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>

backends/Makefile.objs

@@ -6,3 +6,5 @@ common-obj-$(CONFIG_BRLAPI) += baum.o
 baum.o-cflags := $(SDL_CFLAGS)
 
 common-obj-$(CONFIG_TPM) += tpm.o
+
+common-obj-y += hostmem.o hostmem-ram.o

backends/hostmem-ram.c

@@ -0,0 +1,54 @@
+/*
+ * 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.
+ */
+#include "sysemu/hostmem.h"
+#include "qom/object_interfaces.h"
+
+#define TYPE_MEMORY_BACKEND_RAM "memory-backend-ram"
+
+
+static void
+ram_backend_memory_init(UserCreatable *uc, Error **errp)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(uc);
+    char *path;
+
+    if (!backend->size) {
+        error_setg(errp, "can't create backend with size 0");
+        return;
+    }
+
+    path = object_get_canonical_path_component(OBJECT(backend));
+    memory_region_init_ram(&backend->mr, OBJECT(backend), path,
+                           backend->size);
+    g_free(path);
+}
+
+static void
+ram_backend_class_init(ObjectClass *oc, void *data)
+{
+    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
+
+    ucc->complete = ram_backend_memory_init;
+}
+
+static const TypeInfo ram_backend_info = {
+    .name = TYPE_MEMORY_BACKEND_RAM,
+    .parent = TYPE_MEMORY_BACKEND,
+    .class_init = ram_backend_class_init,
+};
+
+static void register_types(void)
+{
+    type_register_static(&ram_backend_info);
+}
+
+type_init(register_types);

backends/hostmem.c

@@ -0,0 +1,97 @@
+/*
+ * 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.
+ */
+#include "sysemu/hostmem.h"
+#include "sysemu/sysemu.h"
+#include "qapi/visitor.h"
+#include "qapi/qmp/qerror.h"
+#include "qemu/config-file.h"
+#include "qom/object_interfaces.h"
+
+static void
+hostmemory_backend_get_size(Object *obj, Visitor *v, void *opaque,
+                            const char *name, Error **errp)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+    uint64_t value = backend->size;
+
+    visit_type_size(v, &value, name, errp);
+}
+
+static void
+hostmemory_backend_set_size(Object *obj, Visitor *v, void *opaque,
+                            const char *name, Error **errp)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+    Error *local_err = NULL;
+    uint64_t value;
+
+    if (memory_region_size(&backend->mr)) {
+        error_setg(&local_err, "cannot change property value");
+        goto out;
+    }
+
+    visit_type_size(v, &value, name, &local_err);
+    if (local_err) {
+        goto out;
+    }
+    if (!value) {
+        error_setg(&local_err, "Property '%s.%s' doesn't take value '%"
+                   PRIu64 "'", object_get_typename(obj), name, value);
+        goto out;
+    }
+    backend->size = value;
+out:
+    error_propagate(errp, local_err);
+}
+
+static void hostmemory_backend_init(Object *obj)
+{
+    object_property_add(obj, "size", "int",
+                        hostmemory_backend_get_size,
+                        hostmemory_backend_set_size, NULL, NULL, NULL);
+}
+
+static void hostmemory_backend_finalize(Object *obj)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+
+    if (memory_region_size(&backend->mr)) {
+        memory_region_destroy(&backend->mr);
+    }
+}
+
+MemoryRegion *
+host_memory_backend_get_memory(HostMemoryBackend *backend, Error **errp)
+{
+    return memory_region_size(&backend->mr) ? &backend->mr : NULL;
+}
+
+static const TypeInfo hostmemory_backend_info = {
+    .name = TYPE_MEMORY_BACKEND,
+    .parent = TYPE_OBJECT,
+    .abstract = true,
+    .class_size = sizeof(HostMemoryBackendClass),
+    .instance_size = sizeof(HostMemoryBackend),
+    .instance_init = hostmemory_backend_init,
+    .instance_finalize = hostmemory_backend_finalize,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_USER_CREATABLE },
+        { }
+    }
+};
+
+static void register_types(void)
+{
+    type_register_static(&hostmemory_backend_info);
+}
+
+type_init(register_types);

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