On 24/10/2016 17:03, Radim Krčmář wrote:
> I have only compile-tested it, but it should optimize the switch and
> also fix two bugs. The first one is major.
> This needs that the deadline clearing in [5/5] is fixed.
> ---8<---
> We must start the hrimer even if the expiration is already in the past,
> otherwise the periodic timer would not rearm the hrtimer.
>
> And computing next expiration of a period timer does not require current
> time. The period should be constant, so it is more precise to add the
> period to the last expiration time. This fixes a time difference
> between hrtimer expiration and apic->lapic_timer.target_expiration.
>
> Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> ---
> arch/x86/kvm/lapic.c | 38 +++++++++++++-------------------------
> 1 file changed, 13 insertions(+), 25 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index f4734fe12803..6244988418be 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1350,19 +1350,19 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
>
> static void start_sw_period(struct kvm_lapic *apic)
> {
> - ktime_t now;
> -
> - now = apic->lapic_timer.timer.base->get_time();
> -
> if (!apic->lapic_timer.period)
> return;
>
> - if (likely(ktime_after(apic->lapic_timer.target_expiration, now)))
> - hrtimer_start(&apic->lapic_timer.timer,
> - apic->lapic_timer.target_expiration,
> - HRTIMER_MODE_ABS_PINNED);
> - else
> + if (apic_lvtt_oneshot(apic) &&
> + ktime_after(apic->lapic_timer.target_expiration,
> + apic->lapic_timer.timer.base->get_time())) {
> apic_timer_expired(apic);
> + return;
> + }
> +
> + hrtimer_start(&apic->lapic_timer.timer,
> + apic->lapic_timer.target_expiration,
> + HRTIMER_MODE_ABS_PINNED);
> }
>
> static bool set_target_expiration(struct kvm_lapic *apic)
> @@ -1414,10 +1414,11 @@ static bool set_target_expiration(struct kvm_lapic *apic)
>
> static void advance_periodic_target_expiration(struct kvm_lapic *apic)
> {
> - apic->lapic_timer.tscdeadline = kvm_read_l1_tsc(apic->vcpu, rdtsc()) +
> + apic->lapic_timer.tscdeadline +=
> nsec_to_cycles(apic->vcpu, apic->lapic_timer.period);
> - apic->lapic_timer.target_expiration = ktime_add_ns(apic->lapic_timer.timer.base->get_time(),
> - apic->lapic_timer.period);
> + apic->lapic_timer.target_expiration =
> + ktime_add_ns(apic->lapic_timer.target_expiration,
> + apic->lapic_timer.period);
> }
>
> bool kvm_lapic_hv_timer_in_use(struct kvm_vcpu *vcpu)
> @@ -1481,19 +1482,6 @@ void kvm_lapic_switch_to_hv_timer(struct kvm_vcpu *vcpu)
>
> WARN_ON(apic->lapic_timer.hv_timer_in_use);
>
> - if (apic_lvtt_period(apic)) {
> - ktime_t remaining, now;
> - u64 tscl = rdtsc();
> -
> - now = apic->lapic_timer.timer.base->get_time();
> - remaining = hrtimer_get_remaining(&apic->lapic_timer.timer);
> - if (ktime_to_ns(remaining) < 0)
> - remaining = ktime_set(0, 0);
> -
> - apic->lapic_timer.tscdeadline = kvm_read_l1_tsc(apic->vcpu, tscl) +
> - nsec_to_cycles(apic->vcpu, ktime_to_ns(remaining));
> - apic->lapic_timer.target_expiration = ktime_add_ns(now, ktime_to_ns(remaining));
> - }
> start_hv_timer(apic);
> }
> EXPORT_SYMBOL_GPL(kvm_lapic_switch_to_hv_timer);
>
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Go ahead, squash it into 5/5 and commit to kvm/queue. :)
Paolo
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