The M-profile architecture specifies that the DebugMonitor exception
should be initially disabled, not enabled. It should be controlled
by the DEMCR register's MON_EN bit, but we don't implement that
register yet (like most of the debug architecture for M-profile).

Note that BKPT instructions will still work, because they
will be escalated to HardFault.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/intc/armv7m_nvic.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index 15cba63c964..3a346a682a3 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -2491,10 +2491,12 @@ static void armv7m_nvic_reset(DeviceState *dev)
      * the System Handler Control register
      */
     s->vectors[ARMV7M_EXCP_SVC].enabled = 1;
-    s->vectors[ARMV7M_EXCP_DEBUG].enabled = 1;
     s->vectors[ARMV7M_EXCP_PENDSV].enabled = 1;
     s->vectors[ARMV7M_EXCP_SYSTICK].enabled = 1;
 
+    /* DebugMonitor is enabled via DEMCR.MON_EN */
+    s->vectors[ARMV7M_EXCP_DEBUG].enabled = 0;
+
     resetprio = arm_feature(&s->cpu->env, ARM_FEATURE_V8) ? -4 : -3;
     s->vectors[ARMV7M_EXCP_RESET].prio = resetprio;
     s->vectors[ARMV7M_EXCP_NMI].prio = -2;
-- 
2.20.1