armv7m: Fix condition check for taking exceptions

The M profile condition for when we can take a pending exception or
interrupt is not the same as that for A/R profile.  The code
originally copied from the A/R profile version of the
cpu_exec_interrupt function only worked by chance for the
very simple case of exceptions being masked by PRIMASK.
Replace it with a call to a function in the NVIC code that
correctly compares the priority of the pending exception
against the current execution priority of the CPU.

[Michael Davidsaver's patchset had a patch to do something
similar but the implementation ended up being a rewrite.]

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 38a8e00908..649f237561 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -1356,6 +1356,14 @@ uint32_t arm_phys_excp_target_el(CPUState *cs, uint32_t excp_idx,
                                  uint32_t cur_el, bool secure);
 
 /* Interface between CPU and Interrupt controller.  */
+#ifndef CONFIG_USER_ONLY
+bool armv7m_nvic_can_take_pending_exception(void *opaque);
+#else
+static inline bool armv7m_nvic_can_take_pending_exception(void *opaque)
+{
+    return true;
+}
+#endif
 void armv7m_nvic_set_pending(void *opaque, int irq);
 int armv7m_nvic_acknowledge_irq(void *opaque);
 void armv7m_nvic_complete_irq(void *opaque, int irq);