diff --git a/drivers/xen/xen-acpi-memhotplug.c b/drivers/xen/xen-acpi-memhotplug.c
new file mode 100644
index 0000000..2c3759a
--- /dev/null
+++ b/drivers/xen/xen-acpi-memhotplug.c
@@ -0,0 +1,501 @@
+/*
+ * Copyright (C) 2012 Intel Corporation
+ *    Author: Liu Jinsong <jinsong.liu@intel.com>
+ *    Author: Jiang Yunhong <yunhong.jiang@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/acpi.h>
+#include <acpi/acpi_drivers.h>
+#include <xen/acpi.h>
+#include <xen/interface/platform.h>
+#include <asm/xen/hypercall.h>
+
+#define PREFIX "ACPI:xen_memory_hotplug:"
+
+struct acpi_memory_info {
+	struct list_head list;
+	u64 start_addr;		/* Memory Range start physical addr */
+	u64 length;		/* Memory Range length */
+	unsigned short caching;	/* memory cache attribute */
+	unsigned short write_protect;	/* memory read/write attribute */
+				/* copied from buffer getting from _CRS */
+	unsigned int enabled:1;
+};
+
+struct acpi_memory_device {
+	struct acpi_device *device;
+	struct list_head res_list;
+};
+
+static bool acpi_hotmem_initialized __read_mostly;
+
+static int xen_hotadd_memory(int pxm, struct acpi_memory_info *info)
+{
+	int rc;
+	struct xen_platform_op op;
+
+	op.cmd = XENPF_mem_hotadd;
+	op.u.mem_add.spfn = info->start_addr >> PAGE_SHIFT;
+	op.u.mem_add.epfn = (info->start_addr + info->length) >> PAGE_SHIFT;
+	op.u.mem_add.pxm = pxm;
+
+	rc = HYPERVISOR_dom0_op(&op);
+	if (rc)
+		pr_err(PREFIX "Xen Hotplug Memory Add failed on "
+			"0x%lx -> 0x%lx, _PXM: %d, error: %d\n",
+			(unsigned long)info->start_addr,
+			(unsigned long)(info->start_addr + info->length),
+			pxm, rc);
+
+	return rc;
+}
+
+static int xen_acpi_get_pxm(acpi_handle h)
+{
+	unsigned long long pxm;
+	acpi_status status;
+	acpi_handle handle;
+	acpi_handle phandle = h;
+
+	do {
+		handle = phandle;
+		status = acpi_evaluate_integer(handle, "_PXM", NULL, &pxm);
+		if (ACPI_SUCCESS(status))
+			return pxm;
+		status = acpi_get_parent(handle, &phandle);
+	} while (ACPI_SUCCESS(status));
+
+	return -ENXIO;
+}
+
+static int xen_acpi_memory_enable_device(struct acpi_memory_device *mem_device)
+{
+	int pxm, result;
+	int num_enabled = 0;
+	struct acpi_memory_info *info;
+
+	if (!mem_device)
+		return -EINVAL;
+
+	pxm = xen_acpi_get_pxm(mem_device->device->handle);
+	if (pxm < 0)
+		return pxm;
+
+	list_for_each_entry(info, &mem_device->res_list, list) {
+		if (info->enabled) { /* just sanity check...*/
+			num_enabled++;
+			continue;
+		}
+
+		if (!info->length)
+			continue;
+
+		result = xen_hotadd_memory(pxm, info);
+		if (result)
+			continue;
+		info->enabled = 1;
+		num_enabled++;
+	}
+
+	if (!num_enabled)
+		return -ENODEV;
+
+	return 0;
+}
+
+static acpi_status
+acpi_memory_get_resource(struct acpi_resource *resource, void *context)
+{
+	struct acpi_memory_device *mem_device = context;
+	struct acpi_resource_address64 address64;
+	struct acpi_memory_info *info, *new;
+	acpi_status status;
+
+	status = acpi_resource_to_address64(resource, &address64);
+	if (ACPI_FAILURE(status) ||
+	    (address64.resource_type != ACPI_MEMORY_RANGE))
+		return AE_OK;
+
+	list_for_each_entry(info, &mem_device->res_list, list) {
+		if ((info->caching == address64.info.mem.caching) &&
+		    (info->write_protect == address64.info.mem.write_protect) &&
+		    (info->start_addr + info->length == address64.minimum)) {
+			info->length += address64.address_length;
+			return AE_OK;
+		}
+	}
+
+	new = kzalloc(sizeof(struct acpi_memory_info), GFP_KERNEL);
+	if (!new)
+		return AE_ERROR;
+
+	INIT_LIST_HEAD(&new->list);
+	new->caching = address64.info.mem.caching;
+	new->write_protect = address64.info.mem.write_protect;
+	new->start_addr = address64.minimum;
+	new->length = address64.address_length;
+	list_add_tail(&new->list, &mem_device->res_list);
+
