Merge pull request #5485 from Sonicadvance1/150

Windows: Setup `tu_override_uncached_as_cache_coherent` inside of dlls

Source/Windows/ARM64EC/Module.cpp

@@ -28,6 +28,7 @@ $end_info$
 #include <FEXCore/Utils/SignalScopeGuards.h>
 
 #include "Windows/Common/Allocator.h"
+#include "Windows/Common/EnvironmentVariablesHandling.h"
 #include "Common/CallRetStack.h"
 #include "Common/JITGuardPage.h"
 #include "Common/Config.h"
@@ -595,6 +596,8 @@ NTSTATUS ProcessInit() {
   const bool IsWine = !!GetProcAddress(NtDll, "wine_get_version");
   OvercommitTracker.emplace(IsWine);
 
+  FEX::Windows::SetupEnvironmentVariableValues(NtDll);
+
   FEX::Windows::Allocator::SetupHooks(NtDll);
 
   {

Source/Windows/Common/CMakeLists.txt

@@ -9,6 +9,7 @@ target_include_directories(CommonWindowsRuntime PRIVATE "${CMAKE_SOURCE_DIR}/Sou
 add_library(CommonWindows STATIC
   Allocator.cpp
   CPUFeatures.cpp
+  EnvironmentVariablesHandling.cpp
   SHMStats.cpp
   InvalidationTracker.cpp
   ImageTracker.cpp

Source/Windows/Common/EnvironmentVariablesHandling.cpp

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: MIT
+#include <libloaderapi.h>
+#include <stdlib.h>
+#include <winternl.h>
+#include <wine/unixlib.h>
+
+namespace FEX::Windows {
+void SetupEnvironmentVariableValues(HMODULE NtDll) {
+  auto Sym = GetProcAddress(NtDll, "__wine_set_unix_env");
+
+  // On an ARM system we are expecting uncached memory to have marked overhead due to atomic memory usage.
+  // If `tu_override_uncached_as_cache_coherent` isn't already controlled by the user, then set it here.
+  // This lets the `turnip` mesa driver allocate uncached memory types as cached coherent instead if the hardware supports it.
+  //
+  // The only downside for this approach is that the GPU /may/ need to snoop CPU cachelines which could add some additional load
+  // on to the GPU side, but is unlikely to matter due to x86 emulation using excessive load-acquire/store-release semantic memory operations.
+  //
+  // Other UMA ARM platforms will run in to the same problem, with their own workarounds:
+  // - NVIDIA Tegra/Spark: Their proprietary driver always maps uncached as cached-coherent.
+  // - Windows Snapdragon: Same as Tegra
+  // - Asahi,Mali,PowerVR,Exynos,etc: Unknown behaviour
+  //
+  // This `__wine_set_unix_env` path may also not be long-term viable.
+  // Make sure to communicate with the Wine/Proton people if this interface is expected to change!
+  // A /possible/ workaround for Proton would be to set the environment variable in the launch script.
+  // - That would have the downside that arm64 native Windows applications would get workaround set, which isn't strictly necessary.
+  if (Sym && getenv("tu_override_uncached_as_cache_coherent") == nullptr) {
+    auto WineSetEnv = reinterpret_cast<decltype(__wine_set_unix_env)>(Sym);
+    WineSetEnv("tu_override_uncached_as_cache_coherent", "true");
+  }
+}
+} // namespace FEX::Windows

Source/Windows/Common/EnvironmentVariablesHandling.h

@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: MIT
+#pragma once
+#include <winternl.h>
+
+namespace FEX::Windows {
+void SetupEnvironmentVariableValues(HMODULE NtDll);
+}

Source/Windows/WOW64/Module.cpp

@@ -29,6 +29,7 @@ $end_info$
 #include <FEXCore/Utils/SignalScopeGuards.h>
 
 #include "Windows/Common/Allocator.h"
+#include "Windows/Common/EnvironmentVariablesHandling.h"
 #include "Common/CallRetStack.h"
 #include "Common/JITGuardPage.h"
 #include "Common/Config.h"
@@ -563,6 +564,8 @@ void BTCpuProcessInit() {
     WineUnixCall = *reinterpret_cast<decltype(WineUnixCall)*>(Sym);
   }
 
+  FEX::Windows::SetupEnvironmentVariableValues(NtDll);
+
   // wow64.dll will only initialise the cross-process queue if this is set
   GetTLS().Wow64Info().CpuFlags = WOW64_CPUFLAGS_SOFTWARE;
 

Source/Windows/include/wine/unixlib.h

@@ -11,6 +11,8 @@ extern "C" {
 
 typedef UINT64 unixlib_handle_t;
 
+extern NTSTATUS(WINAPI* __wine_set_unix_env)(const char*, const char*);
+
 extern NTSTATUS(WINAPI* __wine_unix_call_dispatcher)(unixlib_handle_t, unsigned int, void*);
 
 static inline NTSTATUS __wine_unix_call(unixlib_handle_t handle, unsigned int code, void* args) {