11 files changed, 273 insertions, 441 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 70547c8b2..d2fcc2c7e 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -178,8 +178,8 @@ add_library(core STATIC
     loader/nso.h
     memory.cpp
     memory.h
+    memory_hook.h
     memory_setup.h
-    mmio.h
     perf_stats.cpp
     perf_stats.h
     settings.cpp
diff --git a/src/core/hle/kernel/vm_manager.cpp b/src/core/hle/kernel/vm_manager.cpp
index 93662a45e..6da77eb58 100644
--- a/src/core/hle/kernel/vm_manager.cpp
+++ b/src/core/hle/kernel/vm_manager.cpp
@@ -10,8 +10,8 @@
 #include "core/hle/kernel/errors.h"
 #include "core/hle/kernel/vm_manager.h"
 #include "core/memory.h"
+#include "core/memory_hook.h"
 #include "core/memory_setup.h"
-#include "core/mmio.h"
 
 namespace Kernel {
 
@@ -60,8 +60,8 @@ void VMManager::Reset() {
     vma_map.emplace(initial_vma.base, initial_vma);
 
     page_table.pointers.fill(nullptr);
+    page_table.special_regions.clear();
     page_table.attributes.fill(Memory::PageType::Unmapped);
-    page_table.cached_res_count.fill(0);
 
     UpdatePageTableForVMA(initial_vma);
 }
@@ -121,7 +121,7 @@ ResultVal<VMManager::VMAHandle> VMManager::MapBackingMemory(VAddr target, u8* me
 
 ResultVal<VMManager::VMAHandle> VMManager::MapMMIO(VAddr target, PAddr paddr, u64 size,
                                                    MemoryState state,
-                                                   Memory::MMIORegionPointer mmio_handler) {
+                                                   Memory::MemoryHookPointer mmio_handler) {
     // This is the appropriately sized VMA that will turn into our allocation.
     CASCADE_RESULT(VMAIter vma_handle, CarveVMA(target, size));
     VirtualMemoryArea& final_vma = vma_handle->second;
diff --git a/src/core/hle/kernel/vm_manager.h b/src/core/hle/kernel/vm_manager.h
index b17385c7c..8de704a60 100644
--- a/src/core/hle/kernel/vm_manager.h
+++ b/src/core/hle/kernel/vm_manager.h
@@ -10,7 +10,7 @@
 #include "common/common_types.h"
 #include "core/hle/result.h"
 #include "core/memory.h"
-#include "core/mmio.h"
+#include "core/memory_hook.h"
 
 namespace Kernel {
 
@@ -81,7 +81,7 @@ struct VirtualMemoryArea {
     // Settings for type = MMIO
     /// Physical address of the register area this VMA maps to.
     PAddr paddr = 0;
-    Memory::MMIORegionPointer mmio_handler = nullptr;
+    Memory::MemoryHookPointer mmio_handler = nullptr;
 
     /// Tests if this area can be merged to the right with `next`.
     bool CanBeMergedWith(const VirtualMemoryArea& next) const;
@@ -160,7 +160,7 @@ public:
      * @param mmio_handler The handler that will implement read and write for this MMIO region.
      */
     ResultVal<VMAHandle> MapMMIO(VAddr target, PAddr paddr, u64 size, MemoryState state,
-                                 Memory::MMIORegionPointer mmio_handler);
+                                 Memory::MemoryHookPointer mmio_handler);
 
     /// Unmaps a range of addresses, splitting VMAs as necessary.
     ResultCode UnmapRange(VAddr target, u64 size);
diff --git a/src/core/memory.cpp b/src/core/memory.cpp
index a3d2d4951..f658271a5 100644
--- a/src/core/memory.cpp
+++ b/src/core/memory.cpp
@@ -2,8 +2,10 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
+#include <algorithm>
 #include <array>
 #include <cstring>
+#include <boost/optional.hpp>
 #include "common/assert.h"
 #include "common/common_types.h"
 #include "common/logging/log.h"
@@ -12,7 +14,6 @@
 #include "core/core.h"
 #include "core/hle/kernel/memory.h"
 #include "core/hle/kernel/process.h"
-#include "core/hle/lock.h"
 #include "core/memory.h"
 #include "core/memory_setup.h"
 #include "video_core/renderer_base.h"
@@ -40,16 +41,12 @@ static void MapPages(PageTable& page_table, VAddr base, u64 size, u8* memory, Pa
     LOG_DEBUG(HW_Memory, "Mapping %p onto %08X-%08X", memory, base * PAGE_SIZE,
               (base + size) * PAGE_SIZE);
 
-    RasterizerFlushVirtualRegion(base << PAGE_BITS, size * PAGE_SIZE,
-                                 FlushMode::FlushAndInvalidate);
-
     VAddr end = base + size;
     while (base != end) {
         ASSERT_MSG(base < PAGE_TABLE_NUM_ENTRIES, "out of range mapping at %08X", base);
 
         page_table.attributes[base] = type;
         page_table.pointers[base] = memory;
-        page_table.cached_res_count[base] = 0;
 
         base += 1;
         if (memory != nullptr)
@@ -63,157 +60,110 @@ void MapMemoryRegion(PageTable& page_table, VAddr base, u64 size, u8* target) {
     MapPages(page_table, base / PAGE_SIZE, size / PAGE_SIZE, target, PageType::Memory);
 }
 
-void MapIoRegion(PageTable& page_table, VAddr base, u64 size, MMIORegionPointer mmio_handler) {
+void MapIoRegion(PageTable& page_table, VAddr base, u64 size, MemoryHookPointer mmio_handler) {
     ASSERT_MSG((size & PAGE_MASK) == 0, "non-page aligned size: %08X", size);
     ASSERT_MSG((base & PAGE_MASK) == 0, "non-page aligned base: %08X", base);
     MapPages(page_table, base / PAGE_SIZE, size / PAGE_SIZE, nullptr, PageType::Special);
 
-    page_table.special_regions.emplace_back(SpecialRegion{base, size, mmio_handler});
+    auto interval = boost::icl::discrete_interval<VAddr>::closed(base, base + size - 1);
+    SpecialRegion region{SpecialRegion::Type::IODevice, mmio_handler};
+    page_table.special_regions.add(std::make_pair(interval, std::set<SpecialRegion>{region}));
 }
 
 void UnmapRegion(PageTable& page_table, VAddr base, u64 size) {
     ASSERT_MSG((size & PAGE_MASK) == 0, "non-page aligned size: %08X", size);
     ASSERT_MSG((base & PAGE_MASK) == 0, "non-page aligned base: %08X", base);
     MapPages(page_table, base / PAGE_SIZE, size / PAGE_SIZE, nullptr, PageType::Unmapped);
-}
-
-/**
- * Gets a pointer to the exact memory at the virtual address (i.e. not page aligned)
- * using a VMA from the current process
- */
-static u8* GetPointerFromVMA(const Kernel::Process& process, VAddr vaddr) {
-    u8* direct_pointer = nullptr;
 
