[dxvk] Add option to clear mapped memory regions to zero

dxvk.conf

@@ -267,6 +267,15 @@
 # d3d11.zeroWorkgroupMemory = False
 
 
+# Clears mapped memory to zero when suballocated memory is freed. This will
+# drastically increase CPU overhead and should only be used as a last resort
+# if a game does not properly initialize mapped buffers on its own.
+#
+# Supported values: True, False
+
+# dxvk.zeroMappedMemory = False
+
+
 # Resource size limit for implicit discards, in kilobytes. For small staging
 # resources mapped with MAP_WRITE, DXVK will sometimes allocate new backing
 # storage in order to avoid GPU synchronization, so setting this too high

src/dxvk/dxvk_memory.cpp

@@ -2,6 +2,8 @@
 #include <iomanip>
 #include <sstream>
 
+#include "../util/util_bit.h"
+
 #include "dxvk_device.h"
 #include "dxvk_memory.h"
 #include "dxvk_sparse.h"
@@ -1254,9 +1256,17 @@ namespace dxvk {
     allocation->m_address = address;
     allocation->m_size = size;
 
-    if (chunk.memory.mapPtr)
+    if (chunk.memory.mapPtr) {
       allocation->m_mapPtr = reinterpret_cast<char*>(chunk.memory.mapPtr) + offset;
 
+      if (unlikely(m_device->config().zeroMappedMemory)) {
+        // Some games will not write mapped buffers and will break if
+        // there is any stale data stored within. Clear when the allocation is
+        // freed, so that subsequent allocations will receive cleared buffers.
+        allocation->m_flags.set(DxvkAllocationFlag::ClearOnFree);
+      }
+    }
+
     if (chunk.memory.buffer) {
       allocation->m_buffer = chunk.memory.buffer;
       allocation->m_bufferOffset = offset;
@@ -1322,6 +1332,11 @@ namespace dxvk {
 
   void DxvkMemoryAllocator::freeAllocation(
           DxvkResourceAllocation* allocation) {
+    if (allocation->m_flags.test(DxvkAllocationFlag::ClearOnFree)) {
+      if (allocation->m_mapPtr)
+        bit::bclear(allocation->m_mapPtr, allocation->m_size);
+    }
+
     if (allocation->m_flags.test(DxvkAllocationFlag::CanCache)) {
       // Return cacheable allocations to the shared cache
       allocation->destroyBufferViews();
@@ -1523,6 +1538,9 @@ namespace dxvk {
           "\n  size: ", memory.size, " bytes"));
       }
 
+      if (m_device->config().zeroMappedMemory)
+        bit::bclear(memory.mapPtr, memory.size);
+
       Logger::debug(str::format("Mapped memory region 0x", std::hex,
         reinterpret_cast<uintptr_t>(memory.mapPtr), " - 0x",
         reinterpret_cast<uintptr_t>(memory.mapPtr) + memory.size - 1u));

src/dxvk/dxvk_memory.h

@@ -465,12 +465,23 @@ namespace dxvk {
    * \brief Resource allocation flags
    */
   enum class DxvkAllocationFlag : uint32_t {
+    /// Allocation owns the given VkDeviceMemory allocation
+    /// and is not suballocated from an existing chunk.
     OwnsMemory  = 0,
+    /// Allocation owns a dedicated VkBuffer object rather
+    /// than the global buffer for the parent chunk, if any.
     OwnsBuffer  = 1,
+    /// Allocation owns a VkImage object.
     OwnsImage   = 2,
+    /// Allocation can use an allocation cache.
     CanCache    = 3,
+    /// Allocation can be relocated for defragmentation.
     CanMove     = 4,
+    /// Allocation is imported from an external API.
     Imported    = 5,
+    /// Memory must be cleared to zero when the allocation
+    /// is freed. Only used to work around app bugs.
+    ClearOnFree = 6,
   };
 
   using DxvkAllocationFlags = Flags<DxvkAllocationFlag>;

src/dxvk/dxvk_options.cpp

@@ -13,6 +13,7 @@ namespace dxvk {
     hud                   = config.getOption<std::string>("dxvk.hud", "");
     tearFree              = config.getOption<Tristate>("dxvk.tearFree",               Tristate::Auto);
     hideIntegratedGraphics = config.getOption<bool>   ("dxvk.hideIntegratedGraphics", false);
+    zeroMappedMemory      = config.getOption<bool>    ("dxvk.zeroMappedMemory",       false);
     deviceFilter          = config.getOption<std::string>("dxvk.deviceFilter",        "");
   }
 

src/dxvk/dxvk_options.h

@@ -42,6 +42,9 @@ namespace dxvk {
     // incorrectly assume monitor layouts.
     bool hideIntegratedGraphics = false;
 
+    /// Clears all mapped memory to zero.
+    bool zeroMappedMemory = false;
+
     // Device name
     std::string deviceFilter;
   };