On Sat, 21 Sep 2019 at 11:17, Philippe Mathieu-Daudé <phi...@redhat.com> wrote:
>
> If the period is too big, the 'delta * period' product result
> might overflow, resulting in a negative number, then the
> next_event ends before the last_event. This is buggy, as there
> is no forward progress. Assert this can not happen.
>
> Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com>
> ---
> hw/core/ptimer.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
> index d58e2dfdb0..88085d4c81 100644
> --- a/hw/core/ptimer.c
> +++ b/hw/core/ptimer.c
> @@ -125,6 +125,9 @@ static void ptimer_reload(ptimer_state *s, int
> delta_adjust)
>
> s->last_event = s->next_event;
> s->next_event = s->last_event + delta * period;
> + /* Verify forward progress */
> + g_assert(s->next_event > s->last_event);
> +
> if (period_frac) {
> s->next_event += ((int64_t)period_frac * delta) >> 32;
> }
> --
Can this only happen if a QEMU timer model using the ptimer
code has a bug, or is it guest-triggerable for some of our
timer models?
thanks
-- PMM
