UBUNTU: SAUCE: xen: Only restore the ACPI SCI interrupt in xen_restore_pirqs.

BugLink: https://bugs.launchpad.net/bugs/1913410

Restoring all PIRQs, which is the right thing to do, was causing problems
on larger instances. This is a horrible workaround until this issue is fully
understood.

Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Reviewed-by: Alakesh Haloi <alakeshh@amazon.com>
Reviewed-by: Anchal Agarwal <anchalag@amazon.com>
Reviewed-by: Qian Lu <luqia@amazon.com>
(cherry picked from 88d49684bde78117795c5cafb8fd326188e9031e https://github.com/amazonlinux/linux.git)
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

Author: fllinden

drivers/xen/events/events_base.c

@@ -64,6 +64,10 @@
 #include <xen/interface/vcpu.h>
 #include <asm/hw_irq.h>
 
+#ifdef CONFIG_ACPI
+#include <linux/acpi.h>
+#endif
+
 #include "events_internal.h"
 
 #undef MODULE_PARAM_PREFIX
@@ -2040,9 +2044,45 @@ void xen_shutdown_pirqs(void)
 	}
 }
 
+/*
+ * For now, only restore the ACPI SCI pirq.
+ */
 void xen_restore_pirqs(void)
 {
-	restore_pirqs();
+#ifdef CONFIG_ACPI
+	int pirq, rc, irq, gsi;
+	struct physdev_map_pirq map_irq;
+	struct irq_info *info;
+
+	list_for_each_entry(info, &xen_irq_list_head, list) {
+		if (info->type != IRQT_PIRQ)
+			continue;
+
+		pirq = info->u.pirq.pirq;
+		gsi = info->u.pirq.gsi;
+		irq = info->irq;
+
+		if (gsi != acpi_gbl_FADT.sci_interrupt)
+			continue;
+
+		map_irq.domid = DOMID_SELF;
+		map_irq.type = MAP_PIRQ_TYPE_GSI;
+		map_irq.index = gsi;
+		map_irq.pirq = pirq;
+
+		rc = HYPERVISOR_physdev_op(PHYSDEVOP_map_pirq, &map_irq);
+		if (rc) {
+			pr_warn("xen: ACPI SCI interrupt map failed, rc=%d\n",
+				rc);
+			xen_free_irq(irq);
+			continue;
+		}
+
+		printk(KERN_DEBUG "xen: restored ACPI SCI interrupt\n");
+
+		__startup_pirq(irq);
+	}
+#endif
 }
 
 static struct irq_chip xen_dynamic_chip __read_mostly = {