From ba37f327b05d94fc5a23ec57d227b16f45915319 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Tue, 29 Sep 2026 13:16:59 -0600
Subject: [PATCH] D3D11: Check Map() results

Map fails after device removal, leaving pData garbage. Skip the upload or
draw instead of writing through it.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
---
 GPU/D3D11/D3D11Util.h            | 15 +++++++++++++--
 GPU/D3D11/DrawEngineD3D11.cpp    | 12 ++++++++++++
 GPU/D3D11/ShaderManagerD3D11.cpp | 15 +++++++++------
 3 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/GPU/D3D11/D3D11Util.h b/GPU/D3D11/D3D11Util.h
index cae9399142..4a749e2b66 100644
--- a/GPU/D3D11/D3D11Util.h
+++ b/GPU/D3D11/D3D11Util.h
@@ -46,7 +46,11 @@ public:
 		nextMapDiscard_ = true;
 	}
 
+	// Returns null if the buffer can't be mapped (after device removal, for example). Skip the draw then.
 	uint8_t *BeginPush(ID3D11DeviceContext *context, UINT *offset, size_t size, int align = 16) {
+		if (!buffer_) {
+			return nullptr;
+		}
 		D3D11_MAPPED_SUBRESOURCE map;
 		pos_ = (pos_ + align - 1) & ~(align - 1);
 		if (pos_ + size > size_) {
@@ -55,7 +59,10 @@ public:
 			pos_ = 0;
 			nextMapDiscard_ = true;
 		}
-		context->Map(buffer_.Get(), 0, nextMapDiscard_ ? D3D11_MAP_WRITE_DISCARD : D3D11_MAP_WRITE_NO_OVERWRITE, 0, &map);
+		if (FAILED(context->Map(buffer_.Get(), 0, nextMapDiscard_ ? D3D11_MAP_WRITE_DISCARD : D3D11_MAP_WRITE_NO_OVERWRITE, 0, &map))) {
+			return nullptr;
+		}
+		mapped_ = true;
 		nextMapDiscard_ = false;
 		*offset = (UINT)pos_;
 		uint8_t *retval = (uint8_t *)map.pData + pos_;
@@ -63,7 +70,10 @@ public:
 		return retval;
 	}
 	void EndPush(ID3D11DeviceContext *context) {
-		context->Unmap(buffer_.Get(), 0);
+		if (mapped_) {
+			context->Unmap(buffer_.Get(), 0);
+			mapped_ = false;
+		}
 	}
 
 private:
@@ -71,6 +81,7 @@ private:
 	size_t pos_ = 0;
 	size_t size_;
 	bool nextMapDiscard_ = false;
+	bool mapped_ = false;
 };
 
 std::vector<uint8_t> CompileShaderToBytecodeD3D11(const char *code, size_t codeSize, const char *target, UINT flags, std::string *errorMessage = nullptr);
diff --git a/GPU/D3D11/DrawEngineD3D11.cpp b/GPU/D3D11/DrawEngineD3D11.cpp
index 576a803513..a75fd7ab9e 100644
--- a/GPU/D3D11/DrawEngineD3D11.cpp
+++ b/GPU/D3D11/DrawEngineD3D11.cpp
@@ -358,6 +358,9 @@ void DrawEngineD3D11::Flush() {
 			UINT vOffset;
 			int vSize = numDecodedVerts_ * dec_->GetDecVtxFmt().stride;
 			uint8_t *vptr = pushVerts_->BeginPush(context_, &vOffset, vSize);
+			if (!vptr) {
+				goto bail;
+			}
 			memcpy(vptr, decoded_, vSize);
 			pushVerts_->EndPush(context_);
 			ID3D11Buffer *buf = pushVerts_->Buf();
@@ -366,6 +369,9 @@ void DrawEngineD3D11::Flush() {
 				UINT iOffset;
 				int iSize = 2 * vertexCount;
 				uint8_t *iptr = pushInds_->BeginPush(context_, &iOffset, iSize);
+				if (!iptr) {
+					goto bail;
+				}
 				memcpy(iptr, decIndex_, iSize);
 				pushInds_->EndPush(context_);
 				context_->IASetIndexBuffer(pushInds_->Buf(), DXGI_FORMAT_R16_UINT, iOffset);
@@ -477,6 +483,9 @@ void DrawEngineD3D11::Flush() {
 			UINT vOffset = 0;
 			int vSize = result.drawVertexCount * stride;
 			uint8_t *vptr = pushVerts_->BeginPush(context_, &vOffset, vSize);
+			if (!vptr) {
+				goto bail;
+			}
 			memcpy(vptr, result.drawBuffer, vSize);
 			pushVerts_->EndPush(context_);
 			ID3D11Buffer *buf = pushVerts_->Buf();
@@ -484,6 +493,9 @@ void DrawEngineD3D11::Flush() {
 			UINT iOffset;
 			int iSize = sizeof(uint16_t) * result.drawIndexCount;
 			uint8_t *iptr = pushInds_->BeginPush(context_, &iOffset, iSize);
+			if (!iptr) {
+				goto bail;
+			}
 			memcpy(iptr, inds, iSize);
 			pushInds_->EndPush(context_);
 			context_->IASetIndexBuffer(pushInds_->Buf(), DXGI_FORMAT_R16_UINT, iOffset);
diff --git a/GPU/D3D11/ShaderManagerD3D11.cpp b/GPU/D3D11/ShaderManagerD3D11.cpp
index 46584a3ca4..d7e3b94300 100644
--- a/GPU/D3D11/ShaderManagerD3D11.cpp
+++ b/GPU/D3D11/ShaderManagerD3D11.cpp
@@ -147,15 +147,18 @@ uint64_t ShaderManagerD3D11::UpdateUniforms(bool useBufferedRendering, bool pixe
 		D3D11_MAPPED_SUBRESOURCE map;
 		if (dirty & DIRTY_BASE_UNIFORMS) {
 			BaseUpdateUniforms(&ub_base, dirty, useBufferedRendering, pixelMapped);
-			context_->Map(push_base.Get(), 0, D3D11_MAP_WRITE_DISCARD, 0, &map);
-			memcpy(map.pData, &ub_base, sizeof(ub_base));
-			context_->Unmap(push_base.Get(), 0);
+			// Map fails after device removal, and map.pData is garbage then.
+			if (SUCCEEDED(context_->Map(push_base.Get(), 0, D3D11_MAP_WRITE_DISCARD, 0, &map))) {
+				memcpy(map.pData, &ub_base, sizeof(ub_base));
+				context_->Unmap(push_base.Get(), 0);
+			}
 		}
 		if (dirty & DIRTY_LIGHT_UNIFORMS) {
 			LightUpdateUniforms(&ub_lights, dirty);
-			context_->Map(push_lights.Get(), 0, D3D11_MAP_WRITE_DISCARD, 0, &map);
-			memcpy(map.pData, &ub_lights, sizeof(ub_lights));
-			context_->Unmap(push_lights.Get(), 0);
+			if (SUCCEEDED(context_->Map(push_lights.Get(), 0, D3D11_MAP_WRITE_DISCARD, 0, &map))) {
+				memcpy(map.pData, &ub_lights, sizeof(ub_lights));
+				context_->Unmap(push_lights.Get(), 0);
+			}
 		}
 	}
 	gstate_c.CleanUniforms();