Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

Jan Kiszka
2014-11-25T19:01:28Z

On 2014-11-25 18:38, Paolo Bonzini wrote:
>
>
> On 25/11/2014 18:21, Marcelo Tosatti wrote:
>> +
>> + if (r == HRTIMER_RESTART) {
>> + do {
>> + ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
>> + if (ret == -ETIME)
>> + hrtimer_add_expires_ns(&ktimer->timer,
>> + ktimer->period);
>
> Is it possible to just compute the time where the next interrupt
> happens? I suspect the printk and WARN_ON below can be easily triggered
> by a guest.

We have a lower bound for the period that a guest can program. Unless
that value is set too low, this should practically not happen if we
avoid disturbances while handling the event and reprogramming the next
one (irqs off?).

Jan

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