From 15a47d10ae9913bb74a58827e8580f9c4822da32 Mon Sep 17 00:00:00 2001
From: squidbus <175574877+squidbus@users.noreply.github.com>
Date: Sat, 15 Feb 2025 21:53:15 -0800
Subject: [PATCH] buffer_cache: Prevent false image-to-buffer sync.

Lowering vertex fetch to formatted buffer surfaced an issue where a CPU modified range may be overwritten with stale GPU modified image data.
---
 src/video_core/buffer_cache/buffer_cache.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/video_core/buffer_cache/buffer_cache.cpp b/src/video_core/buffer_cache/buffer_cache.cpp
index ccb45c095..7eb4ea9e1 100644
--- a/src/video_core/buffer_cache/buffer_cache.cpp
+++ b/src/video_core/buffer_cache/buffer_cache.cpp
@@ -608,7 +608,11 @@ bool BufferCache::SynchronizeBufferFromImage(Buffer& buffer, VAddr device_addr,
         return false;
     }
     Image& image = texture_cache.GetImage(image_id);
-    if (False(image.flags & ImageFlagBits::GpuModified)) {
+    // Only perform sync if image is:
+    // - GPU modified; otherwise there are no changes to synchronize.
+    // - Not CPU modified; otherwise we could overwrite CPU changes with stale GPU changes.
+    if (False(image.flags & ImageFlagBits::GpuModified) ||
+        True(image.flags & ImageFlagBits::CpuDirty)) {
         return false;
     }
     ASSERT_MSG(device_addr == image.info.guest_address,