--- /dev/null
+From 0891fb39ba67bd7ae023ea0d367297ffff010781 Mon Sep 17 00:00:00 2001
+From: Juergen Gross <jgross@suse.com>
+Date: Wed, 30 Sep 2020 11:16:14 +0200
+Subject: xen/events: don't use chip_data for legacy IRQs
+
+From: Juergen Gross <jgross@suse.com>
+
+commit 0891fb39ba67bd7ae023ea0d367297ffff010781 upstream.
+
+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: stable@vger.kernel.org
+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
+Signed-off-by: Juergen Gross <jgross@suse.com>
+[bwh: Backported to 4.9: adjust context]
+Signed-off-by: Ben Hutchings <benh@debian.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/xen/events/events_base.c | 29 +++++++++++++++++++++--------
+ 1 file changed, 21 insertions(+), 8 deletions(-)
+
+--- a/drivers/xen/events/events_base.c
++++ b/drivers/xen/events/events_base.c
+@@ -90,6 +90,8 @@ static bool (*pirq_needs_eoi)(unsigned i
+ /* 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;
+@@ -154,7 +156,18 @@ 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. */
+@@ -375,7 +388,7 @@ 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);
+ }
+@@ -424,14 +437,14 @@ static int __must_check xen_allocate_irq
+
+ 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);
+
+@@ -601,7 +614,7 @@ 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--;
+@@ -1105,7 +1118,7 @@ int bind_ipi_to_irqhandler(enum ipi_vect
+
+ 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;
+@@ -1139,7 +1152,7 @@ int evtchn_make_refcounted(unsigned int
+ if (irq == -1)
+ return -ENOENT;
+
+- info = irq_get_chip_data(irq);
++ info = info_for_irq(irq);
+
+ if (!info)
+ return -ENOENT;
+@@ -1167,7 +1180,7 @@ 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;