-    auto& vm_manager = process.vm_manager;
-
-    auto it = vm_manager.FindVMA(vaddr);
-    ASSERT(it != vm_manager.vma_map.end());
-
-    auto& vma = it->second;
-    switch (vma.type) {
-    case Kernel::VMAType::AllocatedMemoryBlock:
-        direct_pointer = vma.backing_block->data() + vma.offset;
-        break;
-    case Kernel::VMAType::BackingMemory:
-        direct_pointer = vma.backing_memory;
-        break;
-    case Kernel::VMAType::Free:
-        return nullptr;
-    default:
-        UNREACHABLE();
-    }
+    auto interval = boost::icl::discrete_interval<VAddr>::closed(base, base + size - 1);
+    page_table.special_regions.erase(interval);
+}
 
-    return direct_pointer + (vaddr - vma.base);
+void AddDebugHook(PageTable& page_table, VAddr base, u64 size, MemoryHookPointer hook) {
+    auto interval = boost::icl::discrete_interval<VAddr>::closed(base, base + size - 1);
+    SpecialRegion region{SpecialRegion::Type::DebugHook, hook};
+    page_table.special_regions.add(std::make_pair(interval, std::set<SpecialRegion>{region}));
 }
 
-/**
- * Gets a pointer to the exact memory at the virtual address (i.e. not page aligned)
- * using a VMA from the current process.
- */
-static u8* GetPointerFromVMA(VAddr vaddr) {
-    return GetPointerFromVMA(*Kernel::g_current_process, vaddr);
+void RemoveDebugHook(PageTable& page_table, VAddr base, u64 size, MemoryHookPointer hook) {
+    auto interval = boost::icl::discrete_interval<VAddr>::closed(base, base + size - 1);
+    SpecialRegion region{SpecialRegion::Type::DebugHook, hook};
+    page_table.special_regions.subtract(std::make_pair(interval, std::set<SpecialRegion>{region}));
 }
 
 /**
  * This function should only be called for virtual addreses with attribute `PageType::Special`.
  */
-static MMIORegionPointer GetMMIOHandler(const PageTable& page_table, VAddr vaddr) {
-    for (const auto& region : page_table.special_regions) {
-        if (vaddr >= region.base && vaddr < (region.base + region.size)) {
-            return region.handler;
+static std::set<MemoryHookPointer> GetSpecialHandlers(const PageTable& page_table, VAddr vaddr,
+                                                      u64 size) {
+    std::set<MemoryHookPointer> result;
+    auto interval = boost::icl::discrete_interval<VAddr>::closed(vaddr, vaddr + size - 1);
+    auto interval_list = page_table.special_regions.equal_range(interval);
+    for (auto it = interval_list.first; it != interval_list.second; ++it) {
+        for (const auto& region : it->second) {
+            result.insert(region.handler);
         }
     }
-    ASSERT_MSG(false, "Mapped IO page without a handler @ %08X", vaddr);
-    return nullptr; // Should never happen
+    return result;
 }
 
-static MMIORegionPointer GetMMIOHandler(VAddr vaddr) {
+static std::set<MemoryHookPointer> GetSpecialHandlers(VAddr vaddr, u64 size) {
     const PageTable& page_table = Kernel::g_current_process->vm_manager.page_table;
-    return GetMMIOHandler(page_table, vaddr);
+    return GetSpecialHandlers(page_table, vaddr, size);
 }
 
 template <typename T>
-T ReadMMIO(MMIORegionPointer mmio_handler, VAddr addr);
+boost::optional<T> ReadSpecial(VAddr addr);
 
 template <typename T>
 T Read(const VAddr vaddr) {
-    const u8* page_pointer = current_page_table->pointers[vaddr >> PAGE_BITS];
-    if (page_pointer) {
-        // NOTE: Avoid adding any extra logic to this fast-path block
-        T value;
-        std::memcpy(&value, &page_pointer[vaddr & PAGE_MASK], sizeof(T));
-        return value;
-    }
-
-    // The memory access might do an MMIO or cached access, so we have to lock the HLE kernel state
-    std::lock_guard<std::recursive_mutex> lock(HLE::g_hle_lock);
-
-    PageType type = current_page_table->attributes[vaddr >> PAGE_BITS];
+    const PageType type = current_page_table->attributes[vaddr >> PAGE_BITS];
     switch (type) {
     case PageType::Unmapped:
-        LOG_ERROR(HW_Memory, "unmapped Read%lu @ 0x%llx", sizeof(T) * 8, vaddr);
+        LOG_ERROR(HW_Memory, "unmapped Read%lu @ 0x%016llX", sizeof(T) * 8, vaddr);
         return 0;
-    case PageType::Memory:
-        ASSERT_MSG(false, "Mapped memory page without a pointer @ %08X", vaddr);
-        break;
-    case PageType::RasterizerCachedMemory: {
-        RasterizerFlushVirtualRegion(vaddr, sizeof(T), FlushMode::Flush);
+    case PageType::Special: {
+        if (auto result = ReadSpecial<T>(vaddr))
+            return *result;
+        [[fallthrough]];
+    }
+    case PageType::Memory: {
+        const u8* page_pointer = current_page_table->pointers[vaddr >> PAGE_BITS];
+        ASSERT_MSG(page_pointer, "Mapped memory page without a pointer @ %08X", vaddr);
 
