diff --git a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c
index 3e02778492..1d3d10ad73 100644
--- a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c
+++ b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c
@@ -132,6 +132,13 @@ InitRootBridge (
   RootBus->MemAbove4G.Base      = 0;
   RootBus->MemAbove4G.Limit     = 0;
 
+  if (PcdGet64 (PcdPciMmio64Size) > 0) {
+    RootBus->AllocationAttributes |= EFI_PCI_HOST_BRIDGE_MEM64_DECODE;
+    RootBus->MemAbove4G.Base       = PcdGet64 (PcdPciMmio64Base);
+    RootBus->MemAbove4G.Limit      = PcdGet64 (PcdPciMmio64Base) +
+                                     (PcdGet64 (PcdPciMmio64Size) - 1);
+  }
+
   RootBus->Bus.Base  = RootBusNumber;
   RootBus->Bus.Limit = MaxSubBusNumber;
   RootBus->Io.Base   = PcdGet64 (PcdPciIoBase);
diff --git a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf
index bbec74645c..7a964c74c6 100644
--- a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf
+++ b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf
@@ -51,4 +51,6 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdPciIoSize
   gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio32Base
   gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio32Size
+  gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio64Base
+  gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio64Size
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfHostBridgePciDevId