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

[Juergen Gross <jgross@suse.com>]

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.

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 <jgross@suse.com>
Tested-by: Stefan Bader <stefan.bader@canonical.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20200930091614.13660-1-jgross@suse.com
---
This is a backport for stable kernel 5.4.y and older
---
 drivers/xen/events/events_base.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 55f2b834cf13..e402620b8920 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -91,6 +91,8 @@ static bool (*pirq_needs_eoi)(unsigned irq);
 /* 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;
@@ -155,7 +157,18 @@ int get_evtchn_to_irq(unsigned evtchn)
 /* 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. */
@@ -376,7 +389,7 @@ static void xen_irq_init(unsigned irq)
 	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);
 }
@@ -425,14 +438,14 @@ static int __must_check xen_allocate_irq_gsi(unsigned gsi)
 
 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);
 
@@ -602,7 +615,7 @@ EXPORT_SYMBOL_GPL(xen_irq_from_gsi);
 static void __unbind_from_irq(unsigned int irq)
 {
 	int 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--;
@@ -1106,7 +1119,7 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
 
 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;
@@ -1140,7 +1153,7 @@ int evtchn_make_refcounted(unsigned int evtchn)
 	if (irq == -1)
 		return -ENOENT;
 
-	info = irq_get_chip_data(irq);
+	info = info_for_irq(irq);
 
 	if (!info)
 		return -ENOENT;
@@ -1168,7 +1181,7 @@ int evtchn_get(unsigned int evtchn)
 	if (irq == -1)
 		goto done;
 
-	info = irq_get_chip_data(irq);
+	info = info_for_irq(irq);
 
 	if (!info)
 		goto done;
-- 
2.26.2