diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 4d1ce2e..1c409c7 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -26,6 +26,8 @@
 # Build Intel IOMMU support
 obj-$(CONFIG_DMAR) += dmar.o iova.o intel-iommu.o
 
+obj-$(CONFIG_INTR_REMAP) += dmar.o intr_remapping.o
+
 #
 # Some architectures use the generic PCI setup functions
 #
diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index 903f170..127764c 100644
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -423,6 +423,9 @@
 		printk(KERN_INFO PREFIX "No RMRR found\n");
 #endif
 
+#ifdef CONFIG_INTR_REMAP
+	parse_ioapics_under_ir();
+#endif
 	return 0;
 }
 
diff --git a/drivers/pci/intel-iommu.h b/drivers/pci/intel-iommu.h
index 371e3b9..eb167e3 100644
--- a/drivers/pci/intel-iommu.h
+++ b/drivers/pci/intel-iommu.h
@@ -114,6 +114,8 @@
 #define ecap_max_iotlb_offset(e) \
 	(ecap_iotlb_offset(e) + ecap_niotlb_iunits(e) * 16)
 #define ecap_coherent(e)	((e) & 0x1)
+#define ecap_eim_support(e)	((e >> 4) & 0x1)
+#define ecap_ir_support(e)	((e >> 3) & 0x1)
 
 
 /* IOTLB_REG */
diff --git a/drivers/pci/intr_remapping.c b/drivers/pci/intr_remapping.c
new file mode 100644
index 0000000..a80b879
--- /dev/null
+++ b/drivers/pci/intr_remapping.c
@@ -0,0 +1,70 @@
+#include <linux/dmar.h>
+#include <asm/io_apic.h>
+#include "intel-iommu.h"
+#include "intr_remapping.h"
+
+static struct ioapic_scope ir_ioapic[MAX_IO_APICS];
+static int ir_ioapic_num;
+
+static int ir_parse_ioapic_scope(struct acpi_dmar_header *header,
+				 struct intel_iommu *iommu)
+{
+	struct acpi_dmar_hardware_unit *drhd;
+	struct acpi_dmar_device_scope *scope;
+	void *start, *end;
+
+	drhd = (struct acpi_dmar_hardware_unit *)header;
+
+	start = (void *)(drhd + 1);
+	end = ((void *)drhd) + header->length;
+
+	while (start < end) {
+		scope = start;
+		if (scope->entry_type == ACPI_DMAR_SCOPE_TYPE_IOAPIC) {
+			if (ir_ioapic_num == MAX_IO_APICS) {
+				printk(KERN_WARNING "Exceeded Max IO APICS\n");
+				return -1;
+			}
+
+			printk(KERN_INFO "IOAPIC id %d under DRHD base"
+			       " 0x%Lx\n", scope->enumeration_id,
+			       drhd->address);
+
+			ir_ioapic[ir_ioapic_num].iommu = iommu;
+			ir_ioapic[ir_ioapic_num].id = scope->enumeration_id;
+			ir_ioapic_num++;
+		}
+		start += scope->length;
+	}
+
+	return 0;
+}
+
+/*
+ * Finds the assocaition between IOAPIC's and its Interrupt-remapping
+ * hardware unit.
+ */
+int __init parse_ioapics_under_ir(void)
+{
+	struct dmar_drhd_unit *drhd;
+	int ir_supported = 0;
+
+	for_each_drhd_unit(drhd) {
+		struct intel_iommu *iommu = drhd->iommu;
+
+		if (ecap_ir_support(iommu->ecap)) {
+			if (ir_parse_ioapic_scope(drhd->hdr, iommu))
+				return -1;
+
+			ir_supported = 1;
+		}
+	}
+
+	if (ir_supported && ir_ioapic_num != nr_ioapics) {
+		printk(KERN_WARNING
+		       "Not all IO-APIC's listed under remapping hardware\n");
+		return -1;
+	}
+
+	return ir_supported;
+}
diff --git a/drivers/pci/intr_remapping.h b/drivers/pci/intr_remapping.h
new file mode 100644
index 0000000..c4a40b2
--- /dev/null
+++ b/drivers/pci/intr_remapping.h
@@ -0,0 +1,6 @@
+#include "intel-iommu.h"
+
+struct ioapic_scope {
+	struct intel_iommu *iommu;
+	unsigned int id;
+};
diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index 3ab07e4..c4e96eb 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -47,6 +47,7 @@
 extern int dmar_table_init(void);
 extern int early_dmar_detect(void);
 extern int dmar_dev_scope_init(void);
+extern int parse_ioapics_under_ir(void);
 
 extern struct list_head dmar_drhd_units;
 extern struct list_head dmar_rmrr_units;