diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
index 3eeb9bea7630..224df03ce42e 100644
--- a/drivers/xen/pci.c
+++ b/drivers/xen/pci.c
@@ -17,6 +17,8 @@
 #include "../pci/pci.h"
 #ifdef CONFIG_PCI_MMCONFIG
 #include <asm/pci_x86.h>
+
+static int xen_mcfg_late(void);
 #endif
 
 static bool __read_mostly pci_seg_supported = true;
@@ -28,7 +30,18 @@ static int xen_add_device(struct device *dev)
 #ifdef CONFIG_PCI_IOV
 	struct pci_dev *physfn = pci_dev->physfn;
 #endif
-
+#ifdef CONFIG_PCI_MMCONFIG
+	static bool pci_mcfg_reserved = false;
+	/*
+	 * Reserve MCFG areas in Xen on first invocation due to this being
+	 * potentially called from inside of acpi_init immediately after
+	 * MCFG table has been finally parsed.
+	 */
+	if (!pci_mcfg_reserved) {
+		xen_mcfg_late();
+		pci_mcfg_reserved = true;
+	}
+#endif
 	if (pci_seg_supported) {
 		struct {
 			struct physdev_pci_device_add add;
@@ -201,7 +214,7 @@ static int __init register_xen_pci_notifier(void)
 arch_initcall(register_xen_pci_notifier);
 
 #ifdef CONFIG_PCI_MMCONFIG
-static int __init xen_mcfg_late(void)
+static int xen_mcfg_late(void)
 {
 	struct pci_mmcfg_region *cfg;
 	int rc;
@@ -240,8 +253,4 @@ static int __init xen_mcfg_late(void)
 	}
 	return 0;
 }
-/*
- * Needs to be done after acpi_init which are subsys_initcall.
- */
-subsys_initcall_sync(xen_mcfg_late);
 #endif