Re: [RFC][PATCH 1/3] Introduce a workqueue to deliver PIT timer interrupts.

Avi Kivity
2010-06-09T10:55:18Z

On 06/08/2010 08:55 PM, Chris Lalancette wrote:
> We really want to "kvm_set_irq" during the hrtimer callback,
> but that is risky because that is during interrupt context.
> Instead, offload the work to a workqueue, which is a bit safer
> and should provide most of the same functionality.
>
>
>
>
> +static void pit_do_work(struct work_struct *work)
> +{
> + struct kvm_pit *pit = container_of(work, struct kvm_pit, expired);
> + struct kvm *kvm = pit->kvm;
> + struct kvm_vcpu *vcpu;
> + int i;
> + struct kvm_kpit_state *ps =&pit->pit_state;
> + int inject = 0;
> +
> + /* Try to inject pending interrupts when
> + * last one has been acked.
> + */
> + raw_spin_lock(&ps->inject_lock);
> + if (ps->irq_ack) {
> + ps->irq_ack = 0;
> + inject = 1;
> + }
> + raw_spin_unlock(&ps->inject_lock);
>

I don't think this needs to be a raw spinlock any longer (a nice side
effect).+
> +static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
> +{
> + struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
> + struct kvm_pit *pt = ktimer->kvm->arch.vpit;
> +
> + queue_work(pit_wq,&pt->expired);
> +
> + if (ktimer->t_ops->is_periodic(ktimer)) {
> + hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
>

spaces/tabs

> + return HRTIMER_RESTART;
> + }
> + else
> + return HRTIMER_NORESTART;
> +}
> +
>

Somewhere, you have to cancel a pending work struct. At least during
destruction, but perhaps also if the pit is configured not to generate
interrupts any more.

--
error compiling committee.c: too many arguments to function