xen: events: add xen_allocate_irq_{dynamic, gsi} and xen_free_irq

This is neater than open-coded calls to irq_alloc_desc_at and
irq_free_desc.

No intended behavioural change.

Note that we previously were not checking the return value of
irq_alloc_desc_at which would be failing for GSI<NR_IRQS_LEGACY
because the core architecture code has already allocated those for
us. Hence the additional check against NR_IRQS_LEGACY in
xen_allocate_irq_gsi.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>

drivers/xen/events.c

@@ -387,7 +387,7 @@ static int get_nr_hw_irqs(void)
 	return ret;
 }
 
-static int find_unbound_irq(void)
+static int xen_allocate_irq_dynamic(void)
 {
 	struct irq_data *data;
 	int irq, res;
@@ -436,6 +436,30 @@ static bool identity_mapped_irq(unsigned irq)
 	return irq < get_nr_hw_irqs();
 }
 
+static int xen_allocate_irq_gsi(unsigned gsi)
+{
+	int irq;
+
+	if (!identity_mapped_irq(gsi) &&
+	    (xen_initial_domain() || !xen_pv_domain()))
+		return xen_allocate_irq_dynamic();
+
+	/* Legacy IRQ descriptors are already allocated by the arch. */
+	if (gsi < NR_IRQS_LEGACY)
+		return gsi;
+
+	irq = irq_alloc_desc_at(gsi, -1);
+	if (irq < 0)
+		panic("Unable to allocate to IRQ%d (%d)\n", gsi, irq);
+
+	return irq;
+}
+
+static void xen_free_irq(unsigned irq)
+{
+	irq_free_desc(irq);
+}
+
 static void pirq_unmask_notify(int irq)
 {
 	struct physdev_eoi eoi = { .irq = pirq_from_irq(irq) };
@@ -621,14 +645,7 @@ int xen_map_pirq_gsi(unsigned pirq, unsigned gsi, int shareable, char *name)
 		goto out;	/* XXX need refcount? */
 	}
 
-	/* If we are a PV guest, we don't have GSIs (no ACPI passed). Therefore
-	 * we are using the !xen_initial_domain() to drop in the function.*/
-	if (identity_mapped_irq(gsi) || (!xen_initial_domain() &&
-				xen_pv_domain())) {
-		irq = gsi;
-		irq_alloc_desc_at(irq, -1);
-	} else
-		irq = find_unbound_irq();
+	irq = xen_allocate_irq_gsi(gsi);
 
 	set_irq_chip_and_handler_name(irq, &xen_pirq_chip,
 				      handle_level_irq, name);
@@ -641,7 +658,7 @@ int xen_map_pirq_gsi(unsigned pirq, unsigned gsi, int shareable, char *name)
 	 * this in the priv domain. */
 	if (xen_initial_domain() &&
 	    HYPERVISOR_physdev_op(PHYSDEVOP_alloc_irq_vector, &irq_op)) {
-		irq_free_desc(irq);
+		xen_free_irq(irq);
 		irq = -ENOSPC;
 		goto out;
 	}
@@ -682,7 +699,7 @@ void xen_allocate_pirq_msi(char *name, int *irq, int *pirq, int alloc)
 	spin_lock(&irq_mapping_update_lock);
 
 	if (alloc & XEN_ALLOC_IRQ) {
-		*irq = find_unbound_irq();
+		*irq = xen_allocate_irq_dynamic();
 		if (*irq == -1)
 			goto out;
 	}
@@ -732,7 +749,7 @@ int xen_create_msi_irq(struct pci_dev *dev, struct msi_desc *msidesc, int type)
 
 	spin_lock(&irq_mapping_update_lock);
 
-	irq = find_unbound_irq();
+	irq = xen_allocate_irq_dynamic();
 
 	if (irq == -1)
 		goto out;
@@ -741,7 +758,7 @@ int xen_create_msi_irq(struct pci_dev *dev, struct msi_desc *msidesc, int type)
 	if (rc) {
 		printk(KERN_WARNING "xen map irq failed %d\n", rc);
 
-		irq_free_desc(irq);
+		xen_free_irq(irq);
 
 		irq = -1;
 		goto out;
@@ -783,7 +800,7 @@ int xen_destroy_irq(int irq)
 	}
 	irq_info[irq] = mk_unbound_info();
 
-	irq_free_desc(irq);
+	xen_free_irq(irq);
 
 out:
 	spin_unlock(&irq_mapping_update_lock);
@@ -814,7 +831,7 @@ int bind_evtchn_to_irq(unsigned int evtchn)
 	irq = evtchn_to_irq[evtchn];
 
 	if (irq == -1) {
-		irq = find_unbound_irq();
+		irq = xen_allocate_irq_dynamic();
 
 		set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
 					      handle_fasteoi_irq, "event");
@@ -839,7 +856,7 @@ static int bind_ipi_to_irq(unsigned int ipi, unsigned int cpu)
 	irq = per_cpu(ipi_to_irq, cpu)[ipi];
 
 	if (irq == -1) {
-		irq = find_unbound_irq();
+		irq = xen_allocate_irq_dynamic();
 		if (irq < 0)
 			goto out;
 
@@ -875,7 +892,7 @@ int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
 	irq = per_cpu(virq_to_irq, cpu)[virq];
 
 	if (irq == -1) {
-		irq = find_unbound_irq();
+		irq = xen_allocate_irq_dynamic();
 
 		set_irq_chip_and_handler_name(irq, &xen_percpu_chip,
 					      handle_percpu_irq, "virq");
@@ -934,7 +951,7 @@ static void unbind_from_irq(unsigned int irq)
 	if (irq_info[irq].type != IRQT_UNBOUND) {
 		irq_info[irq] = mk_unbound_info();
 
-		irq_free_desc(irq);
+		xen_free_irq(irq);
 	}
 
 	spin_unlock(&irq_mapping_update_lock);