From e48258009d941891fca35348986b8d280caf31cd Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Wed, 24 Sep 2008 20:28:34 -0300 Subject: KVM: PIC: enhance IPI avoidance The PIC code makes little effort to avoid kvm_vcpu_kick(), resulting in unnecessary guest exits in some conditions. For example, if the timer interrupt is routed through the IOAPIC, IRR for IRQ 0 will get set but not cleared, since the APIC is handling the acks. This means that everytime an interrupt < 16 is triggered, the priority logic will find IRQ0 pending and send an IPI to vcpu0 (in case IRQ0 is not masked, which is Linux's case). Introduce a new variable isr_ack to represent the IRQ's for which the guest has been signalled / cleared the ISR. Use it to avoid more than one IPI per trigger-ack cycle, in addition to the avoidance when ISR is set in get_priority(). Signed-off-by: Marcelo Tosatti Signed-off-by: Avi Kivity --- arch/x86/kvm/i8259.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) (limited to 'arch/x86/kvm/i8259.c') diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c index 71e3eeeccae8..17e41e165f1a 100644 --- a/arch/x86/kvm/i8259.c +++ b/arch/x86/kvm/i8259.c @@ -33,6 +33,14 @@ static void pic_clear_isr(struct kvm_kpic_state *s, int irq) { s->isr &= ~(1 << irq); + s->isr_ack |= (1 << irq); +} + +void kvm_pic_clear_isr_ack(struct kvm *kvm) +{ + struct kvm_pic *s = pic_irqchip(kvm); + s->pics[0].isr_ack = 0xff; + s->pics[1].isr_ack = 0xff; } /* @@ -213,6 +221,7 @@ void kvm_pic_reset(struct kvm_kpic_state *s) s->irr = 0; s->imr = 0; s->isr = 0; + s->isr_ack = 0xff; s->priority_add = 0; s->irq_base = 0; s->read_reg_select = 0; @@ -444,10 +453,14 @@ static void pic_irq_request(void *opaque, int level) { struct kvm *kvm = opaque; struct kvm_vcpu *vcpu = kvm->vcpus[0]; + struct kvm_pic *s = pic_irqchip(kvm); + int irq = pic_get_irq(&s->pics[0]); - pic_irqchip(kvm)->output = level; - if (vcpu) + s->output = level; + if (vcpu && level && (s->pics[0].isr_ack & (1 << irq))) { + s->pics[0].isr_ack &= ~(1 << irq); kvm_vcpu_kick(vcpu); + } } struct kvm_pic *kvm_create_pic(struct kvm *kvm) -- cgit v1.2.3