KVM: Keep track of missed timer irq injections

APIC timer IRQ is set every time when a certain period
expires at host time, but the guest may be descheduled
at that time and thus the irq be overwritten by later fire.
This patch keep track of firing irq numbers and decrease
only when the IRQ is injected to guest or buffered in
APIC.

Signed-off-by: Yaozu (Eddie) Dong <Eddie.Dong@intel.com>
Signed-off-by: Qing He <qing.he@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 38 insertions, 20 deletions

diff --git a/drivers/kvm/lapic.c b/drivers/kvm/lapic.c
index 68bbbb38edad..490d4939dba7 100644
--- a/drivers/kvm/lapic.c
+++ b/drivers/kvm/lapic.c
@@ -313,6 +313,7 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
                              int vector, int level, int trig_mode)
 {
         int result = 0;
+        int orig_irr;
 
         switch (delivery_mode) {
         case APIC_DM_FIXED:
@@ -321,7 +322,8 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
                 if (unlikely(!apic_enabled(apic)))
                         break;
 
-                if (apic_test_and_set_irr(vector, apic) && trig_mode) {
+                orig_irr = apic_test_and_set_irr(vector, apic);
+                if (orig_irr && trig_mode) {
                         apic_debug("level trig mode repeatedly for vector %d",
                                    vector);
                         break;
@@ -335,7 +337,7 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
 
                 kvm_vcpu_kick(apic->vcpu);
 
-                result = 1;
+                result = (orig_irr == 0);
                 break;
 
         case APIC_DM_REMRD:
@@ -831,38 +833,33 @@ EXPORT_SYMBOL_GPL(kvm_lapic_enabled);
  * timer interface
  *----------------------------------------------------------------------
  */
+
+/* TODO: make sure __apic_timer_fn runs in current pCPU */
 static int __apic_timer_fn(struct kvm_lapic *apic)
 {
-        u32 vector;
         int result = 0;
+        wait_queue_head_t *q = &apic->vcpu->wq;
 
-        if (unlikely(!apic_enabled(apic) ||
-                     !apic_lvt_enabled(apic, APIC_LVTT))) {
-                apic_debug("%s: time interrupt although apic is down\n",
-                           __FUNCTION__);
-                return 0;
-        }
-
-        vector = apic_lvt_vector(apic, APIC_LVTT);
-        apic->timer.last_update = apic->timer.dev.expires;
         atomic_inc(&apic->timer.pending);
-        __apic_accept_irq(apic, APIC_DM_FIXED, vector, 1, 0);
-
+        if (waitqueue_active(q))
+                wake_up_interruptible(q);
         if (apic_lvtt_period(apic)) {
-                u32 offset;
-                u32 tmict = apic_get_reg(apic, APIC_TMICT);
-
-                offset = APIC_BUS_CYCLE_NS * apic->timer.divide_count * tmict;
-
                 result = 1;
                 apic->timer.dev.expires = ktime_add_ns(
                                         apic->timer.dev.expires,
                                         apic->timer.period);
         }
-
         return result;
 }
 
+static int __inject_apic_timer_irq(struct kvm_lapic *apic)
+{
+        int vector;
+
+        vector = apic_lvt_vector(apic, APIC_LVTT);
+        return __apic_accept_irq(apic, APIC_DM_FIXED, vector, 1, 0);
+}
+
 static enum hrtimer_restart apic_timer_fn(struct hrtimer *data)
 {
         struct kvm_lapic *apic;
@@ -935,6 +932,27 @@ int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
         return highest_irr;
 }
 
+void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu)
+{
+        struct kvm_lapic *apic = vcpu->apic;
+
+        if (apic && apic_lvt_enabled(apic, APIC_LVTT) &&
+                atomic_read(&apic->timer.pending) > 0) {
+                if (__inject_apic_timer_irq(apic))
+                        atomic_dec(&apic->timer.pending);
+        }
+}
+
+void kvm_apic_timer_intr_post(struct kvm_vcpu *vcpu, int vec)
+{
+        struct kvm_lapic *apic = vcpu->apic;
+
+        if (apic && apic_lvt_vector(apic, APIC_LVTT) == vec)
+                apic->timer.last_update = ktime_add_ns(
+                                apic->timer.last_update,
+                                apic->timer.period);
+}
+
 int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
 {
         int vector = kvm_apic_has_interrupt(vcpu);