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[PATCH 0/5] KVM: LAPIC: Add APIC Timer periodic/oneshot mode VMX preemption timer support

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  [PATCH 0/5] KVM: LAPIC: Add APIC Timer periodic/oneshot mode VMX preemption timer support Wanpeng Li <kernellwp@gmail.com> - 2016-10-17 09:50 +0200
    [PATCH 1/5] KVM: LAPIC: extract start_sw_period() to handle periodic/oneshot mode Wanpeng Li <kernellwp@gmail.com> - 2016-10-17 09:50 +0200

#1501659 — [PATCH 0/5] KVM: LAPIC: Add APIC Timer periodic/oneshot mode VMX preemption timer support

Most windows guests which I have on hand currently still utilize APIC Timer
periodic/oneshot mode instead of APIC Timer tsc-deadline mode:
- windows 2008 server r2
- windows 2012 server r2
- windows 7
- windows 10

This patchset adds the APIC Timer periodic/oneshot mode VMX preemption
timer support.

I test the patchset by adding kvm-unit-test/apic_timer_latency.flat to test 100 thousands 
times APIC timer operations.

The patchset reduces ~3800+ clock cycles for each APIC timer periodic mode
operation virtualization. 

V1 -> RFC v3:
 * squash patch 3 into patch 6
 * fix switch sw to hv timer

RFC v2 -> RFC v3:
 * remove kvm_lapic_hv_timer_in_use() check in apic_get_tmcc, replace
   the hritmer_get_remaining() by target_expiration - now
 * rename expired_period to target_expiration
 * introduce set_target_expiration() helper
 * move the checking of minimal period to set_target_expiration()
 * cleanup kvm_get_lapic_target_deadline_tsc()

RFC v1 -> RFC v2:
 * remember the timeout when setting up the timer to get a correct TMCCT
 * move apic->lapic_timer.period/tscdeadline caculations to start_apic_timer()

Wanpeng Li (5):
  KVM: LAPIC: extract start_sw_period() to handle periodic/oneshot mode
  KVM: LAPIC: guarantee the timer is in tsc-deadline mode when rdmsr MSR_IA32_TSCDEADLINE
  KVM: LAPIC: introduce kvm_get_lapic_target_expiration_tsc()
  KVM: LAPIC: rename start/cancel_hv_tscdeadline to start/cancel_hv_timer
  KVM: LAPIC: add APIC Timer periodic/oneshot mode VMX preemption timer support

 arch/x86/kvm/lapic.c | 193 +++++++++++++++++++++++++++++++++------------------
 arch/x86/kvm/lapic.h |   2 +
 arch/x86/kvm/x86.c   |   2 +-
 3 files changed, 129 insertions(+), 68 deletions(-)

-- 
1.9.1

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#1501661 — [PATCH 1/5] KVM: LAPIC: extract start_sw_period() to handle periodic/oneshot mode

From: Wanpeng Li <wanpeng.li@hotmail.com>

Extract start_sw_period() to handle periodic/oneshot mode, it will be
used by later patch.

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>
---
 arch/x86/kvm/lapic.c | 89 +++++++++++++++++++++++++++-------------------------
 1 file changed, 47 insertions(+), 42 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 23b99f3..dad743e 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1347,6 +1347,50 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
 	local_irq_restore(flags);
 }
 
+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)));
+}
+
 bool kvm_lapic_hv_timer_in_use(struct kvm_vcpu *vcpu)
 {
 	if (!lapic_in_kernel(vcpu))
@@ -1424,50 +1468,11 @@ EXPORT_SYMBOL_GPL(kvm_lapic_switch_to_sw_timer);
 
 static void start_apic_timer(struct kvm_lapic *apic)
 {
-	ktime_t now;
-
 	atomic_set(&apic->lapic_timer.pending, 0);
 
-	if (apic_lvtt_period(apic) || apic_lvtt_oneshot(apic)) {
-		/* 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)));
-	} else if (apic_lvtt_tscdeadline(apic)) {
+	if (apic_lvtt_period(apic) || apic_lvtt_oneshot(apic))
+		start_sw_period(apic);
+	else if (apic_lvtt_tscdeadline(apic)) {
 		if (!(kvm_x86_ops->set_hv_timer && start_hv_tscdeadline(apic)))
 			start_sw_tscdeadline(apic);
 	}
-- 
1.9.1

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