From: Paolo Bonzini <pbonzini@redhat.com>
To: "Radim Krčmář" <rkrcmar@redhat.com>, "Wanpeng Li" <kernellwp@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Yunhong Jiang <yunhong.jiang@intel.com>,
Wanpeng Li <wanpeng.li@hotmail.com>
Subject: Re: [PATCH 6/5] KVM: x86: fix periodic lapic timer with hrtimers
Date: Mon, 24 Oct 2016 17:09:01 +0200 [thread overview]
Message-ID: <fa03f516-25ea-40e7-dd47-4dc9753d1b5b@redhat.com> (raw)
In-Reply-To: <20161024150323.GB2247@potion>
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@redhat.com>
> ---
> 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@redhat.com>
Go ahead, squash it into 5/5 and commit to kvm/queue. :)
Paolo
next prev parent reply other threads:[~2016-10-24 15:09 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-24 10:23 [PATCH v3 0/5] KVM: LAPIC: Add APIC Timer periodic/oneshot mode VMX preemption timer support Wanpeng Li
2016-10-24 10:23 ` [PATCH v3 1/5] KVM: LAPIC: extract start_sw_period() to handle periodic/oneshot mode Wanpeng Li
2016-10-24 10:23 ` [PATCH v3 2/5] KVM: LAPIC: guarantee the timer is in tsc-deadline mode Wanpeng Li
2016-10-24 10:23 ` [PATCH v3 3/5] KVM: LAPIC: introduce kvm_get_lapic_target_expiration_tsc() Wanpeng Li
2016-10-24 10:23 ` [PATCH v3 4/5] KVM: LAPIC: rename start/cancel_hv_tscdeadline to start/cancel_hv_timer Wanpeng Li
2016-10-24 10:23 ` [PATCH v3 5/5] KVM: LAPIC: add APIC Timer periodic/oneshot mode VMX preemption timer support Wanpeng Li
2016-10-24 14:50 ` Radim Krčmář
2016-10-24 23:33 ` Wanpeng Li
2016-10-24 15:03 ` [PATCH 6/5] KVM: x86: fix periodic lapic timer with hrtimers Radim Krčmář
2016-10-24 15:09 ` Paolo Bonzini [this message]
2016-10-24 15:27 ` Radim Krčmář
2016-10-24 23:39 ` Wanpeng Li
2016-10-25 11:43 ` Radim Krčmář
2016-10-25 11:55 ` Paolo Bonzini
2016-10-26 6:02 ` Wanpeng Li
2016-10-26 6:08 ` Wanpeng Li
2016-10-26 14:01 ` Radim Krčmář
2016-10-27 2:33 ` Wanpeng Li
2016-10-26 13:32 ` Radim Krčmář
2016-10-27 2:11 ` Wanpeng Li
2016-10-26 10:23 ` Wanpeng Li
2016-10-26 11:15 ` Paolo Bonzini
2016-10-26 11:26 ` Wanpeng Li
[not found] ` <SG2PR02MB1550E0FF04F2614BE0E262BC80A80@SG2PR02MB1550.apcprd02.prod.outlook.com>
2016-10-25 13:03 ` Radim Krčmář
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