1 files changed, 24 insertions, 2 deletions

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 8214724ce54d..fe008309ffec 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -333,6 +333,7 @@ static int xen_register_pirq(u32 gsi, int triggering)
         struct physdev_map_pirq map_irq;
         int shareable = 0;
         char *name;
+        bool gsi_override = false;
 
         if (!xen_pv_domain())
                 return -1;
@@ -349,11 +350,32 @@ static int xen_register_pirq(u32 gsi, int triggering)
         if (pirq < 0)
                 goto out;
 
-        irq = xen_bind_pirq_gsi_to_irq(gsi, pirq, shareable, name);
+        /* Before we bind the GSI to a Linux IRQ, check whether
+         * we need to override it with bus_irq (IRQ) value. Usually for
+         * IRQs below IRQ_LEGACY_IRQ this holds IRQ == GSI, as so:
+         *  ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 low level)
+         * but there are oddballs where the IRQ != GSI:
+         *  ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 20 low level)
+         * which ends up being: gsi_to_irq[9] == 20
+         * (which is what acpi_gsi_to_irq ends up calling when starting the
+         * the ACPI interpreter and keels over since IRQ 9 has not been
+         * setup as we had setup IRQ 20 for it).
+         */
+        if (gsi == acpi_sci_override_gsi) {
+                /* Check whether the GSI != IRQ */
+                acpi_gsi_to_irq(gsi, &irq);
+                if (irq != gsi)
+                        /* Bugger, we MUST have that IRQ. */
+                        gsi_override = true;
+        }
+        if (gsi_override)
+                irq = xen_bind_pirq_gsi_to_irq(irq, pirq, shareable, name);
+        else
+                irq = xen_bind_pirq_gsi_to_irq(gsi, pirq, shareable, name);
         if (irq < 0)
                 goto out;
 
-        printk(KERN_DEBUG "xen: --> pirq=%d -> irq=%d\n", pirq, irq);
+        printk(KERN_DEBUG "xen: --> pirq=%d -> irq=%d (gsi=%d)\n", pirq, irq, gsi);
 
         map_irq.domid = DOMID_SELF;
         map_irq.type = MAP_PIRQ_TYPE_GSI;