         T value;
-        std::memcpy(&value, GetPointerFromVMA(vaddr), sizeof(T));
+        std::memcpy(&value, &page_pointer[vaddr & PAGE_MASK], sizeof(T));
         return value;
     }
-    case PageType::Special:
-        return ReadMMIO<T>(GetMMIOHandler(vaddr), vaddr);
-    case PageType::RasterizerCachedSpecial: {
-        RasterizerFlushVirtualRegion(vaddr, sizeof(T), FlushMode::Flush);
-        return ReadMMIO<T>(GetMMIOHandler(vaddr), vaddr);
-    }
-    default:
-        UNREACHABLE();
     }
+    UNREACHABLE();
+    return 0;
 }
 
 template <typename T>
-void WriteMMIO(MMIORegionPointer mmio_handler, VAddr addr, const T data);
+bool WriteSpecial(VAddr addr, const T data);
 
 template <typename T>
 void Write(const VAddr vaddr, const T data) {
-    u8* page_pointer = current_page_table->pointers[vaddr >> PAGE_BITS];
-    if (page_pointer) {
-        // NOTE: Avoid adding any extra logic to this fast-path block
-        std::memcpy(&page_pointer[vaddr & PAGE_MASK], &data, sizeof(T));
-        return;
-    }
-
-    // The memory access might do an MMIO or cached access, so we have to lock the HLE kernel state
-    std::lock_guard<std::recursive_mutex> lock(HLE::g_hle_lock);
-
-    PageType type = current_page_table->attributes[vaddr >> PAGE_BITS];
+    const PageType type = current_page_table->attributes[vaddr >> PAGE_BITS];
     switch (type) {
     case PageType::Unmapped:
         LOG_ERROR(HW_Memory, "unmapped Write%lu 0x%08X @ 0x%08X", sizeof(data) * 8, (u32)data,
                   vaddr);
         return;
-    case PageType::Memory:
-        ASSERT_MSG(false, "Mapped memory page without a pointer @ %08X", vaddr);
-        break;
-    case PageType::RasterizerCachedMemory: {
-        RasterizerFlushVirtualRegion(vaddr, sizeof(T), FlushMode::FlushAndInvalidate);
-        std::memcpy(GetPointerFromVMA(vaddr), &data, sizeof(T));
-        break;
+    case PageType::Special: {
+        if (WriteSpecial<T>(vaddr, data))
+            return;
+        [[fallthrough]];
     }
-    case PageType::Special:
-        WriteMMIO<T>(GetMMIOHandler(vaddr), vaddr, data);
-        break;
-    case PageType::RasterizerCachedSpecial: {
-        RasterizerFlushVirtualRegion(vaddr, sizeof(T), FlushMode::FlushAndInvalidate);
-        WriteMMIO<T>(GetMMIOHandler(vaddr), vaddr, data);
-        break;
+    case PageType::Memory: {
+        u8* page_pointer = current_page_table->pointers[vaddr >> PAGE_BITS];
+        ASSERT_MSG(page_pointer, "Mapped memory page without a pointer @ %08X", vaddr);
+        std::memcpy(&page_pointer[vaddr & PAGE_MASK], &data, sizeof(T));
+        return;
     }
-    default:
-        UNREACHABLE();
     }
+    UNREACHABLE();
 }
 
 bool IsValidVirtualAddress(const Kernel::Process& process, const VAddr vaddr) {
@@ -222,21 +172,20 @@ bool IsValidVirtualAddress(const Kernel::Process& process, const VAddr vaddr) {
     if ((vaddr >> PAGE_BITS) >= PAGE_TABLE_NUM_ENTRIES)
         return false;
 
-    const u8* page_pointer = page_table.pointers[vaddr >> PAGE_BITS];
-    if (page_pointer)
-        return true;
-
-    if (page_table.attributes[vaddr >> PAGE_BITS] == PageType::RasterizerCachedMemory)
-        return true;
-
-    if (page_table.attributes[vaddr >> PAGE_BITS] != PageType::Special)
+    const PageType type = current_page_table->attributes[vaddr >> PAGE_BITS];
+    switch (type) {
+    case PageType::Unmapped:
         return false;
-
-    MMIORegionPointer mmio_region = GetMMIOHandler(page_table, vaddr);
-    if (mmio_region) {
-        return mmio_region->IsValidAddress(vaddr);
+    case PageType::Memory:
+        return true;
+    case PageType::Special: {
+        for (auto handler : GetSpecialHandlers(page_table, vaddr, 1))
+            if (auto result = handler->IsValidAddress(vaddr))
+                return *result;
+        return current_page_table->pointers[vaddr >> PAGE_BITS] != nullptr;
     }
-
+    }
+    UNREACHABLE();
     return false;
 }
 
@@ -254,10 +203,6 @@ u8* GetPointer(const VAddr vaddr) {
         return page_pointer + (vaddr & PAGE_MASK);
     }
 
-    if (current_page_table->attributes[vaddr >> PAGE_BITS] == PageType::RasterizerCachedMemory) {
-        return GetPointerFromVMA(vaddr);
-    }
-
     LOG_ERROR(HW_Memory, "unknown GetPointer @ 0x%08x", vaddr);
     return nullptr;
 }
@@ -335,97 +280,6 @@ u8* GetPhysicalPointer(PAddr address) {
     return target_pointer;
 }
 
-void RasterizerMarkRegionCached(PAddr start, u64 size, int count_delta) {
-    if (start == 0) {
-        return;
-    }
-
-    u64 num_pages = ((start + size - 1) >> PAGE_BITS) - (start >> PAGE_BITS) + 1;
-    PAddr paddr = start;
-
-    for (unsigned i = 0; i < num_pages; ++i, paddr += PAGE_SIZE) {
-        boost::optional<VAddr> maybe_vaddr = PhysicalToVirtualAddress(paddr);
-        // While the physical <-> virtual mapping is 1:1 for the regions supported by the cache,
-        // some games (like Pokemon Super Mystery Dungeon) will try to use textures that go beyond
-        // the end address of VRAM, causing the Virtual->Physical translation to fail when flushing
-        // parts of the texture.
-        if (!maybe_vaddr) {
-            LOG_ERROR(HW_Memory,
-                      "Trying to flush a cached region to an invalid physical address %08X", paddr);
-            continue;
-        }
-        VAddr vaddr = *maybe_vaddr;
-
-        u8& res_count = current_page_table->cached_res_count[vaddr >> PAGE_BITS];
-        ASSERT_MSG(count_delta <= UINT8_MAX - res_count,
-                   "Rasterizer resource cache counter overflow!");
-        ASSERT_MSG(count_delta >= -res_count, "Rasterizer resource cache counter underflow!");
-
-        // Switch page type to cached if now cached
-        if (res_count == 0) {
-            PageType& page_type = current_page_table->attributes[vaddr >> PAGE_BITS];
-            switch (page_type) {
-            case PageType::Unmapped:
-                // It is not necessary for a process to have this region mapped into its address
-                // space, for example, a system module need not have a VRAM mapping.
-                break;
-            case PageType::Memory:
-                page_type = PageType::RasterizerCachedMemory;
-                current_page_table->pointers[vaddr >> PAGE_BITS] = nullptr;
-                break;
-            case PageType::Special:
-                page_type = PageType::RasterizerCachedSpecial;
-                break;
-            default:
-                UNREACHABLE();
-            }
-        }
-
-        res_count += count_delta;
-
-        // Switch page type to uncached if now uncached
-        if (res_count == 0) {
-            PageType& page_type = current_page_table->attributes[vaddr >> PAGE_BITS];
-            switch (page_type) {
-            case PageType::Unmapped:
-                // It is not necessary for a process to have this region mapped into its address
-                // space, for example, a system module need not have a VRAM mapping.
-                break;
-            case PageType::RasterizerCachedMemory: {
-                u8* pointer = GetPointerFromVMA(vaddr & ~PAGE_MASK);
-                if (pointer == nullptr) {
-                    // It's possible that this function has called been while updating the pagetable
-                    // after unmapping a VMA. In that case the underlying VMA will no longer exist,
-                    // and we should just leave the pagetable entry blank.
-                    page_type = PageType::Unmapped;
-                } else {
-                    page_type = PageType::Memory;
-                    current_page_table->pointers[vaddr >> PAGE_BITS] = pointer;
-                }
-                break;
-            }
-            case PageType::RasterizerCachedSpecial:
-                page_type = PageType::Special;
-                break;
-            default:
-                UNREACHABLE();
-            }
-        }
-    }
-}
-
-void RasterizerFlushRegion(PAddr start, u64 size) {}
-
-void RasterizerFlushAndInvalidateRegion(PAddr start, u64 size) {
-    // Since pages are unmapped on shutdown after video core is shutdown, the renderer may be
-    // null here
-}
-
-void RasterizerFlushVirtualRegion(VAddr start, u64 size, FlushMode mode) {
-    // Since pages are unmapped on shutdown after video core is shutdown, the renderer may be
-    // null here
-}
-
 u8 Read8(const VAddr addr) {
     return Read<u8>(addr);
 }
@@ -442,6 +296,17 @@ u64 Read64(const VAddr addr) {
     return Read<u64_le>(addr);
 }
 
