[PATCH 079/104] KVM: deliver PIC interrupt only to vcpu0

Avi Kivity
2007-09-17T08:32:01Z

From: Qing He <qing.he-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

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-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Qing He <qing.he-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
---
drivers/kvm/irq.c | 15 ++++++++++-----
drivers/kvm/irq.h | 1 +
drivers/kvm/lapic.c | 17 +++++++++++++++++
3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/drivers/kvm/irq.c b/drivers/kvm/irq.c
index b88e501..7628c7f 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 f324cfb..ec46a09 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 2706ec3..01e7696 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;