diff --git a/arch/x86_64/pci/mmconfig.c b/arch/x86_64/pci/mmconfig.c
index 09cfcc12..657e88a 100644
--- a/arch/x86_64/pci/mmconfig.c
+++ b/arch/x86_64/pci/mmconfig.c
@@ -13,17 +13,44 @@
 #define MMCONFIG_APER_SIZE (256*1024*1024)
 
 /* Static virtual mapping of the MMCONFIG aperture */
-static char *pci_mmcfg_virt;
+struct mmcfg_virt {
+	struct acpi_table_mcfg_config *cfg;
+	char *virt;
+};
+static struct mmcfg_virt *pci_mmcfg_virt;
 
-static inline char *pci_dev_base(unsigned int bus, unsigned int devfn)
+static char *get_virt(unsigned int seg, int bus)
 {
-	return pci_mmcfg_virt + ((bus << 20) | (devfn << 12));
+	int cfg_num = -1;
+	struct acpi_table_mcfg_config *cfg;
+
+	while (1) {
+		++cfg_num;
+		if (cfg_num >= pci_mmcfg_config_num) {
+			/* something bad is going on, no cfg table is found. */
+			/* so we fall back to the old way we used to do this */
+			/* and just rely on the first entry to be correct. */
+			return pci_mmcfg_virt[0].virt;
+		}
+		cfg = pci_mmcfg_virt[cfg_num].cfg;
+		if (cfg->pci_segment_group_number != seg)
+			continue;
+		if ((cfg->start_bus_number <= bus) &&
+		    (cfg->end_bus_number >= bus))
+			return pci_mmcfg_virt[cfg_num].virt;
+	}
+}
+
+static inline char *pci_dev_base(unsigned int seg, unsigned int bus, unsigned int devfn)
+{
+
+	return get_virt(seg, bus) + ((bus << 20) | (devfn << 12));
 }
 
 static int pci_mmcfg_read(unsigned int seg, unsigned int bus,
 			  unsigned int devfn, int reg, int len, u32 *value)
 {
-	char *addr = pci_dev_base(bus, devfn); 
+	char *addr = pci_dev_base(seg, bus, devfn);
 
 	if (unlikely(!value || (bus > 255) || (devfn > 255) || (reg > 4095)))
 		return -EINVAL;
@@ -46,7 +73,7 @@
 static int pci_mmcfg_write(unsigned int seg, unsigned int bus,
 			   unsigned int devfn, int reg, int len, u32 value)
 {
-	char *addr = pci_dev_base(bus,devfn);
+	char *addr = pci_dev_base(seg, bus, devfn);
 
 	if (unlikely((bus > 255) || (devfn > 255) || (reg > 4095)))
 		return -EINVAL;
@@ -73,6 +100,8 @@
 
 static int __init pci_mmcfg_init(void)
 {
+	int i;
+
 	if ((pci_probe & PCI_PROBE_MMCONF) == 0)
 		return 0;
 
@@ -90,13 +119,22 @@
 		return 0; 
 
 	/* RED-PEN i386 doesn't do _nocache right now */
-	pci_mmcfg_virt = ioremap_nocache(pci_mmcfg_config[0].base_address, MMCONFIG_APER_SIZE);
-	if (!pci_mmcfg_virt) { 
-		printk("PCI: Cannot map mmconfig aperture\n");
+	pci_mmcfg_virt = kmalloc(sizeof(*pci_mmcfg_virt) * pci_mmcfg_config_num, GFP_KERNEL);
+	if (pci_mmcfg_virt == NULL) {
+		printk("PCI: Can not allocate memory for mmconfig structures\n");
 		return 0;
-	}	
+	}
+	for (i = 0; i < pci_mmcfg_config_num; ++i) {
+		pci_mmcfg_virt[i].cfg = &pci_mmcfg_config[i];
+		pci_mmcfg_virt[i].virt = ioremap_nocache(pci_mmcfg_config[i].base_address, MMCONFIG_APER_SIZE);
+		if (!pci_mmcfg_virt[i].virt) {
+			printk("PCI: Cannot map mmconfig aperture for segment %d\n",
+			       pci_mmcfg_config[i].pci_segment_group_number);
+			return 0;
+		}
+		printk(KERN_INFO "PCI: Using MMCONFIG at %x\n", pci_mmcfg_config[i].base_address);
+	}
 
-	printk(KERN_INFO "PCI: Using MMCONFIG at %x\n", pci_mmcfg_config[0].base_address);
 	raw_pci_ops = &pci_mmcfg;
 	pci_probe = (pci_probe & ~PCI_PROBE_MASK) | PCI_PROBE_MMCONF;