KVM: deliver PIC interrupt only to vcpu0

This patch changes the PIC interrupts delivery. Now it is only delivered
to vcpu0 when either condition is met (on vcpu0):
  1. local APIC is hardware disabled
  2. LVT0 is unmasked and configured to delivery mode ExtInt

It fixes the 2x faster wall clock on x86_64 and SMP i386 Linux guests

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

3 files changed, 28 insertions, 5 deletions

diff --git a/drivers/kvm/irq.c b/drivers/kvm/irq.c
index b88e5011558..7628c7ff628 100644
--- a/drivers/kvm/irq.c
+++ b/drivers/kvm/irq.c
@@ -33,8 +33,11 @@ int kvm_cpu_has_interrupt(struct kvm_vcpu *v)
         struct kvm_pic *s;
 
         if (kvm_apic_has_interrupt(v) == -1) {  /* LAPIC */
-                s = pic_irqchip(v->kvm);        /* PIC */
-                return s->output;
+                if (kvm_apic_accept_pic_intr(v)) {
+                        s = pic_irqchip(v->kvm);        /* PIC */
+                        return s->output;
+                } else
+                        return 0;
         }
         return 1;
 }
@@ -50,9 +53,11 @@ int kvm_cpu_get_interrupt(struct kvm_vcpu *v)
 
         vector = kvm_get_apic_interrupt(v);     /* APIC */
         if (vector == -1) {
-                s = pic_irqchip(v->kvm);
-                s->output = 0;          /* PIC */
-                vector = kvm_pic_read_irq(s);
+                if (kvm_apic_accept_pic_intr(v)) {
+                        s = pic_irqchip(v->kvm);
+                        s->output = 0;          /* PIC */
+                        vector = kvm_pic_read_irq(s);
+                }
         }
         return vector;
 }
diff --git a/drivers/kvm/irq.h b/drivers/kvm/irq.h
index f324cfb4008..ec46a09e213 100644
--- a/drivers/kvm/irq.h
+++ b/drivers/kvm/irq.h
@@ -135,6 +135,7 @@ do {									\
 
 void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
 int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu);
+int kvm_apic_accept_pic_intr(struct kvm_vcpu *vcpu);
 int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu);
 int kvm_create_lapic(struct kvm_vcpu *vcpu);
 void kvm_free_apic(struct kvm_lapic *apic);
diff --git a/drivers/kvm/lapic.c b/drivers/kvm/lapic.c
index 2706ec36c25..01e769672dc 100644
--- a/drivers/kvm/lapic.c
+++ b/drivers/kvm/lapic.c
@@ -788,6 +788,8 @@ static void lapic_reset(struct kvm_vcpu *vcpu)
 
         for (i = 0; i < APIC_LVT_NUM; i++)
                 apic_set_reg(apic, APIC_LVTT + 0x10 * i, APIC_LVT_MASKED);
+        apic_set_reg(apic, APIC_LVT0,
+                     SET_APIC_DELIVERY_MODE(0, APIC_MODE_EXTINT));
 
         apic_set_reg(apic, APIC_DFR, 0xffffffffU);
         apic_set_reg(apic, APIC_SPIV, 0xff);
@@ -932,6 +934,21 @@ int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
         return highest_irr;
 }
 
+int kvm_apic_accept_pic_intr(struct kvm_vcpu *vcpu)
+{
+        u32 lvt0 = apic_get_reg(vcpu->apic, APIC_LVT0);
+        int r = 0;
+
+        if (vcpu->vcpu_id == 0) {
+                if (!apic_hw_enabled(vcpu->apic))
+                        r = 1;
+                if ((lvt0 & APIC_LVT_MASKED) == 0 &&
+                    GET_APIC_DELIVERY_MODE(lvt0) == APIC_MODE_EXTINT)
+                        r = 1;
+        }
+        return r;
+}
+
 void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu)
 {
         struct kvm_lapic *apic = vcpu->apic;