[PATCH v2 1/3] hw/arm/aspeed: Remove extraneous MemoryRegion object owner

[Philippe Mathieu-Daudé]

I'm confused by this code, 'bmc' is created as:

  bmc = g_new0(AspeedBoardState, 1);

Then we use it as QOM owner for different MemoryRegion objects.
But looking at memory_region_init_ram (similarly for ROM):

  void memory_region_init_ram(MemoryRegion *mr,
                              struct Object *owner,
                              const char *name,
                              uint64_t size,
                              Error **errp)
  {
      DeviceState *owner_dev;
      Error *err = NULL;

      memory_region_init_ram_nomigrate(mr, owner, name, size, &err);
      if (err) {
          error_propagate(errp, err);
          return;
      }
      /* This will assert if owner is neither NULL nor a DeviceState.
       * We only want the owner here for the purposes of defining a
       * unique name for migration. TODO: Ideally we should implement
       * a naming scheme for Objects which are not DeviceStates, in
       * which case we can relax this restriction.
       */
      owner_dev = DEVICE(owner);
      vmstate_register_ram(mr, owner_dev);
  }

The expected assertion is not triggered ('bmc' is not NULL neither
a DeviceState).

'bmc' structure is defined as:

  struct AspeedBoardState {
      AspeedSoCState soc;
      MemoryRegion ram_container;
      MemoryRegion max_ram;
  };

What happens is when using 'OBJECT(bmc)', the QOM macros cast the
memory pointed by bmc, which first member is 'soc', which is
initialized ...:

  object_initialize_child(OBJECT(machine), "soc",
                          &bmc->soc, amc->soc_name);

The 'soc' object is indeed a DeviceState, so the assertion passes.

Since this is fragile and only happens to work by luck, remove the
dangerous OBJECT(bmc) owner argument.

Note, this probably breaks migration for this machine.

Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/arm/aspeed.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
index 0ad08a2b4c..31765792a2 100644
--- a/hw/arm/aspeed.c
+++ b/hw/arm/aspeed.c
@@ -329,12 +329,12 @@ static void aspeed_machine_init(MachineState *machine)
          * needed by the flash modules of the Aspeed machines.
          */
         if (ASPEED_MACHINE(machine)->mmio_exec) {
-            memory_region_init_alias(boot_rom, OBJECT(bmc), "aspeed.boot_rom",
+            memory_region_init_alias(boot_rom, NULL, "aspeed.boot_rom",
                                      &fl->mmio, 0, fl->size);
             memory_region_add_subregion(get_system_memory(), FIRMWARE_ADDR,
                                         boot_rom);
         } else {
-            memory_region_init_rom(boot_rom, OBJECT(bmc), "aspeed.boot_rom",
+            memory_region_init_rom(boot_rom, NULL, "aspeed.boot_rom",
                                    fl->size, &error_abort);
             memory_region_add_subregion(get_system_memory(), FIRMWARE_ADDR,
                                         boot_rom);
@@ -345,7 +345,7 @@ static void aspeed_machine_init(MachineState *machine)
     if (machine->kernel_filename && sc->num_cpus > 1) {
         /* With no u-boot we must set up a boot stub for the secondary CPU */
         MemoryRegion *smpboot = g_new(MemoryRegion, 1);
-        memory_region_init_ram(smpboot, OBJECT(bmc), "aspeed.smpboot",
+        memory_region_init_ram(smpboot, NULL, "aspeed.smpboot",
                                0x80, &error_abort);
         memory_region_add_subregion(get_system_memory(),
                                     AST_SMP_MAILBOX_BASE, smpboot);
-- 
2.21.3