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>
diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index 479a3d2..4748532 100644
--- a/arch/x86/kvm/irq.h
+++ b/arch/x86/kvm/irq.h
@@ -42,6 +42,7 @@
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 @@
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)
{