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Date: Thu, 13 Oct 2016 19:34:18 +0800
From: Wanpeng Li <kernellwp@...il.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Yunhong Jiang <yunhong.jiang@...el.com>,
Wanpeng Li <wanpeng.li@...mail.com>
Subject: [PATCH RFC V3 6/6] KVM: LAPIC: Add APIC Timer periodic/oneshot mode VMX preemption timer support
From: Wanpeng Li <wanpeng.li@...mail.com>
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.
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Yunhong Jiang <yunhong.jiang@...el.com>
Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
---
arch/x86/kvm/lapic.c | 100 ++++++++++++++++++++-------------------------------
1 file changed, 39 insertions(+), 61 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e93e549..7663246 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -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);
@@ -1349,46 +1350,9 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
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();
- 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;
- /*
- * Do not allow the guest to program periodic timers with small
- * interval, since the hrtimers are not throttled by the host
- * scheduler.
- */
- if (apic_lvtt_period(apic)) {
- s64 min_period = min_timer_period_us * 1000LL;
-
- if (apic->lapic_timer.period < min_period) {
- pr_info_ratelimited(
- "kvm: vcpu %i: requested %lld ns "
- "lapic timer period limited to %lld ns\n",
- apic->vcpu->vcpu_id,
- apic->lapic_timer.period, min_period);
- apic->lapic_timer.period = min_period;
- }
- }
-
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, "
- "expire @ 0x%016" PRIx64 ".\n", __func__,
- APIC_BUS_CYCLE_NS, ktime_to_ns(now),
- kvm_lapic_get_reg(apic, APIC_TMICT),
- apic->lapic_timer.period,
- ktime_to_ns(ktime_add_ns(now,
- apic->lapic_timer.period)));
+ apic->lapic_timer.target_expiration,
+ HRTIMER_MODE_ABS_PINNED);
}
static bool set_target_expiration(struct kvm_lapic *apic)
@@ -1453,22 +1417,12 @@ 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);
@@ -1477,7 +1431,8 @@ 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,
@@ -1485,14 +1440,29 @@ 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) &&
+ 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);
+ start_hv_timer(apic);
}
EXPORT_SYMBOL_GPL(kvm_lapic_switch_to_hv_timer);
@@ -1509,7 +1479,10 @@ 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);
@@ -1517,9 +1490,11 @@ 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);
}
@@ -2052,8 +2027,11 @@ 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);
}
}
--
1.9.1
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