On 25/04/2018 16:07, Anthoine Bourgeois wrote:
> The root cause of the problem is starting hrtimer with an expiry time
> already in the past can take a long time to trigger the timer function.
> It can be solved by executing such past timers immediately, rather than
> submitting them to hrtimer_start().
The change makes more sense now indeed, but I would like an explanation
of one thing: what is "a long time" and why does it cause the issue?
What period is used by Windows?
Code-wise, just a simple change:
> @@ -1537,6 +1520,26 @@ static bool set_target_expiration(struct kvm_lapic *apic)
> return true;
> }
>
> +static void start_sw_period(struct kvm_lapic *apic)
> +{
> + if (!apic->lapic_timer.period)
> + return;
> +
> + if (ktime_after(ktime_get(),
> + apic->lapic_timer.target_expiration)) {
> + apic_timer_expired(apic);
> +
> + if (apic_lvtt_oneshot(apic))
> + return;
> +
> + set_target_expiration(apic);
This last line should be
advance_periodic_target_expiration(apic);
(a simpler version of set_target_expiration).
Paolo
