KVM: Report IRQ injection status to userspace.

IRQ injection status is either -1 (if there was no CPU found
that should except the interrupt because IRQ was masked or
ioapic was misconfigured or ...) or >= 0 in that case the
number indicates to how many CPUs interrupt was injected.
If the value is 0 it means that the interrupt was coalesced
and probably should be reinjected.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 45 insertions, 21 deletions

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 1c986ac..c3b99de 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -83,19 +83,22 @@ static unsigned long ioapic_read_indirect(struct kvm_ioapic *ioapic,
 	return result;
 }
 
-static void ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx)
+static int ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx)
 {
 	union ioapic_redir_entry *pent;
+	int injected = -1;
 
 	pent = &ioapic->redirtbl[idx];
 
 	if (!pent->fields.mask) {
-		int injected = ioapic_deliver(ioapic, idx);
+		injected = ioapic_deliver(ioapic, idx);
 		if (injected && pent->fields.trig_mode == IOAPIC_LEVEL_TRIG)
 			pent->fields.remote_irr = 1;
 	}
 	if (!pent->fields.trig_mode)
 		ioapic->irr &= ~(1 << idx);
+
+	return injected;
 }
 
 static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
@@ -207,7 +210,7 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
 	u8 trig_mode = ioapic->redirtbl[irq].fields.trig_mode;
 	u32 deliver_bitmask;
 	struct kvm_vcpu *vcpu;
-	int vcpu_id, r = 0;
+	int vcpu_id, r = -1;
 
 	ioapic_debug("dest=%x dest_mode=%x delivery_mode=%x "
 		     "vector=%x trig_mode=%x\n",
@@ -247,7 +250,9 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
 			deliver_bitmask &= ~(1 << vcpu_id);
 			vcpu = ioapic->kvm->vcpus[vcpu_id];
 			if (vcpu) {
-				r = ioapic_inj_irq(ioapic, vcpu, vector,
+				if (r < 0)
+					r = 0;
+				r += ioapic_inj_irq(ioapic, vcpu, vector,
 					       trig_mode, delivery_mode);
 			}
 		}
@@ -258,8 +263,10 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
 				continue;
 			deliver_bitmask &= ~(1 << vcpu_id);
 			vcpu = ioapic->kvm->vcpus[vcpu_id];
-			if (vcpu)
+			if (vcpu) {
 				ioapic_inj_nmi(vcpu);
+				r = 1;
+			}
 			else
 				ioapic_debug("NMI to vcpu %d failed\n",
 						vcpu->vcpu_id);
@@ -273,11 +280,12 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
 	return r;
 }
 
-void kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
+int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
 {
 	u32 old_irr = ioapic->irr;
 	u32 mask = 1 << irq;
 	union ioapic_redir_entry entry;
+	int ret = 1;
 
 	if (irq >= 0 && irq < IOAPIC_NUM_PINS) {
 		entry = ioapic->redirtbl[irq];
@@ -288,9 +296,10 @@ void kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
 			ioapic->irr |= mask;
 			if ((!entry.fields.trig_mode && old_irr != ioapic->irr)
 			    || !entry.fields.remote_irr)
-				ioapic_service(ioapic, irq);
+				ret = ioapic_service(ioapic, irq);
 		}
 	}
+	return ret;
 }
 
 static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int pin,
diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h
index 49c9581..a34bd5e 100644
--- a/virt/kvm/ioapic.h
+++ b/virt/kvm/ioapic.h
@@ -83,7 +83,7 @@ struct kvm_vcpu *kvm_get_lowest_prio_vcpu(struct kvm *kvm, u8 vector,
 				       unsigned long bitmap);
 void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode);
 int kvm_ioapic_init(struct kvm *kvm);
-void kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
+int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
 void kvm_ioapic_reset(struct kvm_ioapic *ioapic);
 u32 kvm_ioapic_get_delivery_bitmask(struct kvm_ioapic *ioapic, u8 dest,
 				u8 dest_mode);
diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 6bc7439..be8aba7 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -29,22 +29,24 @@
 
 #include "ioapic.h"
 
-static void kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
-			    struct kvm *kvm, int level)
+static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
+			   struct kvm *kvm, int level)
 {
 #ifdef CONFIG_X86
-	kvm_pic_set_irq(pic_irqchip(kvm), e->irqchip.pin, level);
+	return kvm_pic_set_irq(pic_irqchip(kvm), e->irqchip.pin, level);
+#else
+	return -1;
 #endif
 }
 
-static void kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
-			       struct kvm *kvm, int level)
+static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
+			      struct kvm *kvm, int level)
 {
-	kvm_ioapic_set_irq(kvm->arch.vioapic, e->irqchip.pin, level);
+	return kvm_ioapic_set_irq(kvm->arch.vioapic, e->irqchip.pin, level);
 }
 
-static void kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
-			struct kvm *kvm, int level)
+static int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
+		       struct kvm *kvm, int level)
 {
 	int vcpu_id;
 	struct kvm_vcpu *vcpu;
@@ -88,13 +90,20 @@ static void kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
 	default:
 		break;
 	}
+	return 1;
 }
 
-/* This should be called with the kvm->lock mutex held */
-void kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
+/* This should be called with the kvm->lock mutex held
+ * Return value:
+ *  < 0   Interrupt was ignored (masked or not delivered for other reasons)
+ *  = 0   Interrupt was coalesced (previous irq is still pending)
+ *  > 0   Number of CPUs interrupt was delivered to
+ */
+int kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
 {
 	struct kvm_kernel_irq_routing_entry *e;
 	unsigned long *irq_state, sig_level;
+	int ret = -1;
 
 	if (irq < KVM_IOAPIC_NUM_PINS) {
 		irq_state = (unsigned long *)&kvm->arch.irq_states[irq];
@@ -113,8 +122,14 @@ void kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
 	 * writes to the unused one.
 	 */
 	list_for_each_entry(e, &kvm->irq_routing, link)
-		if (e->gsi == irq)
-			e->set(e, kvm, sig_level);
+		if (e->gsi == irq) {
+			int r = e->set(e, kvm, sig_level);
+			if (r < 0)
+				continue;
+
+			ret = r + ((ret < 0) ? 0 : ret);
+		}
+	return ret;
 }
 
 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
@@ -232,7 +247,7 @@ int setup_routing_entry(struct kvm_kernel_irq_routing_entry *e,
 			e->set = kvm_set_pic_irq;
 			break;
 		case KVM_IRQCHIP_PIC_SLAVE:
-				e->set = kvm_set_pic_irq;
+			e->set = kvm_set_pic_irq;
 			delta = 8;
 			break;
 		case KVM_IRQCHIP_IOAPIC: