[Qemu-trivial] [PATCH] arm: fix reset operation on netduino2 board.

[Marko Klopcic]

Because roms are located on aliased addresses on netduino2 (Cortex M3,
STM32F205), PC and SP are not read from loaded kernel, which means
that the first reset fails. This fix adds additional call to reset.
See more details in code comment below.

Signed-off-by: Marko Klopcic <address@hidden>

---
 hw/arm/netduino2.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/hw/arm/netduino2.c b/hw/arm/netduino2.c
index f936017d4a..a2f102b14b 100644
--- a/hw/arm/netduino2.c
+++ b/hw/arm/netduino2.c
@@ -25,6 +25,7 @@
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "hw/boards.h"
+#include "hw/loader.h"
 #include "qemu/error-report.h"
 #include "hw/arm/stm32f205_soc.h"
 #include "hw/arm/arm.h"
@@ -39,6 +40,32 @@ static void netduino2_init(MachineState *machine)
 
     armv7m_load_kernel(ARM_CPU(first_cpu), machine->kernel_filename,
                        FLASH_SIZE);
+
+    /*
+      The following two calls are a workaround for problem with rom on aliased
+      addresses on STM32.
+      Kernel is loaded into Rom objects, which are stored in loader.c. Roms
+      are copied to memory in:
+     
+      void rom_reset() {
+        ...
+         cpu_physical_memory_write_rom(rom->as, rom->addr, rom->data,
+                                       rom->datasize);
+        ...
+      }
+
+      However, since CPU reset is registered BEFORE
+      rom_reset(), SP and PC are read from memory BEFORE roms are copied to
+      memory. CPU reset also checks Roms for data, so this is normally not a
+      problem, but in STM32 PC and SP are read from aliased memory, and these
+      memory addresses are not mapped to Roms. Since ROMs are private in
+      loader.c the only option to copy Roms to memory is through reset. So we
+      first have to register Roms for reset, and then trigger system reset, which
+      copies Roms to mem, so that reset vectors are in memory, when
+      qemu_system_reset() is called again from main().
+     */
+    rom_check_and_register_reset();
+    qemu_system_reset(SHUTDOWN_CAUSE_NONE);
 }
 
 static void netduino2_machine_init(MachineClass *mc)
--
2.14.1