+static bool ReadSpecialBlock(const Kernel::Process& process, const VAddr src_addr,
+                             void* dest_buffer, const size_t size) {
+    auto& page_table = process.vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, src_addr, size)) {
+        if (handler->ReadBlock(src_addr, dest_buffer, size)) {
+            return true;
+        }
+    }
+    return false;
+}
+
 void ReadBlock(const Kernel::Process& process, const VAddr src_addr, void* dest_buffer,
                const size_t size) {
     auto& page_table = process.vm_manager.page_table;
@@ -455,11 +320,15 @@ void ReadBlock(const Kernel::Process& process, const VAddr src_addr, void* dest_
         const VAddr current_vaddr = static_cast<VAddr>((page_index << PAGE_BITS) + page_offset);
 
         switch (page_table.attributes[page_index]) {
-        case PageType::Unmapped: {
+        case PageType::Unmapped:
             LOG_ERROR(HW_Memory, "unmapped ReadBlock @ 0x%08X (start address = 0xllx, size = %zu)",
                       current_vaddr, src_addr, size);
             std::memset(dest_buffer, 0, copy_amount);
             break;
+        case PageType::Special: {
+            if (ReadSpecialBlock(process, current_vaddr, dest_buffer, copy_amount))
+                break;
+            [[fallthrough]];
         }
         case PageType::Memory: {
             DEBUG_ASSERT(page_table.pointers[page_index]);
@@ -468,26 +337,6 @@ void ReadBlock(const Kernel::Process& process, const VAddr src_addr, void* dest_
             std::memcpy(dest_buffer, src_ptr, copy_amount);
             break;
         }
-        case PageType::Special: {
-            MMIORegionPointer handler = GetMMIOHandler(page_table, current_vaddr);
-            DEBUG_ASSERT(handler);
-            handler->ReadBlock(current_vaddr, dest_buffer, copy_amount);
-            break;
-        }
-        case PageType::RasterizerCachedMemory: {
-            RasterizerFlushVirtualRegion(current_vaddr, static_cast<u32>(copy_amount),
-                                         FlushMode::Flush);
-            std::memcpy(dest_buffer, GetPointerFromVMA(process, current_vaddr), copy_amount);
-            break;
-        }
-        case PageType::RasterizerCachedSpecial: {
-            MMIORegionPointer handler = GetMMIOHandler(page_table, current_vaddr);
-            DEBUG_ASSERT(handler);
-            RasterizerFlushVirtualRegion(current_vaddr, static_cast<u32>(copy_amount),
-                                         FlushMode::Flush);
-            handler->ReadBlock(current_vaddr, dest_buffer, copy_amount);
-            break;
-        }
         default:
             UNREACHABLE();
         }
@@ -519,6 +368,17 @@ void Write64(const VAddr addr, const u64 data) {
     Write<u64_le>(addr, data);
 }
 
+static bool WriteSpecialBlock(const Kernel::Process& process, const VAddr dest_addr,
+                              const void* src_buffer, const size_t size) {
+    auto& page_table = process.vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, dest_addr, size)) {
+        if (handler->WriteBlock(dest_addr, src_buffer, size)) {
+            return true;
+        }
+    }
+    return false;
+}
+
 void WriteBlock(const Kernel::Process& process, const VAddr dest_addr, const void* src_buffer,
                 const size_t size) {
     auto& page_table = process.vm_manager.page_table;
@@ -531,12 +391,15 @@ void WriteBlock(const Kernel::Process& process, const VAddr dest_addr, const voi
         const VAddr current_vaddr = static_cast<VAddr>((page_index << PAGE_BITS) + page_offset);
 
         switch (page_table.attributes[page_index]) {
-        case PageType::Unmapped: {
+        case PageType::Unmapped:
             LOG_ERROR(HW_Memory,
                       "unmapped WriteBlock @ 0x%08X (start address = 0x%08X, size = %zu)",
                       current_vaddr, dest_addr, size);
             break;
-        }
+        case PageType::Special:
+            if (WriteSpecialBlock(process, current_vaddr, src_buffer, copy_amount))
+                break;
+            [[fallthrough]];
         case PageType::Memory: {
             DEBUG_ASSERT(page_table.pointers[page_index]);
 
