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[Qemu-devel] [PATCH] KVM: PIC: Only commit irq routing when necessary

From: Alexander Graf
Subject: [Qemu-devel] [PATCH] KVM: PIC: Only commit irq routing when necessary
Date: Wed, 24 Apr 2013 22:51:24 +0200

The current logic updates KVM's view of our interrupt map every time we
change it. While this is nice and bullet proof, it slows things down
badly for me. QEMU spends about 3 seconds on every start telling KVM what
news it has on its routing maps.

Instead, let's just synchronize the whole irq routing map as a whole when
we're done constructing it. For things that change during runtime, we can
still update the routing table on demand.

Signed-off-by: Alexander Graf <address@hidden>
CC: Jan Kiszka <address@hidden>

diff --git a/hw/kvm/ioapic.c b/hw/kvm/ioapic.c
index 23877d4..3d561a5 100644
--- a/hw/kvm/ioapic.c
+++ b/hw/kvm/ioapic.c
@@ -40,6 +40,7 @@ void kvm_pc_setup_irq_routing(bool pci_enabled)
+        kvm_irqchip_commit_routes(s);
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index df43951..8a9ebda 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -210,6 +210,7 @@ int kvm_set_irq(KVMState *s, int irq, int level);
 int kvm_irqchip_send_msi(KVMState *s, MSIMessage msg);
 void kvm_irqchip_add_irq_route(KVMState *s, int gsi, int irqchip, int pin);
+void kvm_irqchip_commit_routes(KVMState *s);
 void kvm_put_apic_state(DeviceState *d, struct kvm_lapic_state *kapic);
 void kvm_get_apic_state(DeviceState *d, struct kvm_lapic_state *kapic);
diff --git a/kvm-all.c b/kvm-all.c
index 73dea26..130cdbc 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -900,7 +900,7 @@ void kvm_init_irq_routing(KVMState *s)
-static void kvm_irqchip_commit_routes(KVMState *s)
+void kvm_irqchip_commit_routes(KVMState *s)
     int ret;
@@ -934,8 +934,6 @@ static void kvm_add_routing_entry(KVMState *s,
     new->u = entry->u;
     set_gsi(s, entry->gsi);
-    kvm_irqchip_commit_routes(s);
 static int kvm_update_routing_entry(KVMState *s,
@@ -1086,6 +1084,7 @@ int kvm_irqchip_send_msi(KVMState *s, MSIMessage msg)
         route->kroute.u.msi.data = le32_to_cpu(msg.data);
         kvm_add_routing_entry(s, &route->kroute);
+        kvm_irqchip_commit_routes(s);
         QTAILQ_INSERT_TAIL(&s->msi_hashtab[kvm_hash_msi(msg.data)], route,
@@ -1118,6 +1117,7 @@ int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg)
     kroute.u.msi.data = le32_to_cpu(msg.data);
     kvm_add_routing_entry(s, &kroute);
+    kvm_irqchip_commit_routes(s);
     return virq;

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