Reuse SVM storage on writeBuffer call.

- Instead of creating new allocation, look if it already exists if so
re-use it.

Change-Id: I23bc4ac8b8e59e96fce7d48546b76289bedc157f
Signed-off-by: Michal Mrozek <michal.mrozek@intel.com>

runtime/command_queue/enqueue_write_buffer.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2017-2019 Intel Corporation
+ * Copyright (C) 2017-2020 Intel Corporation
  *
  * SPDX-License-Identifier: MIT
  *
@@ -7,6 +7,7 @@
 
 #pragma once
 #include "core/helpers/string.h"
+#include "core/memory_manager/unified_memory_manager.h"
 #include "runtime/built_ins/built_ins.h"
 #include "runtime/command_queue/command_queue_hw.h"
 #include "runtime/command_stream/command_stream_receiver.h"
@@ -65,6 +66,14 @@ cl_int CommandQueueHw<GfxFamily>::enqueueWriteBuffer(
     GeneralSurface mapSurface;
     Surface *surfaces[] = {&bufferSurf, nullptr};
 
+    //check if we are dealing with SVM pointer here for which we already have an allocation
+    if (!mapAllocation && this->getContext().getSVMAllocsManager()) {
+        auto svmEntry = this->getContext().getSVMAllocsManager()->getSVMAlloc(ptr);
+        if (svmEntry) {
+            mapAllocation = svmEntry->cpuAllocation ? svmEntry->cpuAllocation : svmEntry->gpuAllocation;
+        }
+    }
+
     if (mapAllocation) {
         surfaces[1] = &mapSurface;
         mapSurface.setGraphicsAllocation(mapAllocation);