graphics: streamline staging-buffer writes

tests/ShaderRecompilerComputeTests.cpp

@@ -164,6 +164,13 @@ struct BufferCacheTestAccess {
     return cache.m_download_buffer;
   }
 
+  static void SetUnusedStagingBufferSize(BufferCache &cache, uint64_t size) {
+    // Called immediately after cache construction, before any staging reservation.
+    std::destroy_at(&cache.m_staging_buffer);
+    std::construct_at(&cache.m_staging_buffer, cache.m_graphics, cache.m_scheduler,
+                      MemoryUsage::Upload, size);
+  }
+
   static bool SynchronizeBufferFromImage(BufferCache &cache, Buffer &buffer,
                                          uint64_t address, uint64_t size) {
     return cache.SynchronizeBufferFromImage(buffer, address, size);
@@ -5109,6 +5116,67 @@ public:
     std::printf("[host]    %-32s ok\n", name);
   }
 
+  void CheckBdaPageTableUploads() {
+    constexpr const char *name = "BdaPageTableUploads";
+    constexpr uintptr_t base = 0x0000000207b00000ull;
+    constexpr uint64_t page = BufferCache::CACHING_PAGESIZE;
+    constexpr std::array<uint64_t, 3> page_counts{2, 521, 525};
+    constexpr uint64_t result_entries = page_counts[0] + page_counts[1] + page_counts[2];
+    EnsureRuntimeContext();
+    RenderContext context(m_runtime_context);
+    auto &scheduler = context.GetCommandScheduler();
+    HW::Context registers{};
+    HW::UserConfig user_config{};
+    HW::Shader shaders{};
+    scheduler.Begin(registers, user_config, shaders);
+    auto &cache = context.GetBufferCache();
+    // A small real ring exercises chunking and waits for same-command-buffer reuse.
+    BufferCacheTestAccess::SetUnusedStagingBufferSize(cache, 4096);
+    auto &table = *cache.GetBdaPageTableBuffer();
+    const auto table_offset = BufferCache::PageIndex(base) * sizeof(vk::DeviceAddress);
+    auto readback = CreateHostBuffer(name, result_entries * sizeof(vk::DeviceAddress),
+                                    vk::BufferUsageFlagBits::eTransferDst, {});
+    std::vector<uint64_t> expected;
+    expected.reserve(result_entries);
+    for (const auto pages : page_counts) {
+      // The destination has a preceding GPU write and, after the first iteration,
+      // a preceding read. Registration must preserve both ordering requirements.
+      table.Fill(table_offset, pages * sizeof(vk::DeviceAddress), 0xa5a5a5a5u);
+      const auto previous_tick = scheduler.CurrentTick();
+      const auto id = cache.FindBuffer(base, pages * page);
+      const auto &buffer = cache.GetBuffer(id);
+      const auto destination_offset = expected.size() * sizeof(vk::DeviceAddress);
+      for (uint64_t index = 0; index < pages; ++index) {
+        expected.push_back(buffer.BufferDeviceAddress() + index * page);
+      }
+      const vk::BufferCopy copy{table_offset, destination_offset,
+                                pages * sizeof(vk::DeviceAddress)};
+      scheduler.Current().Handle().copyBuffer(table.Handle(), readback.buffer, 1, &copy);
+      Require(name, "chunked registration",
+              buffer.CpuAddress() == base && buffer.Size() == pages * page &&
+                  (pages == page_counts.front() || scheduler.CurrentTick() > previous_tick),
+              "BDA registration failed to replace its owner or wait for staging-ring reuse");
+    }
+    vk::BufferMemoryBarrier barrier{};
+    barrier.srcAccessMask = vk::AccessFlagBits::eTransferWrite;
+    barrier.dstAccessMask = vk::AccessFlagBits::eHostRead;
+    barrier.srcQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;
+    barrier.dstQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;
+    barrier.buffer = readback.buffer;
+    barrier.size = readback.size;
+    scheduler.Current().Handle().pipelineBarrier(vk::PipelineStageFlagBits::eTransfer,
+        vk::PipelineStageFlagBits::eHost, {}, 0, nullptr, 1, &barrier, 0, nullptr);
+    scheduler.Finish();
+    const auto words = ReadBuffer(name, readback, result_entries * 2);
+    for (size_t index = 0; index < expected.size(); ++index) {
+      const auto actual = uint64_t{words[index * 2]} | (uint64_t{words[index * 2 + 1]} << 32);
+      Require(name, "GPU page-table snapshot", actual == expected[index],
+              "staged BDA updates were stale, overwritten before their read, or incompletely flushed");
+    }
+    DestroyBuffer(&readback);
+    std::printf("[gpu]     %-32s ok\n", name);
+  }
+
   void CheckUnifiedTextureCacheFlow() {
     constexpr const char *name = "UnifiedTextureCacheFlow";
     constexpr uintptr_t base = 0x0000000200600000ull;
@@ -41922,6 +41990,11 @@ int main(int argc, char **argv) {
     CheckDepthTargetFootprints();
     return 0;
   }
+  if (argc == 2 && std::strcmp(argv[1], "--bda-page-table-only") == 0) {
+    VulkanHarness vulkan;
+    vulkan.CheckBdaPageTableUploads();
+    return 0;
+  }
   if (argc == 2 && std::strcmp(argv[1], "--buffer-cache-range-only") == 0) {
     VulkanHarness vulkan;
     vulkan.CheckUnifiedTextureCacheFlow();
@@ -42123,6 +42196,7 @@ int main(int argc, char **argv) {
   vulkan.CheckGpuTilerCpuParity();
   vulkan.CheckNativeIndirectDispatch();
   CheckComputeLdsLimit(vulkan);
+  vulkan.CheckBdaPageTableUploads();
   vulkan.CheckUnifiedTextureCacheFlow();
   vulkan.CheckUnifiedImageViewCache();
   vulkan.CheckPackedTextureComponents();