[PATCH] Revert "x86/xen: Treat SCI interrupt as normal GSI interrupt"

["Ville Syrjälä" <syrjala@sci.fi>]

This reverts commit b568b8601f05a591a7ff09d8ee1cedb5b2e815fe.

The commit in question causes a nasty regression on HP/Compaq
nc6000 where we fail to register the ACPI interrupt, and thus
lose eg. thermal notifications leading a potentially overheated
machine.

wdiff of /proc/interrupts shows:
9:         [-98-]          {+6+}    XT-PIC  [-acpi-]

Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Sander Eikelenboom <linux@eikelenboom.it>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Len Brown <len.brown@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ville Syrjälä <syrjala@sci.fi>
---
 arch/x86/kernel/acpi/boot.c | 26 ++++++++++++-------------
 arch/x86/pci/xen.c          | 47 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index ae97ed0..5c40e9a 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -611,20 +611,20 @@ void __init acpi_pic_sci_set_trigger(unsigned int irq, u16 trigger)
 
 int acpi_gsi_to_irq(u32 gsi, unsigned int *irqp)
 {
-	int rc, irq, trigger, polarity;
-
-	rc = acpi_get_override_irq(gsi, &trigger, &polarity);
-	if (rc == 0) {
-		trigger = trigger ? ACPI_LEVEL_SENSITIVE : ACPI_EDGE_SENSITIVE;
-		polarity = polarity ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH;
-		irq = acpi_register_gsi(NULL, gsi, trigger, polarity);
-		if (irq >= 0) {
-			*irqp = irq;
-			return 0;
-		}
-	}
+	int irq;
 
-	return -1;
+	if (acpi_irq_model == ACPI_IRQ_MODEL_PIC) {
+		*irqp = gsi;
+	} else {
+		mutex_lock(&acpi_ioapic_lock);
+		irq = mp_map_gsi_to_irq(gsi,
+					IOAPIC_MAP_ALLOC | IOAPIC_MAP_CHECK);
+		mutex_unlock(&acpi_ioapic_lock);
+		if (irq < 0)
+			return -1;
+		*irqp = irq;
+	}
+	return 0;
 }
 EXPORT_SYMBOL_GPL(acpi_gsi_to_irq);
 
diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index d22f4b5..3db4de0 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -476,6 +476,52 @@ int __init pci_xen_hvm_init(void)
 }
 
 #ifdef CONFIG_XEN_DOM0
+static __init void xen_setup_acpi_sci(void)
+{
+	int rc;
+	int trigger, polarity;
+	int gsi = acpi_sci_override_gsi;
+	int irq = -1;
+	int gsi_override = -1;
+
+	if (!gsi)
+		return;
+
+	rc = acpi_get_override_irq(gsi, &trigger, &polarity);
+	if (rc) {
+		printk(KERN_WARNING "xen: acpi_get_override_irq failed for acpi"
+				" sci, rc=%d\n", rc);
+		return;
+	}
+	trigger = trigger ? ACPI_LEVEL_SENSITIVE : ACPI_EDGE_SENSITIVE;
+	polarity = polarity ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH;
+
+	printk(KERN_INFO "xen: sci override: global_irq=%d trigger=%d "
+			"polarity=%d\n", gsi, trigger, polarity);
+
+	/* 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 (acpi_gsi_to_irq(gsi, &irq) == 0) {
+		/* Use the provided value if it's valid. */
+		if (irq >= 0)
+			gsi_override = irq;
+	}
+
+	gsi = xen_register_gsi(gsi, gsi_override, trigger, polarity);
+	printk(KERN_INFO "xen: acpi sci %d\n", gsi);
+
+	return;
+}
+
 int __init pci_xen_initial_domain(void)
 {
 	int irq;
@@ -486,6 +532,7 @@ int __init pci_xen_initial_domain(void)
 	x86_msi.restore_msi_irqs = xen_initdom_restore_msi_irqs;
 	pci_msi_ignore_mask = 1;
 #endif
+	xen_setup_acpi_sci();
 	__acpi_register_gsi = acpi_register_gsi_xen;
 	__acpi_unregister_gsi = NULL;
 	/* Pre-allocate legacy irqs */
-- 
2.0.5