xen/irq: If we fail during msi_capability_init return proper error code.

There are three different modes: PV, HVM, and initial domain 0. In all
the cases we would return -1 for failure instead of a proper error code.
Fix this by propagating the error code from the generic IRQ code.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

arch/x86/pci/xen.c

@@ -175,8 +175,10 @@ static int xen_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
 					       "pcifront-msi-x" :
 					       "pcifront-msi",
 						DOMID_SELF);
-		if (irq < 0)
+		if (irq < 0) {
+			ret = irq;
 			goto free;
+		}
 		i++;
 	}
 	kfree(v);
@@ -221,8 +223,10 @@ static int xen_hvm_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
 		if (msg.data != XEN_PIRQ_MSI_DATA ||
 		    xen_irq_from_pirq(pirq) < 0) {
 			pirq = xen_allocate_pirq_msi(dev, msidesc);
-			if (pirq < 0)
+			if (pirq < 0) {
+				irq = -ENODEV;
 				goto error;
+			}
 			xen_msi_compose_msg(dev, pirq, &msg);
 			__write_msi_msg(msidesc, &msg);
 			dev_dbg(&dev->dev, "xen: msi bound to pirq=%d\n", pirq);
@@ -244,7 +248,7 @@ static int xen_hvm_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
 error:
 	dev_err(&dev->dev,
 		"Xen PCI frontend has not registered MSI/MSI-X support!\n");
-	return -ENODEV;
+	return irq;
 }
 
 #ifdef CONFIG_XEN_DOM0

drivers/xen/events.c

@@ -432,6 +432,7 @@ static int __must_check xen_allocate_irq_dynamic(void)
 
 	irq = irq_alloc_desc_from(first, -1);
 
+	if (irq >= 0)
 		xen_irq_init(irq);
 
 	return irq;
@@ -713,7 +714,7 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct msi_desc *msidesc,
 	mutex_lock(&irq_mapping_update_lock);
 
 	irq = xen_allocate_irq_dynamic();
-	if (irq == -1)
+	if (irq < 0)
 		goto out;
 
 	irq_set_chip_and_handler_name(irq, &xen_pirq_chip, handle_edge_irq,
@@ -729,7 +730,7 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct msi_desc *msidesc,
 error_irq:
 	mutex_unlock(&irq_mapping_update_lock);
 	xen_free_irq(irq);
-	return -1;
+	return ret;
 }
 #endif