kvm: remove an atomic on EOI
TMR is set with IRR but does not need to be
cleared on EOI. So we can save an atomic
operation on EOI by checking whether ioapic
needs a specific vector first.
For consistency, don't clear TMR for handled
vectors either: the spec doesn't say that
it needs to be cleared on EOI.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 8584322..992b4ea 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -92,6 +92,11 @@
return test_and_clear_bit(VEC_POS(vec), (bitmap) + REG_POS(vec));
}
+static inline int apic_test_vector(int vec, void *bitmap)
+{
+ return test_bit(VEC_POS(vec), (bitmap) + REG_POS(vec));
+}
+
static inline void apic_set_vector(int vec, void *bitmap)
{
set_bit(VEC_POS(vec), (bitmap) + REG_POS(vec));
@@ -480,7 +485,6 @@
static void apic_set_eoi(struct kvm_lapic *apic)
{
int vector = apic_find_highest_isr(apic);
- int trigger_mode;
/*
* Not every write EOI will has corresponding ISR,
* one example is when Kernel check timer on setup_IO_APIC
@@ -491,12 +495,15 @@
apic_clear_vector(vector, apic->regs + APIC_ISR);
apic_update_ppr(apic);
- if (apic_test_and_clear_vector(vector, apic->regs + APIC_TMR))
- trigger_mode = IOAPIC_LEVEL_TRIG;
- else
- trigger_mode = IOAPIC_EDGE_TRIG;
- if (!(apic_get_reg(apic, APIC_SPIV) & APIC_SPIV_DIRECTED_EOI))
+ if (!(apic_get_reg(apic, APIC_SPIV) & APIC_SPIV_DIRECTED_EOI) &&
+ kvm_ioapic_handles_vector(apic->vcpu->kvm, vector)) {
+ int trigger_mode;
+ if (apic_test_vector(vector, apic->regs + APIC_TMR))
+ trigger_mode = IOAPIC_LEVEL_TRIG;
+ else
+ trigger_mode = IOAPIC_EDGE_TRIG;
kvm_ioapic_update_eoi(apic->vcpu->kvm, vector, trigger_mode);
+ }
kvm_make_request(KVM_REQ_EVENT, apic->vcpu);
}
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index dcaf272c26..26fd54d 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -254,13 +254,17 @@
}
}
+bool kvm_ioapic_handles_vector(struct kvm *kvm, int vector)
+{
+ struct kvm_ioapic *ioapic = kvm->arch.vioapic;
+ smp_rmb();
+ return test_bit(vector, ioapic->handled_vectors);
+}
+
void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode)
{
struct kvm_ioapic *ioapic = kvm->arch.vioapic;
- smp_rmb();
- if (!test_bit(vector, ioapic->handled_vectors))
- return;
spin_lock(&ioapic->lock);
__kvm_ioapic_update_eoi(ioapic, vector, trigger_mode);
spin_unlock(&ioapic->lock);
diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h
index 0b190c3..32872a0 100644
--- a/virt/kvm/ioapic.h
+++ b/virt/kvm/ioapic.h
@@ -71,6 +71,7 @@
int short_hand, int dest, int dest_mode);
int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2);
void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode);
+bool kvm_ioapic_handles_vector(struct kvm *kvm, int vector);
int kvm_ioapic_init(struct kvm *kvm);
void kvm_ioapic_destroy(struct kvm *kvm);
int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
