[PATCH] hw/ppc: Fix iothread locking in the 405 code

[Thomas Huth <thuth@redhat.com>]

When using u-boot as firmware with the taihu board, QEMU aborts with
this assertion:

 ERROR:../accel/tcg/tcg-accel-ops.c:79:tcg_handle_interrupt: assertion failed:
  (qemu_mutex_iothread_locked())

Running QEMU with "-d in_asm" shows that the crash happens when writing
to SPR 0x3f2, so we are missing to lock the iothread in the code path
here.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 hw/ppc/ppc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index f5d012f860..bb57f1c9ed 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -336,6 +336,8 @@ void store_40x_dbcr0(CPUPPCState *env, uint32_t val)
 {
     PowerPCCPU *cpu = env_archcpu(env);
 
+    qemu_mutex_lock_iothread();
+
     switch ((val >> 28) & 0x3) {
     case 0x0:
         /* No action */
@@ -353,6 +355,8 @@ void store_40x_dbcr0(CPUPPCState *env, uint32_t val)
         ppc40x_system_reset(cpu);
         break;
     }
+
+    qemu_mutex_unlock_iothread();
 }
 
 /* PowerPC 40x internal IRQ controller */
-- 
2.27.0