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authorAvi Kivity <avi@redhat.com>2009-12-28 07:08:30 -0500
committerMarcelo Tosatti <mtosatti@redhat.com>2010-03-01 10:35:46 -0500
commit46a929bc15fcd48e1e0e770a44040a6949cae133 (patch)
tree5351d75586821e74d82c59f1e1cde10806a25237 /virt/kvm
parentf4c9e87c83a9f5bc1800db27dbb39e5cd1254c0a (diff)
KVM: avoid taking ioapic mutex for non-ioapic EOIs
When the guest acknowledges an interrupt, it sends an EOI message to the local apic, which broadcasts it to the ioapic. To handle the EOI, we need to take the ioapic mutex. On large guests, this causes a lot of contention on this mutex. Since large guests usually don't route interrupts via the ioapic (they use msi instead), this is completely unnecessary. Avoid taking the mutex by introducing a handled_vectors bitmap. Before taking the mutex, check if the ioapic was actually responsible for the acked vector. If not, we can return early. Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'virt/kvm')
-rw-r--r--virt/kvm/ioapic.c19
-rw-r--r--virt/kvm/ioapic.h1
2 files changed, 20 insertions, 0 deletions
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index f01392f51e86..a2edfd177faf 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -100,6 +100,19 @@ static int ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx)
100 return injected; 100 return injected;
101} 101}
102 102
103static void update_handled_vectors(struct kvm_ioapic *ioapic)
104{
105 DECLARE_BITMAP(handled_vectors, 256);
106 int i;
107
108 memset(handled_vectors, 0, sizeof(handled_vectors));
109 for (i = 0; i < IOAPIC_NUM_PINS; ++i)
110 __set_bit(ioapic->redirtbl[i].fields.vector, handled_vectors);
111 memcpy(ioapic->handled_vectors, handled_vectors,
112 sizeof(handled_vectors));
113 smp_wmb();
114}
115
103static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val) 116static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
104{ 117{
105 unsigned index; 118 unsigned index;
@@ -134,6 +147,7 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
134 e->bits |= (u32) val; 147 e->bits |= (u32) val;
135 e->fields.remote_irr = 0; 148 e->fields.remote_irr = 0;
136 } 149 }
150 update_handled_vectors(ioapic);
137 mask_after = e->fields.mask; 151 mask_after = e->fields.mask;
138 if (mask_before != mask_after) 152 if (mask_before != mask_after)
139 kvm_fire_mask_notifiers(ioapic->kvm, index, mask_after); 153 kvm_fire_mask_notifiers(ioapic->kvm, index, mask_after);
@@ -241,6 +255,9 @@ void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode)
241{ 255{
242 struct kvm_ioapic *ioapic = kvm->arch.vioapic; 256 struct kvm_ioapic *ioapic = kvm->arch.vioapic;
243 257
258 smp_rmb();
259 if (!test_bit(vector, ioapic->handled_vectors))
260 return;
244 mutex_lock(&ioapic->lock); 261 mutex_lock(&ioapic->lock);
245 __kvm_ioapic_update_eoi(ioapic, vector, trigger_mode); 262 __kvm_ioapic_update_eoi(ioapic, vector, trigger_mode);
246 mutex_unlock(&ioapic->lock); 263 mutex_unlock(&ioapic->lock);
@@ -352,6 +369,7 @@ void kvm_ioapic_reset(struct kvm_ioapic *ioapic)
352 ioapic->ioregsel = 0; 369 ioapic->ioregsel = 0;
353 ioapic->irr = 0; 370 ioapic->irr = 0;
354 ioapic->id = 0; 371 ioapic->id = 0;
372 update_handled_vectors(ioapic);
355} 373}
356 374
357static const struct kvm_io_device_ops ioapic_mmio_ops = { 375static const struct kvm_io_device_ops ioapic_mmio_ops = {
@@ -401,6 +419,7 @@ int kvm_set_ioapic(struct kvm *kvm, struct kvm_ioapic_state *state)
401 419
402 mutex_lock(&ioapic->lock); 420 mutex_lock(&ioapic->lock);
403 memcpy(ioapic, state, sizeof(struct kvm_ioapic_state)); 421 memcpy(ioapic, state, sizeof(struct kvm_ioapic_state));
422 update_handled_vectors(ioapic);
404 mutex_unlock(&ioapic->lock); 423 mutex_unlock(&ioapic->lock);
405 return 0; 424 return 0;
406} 425}
diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h
index 419c43b667ab..a505ce9054f3 100644
--- a/virt/kvm/ioapic.h
+++ b/virt/kvm/ioapic.h
@@ -46,6 +46,7 @@ struct kvm_ioapic {
46 struct kvm *kvm; 46 struct kvm *kvm;
47 void (*ack_notifier)(void *opaque, int irq); 47 void (*ack_notifier)(void *opaque, int irq);
48 struct mutex lock; 48 struct mutex lock;
49 DECLARE_BITMAP(handled_vectors, 256);
49}; 50};
50 51
51#ifdef DEBUG 52#ifdef DEBUG