@@ -544,26 +407,6 @@ void WriteBlock(const Kernel::Process& process, const VAddr dest_addr, const voi
             std::memcpy(dest_ptr, src_buffer, copy_amount);
             break;
         }
-        case PageType::Special: {
-            MMIORegionPointer handler = GetMMIOHandler(page_table, current_vaddr);
-            DEBUG_ASSERT(handler);
-            handler->WriteBlock(current_vaddr, src_buffer, copy_amount);
-            break;
-        }
-        case PageType::RasterizerCachedMemory: {
-            RasterizerFlushVirtualRegion(current_vaddr, static_cast<u32>(copy_amount),
-                                         FlushMode::FlushAndInvalidate);
-            std::memcpy(GetPointerFromVMA(process, current_vaddr), src_buffer, copy_amount);
-            break;
-        }
-        case PageType::RasterizerCachedSpecial: {
-            MMIORegionPointer handler = GetMMIOHandler(page_table, current_vaddr);
-            DEBUG_ASSERT(handler);
-            RasterizerFlushVirtualRegion(current_vaddr, static_cast<u32>(copy_amount),
-                                         FlushMode::FlushAndInvalidate);
-            handler->WriteBlock(current_vaddr, src_buffer, copy_amount);
-            break;
-        }
         default:
             UNREACHABLE();
         }
@@ -580,6 +423,8 @@ void WriteBlock(const VAddr dest_addr, const void* src_buffer, const size_t size
 }
 
 void ZeroBlock(const VAddr dest_addr, const size_t size) {
+    const auto& process = *Kernel::g_current_process;
+
     size_t remaining_size = size;
     size_t page_index = dest_addr >> PAGE_BITS;
     size_t page_offset = dest_addr & PAGE_MASK;
@@ -591,11 +436,14 @@ void ZeroBlock(const VAddr dest_addr, const size_t size) {
         const VAddr current_vaddr = static_cast<VAddr>((page_index << PAGE_BITS) + page_offset);
 
         switch (current_page_table->attributes[page_index]) {
-        case PageType::Unmapped: {
+        case PageType::Unmapped:
             LOG_ERROR(HW_Memory, "unmapped ZeroBlock @ 0x%08X (start address = 0x%08X, size = %zu)",
                       current_vaddr, dest_addr, size);
             break;
-        }
+        case PageType::Special:
+            if (WriteSpecialBlock(process, current_vaddr, zeros.data(), copy_amount))
+                break;
+            [[fallthrough]];
         case PageType::Memory: {
             DEBUG_ASSERT(current_page_table->pointers[page_index]);
 
@@ -603,25 +451,6 @@ void ZeroBlock(const VAddr dest_addr, const size_t size) {
             std::memset(dest_ptr, 0, copy_amount);
             break;
         }
-        case PageType::Special: {
-            DEBUG_ASSERT(GetMMIOHandler(current_vaddr));
-
-            GetMMIOHandler(current_vaddr)->WriteBlock(current_vaddr, zeros.data(), copy_amount);
-            break;
-        }
-        case PageType::RasterizerCachedMemory: {
-            RasterizerFlushVirtualRegion(current_vaddr, static_cast<u32>(copy_amount),
-                                         FlushMode::FlushAndInvalidate);
-            std::memset(GetPointerFromVMA(current_vaddr), 0, copy_amount);
-            break;
-        }
-        case PageType::RasterizerCachedSpecial: {
-            DEBUG_ASSERT(GetMMIOHandler(current_vaddr));
-            RasterizerFlushVirtualRegion(current_vaddr, static_cast<u32>(copy_amount),
-                                         FlushMode::FlushAndInvalidate);
-            GetMMIOHandler(current_vaddr)->WriteBlock(current_vaddr, zeros.data(), copy_amount);
-            break;
-        }
         default:
             UNREACHABLE();
         }
@@ -633,6 +462,8 @@ void ZeroBlock(const VAddr dest_addr, const size_t size) {
 }
 
 void CopyBlock(VAddr dest_addr, VAddr src_addr, const size_t size) {
+    const auto& process = *Kernel::g_current_process;
+
     size_t remaining_size = size;
     size_t page_index = src_addr >> PAGE_BITS;
     size_t page_offset = src_addr & PAGE_MASK;
@@ -642,11 +473,18 @@ void CopyBlock(VAddr dest_addr, VAddr src_addr, const size_t size) {
         const VAddr current_vaddr = static_cast<VAddr>((page_index << PAGE_BITS) + page_offset);
 
         switch (current_page_table->attributes[page_index]) {
-        case PageType::Unmapped: {
+        case PageType::Unmapped:
             LOG_ERROR(HW_Memory, "unmapped CopyBlock @ 0x%08X (start address = 0x%08X, size = %zu)",
                       current_vaddr, src_addr, size);
             ZeroBlock(dest_addr, copy_amount);
             break;
+        case PageType::Special: {
+            std::vector<u8> buffer(copy_amount);
+            if (ReadSpecialBlock(process, current_vaddr, buffer.data(), buffer.size())) {
+                WriteBlock(dest_addr, buffer.data(), buffer.size());
+                break;
+            }
+            [[fallthrough]];
         }
         case PageType::Memory: {
             DEBUG_ASSERT(current_page_table->pointers[page_index]);
@@ -654,30 +492,6 @@ void CopyBlock(VAddr dest_addr, VAddr src_addr, const size_t size) {
             WriteBlock(dest_addr, src_ptr, copy_amount);
             break;
         }
-        case PageType::Special: {
-            DEBUG_ASSERT(GetMMIOHandler(current_vaddr));
-
-            std::vector<u8> buffer(copy_amount);
-            GetMMIOHandler(current_vaddr)->ReadBlock(current_vaddr, buffer.data(), buffer.size());
-            WriteBlock(dest_addr, buffer.data(), buffer.size());
-            break;
-        }
-        case PageType::RasterizerCachedMemory: {
-            RasterizerFlushVirtualRegion(current_vaddr, static_cast<u32>(copy_amount),
-                                         FlushMode::Flush);
-            WriteBlock(dest_addr, GetPointerFromVMA(current_vaddr), copy_amount);
-            break;
-        }
-        case PageType::RasterizerCachedSpecial: {
-            DEBUG_ASSERT(GetMMIOHandler(current_vaddr));
-            RasterizerFlushVirtualRegion(current_vaddr, static_cast<u32>(copy_amount),
-                                         FlushMode::Flush);
-
-            std::vector<u8> buffer(copy_amount);
-            GetMMIOHandler(current_vaddr)->ReadBlock(current_vaddr, buffer.data(), buffer.size());
-            WriteBlock(dest_addr, buffer.data(), buffer.size());
-            break;
-        }
         default:
             UNREACHABLE();
         }
@@ -691,43 +505,75 @@ void CopyBlock(VAddr dest_addr, VAddr src_addr, const size_t size) {
 }
 
 template <>
-u8 ReadMMIO<u8>(MMIORegionPointer mmio_handler, VAddr addr) {
-    return mmio_handler->Read8(addr);
+boost::optional<u8> ReadSpecial<u8>(VAddr addr) {
+    const PageTable& page_table = Kernel::g_current_process->vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, addr, sizeof(u8)))
+        if (auto result = handler->Read8(addr))
+            return *result;
+    return {};
 }
 
