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authorMarcelo Tosatti <mtosatti@redhat.com>2008-09-24 20:28:34 -0300
committerAvi Kivity <avi@redhat.com>2008-10-15 14:25:28 +0200
commite48258009d941891fca35348986b8d280caf31cd (patch)
tree73d1fb56a9fc22c1e55160bb04e772bd6b2244fb /arch
parent582801a95d2f2ceab841779e1dec0e11dfec44c0 (diff)
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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')
-rw-r--r--arch/x86/kvm/i8259.c17
-rw-r--r--arch/x86/kvm/irq.h2
-rw-r--r--arch/x86/kvm/x86.c1
3 files changed, 18 insertions, 2 deletions
diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 71e3eeeccae..17e41e165f1 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)
diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index 479a3d2d561..4748532fd1d 100644
--- a/arch/x86/kvm/irq.h
+++ b/arch/x86/kvm/irq.h
@@ -42,6 +42,7 @@ struct kvm_kpic_state {
u8 irr; /* interrupt request register */
u8 imr; /* interrupt mask register */
u8 isr; /* interrupt service register */
+ u8 isr_ack; /* interrupt ack detection */
u8 priority_add; /* highest irq priority */
u8 irq_base;
u8 read_reg_select;
@@ -70,6 +71,7 @@ struct kvm_pic *kvm_create_pic(struct kvm *kvm);
void kvm_pic_set_irq(void *opaque, int irq, int level);
int kvm_pic_read_irq(struct kvm *kvm);
void kvm_pic_update_irq(struct kvm_pic *s);
+void kvm_pic_clear_isr_ack(struct kvm *kvm);
static inline struct kvm_pic *pic_irqchip(struct kvm *kvm)
{
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1c5864ac083..4cfdd1b6df0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3963,6 +3963,7 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
pr_debug("Set back pending irq %d\n",
pending_vec);
}
+ kvm_pic_clear_isr_ack(vcpu->kvm);
}
kvm_set_segment(vcpu, &sregs->cs, VCPU_SREG_CS);