.resize(num_page_table_entries);
-    backing_addr.shrink_to_fit();
+
+    if (has_attribute) {
+        attributes.resize(num_page_table_entries);
+    }
 }
 
 } // namespace Common
diff --git a/src/common/page_table.h b/src/common/page_table.h
index dbc272ab7..1e8bd3187 100644
--- a/src/common/page_table.h
+++ b/src/common/page_table.h
@@ -5,9 +5,12 @@
 #pragma once
 
 #include <vector>
+
 #include <boost/icl/interval_map.hpp>
+
 #include "common/common_types.h"
 #include "common/memory_hook.h"
+#include "common/virtual_buffer.h"
 
 namespace Common {
 
@@ -47,7 +50,7 @@ struct SpecialRegion {
  * mimics the way a real CPU page table works.
  */
 struct PageTable {
-    explicit PageTable(std::size_t page_size_in_bits);
+    PageTable();
     ~PageTable();
 
     /**
@@ -56,40 +59,18 @@ struct PageTable {
      *
      * @param address_space_width_in_bits The address size width in bits.
      */
-    void Resize(std::size_t address_space_width_in_bits);
+    void Resize(std::size_t address_space_width_in_bits, std::size_t page_size_in_bits,
+                bool has_attribute);
 
     /**
      * Vector of memory pointers backing each page. An entry can only be non-null if the
      * corresponding entry in the `attributes` vector is of type `Memory`.
      */
-    std::vector<u8*> pointers;
+    VirtualBuffer<u8*> pointers;
 
-    /**
-     * Contains MMIO handlers that back memory regions whose entries in the `attribute` vector is
-     * of type `Special`.
-     */
-    boost::icl::interval_map<u64, std::set<SpecialRegion>> special_regions;
+    VirtualBuffer<u64> backing_addr;
 
-    /**
-     * Vector of fine grained page attributes. If it is set to any value other than `Memory`, then
-     * the corresponding entry in `pointers` MUST be set to null.
-     */
-    std::vector<PageType> attributes;
-
-    const std::size_t page_size_in_bits{};
-};
-
-/**
- * A more advanced Page Table with the ability to save a backing address when using it
- * depends on another MMU.
- */
-struct BackingPageTable : PageTable {
-    explicit BackingPageTable(std::size_t page_size_in_bits);
-    ~BackingPageTable();
-
-    void Resize(std::size_t address_space_width_in_bits);
-
-    std::vector<u64> backing_addr;
+    VirtualBuffer<PageType> attributes;
 };
 
 } // namespace Common