From 72c794025973a56d491a2a275960bf7be55ab009 Mon Sep 17 00:00:00 2001
From: DH <dh.rpcs3@gmail.com>
Date: Sun, 6 Aug 2023 17:18:40 +0300
Subject: [PATCH] [bridge] implement lazy cache lock

---
 hw/amdgpu/bridge/include/amdgpu/bridge/bridge.hpp |  2 ++
 rpcsx-os/main.cpp                                 | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/hw/amdgpu/bridge/include/amdgpu/bridge/bridge.hpp b/hw/amdgpu/bridge/include/amdgpu/bridge/bridge.hpp
index e8e8852b6..8e8642981 100644
--- a/hw/amdgpu/bridge/include/amdgpu/bridge/bridge.hpp
+++ b/hw/amdgpu/bridge/include/amdgpu/bridge/bridge.hpp
@@ -45,6 +45,7 @@ enum {
   kPageWriteWatch = 1 << 0,
   kPageReadWriteLock = 1 << 1,
   kPageInvalidated = 1 << 2,
+  kPageLazyLock = 1 << 3
 };
 
 static constexpr auto kHostPageSize = 0x1000;
@@ -71,6 +72,7 @@ struct BridgeHeader {
   // orbis::shared_mutex cacheCommandMtx;
   // orbis::shared_cv cacheCommandCv;
   std::atomic<std::uint64_t> cacheCommands[4];
+  std::atomic<std::uint32_t> gpuCacheCommand;
   std::atomic<std::uint8_t> cachePages[0x100'0000'0000 / kHostPageSize];
 
   volatile std::uint64_t pull;
diff --git a/rpcsx-os/main.cpp b/rpcsx-os/main.cpp
index f69cb679e..89b8c5402 100644
--- a/rpcsx-os/main.cpp
+++ b/rpcsx-os/main.cpp
@@ -66,6 +66,18 @@ handle_signal(int sig, siginfo_t *info, void *ucontext) {
         auto flags = bridge->cachePages[page].load(std::memory_order::relaxed);
 
         if ((flags & amdgpu::bridge::kPageReadWriteLock) != 0) {
+          if ((flags & amdgpu::bridge::kPageLazyLock) != 0) {
+            if (std::uint32_t gpuCommand = 0;
+                !bridge->gpuCacheCommand.compare_exchange_weak(gpuCommand,
+                                                               page)) {
+              continue;
+            }
+
+            while (!bridge->cachePages[page].compare_exchange_weak(
+                flags, flags & ~amdgpu::bridge::kPageLazyLock,
+                std::memory_order::relaxed)) {
+            }
+          }
           continue;
         }