kvm: Conditionally register IRQ bypass consumer

If we don't support a mechanism for bypassing IRQs, don't register as
a consumer.  This eliminates meaningless dev_info()s when the connect
fails between producer and consumer, such as on AMD systems where
kvm_x86_ops->update_pi_irte is not implemented
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -8358,19 +8358,21 @@ bool kvm_arch_has_noncoherent_dma(struct kvm *kvm)
 }
 EXPORT_SYMBOL_GPL(kvm_arch_has_noncoherent_dma);
 
+bool kvm_arch_has_irq_bypass(void)
+{
+	return kvm_x86_ops->update_pi_irte != NULL;
+}
+
 int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *cons,
 				      struct irq_bypass_producer *prod)
 {
 	struct kvm_kernel_irqfd *irqfd =
 		container_of(cons, struct kvm_kernel_irqfd, consumer);
 
-	if (kvm_x86_ops->update_pi_irte) {
-		irqfd->producer = prod;
-		return kvm_x86_ops->update_pi_irte(irqfd->kvm,
-				prod->irq, irqfd->gsi, 1);
-	}
+	irqfd->producer = prod;
 
-	return -EINVAL;
+	return kvm_x86_ops->update_pi_irte(irqfd->kvm,
+					   prod->irq, irqfd->gsi, 1);
 }
 
 void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
@@ -8380,11 +8382,6 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
 	struct kvm_kernel_irqfd *irqfd =
 		container_of(cons, struct kvm_kernel_irqfd, consumer);
 
-	if (!kvm_x86_ops->update_pi_irte) {
-		WARN_ON(irqfd->producer != NULL);
-		return;
-	}
-
 	WARN_ON(irqfd->producer != prod);
 	irqfd->producer = NULL;
 

include/linux/kvm_host.h

@@ -1185,6 +1185,7 @@ static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
 #endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
 
 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
+bool kvm_arch_has_irq_bypass(void);
 int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *,
 			   struct irq_bypass_producer *);
 void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *,

virt/kvm/eventfd.c

@@ -408,15 +408,17 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
 	 */
 	fdput(f);
 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
-	irqfd->consumer.token = (void *)irqfd->eventfd;
-	irqfd->consumer.add_producer = kvm_arch_irq_bypass_add_producer;
-	irqfd->consumer.del_producer = kvm_arch_irq_bypass_del_producer;
-	irqfd->consumer.stop = kvm_arch_irq_bypass_stop;
-	irqfd->consumer.start = kvm_arch_irq_bypass_start;
-	ret = irq_bypass_register_consumer(&irqfd->consumer);
-	if (ret)
-		pr_info("irq bypass consumer (token %p) registration fails: %d\n",
+	if (kvm_arch_has_irq_bypass()) {
+		irqfd->consumer.token = (void *)irqfd->eventfd;
+		irqfd->consumer.add_producer = kvm_arch_irq_bypass_add_producer;
+		irqfd->consumer.del_producer = kvm_arch_irq_bypass_del_producer;
+		irqfd->consumer.stop = kvm_arch_irq_bypass_stop;
+		irqfd->consumer.start = kvm_arch_irq_bypass_start;
+		ret = irq_bypass_register_consumer(&irqfd->consumer);
+		if (ret)
+			pr_info("irq bypass consumer (token %p) registration fails: %d\n",
 				irqfd->consumer.token, ret);
+	}
 #endif
 
 	return 0;