Re: [Qemu-devel] ppc emulation and interrupts

[Blue Swirl <blauwirbel@gmail.com>]

On 1/21/09, Stefano Stabellini <stefano.stabellini@eu.citrix.com> wrote:
> Hi all,
>  one of the recent problems, noticed after the displaystate change,
>  affects ppc emulation only and is due to the fact that none on ppc
>  emulation is issuing any interrupt request of the CPU_INTERRUPT_EXIT
>  kind if the gui timer is disabled.
>  Hence qemu never leaves the loop in cpu-exec.c:cpu_exec.
>  If the gui timer is enabled qemu is able to leave the loop because the
>  condition (interrupt_request & CPU_INTERRUPT_EXIT) is true when the
>  timer is triggered.
>  I think this is a problem with the ppc emulation but if you ppc guys
>  need the gui timer to be always on, I can arrange for it to be.
>  Regards,

It's not only PPC problem, Sparc64 with -nographic never exits cpu
loop because no timers are running. Serial input does not work,
because IO does not cause exit from cpu loop.

We could add a dummy timer just to exit the cpu loop, but that's a bit ugly.

I think SIGIO was discussed at some point, but rejected.

Would it be very hard to move to the IO thread model?