diff --git a/arch/x86/pci/mmconfig_64.c b/arch/x86/pci/mmconfig_64.c
index 30007ff..94349f8 100644
--- a/arch/x86/pci/mmconfig_64.c
+++ b/arch/x86/pci/mmconfig_64.c
@@ -112,13 +112,18 @@
 static void __iomem * __init mcfg_ioremap(struct acpi_mcfg_allocation *cfg)
 {
 	void __iomem *addr;
-	u32 size;
+	u64 start, size;
 
-	size = (cfg->end_bus_number + 1) << 20;
-	addr = ioremap_nocache(cfg->address, size);
+	start = cfg->start_bus_number;
+	start <<= 20;
+	start += cfg->address;
+	size = cfg->end_bus_number + 1 - cfg->start_bus_number;
+	size <<= 20;
+	addr = ioremap_nocache(start, size);
 	if (addr) {
 		printk(KERN_INFO "PCI: Using MMCONFIG at %Lx - %Lx\n",
-		       cfg->address, cfg->address + size - 1);
+		       start, start + size - 1);
+		addr -= cfg->start_bus_number << 20;
 	}
 	return addr;
 }
@@ -157,7 +162,7 @@
 
 	for (i = 0; i < pci_mmcfg_config_num; ++i) {
 		if (pci_mmcfg_virt[i].virt) {
-			iounmap(pci_mmcfg_virt[i].virt);
+			iounmap(pci_mmcfg_virt[i].virt + (pci_mmcfg_virt[i].cfg->start_bus_number << 20));
 			pci_mmcfg_virt[i].virt = NULL;
 			pci_mmcfg_virt[i].cfg = NULL;
 		}