xen/events: don't use chip_data for legacy IRQs

Since commit c330fb1ddc0a ("XEN uses irqdesc::irq_data_common::handler_data to store a per interrupt XEN data pointer which contains XEN specific information.")
Xen is using the chip_data pointer for storing IRQ specific data. When
running as a HVM domain this can result in problems for legacy IRQs, as
those might use chip_data for their own purposes.

Use a local array for this purpose in case of legacy IRQs, avoiding the
double use.

Cc: [e-mail]
Fixes: c330fb1ddc0a ("XEN uses irqdesc::irq_data_common::handler_data to store a per interrupt XEN data pointer which contains XEN specific information.")
Signed-off-by: Juergen Gross <[e-mail]>
Tested-by: Stefan Bader <[e-mail]>
Reviewed-by: Boris Ostrovsky <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Juergen Gross <[e-mail]>

drivers/xen/events/events_base.c

···
 /* Xen will never allocate port zero for any purpose. */
 #define VALID_EVTCHN(chn)	((chn) != 0)
 
+static struct irq_info *legacy_info_ptrs[NR_IRQS_LEGACY];
+
 static struct irq_chip xen_dynamic_chip;
 static struct irq_chip xen_percpu_chip;
 static struct irq_chip xen_pirq_chip;
···
 /* Get info for IRQ */
 struct irq_info *info_for_irq(unsigned irq)
 {
-	return irq_get_chip_data(irq);
+	if (irq < nr_legacy_irqs())
+		return legacy_info_ptrs[irq];
+	else
+		return irq_get_chip_data(irq);
+}
+
+static void set_info_for_irq(unsigned int irq, struct irq_info *info)
+{
+	if (irq < nr_legacy_irqs())
+		legacy_info_ptrs[irq] = info;
+	else
+		irq_set_chip_data(irq, info);
 }
 
 /* Constructors for packed IRQ information. */
···
 	info->type = IRQT_UNBOUND;
 	info->refcnt = -1;
 
-	irq_set_chip_data(irq, info);
+	set_info_for_irq(irq, info);
 
 	list_add_tail(&info->list, &xen_irq_list_head);
 }
···
 
 static void xen_free_irq(unsigned irq)
 {
-	struct irq_info *info = irq_get_chip_data(irq);
+	struct irq_info *info = info_for_irq(irq);
 
 	if (WARN_ON(!info))
 		return;
 
 	list_del(&info->list);
 
-	irq_set_chip_data(irq, NULL);
+	set_info_for_irq(irq, NULL);
 
 	WARN_ON(info->refcnt > 0);
 
···
 static void __unbind_from_irq(unsigned int irq)
 {
 	evtchn_port_t evtchn = evtchn_from_irq(irq);
-	struct irq_info *info = irq_get_chip_data(irq);
+	struct irq_info *info = info_for_irq(irq);
 
 	if (info->refcnt > 0) {
 		info->refcnt--;
···
 
 void unbind_from_irqhandler(unsigned int irq, void *dev_id)
 {
-	struct irq_info *info = irq_get_chip_data(irq);
+	struct irq_info *info = info_for_irq(irq);
 
 	if (WARN_ON(!info))
 		return;
···
 	if (irq == -1)
 		return -ENOENT;
 
-	info = irq_get_chip_data(irq);
+	info = info_for_irq(irq);
 
 	if (!info)
 		return -ENOENT;
···
 	if (irq == -1)
 		goto done;
 
-	info = irq_get_chip_data(irq);
+	info = info_for_irq(irq);
 
 	if (!info)
 		goto done;