diff options
| author | Marcelo Tosatti <mtosatti@redhat.com> | 2008-09-24 20:28:34 -0300 |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2008-10-15 14:25:28 +0200 |
| commit | e48258009d941891fca35348986b8d280caf31cd (patch) | |
| tree | 73d1fb56a9fc22c1e55160bb04e772bd6b2244fb /arch/x86/kvm/i8259.c | |
| parent | 582801a95d2f2ceab841779e1dec0e11dfec44c0 (diff) | |
| download | linux-e48258009d941891fca35348986b8d280caf31cd.tar.bz2 | |
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 <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch/x86/kvm/i8259.c')
| -rw-r--r-- | arch/x86/kvm/i8259.c | 17 |
1 files changed, 15 insertions, 2 deletions
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) |