oops

Yxzx presumes this:
// The NVN driver buffer (index 0) is known to pack the SSBO address followed by its size.
But in MCI i`ve discovered that there are no sizes, both registers are GPU addresses (hence the 2.8gb allocation, it was an address actually)

Method could be much simpler but for safety i`ve routed both old and new worlds.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3206
Reviewed-by: Caio Oliveira <caiooliveirafarias0@gmail.com>
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Co-authored-by: xbzk <xbzk@eden-emu.dev>
Co-committed-by: xbzk <xbzk@eden-emu.dev>

src/common/host_memory.cpp

@@ -219,11 +219,6 @@ 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();
@@ -617,24 +612,6 @@ public:
         ASSERT_MSG(ret == 0, "mprotect failed: {}", strerror(errno));
     }
 
-    bool ClearBackingRegion(size_t physical_offset, size_t length) {
-#ifdef __linux__
-        // Only incur syscall cost IF memset would be slower (theshold = 16MiB)
-        // TODO(lizzie): Smarter way to dynamically get this threshold (broadwell != raptor lake) for example
-        if (length >= 2097152UL * 8) {
-            // 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;
-        }
-#else
-        return false;
-#endif
-    }
-
     void EnableDirectMappedAddress() {
         virtual_base = nullptr;
     }
@@ -762,9 +739,7 @@ void HostMemory::Protect(size_t virtual_offset, size_t length, MemoryPermission
 }
 
 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);
-        std::memset(backing_base + physical_offset, fill_value, length);
-    }
 }
 
 void HostMemory::EnableDirectMappedAddress() {

src/video_core/buffer_cache/buffer_cache.h

@@ -1705,21 +1705,26 @@ Binding BufferCache<P>::StorageBufferBinding(GPUVAddr ssbo_addr, u32 cbuf_index,
         return NULL_BINDING;
     }
 
+    // xbzk: New size logic. Fixes MCI.
+    // If ever the * comment below prove wrong, the 'if' block may be removed.
     const auto size = [&]() {
         const bool is_nvn_cbuf = cbuf_index == 0;
-        // The NVN driver buffer (index 0) is known to pack the SSBO address followed by its size.
         if (is_nvn_cbuf) {
-            const u32 ssbo_size = gpu_memory->Read<u32>(ssbo_addr + 8);
+            // * The NVN driver buffer (index 0) is known to pack the SSBO address followed by its size.
-            if (ssbo_size != 0) {
+            const u64 next_qword = gpu_memory->Read<u64>(ssbo_addr + 8);
-                return ssbo_size;
+            const u32 upper_32 = static_cast<u32>(next_qword >> 32);
+            // Hardware-based detection: GPU addresses have non-zero upper bits
+            if (upper_32 == 0) {
+                // This is a size field, not a GPU address
+                return static_cast<u32>(next_qword);  // Return lower_32
             }
         }
-        // Other titles (notably Doom Eternal) may use STG/LDG on buffer addresses in custom defined
+        // Fall through: either not NVN cbuf (Doom Eternal & +), or NVN but ssbo_addr+8 is a GPU address (MCI)
-        // cbufs, which do not store the sizes adjacent to the addresses, so use the fully
-        // mapped buffer size for now.
         const u32 memory_layout_size = static_cast<u32>(gpu_memory->GetMemoryLayoutSize(gpu_addr));
+        // Cap at 8MB to prevent allocator overflow from misinterpreted addresses
         return (std::min)(memory_layout_size, static_cast<u32>(8_MiB));
     }();
+
     // Alignment only applies to the offset of the buffer
     const u32 alignment = runtime.GetStorageBufferAlignment();
     const GPUVAddr aligned_gpu_addr = Common::AlignDown(gpu_addr, alignment);