diff --git a/hw/xen_pt.c b/hw/xen_pt.c
index 307119a12f795cdbb707056ee9e84ebf413ae29c..838bcea4d6760e2c4307505d25bcf7866c7a6f49 100644
--- a/hw/xen_pt.c
+++ b/hw/xen_pt.c
@@ -410,14 +410,17 @@ static int xen_pt_register_regions(XenPCIPassthroughState *s)
             if (r->type & XEN_HOST_PCI_REGION_TYPE_PREFETCH) {
                 type |= PCI_BASE_ADDRESS_MEM_PREFETCH;
             }
+            if (r->type & XEN_HOST_PCI_REGION_TYPE_MEM_64) {
+                type |= PCI_BASE_ADDRESS_MEM_TYPE_64;
+            }
         }
 
         memory_region_init_io(&s->bar[i], &ops, &s->dev,
                               "xen-pci-pt-bar", r->size);
         pci_register_bar(&s->dev, i, type, &s->bar[i]);
 
-        XEN_PT_LOG(&s->dev, "IO region %i registered (size=0x%08"PRIx64
-                   " base_addr=0x%08"PRIx64" type: %#x)\n",
+        XEN_PT_LOG(&s->dev, "IO region %i registered (size=0x%lx"PRIx64
+                   " base_addr=0x%lx"PRIx64" type: %#x)\n",
                    i, r->size, r->base_addr, type);
     }
 
diff --git a/hw/xen_pt_config_init.c b/hw/xen_pt_config_init.c
index e524a4094d0b8d69cbaa025903dc30b1db593748..0a5f82cb80029025b601579905b864e804c35195 100644
--- a/hw/xen_pt_config_init.c
+++ b/hw/xen_pt_config_init.c
@@ -342,6 +342,23 @@ static int xen_pt_cmd_reg_write(XenPCIPassthroughState *s, XenPTReg *cfg_entry,
 #define XEN_PT_BAR_IO_RO_MASK     0x00000003  /* BAR ReadOnly mask(I/O) */
 #define XEN_PT_BAR_IO_EMU_MASK    0xFFFFFFFC  /* BAR emul mask(I/O) */
 
+static bool is_64bit_bar(PCIIORegion *r)
+{
+    return !!(r->type & PCI_BASE_ADDRESS_MEM_TYPE_64);
+}
+
+static uint64_t xen_pt_get_bar_size(PCIIORegion *r)
+{
+    if (is_64bit_bar(r)) {
+        uint64_t size64;
+        size64 = (r + 1)->size;
+        size64 <<= 32;
+        size64 += r->size;
+        return size64;
+    }
+    return r->size;
+}
+
 static XenPTBarFlag xen_pt_bar_reg_parse(XenPCIPassthroughState *s,
                                          XenPTRegInfo *reg)
 {
@@ -366,7 +383,7 @@ static XenPTBarFlag xen_pt_bar_reg_parse(XenPCIPassthroughState *s,
 
     /* check unused BAR */
     r = &d->io_regions[index];
-    if (r->size == 0) {
+    if (!xen_pt_get_bar_size(r)) {
         return XEN_PT_BAR_FLAG_UNUSED;
     }
 
@@ -481,7 +498,12 @@ static int xen_pt_bar_reg_write(XenPCIPassthroughState *s, XenPTReg *cfg_entry,
     switch (s->bases[index].bar_flag) {
     case XEN_PT_BAR_FLAG_MEM:
         bar_emu_mask = XEN_PT_BAR_MEM_EMU_MASK;
-        bar_ro_mask = XEN_PT_BAR_MEM_RO_MASK | (r_size - 1);
+        if (!r_size) {
+            /* low 32 bits mask for 64 bit bars */
+            bar_ro_mask = XEN_PT_BAR_ALLF;
+        } else {
+            bar_ro_mask = XEN_PT_BAR_MEM_RO_MASK | (r_size - 1);
+        }
         break;
     case XEN_PT_BAR_FLAG_IO:
         bar_emu_mask = XEN_PT_BAR_IO_EMU_MASK;
@@ -489,7 +511,7 @@ static int xen_pt_bar_reg_write(XenPCIPassthroughState *s, XenPTReg *cfg_entry,
         break;
     case XEN_PT_BAR_FLAG_UPPER:
         bar_emu_mask = XEN_PT_BAR_ALLF;
-        bar_ro_mask = 0;    /* all upper 32bit are R/W */
+        bar_ro_mask = r_size ? r_size - 1 : 0;
         break;
     default:
         break;
@@ -501,22 +523,13 @@ static int xen_pt_bar_reg_write(XenPCIPassthroughState *s, XenPTReg *cfg_entry,
 
     /* check whether we need to update the virtual region address or not */
     switch (s->bases[index].bar_flag) {
+    case XEN_PT_BAR_FLAG_UPPER:
     case XEN_PT_BAR_FLAG_MEM:
         /* nothing to do */
         break;
     case XEN_PT_BAR_FLAG_IO:
         /* nothing to do */
         break;
-    case XEN_PT_BAR_FLAG_UPPER:
-        if (cfg_entry->data) {
-            if (cfg_entry->data != (XEN_PT_BAR_ALLF & ~bar_ro_mask)) {
-                XEN_PT_WARN(d, "Guest attempt to set high MMIO Base Address. "
-                            "Ignore mapping. "
-                            "(offset: 0x%02x, high address: 0x%08x)\n",
-                            reg->offset, cfg_entry->data);
-            }
-        }
-        break;
     default:
         break;
     }