 template <>
-u16 ReadMMIO<u16>(MMIORegionPointer mmio_handler, VAddr addr) {
-    return mmio_handler->Read16(addr);
+boost::optional<u16> ReadSpecial<u16>(VAddr addr) {
+    const PageTable& page_table = Kernel::g_current_process->vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, addr, sizeof(u16)))
+        if (auto result = handler->Read16(addr))
+            return *result;
+    return {};
 }
 
 template <>
-u32 ReadMMIO<u32>(MMIORegionPointer mmio_handler, VAddr addr) {
-    return mmio_handler->Read32(addr);
+boost::optional<u32> ReadSpecial<u32>(VAddr addr) {
+    const PageTable& page_table = Kernel::g_current_process->vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, addr, sizeof(u32)))
+        if (auto result = handler->Read32(addr))
+            return *result;
+    return {};
 }
 
 template <>
-u64 ReadMMIO<u64>(MMIORegionPointer mmio_handler, VAddr addr) {
-    return mmio_handler->Read64(addr);
+boost::optional<u64> ReadSpecial<u64>(VAddr addr) {
+    const PageTable& page_table = Kernel::g_current_process->vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, addr, sizeof(u64)))
+        if (auto result = handler->Read64(addr))
+            return *result;
+    return {};
 }
 
 template <>
-void WriteMMIO<u8>(MMIORegionPointer mmio_handler, VAddr addr, const u8 data) {
-    mmio_handler->Write8(addr, data);
+bool WriteSpecial<u8>(VAddr addr, const u8 data) {
+    const PageTable& page_table = Kernel::g_current_process->vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, addr, sizeof(u8)))
+        if (handler->Write8(addr, data))
+            return true;
+    return false;
 }
 
 template <>
-void WriteMMIO<u16>(MMIORegionPointer mmio_handler, VAddr addr, const u16 data) {
-    mmio_handler->Write16(addr, data);
+bool WriteSpecial<u16>(VAddr addr, const u16 data) {
+    const PageTable& page_table = Kernel::g_current_process->vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, addr, sizeof(u16)))
+        if (handler->Write16(addr, data))
+            return true;
+    return false;
 }
 
 template <>
-void WriteMMIO<u32>(MMIORegionPointer mmio_handler, VAddr addr, const u32 data) {
-    mmio_handler->Write32(addr, data);
+bool WriteSpecial<u32>(VAddr addr, const u32 data) {
+    const PageTable& page_table = Kernel::g_current_process->vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, addr, sizeof(u32)))
+        if (handler->Write32(addr, data))
+            return true;
+    return false;
 }
 
 template <>
-void WriteMMIO<u64>(MMIORegionPointer mmio_handler, VAddr addr, const u64 data) {
-    mmio_handler->Write64(addr, data);
+bool WriteSpecial<u64>(VAddr addr, const u64 data) {
+    const PageTable& page_table = Kernel::g_current_process->vm_manager.page_table;
+    for (const auto& handler : GetSpecialHandlers(page_table, addr, sizeof(u64)))
+        if (handler->Write64(addr, data))
+            return true;
+    return false;
 }
 
 boost::optional<PAddr> TryVirtualToPhysicalAddress(const VAddr addr) {
diff --git a/src/core/memory.h b/src/core/memory.h
index 7e554f394..b2158ca46 100644
--- a/src/core/memory.h
+++ b/src/core/memory.h
@@ -8,10 +8,12 @@
 #include <cstddef>
 #include <map>
 #include <string>
+#include <tuple>
 #include <vector>
+#include <boost/icl/interval_map.hpp>
 #include <boost/optional.hpp>
 #include "common/common_types.h"
-#include "core/mmio.h"
+#include "core/memory_hook.h"
 
 namespace Kernel {
 class Process;
@@ -28,32 +30,35 @@ const u64 PAGE_SIZE = 1 << PAGE_BITS;
 const u64 PAGE_MASK = PAGE_SIZE - 1;
 const size_t PAGE_TABLE_NUM_ENTRIES = 1ULL << (36 - PAGE_BITS);
 
-enum class PageType {
+enum class PageType : u8 {
     /// Page is unmapped and should cause an access error.
     Unmapped,
     /// Page is mapped to regular memory. This is the only type you can get pointers to.
     Memory,
-    /// Page is mapped to regular memory, but also needs to check for rasterizer cache flushing and
-    /// invalidation
-    RasterizerCachedMemory,
-    /// Page is mapped to a I/O region. Writing and reading to this page is handled by functions.
+    /// Page is mapped to a memory hook, which intercepts read and write requests.
     Special,
-    /// Page is mapped to a I/O region, but also needs to check for rasterizer cache flushing and
-    /// invalidation
-    RasterizerCachedSpecial,
 };
 
 struct SpecialRegion {
-    VAddr base;
-    u64 size;
-    MMIORegionPointer handler;
+    enum class Type {
+        DebugHook,
+        IODevice,
+    } type;
+
+    MemoryHookPointer handler;
+
+    bool operator<(const SpecialRegion& other) const {
+        return std::tie(type, handler) < std::tie(other.type, other.handler);
+    }
+
+    bool operator==(const SpecialRegion& other) const {
+        return std::tie(type, handler) == std::tie(other.type, other.handler);
+    }
 };
 
 /**
  * A (reasonably) fast way of allowing switchable and remappable process address spaces. It loosely
- * mimics the way a real CPU page table works, but instead is optimized for minimal decoding and
- * fetching requirements when accessing. In the usual case of an access to regular memory, it only
- * requires an indexed fetch and a check for NULL.
+ * mimics the way a real CPU page table works.
  */
 struct PageTable {
     /**
@@ -66,19 +71,13 @@ struct PageTable {
      * Contains MMIO handlers that back memory regions whose entries in the `attribute` array is of
      * type `Special`.
      */
-    std::vector<SpecialRegion> special_regions;
+    boost::icl::interval_map<VAddr, std::set<SpecialRegion>> special_regions;
 
     /**
      * Array 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::array<PageType, PAGE_TABLE_NUM_ENTRIES> attributes;
-
-    /**
-     * Indicates the number of externally cached resources touching a page that should be
-     * flushed before the memory is accessed
-     */
-    std::array<u8, PAGE_TABLE_NUM_ENTRIES> cached_res_count;
 };
 
 /// Physical memory regions as seen from the ARM11
@@ -243,33 +242,4 @@ boost::optional<VAddr> PhysicalToVirtualAddress(PAddr addr);
  */
 u8* GetPhysicalPointer(PAddr address);
 
