armv7m: VECTCLRACTIVE and VECTRESET are UNPREDICTABLE

The VECTCLRACTIVE and VECTRESET bits in the AIRCR are both
documented as UNPREDICTABLE if you write a 1 to them when
the processor is not halted in Debug state (ie stopped
and under the control of an external JTAG debugger).
Since we don't implement Debug state or emulated JTAG
these bits are always UNPREDICTABLE for us. Instead of
logging them as unimplemented we can simply log writes
as guest errors and ignore them.

Signed-off-by: Michael Davidsaver <mdavidsaver@gmail.com>
[PMM: change extracted from another patch; commit message
 constructed from scratch]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index 9336bca142..456480a3f2 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -716,10 +716,14 @@ static void nvic_writel(NVICState *s, uint32_t offset, uint32_t value)
                 qemu_irq_pulse(s->sysresetreq);
             }
             if (value & 2) {
-                qemu_log_mask(LOG_UNIMP, "VECTCLRACTIVE unimplemented\n");
+                qemu_log_mask(LOG_GUEST_ERROR,
+                              "Setting VECTCLRACTIVE when not in DEBUG mode "
+                              "is UNPREDICTABLE\n");
             }
             if (value & 1) {
-                qemu_log_mask(LOG_UNIMP, "AIRCR system reset unimplemented\n");
+                qemu_log_mask(LOG_GUEST_ERROR,
+                              "Setting VECTRESET when not in DEBUG mode "
+                              "is UNPREDICTABLE\n");
             }
             s->prigroup = extract32(value, 8, 3);
             nvic_irq_update(s);