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Date: Mon, 17 Oct 2016 10:45:28 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Cc: Radim Krčmář <rkrcmar@...hat.com>,
Yunhong Jiang <yunhong.jiang@...el.com>,
Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH 5/5] KVM: LAPIC: add APIC Timer periodic/oneshot mode VMX
preemption timer support
On 17/10/2016 09:45, Wanpeng Li wrote:
> + remaining = ktime_sub(apic->lapic_timer.target_expiration, now);
> if (ktime_to_ns(remaining) < 0)
> remaining = ktime_set(0, 0);
>
> @@ -1351,13 +1352,28 @@ static void start_sw_period(struct kvm_lapic *apic)
> {
> ktime_t now;
>
> - /* lapic timer in oneshot or periodic mode */
> + now = apic->lapic_timer.timer.base->get_time();
> +
> + if (likely(ktime_compare(apic->lapic_timer.target_expiration, now)))
ktime_after, not ktime_compare. Can be fixed on commit, I guess.
Paolo
> + hrtimer_start(&apic->lapic_timer.timer,
> + apic->lapic_timer.target_expiration,
> + HRTIMER_MODE_ABS_PINNED);
> + else
> + apic_timer_expired(apic);
> +}
> +
> +static bool set_target_expiration(struct kvm_lapic *apic)
> +{
> + ktime_t now;
> + u64 tscl = rdtsc();
> +
> now = apic->lapic_timer.timer.base->get_time();
> apic->lapic_timer.period = (u64)kvm_lapic_get_reg(apic, APIC_TMICT)
> - * APIC_BUS_CYCLE_NS * apic->divide_count;
> + * APIC_BUS_CYCLE_NS * apic->divide_count;
>
> if (!apic->lapic_timer.period)
> - return;
> + return false;
> /*
> * Do not allow the guest to program periodic timers with small
> * interval, since the hrtimers are not throttled by the host
> @@ -1376,10 +1392,6 @@ static void start_sw_period(struct kvm_lapic *apic)
> }
> }
>
> - hrtimer_start(&apic->lapic_timer.timer,
> - ktime_add_ns(now, apic->lapic_timer.period),
> - HRTIMER_MODE_ABS_PINNED);
> -
> apic_debug("%s: bus cycle is %" PRId64 "ns, now 0x%016"
> PRIx64 ", "
> "timer initial count 0x%x, period %lldns, "
> @@ -1389,6 +1401,12 @@ static void start_sw_period(struct kvm_lapic *apic)
> apic->lapic_timer.period,
> ktime_to_ns(ktime_add_ns(now,
> apic->lapic_timer.period)));
> +
> + apic->lapic_timer.tscdeadline = kvm_read_l1_tsc(apic->vcpu, tscl) +
> + nsec_to_cycles(apic->vcpu, apic->lapic_timer.period);
> + apic->lapic_timer.target_expiration = ktime_add_ns(now, apic->lapic_timer.period);
> +
> + return true;
> }
>
> bool kvm_lapic_hv_timer_in_use(struct kvm_vcpu *vcpu)
> @@ -1406,22 +1424,12 @@ static void cancel_hv_timer(struct kvm_lapic *apic)
> apic->lapic_timer.hv_timer_in_use = false;
> }
>
> -void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
> -{
> - struct kvm_lapic *apic = vcpu->arch.apic;
> -
> - WARN_ON(!apic->lapic_timer.hv_timer_in_use);
> - WARN_ON(swait_active(&vcpu->wq));
> - cancel_hv_timer(apic);
> - apic_timer_expired(apic);
> -}
> -EXPORT_SYMBOL_GPL(kvm_lapic_expired_hv_timer);
> -
> static bool start_hv_timer(struct kvm_lapic *apic)
> {
> u64 tscdeadline = apic->lapic_timer.tscdeadline;
>
> - if (atomic_read(&apic->lapic_timer.pending) ||
> + if ((atomic_read(&apic->lapic_timer.pending) &&
> + !apic_lvtt_period(apic)) ||
> kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline)) {
