On 20/11/2017 13:50, Peter Maydell wrote:
> More generally, this commit seems to assume that QEMU always
> does:
> * set exception_index to something
> * handle that
> * clear exception_index to -1
>
> but it's not clear to me that it's actually always the case
> that it gets cleared back to -1.
After returning from cpu_handle_interrupt, cpu_exec goes to
cpu_handle_exception which does
if (cpu->exception_index >= EXCP_INTERRUPT) {
*ret = cpu->exception_index;
if (*ret == EXCP_DEBUG) {
cpu_handle_debug_exception(cpu);
}
cpu->exception_index = -1;
return true;
} else {
CPUClass *cc = CPU_GET_CLASS(cpu);
qemu_mutex_lock_iothread();
cc->do_interrupt(cpu);
qemu_mutex_unlock_iothread();
cpu->exception_index = -1;
}
return false;
Does ARM have a case where cc->do_interrupt can longjmp back to the
beginning of cpu_handle_exception? But I still do not understand why
you don't eventually clear exception_index to -1. Maybe there should be
an assertion for that before and after cpu_handle_interrupt.
Thanks,
Paolo
