[common] reuse base mapping on POSIX on MultiLevelPageTable

Signed-off-by: lizzie <lizzie@eden-emu.dev>

src/common/multi_level_page_table.inc

@@ -30,12 +30,9 @@ MultiLevelPageTable<BaseAddr>::MultiLevelPageTable(std::size_t address_space_bit
     void* base{VirtualAlloc(nullptr, alloc_size, MEM_RESERVE, PAGE_READWRITE)};
 #else
     void* base{mmap(nullptr, alloc_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0)};
-
-    if (base == MAP_FAILED) {
+    if (base == MAP_FAILED)
         base = nullptr;
-    }
 #endif
-
     ASSERT(base);
     base_ptr = reinterpret_cast<BaseAddr*>(base);
 }
@@ -56,29 +53,21 @@ template <typename BaseAddr>
 void MultiLevelPageTable<BaseAddr>::ReserveRange(u64 start, std::size_t size) {
     const u64 new_start = start >> first_level_shift;
     const u64 new_end = (start + size) >> first_level_shift;
-    for (u64 i = new_start; i <= new_end; i++) {
-        if (!first_level_map[i]) {
+    for (u64 i = new_start; i <= new_end; i++)
+        if (!first_level_map[i])
             AllocateLevel(i);
-        }
-    }
 }
 
 template <typename BaseAddr>
-void MultiLevelPageTable<BaseAddr>::AllocateLevel(u64 level) {
-    void* ptr = reinterpret_cast<char *>(base_ptr) + level * first_level_chunk_size;
+void MultiLevelPageTable<BaseAddr>::AllocateLevel(u64 index) {
+    void* ptr = reinterpret_cast<char *>(base_ptr) + index * first_level_chunk_size;
 #ifdef _WIN32
-    void* base{VirtualAlloc(ptr, first_level_chunk_size, MEM_COMMIT, PAGE_READWRITE)};
-#else
-    void* base{mmap(ptr, first_level_chunk_size, PROT_READ | PROT_WRITE,
-                    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0)};
-
-    if (base == MAP_FAILED) {
-        base = nullptr;
-    }
-#endif
+    void* base = VirtualAlloc(ptr, first_level_chunk_size, MEM_COMMIT, PAGE_READWRITE);
     ASSERT(base);
-
-    first_level_map[level] = base;
+#else
+    void* base = ptr;
+#endif
+    first_level_map[index] = base;
 }
 
 } // namespace Common