diff --git a/src/pciinit.c b/src/pciinit.c
index 0346423..86c8137 100644
--- a/src/pciinit.c
+++ b/src/pciinit.c
@@ -20,6 +20,7 @@ static void pci_bios_init_device_in_bus(int bus);
 static u32 pci_bios_io_addr;
 static u32 pci_bios_mem_addr;
 static u32 pci_bios_prefmem_addr;
+static u64 pci_bios_64bit_addr;
 /* host irqs corresponding to PCI irqs A-D */
 const u8 pci_irqs[4] = {
     10, 10, 11, 11
@@ -56,9 +57,11 @@ static int pci_bios_allocate_region(u16 bdf, int region_num)
 {
     u32 *paddr;
     u32 ofs = pci_bar(bdf, region_num);
-
     u32 old = pci_config_readl(bdf, ofs);
     u32 mask;
+    u32 limit_addr;
+    int is_64bit;
+
     if (region_num == PCI_ROM_SLOT) {
         mask = PCI_ROM_ADDRESS_MASK;
         pci_config_writel(bdf, ofs, mask);
@@ -73,50 +76,49 @@ static int pci_bios_allocate_region(u16 bdf, int region_num)
     pci_config_writel(bdf, ofs, old);
 
     u32 size = (~(val & mask)) + 1;
-    if (val != 0) {
-        if (val & PCI_BASE_ADDRESS_SPACE_IO) {
-            paddr = &pci_bios_io_addr;
-            if (ALIGN(*paddr, size) + size >= 64 * 1024) {
-                dprintf(1,
-                        "io region of (bdf 0x%x bar %d) can't be mapped.\n",
-                        bdf, region_num);
-                size = 0;
-            }
-        } else if ((val & PCI_BASE_ADDRESS_MEM_PREFETCH) &&
-                 /* keep behaviour on bus = 0 */
-                 pci_bdf_to_bus(bdf) != 0 &&
-                 /* If pci_bios_prefmem_addr == 0, keep old behaviour */
-                 pci_bios_prefmem_addr != 0) {
-            paddr = &pci_bios_prefmem_addr;
-            if (ALIGN(*paddr, size) + size >= BUILD_PCIPREFMEM_END) {
-                dprintf(1,
-                        "prefmem region of (bdf 0x%x bar %d) can't be mapped. "
-                        "decrease BUILD_PCIMEM_SIZE and recompile. size %x\n",
-                        bdf, region_num, BUILD_PCIPREFMEM_SIZE);
-                size = 0;
-            }
-        } else {
-            paddr = &pci_bios_mem_addr;
-            if (ALIGN(*paddr, size) + size >= BUILD_PCIMEM_END) {
+    if (!val || !size)
+        return 0;
+
+    is_64bit = !(val & PCI_BASE_ADDRESS_SPACE_IO) &&
+        (val & PCI_BASE_ADDRESS_MEM_TYPE_MASK) == PCI_BASE_ADDRESS_MEM_TYPE_64;
+
+    if (val & PCI_BASE_ADDRESS_SPACE_IO) {
+        paddr = &pci_bios_io_addr;
+        limit_addr = 64 * 1024;
+    } else if ((val & PCI_BASE_ADDRESS_MEM_PREFETCH) &&
+             /* keep behaviour on bus = 0 */
+             pci_bdf_to_bus(bdf) != 0 &&
+             /* If pci_bios_prefmem_addr == 0, keep old behaviour */
+             pci_bios_prefmem_addr != 0) {
+        paddr = &pci_bios_prefmem_addr;
+        limit_addr = BUILD_PCIPREFMEM_END;
+    } else {
+        paddr = &pci_bios_mem_addr;
+        limit_addr = BUILD_PCIMEM_END;
+    }
+
+    /* The region is out of allowed 32bit mapping range */
+    if ((ALIGN(*paddr, size) + size >= limit_addr) ||
+        (ALIGN(*paddr, size) + size <= *paddr)) {
+            if (!is_64bit) {
                 dprintf(1,
                         "mem region of (bdf 0x%x bar %d) can't be mapped. "
-                        "increase BUILD_PCIMEM_SIZE and recompile. size %x\n",
-                        bdf, region_num, BUILD_PCIMEM_SIZE);
-                size = 0;
+                        "Region size %x\n", bdf, region_num, size);
+                return 0;
             }
-        }
-        if (size > 0) {
-            *paddr = ALIGN(*paddr, size);
-            pci_set_io_region_addr(bdf, region_num, *paddr);
-            *paddr += size;
-        }
+            pci_bios_64bit_addr = ALIGN(pci_bios_64bit_addr, size);
+            pci_set_io_region_addr(bdf, region_num, (u32)pci_bios_64bit_addr);
+            pci_set_io_region_addr(bdf, region_num + 1,
+                                   (u32)(pci_bios_64bit_addr >> 32));
+            pci_bios_64bit_addr += size;
+            return is_64bit;
     }
 
-    int is_64bit = !(val & PCI_BASE_ADDRESS_SPACE_IO) &&
-        (val & PCI_BASE_ADDRESS_MEM_TYPE_MASK) == PCI_BASE_ADDRESS_MEM_TYPE_64;
-    if (is_64bit && size > 0) {
-        pci_config_writel(bdf, ofs + 4, 0);
-    }
+    *paddr = ALIGN(*paddr, size);
+    pci_set_io_region_addr(bdf, region_num, *paddr);
+    if (is_64bit)
+        pci_set_io_region_addr(bdf, region_num + 1, 0);
+    *paddr += size;
     return is_64bit;
 }
 
@@ -409,6 +411,7 @@ pci_setup(void)
     pci_bios_io_addr = 0xc000;
     pci_bios_mem_addr = BUILD_PCIMEM_START;
     pci_bios_prefmem_addr = BUILD_PCIPREFMEM_START;
+    pci_bios_64bit_addr = ALIGN(RamSizeOver4G + 0x100000000ull, 0x100000000ull);
 
     pci_bios_init_bus();