--- linux-3.11/arch/x86/pci/mmconfig-shared.c
+++ head/arch/x86/pci/mmconfig-shared.c
@@ -23,6 +23,10 @@
 #include <asm/pci_x86.h>
 #include <asm/acpi.h>
 
+#ifdef CONFIG_XEN
+#include <xen/interface/physdev.h>
+#endif
+
 #define PREFIX "PCI: "
 
 /* Indicate if the mmcfg resources have been placed into the resource table. */
@@ -437,6 +441,36 @@ static int is_acpi_reserved(u64 start, u
 	return mcfg_res.flags;
 }
 
+static int xen_report_mmconf_reserved(const struct pci_mmcfg_region *cfg,
+				      int valid, int with_e820)
+{
+#ifdef CONFIG_XEN
+	if (!with_e820)	{
+		struct physdev_pci_mmcfg_reserved r = {
+			.address = cfg->address,
+			.segment = cfg->segment,
+			.start_bus = cfg->start_bus,
+			.end_bus = cfg->end_bus,
+			.flags = valid ? XEN_PCI_MMCFG_RESERVED : 0
+		};
+		int rc;
+
+		rc = HYPERVISOR_physdev_op(PHYSDEVOP_pci_mmcfg_reserved, &r);
+		switch (rc) {
+		case 0: case -ENOSYS:
+			break;
+		default:
+			pr_warn(PREFIX "Failed to report MMCONFIG reservation"
+				" state for %04x [bus%02x-%02x] to hypervisor"
+				" (%d)\n",
+				cfg->segment, cfg->start_bus, cfg->end_bus,
+				rc);
+		}
+	}
+#endif
+	return valid;
+}
+
 typedef int (*check_reserved_t)(u64 start, u64 end, unsigned type);
 
 static int __ref is_mmconf_reserved(check_reserved_t is_reserved,
@@ -456,7 +490,7 @@ static int __ref is_mmconf_reserved(chec
 	}
 
 	if (size < (16UL<<20) && size != old_size)
-		return 0;
+		return xen_report_mmconf_reserved(cfg, 0, with_e820);
 
 	if (dev)
 		dev_info(dev, "MMCONFIG at %pR reserved in %s\n",
@@ -488,7 +522,7 @@ static int __ref is_mmconf_reserved(chec
 				&cfg->res, (unsigned long) cfg->address);
 	}
 
-	return 1;
+	return xen_report_mmconf_reserved(cfg, 1, with_e820);
 }
 
 static int __ref pci_mmcfg_check_reserved(struct device *dev,