Re: Question about hrtimer_restart apic_timer_fn in lapic.c

Paolo Bonzini
2014-12-19T11:29:11Z

On 18/12/2014 19:15, nick wrote:
> /*
> * There is a race window between reading and incrementing, but we do
> * not care about potentially losing timer events in the !reinject
> * case anyway. Note: KVM_REQ_PENDING_TIMER is implicitly checked
> * in vcpu_enter_guest.
> */
> if (!atomic_read(&ktimer->pending)) {
> atomic_inc(&ktimer->pending);
> /* FIXME: this code should not know anything about vcpus */
> kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
> }
>
> if (waitqueue_active(q))
> wake_up_interruptible(q);
>
> if (lapic_is_periodic(apic)) {
> hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
> return HRTIMER_RESTART;
> } else
> return HRTIMER_NORESTART;
> }
> What is point of the comment, clearly we need access to vcpu in the call as it's a pointer to the apic structure's vcpu
> and we need to call on that particular CPU a request of KVM_REQ_PENDING_TIMER? Please let me known if I am missing any
> important information.

The idea is that there should be a function in x86.c (something like
kvm_vcpu_set_pending_timer) that calls kvm_make_request, instead of
doing it in lapic.c.

Paolo