KVM: Define a new interface kvm_intr_is_single_vcpu()

This patch defines a new interface kvm_intr_is_single_vcpu(),
which can returns whether the interrupt is for single-CPU or not.

It is used by VT-d PI, since now we only support single-CPU
interrupts, For lowest-priority interrupts, if user configures
it via /proc/irq or uses irqbalance to make it single-CPU, we
can use PI to deliver the interrupts to it. Full functionality
of lowest-priority support will be added later.
Signed-off-by: Feng Wu <feng.wu@intel.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1241,4 +1241,7 @@ int x86_set_memory_region(struct kvm *kvm,
 bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu);
 bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu);
 
+bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
+			     struct kvm_vcpu **dest_vcpu);
+
 #endif /* _ASM_X86_KVM_HOST_H */

arch/x86/kvm/irq_comm.c

@@ -297,6 +297,33 @@ int kvm_set_routing_entry(struct kvm_kernel_irq_routing_entry *e,
 	return r;
 }
 
+bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
+			     struct kvm_vcpu **dest_vcpu)
+{
+	int i, r = 0;
+	struct kvm_vcpu *vcpu;
+
+	if (kvm_intr_is_single_vcpu_fast(kvm, irq, dest_vcpu))
+		return true;
+
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		if (!kvm_apic_present(vcpu))
+			continue;
+
+		if (!kvm_apic_match_dest(vcpu, NULL, irq->shorthand,
+					irq->dest_id, irq->dest_mode))
+			continue;
+
+		if (++r == 2)
+			return false;
+
+		*dest_vcpu = vcpu;
+	}
+
+	return r == 1;
+}
+EXPORT_SYMBOL_GPL(kvm_intr_is_single_vcpu);
+
 #define IOAPIC_ROUTING_ENTRY(irq) \
 	{ .gsi = irq, .type = KVM_IRQ_ROUTING_IRQCHIP,	\
 	  .u.irqchip = { .irqchip = KVM_IRQCHIP_IOAPIC, .pin = (irq) } }

arch/x86/kvm/lapic.c

@@ -755,6 +755,65 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
 	return ret;
 }
 
+bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
+			struct kvm_vcpu **dest_vcpu)
+{
+	struct kvm_apic_map *map;
+	bool ret = false;
+	struct kvm_lapic *dst = NULL;
+
+	if (irq->shorthand)
+		return false;
+
+	rcu_read_lock();
+	map = rcu_dereference(kvm->arch.apic_map);
+
+	if (!map)
+		goto out;
+
+	if (irq->dest_mode == APIC_DEST_PHYSICAL) {
+		if (irq->dest_id == 0xFF)
+			goto out;
+
+		if (irq->dest_id >= ARRAY_SIZE(map->phys_map))
+			goto out;
+
+		dst = map->phys_map[irq->dest_id];
+		if (dst && kvm_apic_present(dst->vcpu))
+			*dest_vcpu = dst->vcpu;
+		else
+			goto out;
+	} else {
+		u16 cid;
+		unsigned long bitmap = 1;
+		int i, r = 0;
+
+		if (!kvm_apic_logical_map_valid(map))
+			goto out;
+
+		apic_logical_id(map, irq->dest_id, &cid, (u16 *)&bitmap);
+
+		if (cid >= ARRAY_SIZE(map->logical_map))
+			goto out;
+
+		for_each_set_bit(i, &bitmap, 16) {
+			dst = map->logical_map[cid][i];
+			if (++r == 2)
+				goto out;
+		}
+
+		if (dst && kvm_apic_present(dst->vcpu))
+			*dest_vcpu = dst->vcpu;
+		else
+			goto out;
+	}
+
+	ret = true;
+out:
+	rcu_read_unlock();
+	return ret;
+}
+
 /*
  * Add a pending IRQ into lapic.
  * Return 1 if successfully added and 0 if discarded.

arch/x86/kvm/lapic.h

@@ -168,4 +168,6 @@ bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector);
 
 void wait_lapic_expire(struct kvm_vcpu *vcpu);
 
+bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq *irq,
+			struct kvm_vcpu **dest_vcpu);
 #endif