-/**
- * Adds the supplied value to the rasterizer resource cache counter of each
- * page touching the region.
- */
-void RasterizerMarkRegionCached(PAddr start, u64 size, int count_delta);
-
-/**
- * Flushes any externally cached rasterizer resources touching the given region.
- */
-void RasterizerFlushRegion(PAddr start, u64 size);
-
-/**
- * Flushes and invalidates any externally cached rasterizer resources touching the given region.
- */
-void RasterizerFlushAndInvalidateRegion(PAddr start, u64 size);
-
-enum class FlushMode {
-    /// Write back modified surfaces to RAM
-    Flush,
-    /// Write back modified surfaces to RAM, and also remove them from the cache
-    FlushAndInvalidate,
-};
-
-/**
- * Flushes and invalidates any externally cached rasterizer resources touching the given virtual
- * address region.
- */
-void RasterizerFlushVirtualRegion(VAddr start, u64 size, FlushMode mode);
-
 } // namespace Memory
diff --git a/src/core/memory_hook.h b/src/core/memory_hook.h
new file mode 100644
index 000000000..feebd850a
--- /dev/null
+++ b/src/core/memory_hook.h
@@ -0,0 +1,46 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <boost/optional.hpp>
+#include "common/common_types.h"
+
+namespace Memory {
+
+/**
+ * Memory hooks have two purposes:
+ * 1. To allow reads and writes to a region of memory to be intercepted. This is used to implement
+ *    texture forwarding and memory breakpoints for debugging.
+ * 2. To allow for the implementation of MMIO devices.
+ *
+ * A hook may be mapped to multiple regions of memory.
+ *
+ * If a boost::none or false is returned from a function, the read/write request is passed through
+ * to the underlying memory region.
+ */
+class MemoryHook {
+public:
+    virtual ~MemoryHook() = default;
+
+    virtual boost::optional<bool> IsValidAddress(VAddr addr) = 0;
+
+    virtual boost::optional<u8> Read8(VAddr addr) = 0;
+    virtual boost::optional<u16> Read16(VAddr addr) = 0;
+    virtual boost::optional<u32> Read32(VAddr addr) = 0;
+    virtual boost::optional<u64> Read64(VAddr addr) = 0;
+
+    virtual bool ReadBlock(VAddr src_addr, void* dest_buffer, size_t size) = 0;
+
+    virtual bool Write8(VAddr addr, u8 data) = 0;
+    virtual bool Write16(VAddr addr, u16 data) = 0;
+    virtual bool Write32(VAddr addr, u32 data) = 0;
+    virtual bool Write64(VAddr addr, u64 data) = 0;
+
+    virtual bool WriteBlock(VAddr dest_addr, const void* src_buffer, size_t size) = 0;
+};
+
+using MemoryHookPointer = std::shared_ptr<MemoryHook>;
+} // namespace Memory
diff --git a/src/core/memory_setup.h b/src/core/memory_setup.h
index 6f82a131e..9a1a4f4be 100644
--- a/src/core/memory_setup.h
+++ b/src/core/memory_setup.h
@@ -5,7 +5,7 @@
 #pragma once
 
 #include "common/common_types.h"
-#include "core/mmio.h"
+#include "core/memory_hook.h"
 
 namespace Memory {
 
@@ -26,7 +26,11 @@ void MapMemoryRegion(PageTable& page_table, VAddr base, u64 size, u8* target);
  * @param size The amount of bytes to map. Must be page-aligned.
  * @param mmio_handler The handler that backs the mapping.
  */
-void MapIoRegion(PageTable& page_table, VAddr base, u64 size, MMIORegionPointer mmio_handler);
+void MapIoRegion(PageTable& page_table, VAddr base, u64 size, MemoryHookPointer mmio_handler);
 
 void UnmapRegion(PageTable& page_table, VAddr base, u64 size);
+
+void AddDebugHook(PageTable& page_table, VAddr base, u64 size, MemoryHookPointer hook);
+void RemoveDebugHook(PageTable& page_table, VAddr base, u64 size, MemoryHookPointer hook);
+
 } // namespace Memory
diff --git a/src/core/mmio.h b/src/core/mmio.h
deleted file mode 100644
index 5e3cc01af..000000000
--- a/src/core/mmio.h
+++ /dev/null
@@ -1,38 +0,0 @@
-// Copyright 2016 Citra Emulator Project
-// Licensed under GPLv2 or any later version
-// Refer to the license.txt file included.
-
-#pragma once
-
-#include <memory>
-#include "common/common_types.h"
-
-namespace Memory {
-
-/**
- * Represents a device with memory mapped IO.
- * A device may be mapped to multiple regions of memory.
- */
-class MMIORegion {
-public:
-    virtual ~MMIORegion() = default;
-
-    virtual bool IsValidAddress(VAddr addr) = 0;
-
-    virtual u8 Read8(VAddr addr) = 0;
-    virtual u16 Read16(VAddr addr) = 0;
-    virtual u32 Read32(VAddr addr) = 0;
-    virtual u64 Read64(VAddr addr) = 0;
-
-    virtual bool ReadBlock(VAddr src_addr, void* dest_buffer, size_t size) = 0;
-
-    virtual void Write8(VAddr addr, u8 data) = 0;
-    virtual void Write16(VAddr addr, u16 data) = 0;
-    virtual void Write32(VAddr addr, u32 data) = 0;
-    virtual void Write64(VAddr addr, u64 data) = 0;
-
-    virtual bool WriteBlock(VAddr dest_addr, const void* src_buffer, size_t size) = 0;
-};
-
-using MMIORegionPointer = std::shared_ptr<MMIORegion>;
-}; // namespace Memory
diff --git a/src/tests/core/arm/arm_test_common.cpp b/src/tests/core/arm/arm_test_common.cpp
index 2339bdfb8..88bbbc95c 100644
--- a/src/tests/core/arm/arm_test_common.cpp
+++ b/src/tests/core/arm/arm_test_common.cpp
@@ -19,8 +19,8 @@ TestEnvironment::TestEnvironment(bool mutable_memory_)
     page_table = &Kernel::g_current_process->vm_manager.page_table;
 
     page_table->pointers.fill(nullptr);
+    page_table->special_regions.clear();
     page_table->attributes.fill(Memory::PageType::Unmapped);
-    page_table->cached_res_count.fill(0);
 
     Memory::MapIoRegion(*page_table, 0x00000000, 0x80000000, test_memory);
     Memory::MapIoRegion(*page_table, 0x80000000, 0x80000000, test_memory);
@@ -62,11 +62,11 @@ void TestEnvironment::ClearWriteRecords() {
 
