On 25/11/2014 17:45, Marcelo Tosatti wrote:
> Since lapic timer handler only wakes up a simple waitqueue,
> it can be executed from hardirq context.
>
> Reduces average cyclictest latency by 3us.
>
> Signed-off-by: Marcelo Tosatti <mtosa...@redhat.com>
Please include k...@vger.kernel.org too.
Paolo
> ---
> arch/x86/kvm/lapic.c | 42 +++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 39 insertions(+), 3 deletions(-)
>
> Index: linux-stable-rt/arch/x86/kvm/lapic.c
> ===================================================================
> --- linux-stable-rt.orig/arch/x86/kvm/lapic.c 2014-11-25 14:14:38.636810068
> -0200
> +++ linux-stable-rt/arch/x86/kvm/lapic.c 2014-11-25 14:17:28.850567059
> -0200
> @@ -1031,8 +1031,38 @@
> apic->divide_count);
> }
>
> +
> +static enum hrtimer_restart apic_timer_fn(struct hrtimer *data);
> +
> +static void apic_timer_expired(struct hrtimer *data)
> +{
> + int ret, i = 0;
> + enum hrtimer_restart r;
> + struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
> +
> + r = apic_timer_fn(data);
> +
> + if (r == HRTIMER_RESTART) {
> + do {
> + ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
> + if (ret == -ETIME)
> + hrtimer_add_expires_ns(&ktimer->timer,
> + ktimer->period);
> + i++;
> + } while (ret == -ETIME && i < 10);
> +
> + if (ret == -ETIME) {
> + printk(KERN_ERR "%s: failed to reprogram timer\n",
> + __func__);
> + WARN_ON(1);
> + }
> + }
> +}
> +
> +
> static void start_apic_timer(struct kvm_lapic *apic)
> {
> + int ret;
> ktime_t now;
> atomic_set(&apic->lapic_timer.pending, 0);
>
> @@ -1062,9 +1092,11 @@
> }
> }
>
> - hrtimer_start(&apic->lapic_timer.timer,
> + ret = hrtimer_start(&apic->lapic_timer.timer,
> ktime_add_ns(now, apic->lapic_timer.period),
> HRTIMER_MODE_ABS);
> + if (ret == -ETIME)
> + apic_timer_expired(&apic->lapic_timer.timer);
>
> apic_debug("%s: bus cycle is %" PRId64 "ns, now 0x%016"
> PRIx64 ", "
> @@ -1094,8 +1126,10 @@
> ns = (tscdeadline - guest_tsc) * 1000000ULL;
> do_div(ns, this_tsc_khz);
> }
> - hrtimer_start(&apic->lapic_timer.timer,
> + ret = hrtimer_start(&apic->lapic_timer.timer,
> ktime_add_ns(now, ns), HRTIMER_MODE_ABS);
> + if (ret == -ETIME)
> + apic_timer_expired(&apic->lapic_timer.timer);
>
> local_irq_restore(flags);
> }
> @@ -1581,6 +1615,7 @@
> hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC,
> HRTIMER_MODE_ABS);
> apic->lapic_timer.timer.function = apic_timer_fn;
> + apic->lapic_timer.timer.irqsafe = 1;
>
> /*
> * APIC is created enabled. This will prevent kvm_lapic_set_base from
> @@ -1699,7 +1734,8 @@
>
> timer = &vcpu->arch.apic->lapic_timer.timer;
> if (hrtimer_cancel(timer))
> - hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
> + if (hrtimer_start_expires(timer, HRTIMER_MODE_ABS) == -ETIME)
> + apic_timer_expired(timer);
> }
>
> /*
>
>
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