diff --git a/linux-2.6-xen-sparse/arch/xen/i386/kernel/acpi/boot.c b/linux-2.6-xen-sparse/arch/xen/i386/kernel/acpi/boot.c
index bce4ef7ed4..19e71d8d2b 100644
--- a/linux-2.6-xen-sparse/arch/xen/i386/kernel/acpi/boot.c
+++ b/linux-2.6-xen-sparse/arch/xen/i386/kernel/acpi/boot.c
@@ -469,6 +469,18 @@ unsigned int acpi_register_gsi(u32 gsi, int edge_level, int active_high_low)
 	unsigned int irq;
 	unsigned int plat_gsi = gsi;
 
+#ifdef CONFIG_PCI
+	/*
+	 * Make sure all (legacy) PCI IRQs are set as level-triggered.
+	 */
+	if (acpi_irq_model == ACPI_IRQ_MODEL_PIC) {
+		extern void eisa_set_level_irq(unsigned int irq);
+
+		if (edge_level == ACPI_LEVEL_SENSITIVE)
+				eisa_set_level_irq(gsi);
+	}
+#endif
+
 #ifdef CONFIG_X86_IO_APIC
 	if (acpi_irq_model == ACPI_IRQ_MODEL_IOAPIC) {
 		plat_gsi = mp_register_gsi(gsi, edge_level, active_high_low);