> if (apic->lapic_timer.hv_timer_in_use)
> cancel_hv_timer(apic);
> @@ -1430,7 +1438,8 @@ static bool start_hv_timer(struct kvm_lapic *apic)
> hrtimer_cancel(&apic->lapic_timer.timer);
>
> /* In case the sw timer triggered in the window */
> - if (atomic_read(&apic->lapic_timer.pending))
> + if (atomic_read(&apic->lapic_timer.pending) &&
> + !apic_lvtt_period(apic))
> cancel_hv_timer(apic);
> }
> trace_kvm_hv_timer_state(apic->vcpu->vcpu_id,
> @@ -1438,14 +1447,42 @@ static bool start_hv_timer(struct kvm_lapic *apic)
> return apic->lapic_timer.hv_timer_in_use;
> }
>
> +void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_lapic *apic = vcpu->arch.apic;
> +
> + WARN_ON(!apic->lapic_timer.hv_timer_in_use);
> + WARN_ON(swait_active(&vcpu->wq));
> + cancel_hv_timer(apic);
> + apic_timer_expired(apic);
> +
> + if (apic_lvtt_period(apic) &&
> + set_target_expiration(apic) &&
> + !start_hv_timer(apic))
> + start_sw_period(apic);
> +}
> +EXPORT_SYMBOL_GPL(kvm_lapic_expired_hv_timer);
> +
> void kvm_lapic_switch_to_hv_timer(struct kvm_vcpu *vcpu)
> {
> struct kvm_lapic *apic = vcpu->arch.apic;
>
> WARN_ON(apic->lapic_timer.hv_timer_in_use);
>
> - if (apic_lvtt_tscdeadline(apic))
> - start_hv_timer(apic);
> + if (apic_lvtt_period(apic) || apic_lvtt_oneshot(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);
>
> @@ -1462,7 +1499,10 @@ void kvm_lapic_switch_to_sw_timer(struct kvm_vcpu *vcpu)
> if (atomic_read(&apic->lapic_timer.pending))
> return;
>
> - start_sw_tscdeadline(apic);
> + if (apic_lvtt_period(apic) || apic_lvtt_oneshot(apic))
> + start_sw_period(apic);
> + else if (apic_lvtt_tscdeadline(apic))
> + start_sw_tscdeadline(apic);
> }
> EXPORT_SYMBOL_GPL(kvm_lapic_switch_to_sw_timer);
>
> @@ -1470,9 +1510,11 @@ static void start_apic_timer(struct kvm_lapic *apic)
> {
> atomic_set(&apic->lapic_timer.pending, 0);
>
> - if (apic_lvtt_period(apic) || apic_lvtt_oneshot(apic))
> - start_sw_period(apic);
> - else if (apic_lvtt_tscdeadline(apic)) {
> + if (apic_lvtt_period(apic) || apic_lvtt_oneshot(apic)) {
> + if (set_target_expiration(apic) &&
> + !(kvm_x86_ops->set_hv_timer && start_hv_timer(apic)))
> + start_sw_period(apic);
> + } else if (apic_lvtt_tscdeadline(apic)) {
> if (!(kvm_x86_ops->set_hv_timer && start_hv_timer(apic)))
> start_sw_tscdeadline(apic);
> }
> @@ -2005,8 +2047,11 @@ void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu)
>
> if (atomic_read(&apic->lapic_timer.pending) > 0) {
> kvm_apic_local_deliver(apic, APIC_LVTT);
> - if (apic_lvtt_tscdeadline(apic))
> + if (!(apic_lvtt_period(apic) &&
> + kvm_lapic_hv_timer_in_use(vcpu))) {
> apic->lapic_timer.tscdeadline = 0;
> + apic->lapic_timer.target_expiration = ktime_set(0, 0);
> + }
> atomic_set(&apic->lapic_timer.pending, 0);
> }
> }
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index 031db26..e0c8023 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -15,6 +15,7 @@
> struct kvm_timer {
> struct hrtimer timer;
> s64 period; /* unit: ns */
> + ktime_t target_expiration;
> u32 timer_mode;
> u32 timer_mode_mask;
> u64 tscdeadline;
>
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