KVM: remove isr_ack logic from PIC

isr_ack logic was added by e48258009d to avoid unnecessary IPIs. Back
then it made sense, but now the code checks that vcpu is ready to accept
interrupt before sending IPI, so this logic is no longer needed. The
patch removes it.

Fixes a regression with Debian/Hurd.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Reported-and-tested-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/i8259.c

@@ -61,9 +61,6 @@ static void pic_unlock(struct kvm_pic *s)
 			}
 		}
 
-		if (!found)
-			found = s->kvm->bsp_vcpu;
-
 		if (!found)
 			return;
 
@@ -75,7 +72,6 @@ static void pic_unlock(struct kvm_pic *s)
 static void pic_clear_isr(struct kvm_kpic_state *s, int irq)
 {
 	s->isr &= ~(1 << irq);
-	s->isr_ack |= (1 << irq);
 	if (s != &s->pics_state->pics[0])
 		irq += 8;
 	/*
@@ -89,16 +85,6 @@ static void pic_clear_isr(struct kvm_kpic_state *s, int irq)
 	pic_lock(s->pics_state);
 }
 
-void kvm_pic_clear_isr_ack(struct kvm *kvm)
-{
-	struct kvm_pic *s = pic_irqchip(kvm);
-
-	pic_lock(s);
-	s->pics[0].isr_ack = 0xff;
-	s->pics[1].isr_ack = 0xff;
-	pic_unlock(s);
-}
-
 /*
  * set irq level. If an edge is detected, then the IRR is set to 1
  */
@@ -281,7 +267,6 @@ 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;
@@ -545,15 +530,11 @@ static int picdev_read(struct kvm_io_device *this,
  */
 static void pic_irq_request(struct kvm *kvm, int level)
 {
-	struct kvm_vcpu *vcpu = kvm->bsp_vcpu;
 	struct kvm_pic *s = pic_irqchip(kvm);
-	int irq = pic_get_irq(&s->pics[0]);
 
-	s->output = level;
-	if (vcpu && level && (s->pics[0].isr_ack & (1 << irq))) {
-		s->pics[0].isr_ack &= ~(1 << irq);
+	if (!s->output)
 		s->wakeup_needed = true;
-	}
+	s->output = level;
 }
 
 static const struct kvm_io_device_ops picdev_ops = {
@@ -575,8 +556,6 @@ struct kvm_pic *kvm_create_pic(struct kvm *kvm)
 	s->pics[1].elcr_mask = 0xde;
 	s->pics[0].pics_state = s;
 	s->pics[1].pics_state = s;
-	s->pics[0].isr_ack = 0xff;
-	s->pics[1].isr_ack = 0xff;
 
 	/*
 	 * Initialize PIO device

arch/x86/kvm/x86.c

@@ -2669,8 +2669,6 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 	vcpu->arch.interrupt.pending = events->interrupt.injected;
 	vcpu->arch.interrupt.nr = events->interrupt.nr;
 	vcpu->arch.interrupt.soft = events->interrupt.soft;
-	if (vcpu->arch.interrupt.pending && irqchip_in_kernel(vcpu->kvm))
-		kvm_pic_clear_isr_ack(vcpu->kvm);
 	if (events->flags & KVM_VCPUEVENT_VALID_SHADOW)
 		kvm_x86_ops->set_interrupt_shadow(vcpu,
 						  events->interrupt.shadow);
@@ -5621,8 +5619,6 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
 	if (pending_vec < max_bits) {
 		kvm_queue_interrupt(vcpu, pending_vec, false);
 		pr_debug("Set back pending irq %d\n", pending_vec);
-		if (irqchip_in_kernel(vcpu->kvm))
-			kvm_pic_clear_isr_ack(vcpu->kvm);
 	}
 
 	kvm_set_segment(vcpu, &sregs->cs, VCPU_SREG_CS);