4 files changed, 47 insertions, 15 deletions

diff --git a/src/common/host_memory.cpp b/src/common/host_memory.cpp
index 4bfc64f2d..e540375b8 100644
--- a/src/common/host_memory.cpp
+++ b/src/common/host_memory.cpp
@@ -11,10 +11,6 @@
 
 #elif defined(__linux__) || defined(__FreeBSD__) // ^^^ Windows ^^^ vvv Linux vvv
 
-#ifdef ANDROID
-#include <android/sharedmem.h>
-#endif
-
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE
 #endif
@@ -193,6 +189,11 @@ public:
         }
     }
 
+    bool ClearBackingRegion(size_t physical_offset, size_t length) {
+        // TODO: This does not seem to be possible on Windows.
+        return false;
+    }
+
     void EnableDirectMappedAddress() {
         // TODO
         UNREACHABLE();
@@ -442,9 +443,7 @@ public:
         }
 
         // Backing memory initialization
-#ifdef ANDROID
-        fd = ASharedMemory_create("HostMemory", backing_size);
-#elif defined(__FreeBSD__) && __FreeBSD__ < 13
+#if defined(__FreeBSD__) && __FreeBSD__ < 13
         // XXX Drop after FreeBSD 12.* reaches EOL on 2024-06-30
         fd = shm_open(SHM_ANON, O_RDWR, 0600);
 #else
@@ -455,7 +454,6 @@ public:
             throw std::bad_alloc{};
         }
 
-#ifndef ANDROID
         // Defined to extend the file with zeros
         int ret = ftruncate(fd, backing_size);
         if (ret != 0) {
@@ -463,7 +461,6 @@ public:
                          strerror(errno));
             throw std::bad_alloc{};
         }
-#endif
 
         backing_base = static_cast<u8*>(
             mmap(nullptr, backing_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
@@ -552,6 +549,19 @@ public:
         ASSERT_MSG(ret == 0, "mprotect failed: {}", strerror(errno));
     }
 
+    bool ClearBackingRegion(size_t physical_offset, size_t length) {
+#ifdef __linux__
+        // Set MADV_REMOVE on backing map to destroy it instantly.
+        // This also deletes the area from the backing file.
+        int ret = madvise(backing_base + physical_offset, length, MADV_REMOVE);
+        ASSERT_MSG(ret == 0, "madvise failed: {}", strerror(errno));
+
+        return true;
+#else
+        return false;
+#endif
+    }
+
     void EnableDirectMappedAddress() {
         virtual_base = nullptr;
     }
@@ -623,6 +633,10 @@ public:
 
     void Protect(size_t virtual_offset, size_t length, bool read, bool write, bool execute) {}
 
+    bool ClearBackingRegion(size_t physical_offset, size_t length) {
+        return false;
+    }
+
     void EnableDirectMappedAddress() {}
 
     u8* backing_base{nullptr};
@@ -698,6 +712,12 @@ void HostMemory::Protect(size_t virtual_offset, size_t length, bool read, bool w
     impl->Protect(virtual_offset + virtual_base_offset, length, read, write, execute);
 }
 
+void HostMemory::ClearBackingRegion(size_t physical_offset, size_t length, u32 fill_value) {
+    if (!impl || fill_value != 0 || !impl->ClearBackingRegion(physical_offset, length)) {
+        std::memset(backing_base + physical_offset, fill_value, length);
+    }
+}
+
 void HostMemory::EnableDirectMappedAddress() {
     if (impl) {
         impl->EnableDirectMappedAddress();
diff --git a/src/common/host_memory.h b/src/common/host_memory.h
index cebfacab2..747c5850c 100644
--- a/src/common/host_memory.h
+++ b/src/common/host_memory.h
@@ -48,6 +48,8 @@ public:
 
     void EnableDirectMappedAddress();
 
+    void ClearBackingRegion(size_t physical_offset, size_t length, u32 fill_value);
+
     [[nodiscard]] u8* BackingBasePointer() noexcept {
         return backing_base;
     }
diff --git a/src/common/settings.cpp b/src/common/settings.cpp
index 4666bd0a0..88f509ba7 100644
--- a/src/common/settings.cpp
+++ b/src/common/settings.cpp
@@ -160,12 +160,16 @@ static bool is_nce_enabled = false;
 
 void SetNceEnabled(bool is_39bit) {
     const bool is_nce_selected = values.cpu_backend.GetValue() == CpuBackend::Nce;
-    is_nce_enabled = IsFastmemEnabled() && is_nce_selected && is_39bit;
-    if (is_nce_selected && !is_nce_enabled) {
+    if (is_nce_selected && !IsFastmemEnabled()) {
+        LOG_WARNING(Common, "Fastmem is required to natively execute code in a performant manner, "
+                            "falling back to Dynarmic");
+    }
+    if (is_nce_selected && !is_39bit) {
         LOG_WARNING(
             Common,
             "Program does not utilize 39-bit address space, unable to natively execute code");
     }
+    is_nce_enabled = IsFastmemEnabled() && is_nce_selected && is_39bit;
 }
 
 bool IsNceEnabled() {
diff --git a/src/common/settings.h b/src/common/settings.h
index 98341ad96..7dc18fffe 100644
--- a/src/common/settings.h
+++ b/src/common/settings.h
@@ -180,14 +180,20 @@ struct Values {
                                              &use_speed_limit};
 
     // Cpu
-    SwitchableSetting<CpuBackend, true> cpu_backend{
-        linkage,         CpuBackend::Dynarmic, CpuBackend::Dynarmic,
+    SwitchableSetting<CpuBackend, true> cpu_backend{linkage,
 #ifdef HAS_NCE
-        CpuBackend::Nce,
+                                                    CpuBackend::Nce,
 #else
                                                     CpuBackend::Dynarmic,
 #endif
-        "cpu_backend",   Category::Cpu};
+                                                    CpuBackend::Dynarmic,
+#ifdef HAS_NCE
+                                                    CpuBackend::Nce,
+#else
+                                                    CpuBackend::Dynarmic,
+#endif
+                                                    "cpu_backend",
+                                                    Category::Cpu};
     SwitchableSetting<CpuAccuracy, true> cpu_accuracy{linkage,           CpuAccuracy::Auto,
                                                       CpuAccuracy::Auto, CpuAccuracy::Paranoid,
                                                       "cpu_accuracy",    Category::Cpu};