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authorMarcelo Tosatti <mtosatti@redhat.com>2008-09-24 19:28:34 -0400
committerAvi Kivity <avi@redhat.com>2008-10-15 08:25:28 -0400
commite48258009d941891fca35348986b8d280caf31cd (patch)
tree73d1fb56a9fc22c1e55160bb04e772bd6b2244fb /arch
parent582801a95d2f2ceab841779e1dec0e11dfec44c0 (diff)
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 71e3eeeccae8..17e41e165f1a 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -33,6 +33,14 @@
33static void pic_clear_isr(struct kvm_kpic_state *s, int irq) 33static void pic_clear_isr(struct kvm_kpic_state *s, int irq)
34{ 34{
35 s->isr &= ~(1 << irq); 35 s->isr &= ~(1 << irq);
36 s->isr_ack |= (1 << irq);
37}
38
39void kvm_pic_clear_isr_ack(struct kvm *kvm)
40{
41 struct kvm_pic *s = pic_irqchip(kvm);
42 s->pics[0].isr_ack = 0xff;
43 s->pics[1].isr_ack = 0xff;
36} 44}
37 45
38/* 46/*
@@ -213,6 +221,7 @@ void kvm_pic_reset(struct kvm_kpic_state *s)
213 s->irr = 0; 221 s->irr = 0;
214 s->imr = 0; 222 s->imr = 0;
215 s->isr = 0; 223 s->isr = 0;
224 s->isr_ack = 0xff;
216 s->priority_add = 0; 225 s->priority_add = 0;
217 s->irq_base = 0; 226 s->irq_base = 0;
218 s->read_reg_select = 0; 227 s->read_reg_select = 0;
@@ -444,10 +453,14 @@ static void pic_irq_request(void *opaque, int level)
444{ 453{
445 struct kvm *kvm = opaque; 454 struct kvm *kvm = opaque;
446 struct kvm_vcpu *vcpu = kvm->vcpus[0]; 455 struct kvm_vcpu *vcpu = kvm->vcpus[0];
456 struct kvm_pic *s = pic_irqchip(kvm);
457 int irq = pic_get_irq(&s->pics[0]);
447 458
448 pic_irqchip(kvm)->output = level; 459 s->output = level;
449 if (vcpu) 460 if (vcpu && level && (s->pics[0].isr_ack & (1 << irq))) {
461 s->pics[0].isr_ack &= ~(1 << irq);
450 kvm_vcpu_kick(vcpu); 462 kvm_vcpu_kick(vcpu);
463 }
451} 464}
452 465
453struct kvm_pic *kvm_create_pic(struct kvm *kvm) 466struct kvm_pic *kvm_create_pic(struct kvm *kvm)
diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index 479a3d2d5614..4748532fd1da 100644
--- a/arch/x86/kvm/irq.h
+++ b/arch/x86/kvm/irq.h
@@ -42,6 +42,7 @@ struct kvm_kpic_state {
42 u8 irr; /* interrupt request register */ 42 u8 irr; /* interrupt request register */
43 u8 imr; /* interrupt mask register */ 43 u8 imr; /* interrupt mask register */
44 u8 isr; /* interrupt service register */ 44 u8 isr; /* interrupt service register */
45 u8 isr_ack; /* interrupt ack detection */
45 u8 priority_add; /* highest irq priority */ 46 u8 priority_add; /* highest irq priority */
46 u8 irq_base; 47 u8 irq_base;
47 u8 read_reg_select; 48 u8 read_reg_select;
@@ -70,6 +71,7 @@ struct kvm_pic *kvm_create_pic(struct kvm *kvm);
70void kvm_pic_set_irq(void *opaque, int irq, int level); 71void kvm_pic_set_irq(void *opaque, int irq, int level);
71int kvm_pic_read_irq(struct kvm *kvm); 72int kvm_pic_read_irq(struct kvm *kvm);
72void kvm_pic_update_irq(struct kvm_pic *s); 73void kvm_pic_update_irq(struct kvm_pic *s);
74void kvm_pic_clear_isr_ack(struct kvm *kvm);
73 75
74static inline struct kvm_pic *pic_irqchip(struct kvm *kvm) 76static inline struct kvm_pic *pic_irqchip(struct kvm *kvm)
75{ 77{
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1c5864ac0837..4cfdd1b6df0b 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,
3963 pr_debug("Set back pending irq %d\n", 3963 pr_debug("Set back pending irq %d\n",
3964 pending_vec); 3964 pending_vec);
3965 } 3965 }
3966 kvm_pic_clear_isr_ack(vcpu->kvm);
3966 } 3967 }
3967 3968
3968 kvm_set_segment(vcpu, &sregs->cs, VCPU_SREG_CS); 3969 kvm_set_segment(vcpu, &sregs->cs, VCPU_SREG_CS);