hw/arm/aspeed: add a 'execute-in-place' property to boot directly from CE0

The overhead for the OpenBMC firmware images using the a custom U-Boot
is around 2 seconds, which is fine, but with a U-Boot from mainline,
it takes an extra 50 seconds or so to reach Linux. A quick survey on
the number of reads performed on the flash memory region gives the
following figures :

  OpenBMC U-Boot      922478 (~ 3.5 MBytes)
  Mainline U-Boot   20569977 (~ 80  MBytes)

QEMU must be trashing the TCG TBs and reloading text very often. Some
addresses are read more than 250.000 times. Until we find a solution
to improve boot time, execution from MMIO is not activated by default.

Setting this option also breaks migration compatibility.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200114103433.30534-5-clg@kaod.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/aspeed.c

@@ -261,11 +261,18 @@ static void aspeed_machine_init(MachineState *machine)
          * SoC and 128MB for the AST2500 SoC, which is twice as big as
          * needed by the flash modules of the Aspeed machines.
          */
-        memory_region_init_rom(boot_rom, OBJECT(bmc), "aspeed.boot_rom",
+        if (ASPEED_MACHINE(machine)->mmio_exec) {
-                               fl->size, &error_abort);
+            memory_region_init_alias(boot_rom, OBJECT(bmc), "aspeed.boot_rom",
-        memory_region_add_subregion(get_system_memory(), FIRMWARE_ADDR,
+                                     &fl->mmio, 0, fl->size);
-                                    boot_rom);
+            memory_region_add_subregion(get_system_memory(), FIRMWARE_ADDR,
-        write_boot_rom(drive0, FIRMWARE_ADDR, fl->size, &error_abort);
+                                        boot_rom);
+        } else {
+            memory_region_init_rom(boot_rom, OBJECT(bmc), "aspeed.boot_rom",
+                                   fl->size, &error_abort);
+            memory_region_add_subregion(get_system_memory(), FIRMWARE_ADDR,
+                                        boot_rom);
+            write_boot_rom(drive0, FIRMWARE_ADDR, fl->size, &error_abort);
+        }
     }
 
     aspeed_board_binfo.ram_size = ram_size;
@@ -399,6 +406,30 @@ static void witherspoon_bmc_i2c_init(AspeedBoardState *bmc)
     /* Bus 11: TODO ucd90160@64 */
 }
 
+static bool aspeed_get_mmio_exec(Object *obj, Error **errp)
+{
+    return ASPEED_MACHINE(obj)->mmio_exec;
+}
+
+static void aspeed_set_mmio_exec(Object *obj, bool value, Error **errp)
+{
+    ASPEED_MACHINE(obj)->mmio_exec = value;
+}
+
+static void aspeed_machine_instance_init(Object *obj)
+{
+    ASPEED_MACHINE(obj)->mmio_exec = false;
+}
+
+static void aspeed_machine_class_props_init(ObjectClass *oc)
+{
+    object_class_property_add_bool(oc, "execute-in-place",
+                                   aspeed_get_mmio_exec,
+                                   aspeed_set_mmio_exec, &error_abort);
+    object_class_property_set_description(oc, "execute-in-place",
+                           "boot directly from CE0 flash device", &error_abort);
+}
+
 static void aspeed_machine_class_init(ObjectClass *oc, void *data)
 {
     MachineClass *mc = MACHINE_CLASS(oc);
@@ -408,6 +439,8 @@ static void aspeed_machine_class_init(ObjectClass *oc, void *data)
     mc->no_floppy = 1;
     mc->no_cdrom = 1;
     mc->no_parallel = 1;
+
+    aspeed_machine_class_props_init(oc);
 }
 
 static void aspeed_machine_palmetto_class_init(ObjectClass *oc, void *data)
@@ -550,6 +583,7 @@ static const TypeInfo aspeed_machine_types[] = {
         .name          = TYPE_ASPEED_MACHINE,
         .parent        = TYPE_MACHINE,
         .instance_size = sizeof(AspeedMachine),
+        .instance_init = aspeed_machine_instance_init,
         .class_size    = sizeof(AspeedMachineClass),
         .class_init    = aspeed_machine_class_init,
         .abstract      = true,

include/hw/arm/aspeed.h

@@ -19,6 +19,8 @@ typedef struct AspeedBoardState AspeedBoardState;
 
 typedef struct AspeedMachine {
     MachineState parent_obj;
+
+    bool mmio_exec;
 } AspeedMachine;
 
 #define ASPEED_MACHINE_CLASS(klass) \