machine: alias -mem-path and -mem-prealloc into memory-foo backend

Allow machine to opt in for hostmem backend based initial RAM
even if user uses old -mem-path/prealloc options by providing
  MachineClass::default_ram_id
Follow up patches will incrementally convert machines to new API,
by dropping memory_region_allocate_system_memory() and setting
default_ram_id that board used to use before conversion to keep
migration stream the same.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20200219160953.13771-4-imammedo@redhat.com>

backends/hostmem-file.c

@@ -18,13 +18,6 @@
 #include "sysemu/sysemu.h"
 #include "qom/object_interfaces.h"
 
-/* hostmem-file.c */
-/**
- * @TYPE_MEMORY_BACKEND_FILE:
- * name of backend that uses mmap on a file descriptor
- */
-#define TYPE_MEMORY_BACKEND_FILE "memory-backend-file"
-
 #define MEMORY_BACKEND_FILE(obj) \
     OBJECT_CHECK(HostMemoryBackendFile, (obj), TYPE_MEMORY_BACKEND_FILE)
 

backends/hostmem-ram.c

@@ -16,8 +16,6 @@
 #include "qemu/module.h"
 #include "qom/object_interfaces.h"
 
-#define TYPE_MEMORY_BACKEND_RAM "memory-backend-ram"
-
 static void
 ram_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
 {

include/hw/boards.h

@@ -170,6 +170,13 @@ typedef struct {
  *    false is returned, an error must be set to show the reason of
  *    the rejection.  If the hook is not provided, all hotplug will be
  *    allowed.
+ * @default_ram_id:
+ *    Specifies inital RAM MemoryRegion name to be used for default backend
+ *    creation if user explicitly hasn't specified backend with "memory-backend"
+ *    property.
+ *    It also will be used as a way to optin into "-m" option support.
+ *    If it's not set by board, '-m' will be ignored and generic code will
+ *    not create default RAM MemoryRegion.
  */
 struct MachineClass {
     /*< private >*/
@@ -226,6 +233,7 @@ struct MachineClass {
     bool nvdimm_supported;
     bool numa_mem_supported;
     bool auto_enable_numa;
+    const char *default_ram_id;
 
     HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
                                            DeviceState *dev);

include/sysemu/hostmem.h

@@ -27,6 +27,22 @@
 #define MEMORY_BACKEND_CLASS(klass) \
     OBJECT_CLASS_CHECK(HostMemoryBackendClass, (klass), TYPE_MEMORY_BACKEND)
 
+/* hostmem-ram.c */
+/**
+ * @TYPE_MEMORY_BACKEND_RAM:
+ * name of backend that uses mmap on the anonymous RAM
+ */
+
+#define TYPE_MEMORY_BACKEND_RAM "memory-backend-ram"
+
+/* hostmem-file.c */
+/**
+ * @TYPE_MEMORY_BACKEND_FILE:
+ * name of backend that uses mmap on a file descriptor
+ */
+#define TYPE_MEMORY_BACKEND_FILE "memory-backend-file"
+
+typedef struct HostMemoryBackend HostMemoryBackend;
 typedef struct HostMemoryBackendClass HostMemoryBackendClass;
 
 /**

vl.c

@@ -75,6 +75,7 @@ int main(int argc, char **argv)
 #include "ui/input.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/numa.h"
+#include "sysemu/hostmem.h"
 #include "exec/gdbstub.h"
 #include "qemu/timer.h"
 #include "chardev/char.h"
@@ -2805,6 +2806,26 @@ static void configure_accelerators(const char *progname)
     }
 }
 
+static void create_default_memdev(MachineState *ms, const char *path,
+                                  bool prealloc)
+{
+    Object *obj;
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+
+    obj = object_new(path ? TYPE_MEMORY_BACKEND_FILE : TYPE_MEMORY_BACKEND_RAM);
+    if (path) {
+        object_property_set_str(obj, path, "mem-path", &error_fatal);
+    }
+    object_property_set_bool(obj, prealloc, "prealloc", &error_fatal);
+    object_property_set_int(obj, ms->ram_size, "size", &error_fatal);
+    object_property_add_child(object_get_objects_root(), mc->default_ram_id,
+                              obj, &error_fatal);
+    user_creatable_complete(USER_CREATABLE(obj), &error_fatal);
+    object_unref(obj);
+    object_property_set_str(OBJECT(ms), mc->default_ram_id, "memory-backend",
+                            &error_fatal);
+}
+
 int main(int argc, char **argv, char **envp)
 {
     int i;
@@ -4268,6 +4289,10 @@ int main(int argc, char **argv, char **envp)
     }
     parse_numa_opts(current_machine);
 
+    if (machine_class->default_ram_id && current_machine->ram_size &&
+        !current_machine->ram_memdev_id) {
+        create_default_memdev(current_machine, mem_path, mem_prealloc);
+    }
     /* do monitor/qmp handling at preconfig state if requested */
     main_loop();