add memdev backend infrastructure

Provides framework for splitting host RAM allocation/
policies into a separate backend that could be used
by devices.

Initially only legacy RAM backend is provided, which
uses memory_region_init_ram() allocator and compatible
with every CLI option that affects memory_region_init_ram().

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/sysemu/hostmem.h

@@ -0,0 +1,60 @@
+/*
+ * QEMU Host Memory Backend
+ *
+ * Copyright (C) 2013-2014 Red Hat Inc
+ *
+ * Authors:
+ *   Igor Mammedov <imammedo@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#ifndef QEMU_RAM_H
+#define QEMU_RAM_H
+
+#include "qom/object.h"
+#include "qapi/error.h"
+#include "exec/memory.h"
+#include "qemu/option.h"
+
+#define TYPE_MEMORY_BACKEND "memory-backend"
+#define MEMORY_BACKEND(obj) \
+    OBJECT_CHECK(HostMemoryBackend, (obj), TYPE_MEMORY_BACKEND)
+#define MEMORY_BACKEND_GET_CLASS(obj) \
+    OBJECT_GET_CLASS(HostMemoryBackendClass, (obj), TYPE_MEMORY_BACKEND)
+#define MEMORY_BACKEND_CLASS(klass) \
+    OBJECT_CLASS_CHECK(HostMemoryBackendClass, (klass), TYPE_MEMORY_BACKEND)
+
+typedef struct HostMemoryBackend HostMemoryBackend;
+typedef struct HostMemoryBackendClass HostMemoryBackendClass;
+
+/**
+ * HostMemoryBackendClass:
+ * @parent_class: opaque parent class container
+ */
+struct HostMemoryBackendClass {
+    ObjectClass parent_class;
+};
+
+/**
+ * @HostMemoryBackend
+ *
+ * @parent: opaque parent object container
+ * @size: amount of memory backend provides
+ * @id: unique identification string in memdev namespace
+ * @mr: MemoryRegion representing host memory belonging to backend
+ */
+struct HostMemoryBackend {
+    /* private */
+    Object parent;
+
+    /* protected */
+    uint64_t size;
+
+    MemoryRegion mr;
+};
+
+MemoryRegion *host_memory_backend_get_memory(HostMemoryBackend *backend,
+                                             Error **errp);
+
+#endif