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authorGleb Natapov <gleb@redhat.com>2009-06-11 11:06:51 +0300
committerAvi Kivity <avi@redhat.com>2009-09-10 08:32:57 +0300
commit33e4c68656a2e461b296ce714ec322978de85412 (patch)
tree9fbadb2c192cc22dca24dc6dfac6804dba5e70e8 /arch/x86/kvm/lapic.c
parent6edf14d8d0df144d6928799040f46fa37b5460ae (diff)
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KVM: Optimize searching for highest IRR
Most of the time IRR is empty, so instead of scanning the whole IRR on each VM entry keep a variable that tells us if IRR is not empty. IRR will have to be scanned twice on each IRQ delivery, but this is much more rare than VM entry. Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch/x86/kvm/lapic.c')
-rw-r--r--arch/x86/kvm/lapic.c24
1 files changed, 21 insertions, 3 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index b1694dc4572..3bde43c3789 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -165,29 +165,46 @@ static int find_highest_vector(void *bitmap)
static inline int apic_test_and_set_irr(int vec, struct kvm_lapic *apic)
{
+ apic->irr_pending = true;
return apic_test_and_set_vector(vec, apic->regs + APIC_IRR);
}
-static inline void apic_clear_irr(int vec, struct kvm_lapic *apic)
+static inline int apic_search_irr(struct kvm_lapic *apic)
{
- apic_clear_vector(vec, apic->regs + APIC_IRR);
+ return find_highest_vector(apic->regs + APIC_IRR);
}
static inline int apic_find_highest_irr(struct kvm_lapic *apic)
{
int result;
- result = find_highest_vector(apic->regs + APIC_IRR);
+ if (!apic->irr_pending)
+ return -1;
+
+ result = apic_search_irr(apic);
ASSERT(result == -1 || result >= 16);
return result;
}
+static inline void apic_clear_irr(int vec, struct kvm_lapic *apic)
+{
+ apic->irr_pending = false;
+ apic_clear_vector(vec, apic->regs + APIC_IRR);
+ if (apic_search_irr(apic) != -1)
+ apic->irr_pending = true;
+}
+
int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu)
{
struct kvm_lapic *apic = vcpu->arch.apic;
int highest_irr;
+ /* This may race with setting of irr in __apic_accept_irq() and
+ * value returned may be wrong, but kvm_vcpu_kick() in __apic_accept_irq
+ * will cause vmexit immediately and the value will be recalculated
+ * on the next vmentry.
+ */
if (!apic)
return 0;
highest_irr = apic_find_highest_irr(apic);
@@ -843,6 +860,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu)
apic_set_reg(apic, APIC_ISR + 0x10 * i, 0);
apic_set_reg(apic, APIC_TMR + 0x10 * i, 0);
}
+ apic->irr_pending = false;
update_divide_count(apic);
atomic_set(&apic->lapic_timer.pending, 0);
if (kvm_vcpu_is_bsp(vcpu))