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KVM: LAPIC: add APIC Timer periodic/oneshot mode VMX preemption timer…
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… 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: Wanpeng Li <wanpeng.li@hotmail.com>
[Squashed with my fixes that were reviewed-by Paolo.]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
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Wanpeng Li authored and Paolo Bonzini committed Nov 2, 2016
1 parent 7e810a3 commit 8003c9a
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Showing 2 changed files with 76 additions and 28 deletions.
103 changes: 75 additions & 28 deletions arch/x86/kvm/lapic.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand All @@ -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);

Expand Down Expand Up @@ -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;
* 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
Expand All @@ -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, "
Expand All @@ -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)
Expand All @@ -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);
Expand All @@ -1430,22 +1450,39 @@ 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,
apic->lapic_timer.hv_timer_in_use);
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);
start_hv_timer(apic);
}
EXPORT_SYMBOL_GPL(kvm_lapic_switch_to_hv_timer);

Expand All @@ -1462,17 +1499,22 @@ 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);

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);
}
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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);
}
}
Expand Down
1 change: 1 addition & 0 deletions arch/x86/kvm/lapic.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down

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