From 41a81ab5e3d88b53b634ed765385874728634e9f Mon Sep 17 00:00:00 2001
From: néo Luigi <85024393+neoluigi4123@users.noreply.github.com>
Date: Sat, 31 Oct 2026 20:08:24 +0100
Subject: Gpu buffer readback to cpu. Fixing visible glitches such as missing
 collision on some object, but can extend to more.

Assisted-by: Claude Opus 5.5 (debugging & implementation)
---
 src/video_core/buffer_cache/buffer_cache.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

(limited to 'src/video_core/buffer_cache/buffer_cache.h')

diff --git a/src/video_core/buffer_cache/buffer_cache.h b/src/video_core/buffer_cache/buffer_cache.h
index 42d7ba066d..e90af3214d 100644
--- a/src/video_core/buffer_cache/buffer_cache.h
+++ b/src/video_core/buffer_cache/buffer_cache.h
@@ -279,8 +279,10 @@ bool BufferCache<P>::DMACopy(GPUVAddr src_address, GPUVAddr dest_address, u64 am
         const DAddr diff = base_address - *cpu_src_address;
         const DAddr new_base_address = *cpu_dest_address + diff;
         tmp_intervals.push_back({new_base_address, size});
-        if (AsyncBufferDownloads()) {
+        if (DownloadsAtFence(new_base_address, size)) {
             uncommitted_gpu_modified_ranges.Add(new_base_address, size);
+        } else {
+            ArmReadTraps(new_base_address, size);
         }
     };
     gpu_modified_ranges.ForEachInRange(*cpu_src_address, amount, mirror);
@@ -1603,8 +1605,10 @@ void BufferCache<P>::MarkWrittenBuffer(BufferId buffer_id, DAddr device_addr, u3
     }
     memory_tracker.MarkRegionAsGpuModified(device_addr, size);
     gpu_modified_ranges.Add(device_addr, size);
-    if (AsyncBufferDownloads()) {
+    if (DownloadsAtFence(device_addr, size)) {
         uncommitted_gpu_modified_ranges.Add(device_addr, size);
+    } else {
+        ArmReadTraps(device_addr, size);
     }
 }
 
@@ -2090,6 +2094,8 @@ void BufferCache<P>::DeleteBuffer(BufferId buffer_id, bool do_not_mark) {
     if constexpr (requires { runtime.OnBufferDeleted(slot_buffers[buffer_id]); }) {
         runtime.OnBufferDeleted(slot_buffers[buffer_id]);
     }
+    read_trapped_ranges.Subtract(slot_buffers[buffer_id].CpuAddr(),
+                                 slot_buffers[buffer_id].SizeBytes());
     bool dirty_index{false};
     boost::container::small_vector<u64, NUM_VERTEX_BUFFERS> dirty_vertex_buffers;
     const auto scalar_replace = [buffer_id](Binding& binding) {
-- 
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