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Commit 8003c9ae authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini
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KVM: LAPIC: add APIC Timer periodic/oneshot mode VMX preemption timer support 



Most windows guests still utilize APIC Timer periodic/oneshot mode
instead of tsc-deadline mode, and the APIC Timer periodic/oneshot
mode are still emulated by high overhead hrtimer on host. This patch
converts the expected expire time of the periodic/oneshot mode to
guest deadline tsc in order to leverage VMX preemption timer logic
for APIC Timer tsc-deadline mode. After each preemption timer vmexit
preemption timer is restarted to emulate LVTT current-count register
is automatically reloaded from the initial-count register when the
count reaches 0. This patch reduces ~5600 cycles for each APIC Timer
periodic mode operation virtualization.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: default avatarWanpeng Li <wanpeng.li@hotmail.com>
[Squashed with my fixes that were reviewed-by Paolo.]
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent 7e810a38

arch/x86/kvm/lapic.c

+75 −28
Original line number Diff line number Diff line
@@ -1090,7 +1090,7 @@ static void apic_send_ipi(struct kvm_lapic *apic) 


static u32 apic_get_tmcct(struct kvm_lapic *apic)

{

	ktime_t remaining;

	ktime_t remaining, now;

	s64 ns;

	u32 tmcct;
@@ -1101,7 +1101,8 @@ static u32 apic_get_tmcct(struct kvm_lapic *apic) 
		apic->lapic_timer.period == 0)

		return 0;



	remaining = hrtimer_get_remaining(&apic->lapic_timer.timer);

	now = apic->lapic_timer.timer.base->get_time();

	remaining = ktime_sub(apic->lapic_timer.target_expiration, now);

	if (ktime_to_ns(remaining) < 0)

		remaining = ktime_set(0, 0);
@@ -1348,16 +1349,34 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic) 
}



static void start_sw_period(struct kvm_lapic *apic)

{

	if (!apic->lapic_timer.period)

		return;



	if (apic_lvtt_oneshot(apic) &&

	    ktime_after(apic->lapic_timer.timer.base->get_time(),

			apic->lapic_timer.target_expiration)) {

		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)

{

	ktime_t now;

	u64 tscl = rdtsc();



	/* lapic timer in oneshot or periodic mode */

	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;



	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 +1395,6 @@ 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 +1404,21 @@ 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;

}



static void advance_periodic_target_expiration(struct kvm_lapic *apic)

{

	apic->lapic_timer.tscdeadline +=

		nsec_to_cycles(apic->vcpu, 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)
@@ -1406,22 +1436,12 @@ 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 +1450,8 @@ 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,
@@ -1438,13 +1459,29 @@ 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) && apic->lapic_timer.period) {

		advance_periodic_target_expiration(apic);

		if (!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);

}

EXPORT_SYMBOL_GPL(kvm_lapic_switch_to_hv_timer);
@@ -1462,6 +1499,9 @@ void kvm_lapic_switch_to_sw_timer(struct kvm_vcpu *vcpu) 
	if (atomic_read(&apic->lapic_timer.pending))

		return;



	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))

	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)) {

	} else if (apic_lvtt_tscdeadline(apic)) {

		if (!(kvm_x86_ops->set_hv_timer && start_hv_timer(apic)))

			start_sw_tscdeadline(apic);

	}
@@ -1923,6 +1965,7 @@ static enum hrtimer_restart apic_timer_fn(struct hrtimer *data) 
	apic_timer_expired(apic);



	if (lapic_is_periodic(apic)) {

		advance_periodic_target_expiration(apic);

		hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);

		return HRTIMER_RESTART;

	} else
@@ -2007,6 +2050,10 @@ void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu) 
		kvm_apic_local_deliver(apic, APIC_LVTT);

		if (apic_lvtt_tscdeadline(apic))

			apic->lapic_timer.tscdeadline = 0;

		if (apic_lvtt_oneshot(apic)) {

			apic->lapic_timer.tscdeadline = 0;

			apic->lapic_timer.target_expiration = ktime_set(0, 0);

		}

		atomic_set(&apic->lapic_timer.pending, 0);

	}

}

arch/x86/kvm/lapic.h

+1 −0
Original line number Diff line number Diff line
@@ -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;