 TestEnvironment::TestMemory::~TestMemory() {}
 
-bool TestEnvironment::TestMemory::IsValidAddress(VAddr addr) {
+boost::optional<bool> TestEnvironment::TestMemory::IsValidAddress(VAddr addr) {
     return true;
 }
 
-u8 TestEnvironment::TestMemory::Read8(VAddr addr) {
+boost::optional<u8> TestEnvironment::TestMemory::Read8(VAddr addr) {
     auto iter = data.find(addr);
     if (iter == data.end()) {
         return addr; // Some arbitrary data
@@ -74,16 +74,16 @@ u8 TestEnvironment::TestMemory::Read8(VAddr addr) {
     return iter->second;
 }
 
-u16 TestEnvironment::TestMemory::Read16(VAddr addr) {
-    return Read8(addr) | static_cast<u16>(Read8(addr + 1)) << 8;
+boost::optional<u16> TestEnvironment::TestMemory::Read16(VAddr addr) {
+    return *Read8(addr) | static_cast<u16>(*Read8(addr + 1)) << 8;
 }
 
-u32 TestEnvironment::TestMemory::Read32(VAddr addr) {
-    return Read16(addr) | static_cast<u32>(Read16(addr + 2)) << 16;
+boost::optional<u32> TestEnvironment::TestMemory::Read32(VAddr addr) {
+    return *Read16(addr) | static_cast<u32>(*Read16(addr + 2)) << 16;
 }
 
-u64 TestEnvironment::TestMemory::Read64(VAddr addr) {
-    return Read32(addr) | static_cast<u64>(Read32(addr + 4)) << 32;
+boost::optional<u64> TestEnvironment::TestMemory::Read64(VAddr addr) {
+    return *Read32(addr) | static_cast<u64>(*Read32(addr + 4)) << 32;
 }
 
 bool TestEnvironment::TestMemory::ReadBlock(VAddr src_addr, void* dest_buffer, size_t size) {
@@ -91,34 +91,38 @@ bool TestEnvironment::TestMemory::ReadBlock(VAddr src_addr, void* dest_buffer, s
     u8* data = static_cast<u8*>(dest_buffer);
 
     for (size_t i = 0; i < size; i++, addr++, data++) {
-        *data = Read8(addr);
+        *data = *Read8(addr);
     }
 
     return true;
 }
 
-void TestEnvironment::TestMemory::Write8(VAddr addr, u8 data) {
+bool TestEnvironment::TestMemory::Write8(VAddr addr, u8 data) {
     env->write_records.emplace_back(8, addr, data);
     if (env->mutable_memory)
         env->SetMemory8(addr, data);
+    return true;
 }
 
-void TestEnvironment::TestMemory::Write16(VAddr addr, u16 data) {
+bool TestEnvironment::TestMemory::Write16(VAddr addr, u16 data) {
     env->write_records.emplace_back(16, addr, data);
     if (env->mutable_memory)
         env->SetMemory16(addr, data);
+    return true;
 }
 
-void TestEnvironment::TestMemory::Write32(VAddr addr, u32 data) {
+bool TestEnvironment::TestMemory::Write32(VAddr addr, u32 data) {
     env->write_records.emplace_back(32, addr, data);
     if (env->mutable_memory)
         env->SetMemory32(addr, data);
+    return true;
 }
 
-void TestEnvironment::TestMemory::Write64(VAddr addr, u64 data) {
+bool TestEnvironment::TestMemory::Write64(VAddr addr, u64 data) {
     env->write_records.emplace_back(64, addr, data);
     if (env->mutable_memory)
         env->SetMemory64(addr, data);
+    return true;
 }
 
 bool TestEnvironment::TestMemory::WriteBlock(VAddr dest_addr, const void* src_buffer, size_t size) {
diff --git a/src/tests/core/arm/arm_test_common.h b/src/tests/core/arm/arm_test_common.h
index 592c28594..b66922d61 100644
--- a/src/tests/core/arm/arm_test_common.h
+++ b/src/tests/core/arm/arm_test_common.h
@@ -7,7 +7,7 @@
 #include <vector>
 
 #include "common/common_types.h"
-#include "core/mmio.h"
+#include "core/memory_hook.h"
 
 namespace ArmTests {
 
@@ -51,25 +51,25 @@ public:
 
 private:
     friend struct TestMemory;
-    struct TestMemory final : Memory::MMIORegion {
+    struct TestMemory final : Memory::MemoryHook {
         explicit TestMemory(TestEnvironment* env_) : env(env_) {}
         TestEnvironment* env;
 
         ~TestMemory() override;
 
-        bool IsValidAddress(VAddr addr) override;
+        boost::optional<bool> IsValidAddress(VAddr addr) override;
 
-        u8 Read8(VAddr addr) override;
-        u16 Read16(VAddr addr) override;
-        u32 Read32(VAddr addr) override;
-        u64 Read64(VAddr addr) override;
+        boost::optional<u8> Read8(VAddr addr) override;
+        boost::optional<u16> Read16(VAddr addr) override;
+        boost::optional<u32> Read32(VAddr addr) override;
+        boost::optional<u64> Read64(VAddr addr) override;
 
         bool ReadBlock(VAddr src_addr, void* dest_buffer, size_t size) override;
 
-        void Write8(VAddr addr, u8 data) override;
-        void Write16(VAddr addr, u16 data) override;
-        void Write32(VAddr addr, u32 data) override;
-        void Write64(VAddr addr, u64 data) override;
+        bool Write8(VAddr addr, u8 data) override;
+        bool Write16(VAddr addr, u16 data) override;
+        bool Write32(VAddr addr, u32 data) override;
+        bool Write64(VAddr addr, u64 data) override;
 
         bool WriteBlock(VAddr dest_addr, const void* src_buffer, size_t size) override;
 
diff --git a/src/video_core/renderer_opengl/renderer_opengl.cpp b/src/video_core/renderer_opengl/renderer_opengl.cpp
index 50396b5c1..8c23128ae 100644
--- a/src/video_core/renderer_opengl/renderer_opengl.cpp
+++ b/src/video_core/renderer_opengl/renderer_opengl.cpp
@@ -266,7 +266,7 @@ void RendererOpenGL::LoadFBToScreenInfo(const FramebufferInfo& framebuffer_info,
     screen_info.display_texture = screen_info.texture.resource.handle;
     screen_info.display_texcoords = MathUtil::Rectangle<float>(0.f, 0.f, 1.f, 1.f);
 
-    Memory::RasterizerFlushRegion(framebuffer_info.address, size_in_bytes);
+    // Memory::RasterizerFlushRegion(framebuffer_info.address, size_in_bytes);
 
     state.texture_units[0].texture_2d = screen_info.texture.resource.handle;
     state.Apply();