+	return AE_OK;
+}
+
+static int
+acpi_memory_get_device_resources(struct acpi_memory_device *mem_device)
+{
+	acpi_status status;
+	struct acpi_memory_info *info, *n;
+
+	if (!list_empty(&mem_device->res_list))
+		return 0;
+
+	status = acpi_walk_resources(mem_device->device->handle,
+		METHOD_NAME__CRS, acpi_memory_get_resource, mem_device);
+
+	if (ACPI_FAILURE(status)) {
+		list_for_each_entry_safe(info, n, &mem_device->res_list, list)
+			kfree(info);
+		INIT_LIST_HEAD(&mem_device->res_list);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int
+acpi_memory_get_device(acpi_handle handle,
+		       struct acpi_memory_device **mem_device)
+{
+	acpi_status status;
+	acpi_handle phandle;
+	struct acpi_device *device = NULL;
+	struct acpi_device *pdevice = NULL;
+	int result;
+
+	if (!acpi_bus_get_device(handle, &device) && device)
+		goto end;
+
+	status = acpi_get_parent(handle, &phandle);
+	if (ACPI_FAILURE(status)) {
+		pr_warn(PREFIX "Cannot find acpi parent\n");
+		return -EINVAL;
+	}
+
+	/* Get the parent device */
+	result = acpi_bus_get_device(phandle, &pdevice);
+	if (result) {
+		pr_warn(PREFIX "Cannot get acpi bus device\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Now add the notified device.  This creates the acpi_device
+	 * and invokes .add function
+	 */
+	result = acpi_bus_add(&device, pdevice, handle, ACPI_BUS_TYPE_DEVICE);
+	if (result) {
+		pr_warn(PREFIX "Cannot add acpi bus\n");
+		return -EINVAL;
+	}
+
+end:
+	*mem_device = acpi_driver_data(device);
+	if (!(*mem_device)) {
+		pr_err(PREFIX "Driver data not found\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int acpi_memory_check_device(struct acpi_memory_device *mem_device)
+{
+	unsigned long long current_status;
+
+	/* Get device present/absent information from the _STA */
+	if (ACPI_FAILURE(acpi_evaluate_integer(mem_device->device->handle,
+				"_STA", NULL, &current_status)))
+		return -ENODEV;
+	/*
+	 * Check for device status. Device should be
+	 * present/enabled/functioning.
+	 */
+	if (!((current_status & ACPI_STA_DEVICE_PRESENT)
+	      && (current_status & ACPI_STA_DEVICE_ENABLED)
+	      && (current_status & ACPI_STA_DEVICE_FUNCTIONING)))
+		return -ENODEV;
+
+	return 0;
+}
+
+static int acpi_memory_disable_device(struct acpi_memory_device *mem_device)
+{
+	pr_debug(PREFIX "Xen does not support memory hotremove\n");
+
+	return -ENOSYS;
+}
+
+static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
+{
+	struct acpi_memory_device *mem_device;
+	struct acpi_device *device;
+	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
+
+	switch (event) {
+	case ACPI_NOTIFY_BUS_CHECK:
+		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+			"\nReceived BUS CHECK notification for device\n"));
+		/* Fall Through */
+	case ACPI_NOTIFY_DEVICE_CHECK:
+		if (event == ACPI_NOTIFY_DEVICE_CHECK)
+			ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+			"\nReceived DEVICE CHECK notification for device\n"));
+
+		if (acpi_memory_get_device(handle, &mem_device)) {
+			pr_err(PREFIX "Cannot find driver data\n");
+			break;
+		}
+
+		ost_code = ACPI_OST_SC_SUCCESS;
+		break;
+
+	case ACPI_NOTIFY_EJECT_REQUEST:
+		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+			"\nReceived EJECT REQUEST notification for device\n"));
+
+		if (acpi_bus_get_device(handle, &device)) {
+			pr_err(PREFIX "Device doesn't exist\n");
+			break;
+		}
+		mem_device = acpi_driver_data(device);
+		if (!mem_device) {
+			pr_err(PREFIX "Driver Data is NULL\n");
+			break;
+		}
+
+		/*
+		 * TBD: implement acpi_memory_disable_device and invoke
+		 * acpi_bus_remove if Xen support hotremove in the future
+		 */
+		acpi_memory_disable_device(mem_device);
+		break;
+
+	default:
+		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+				  "Unsupported event [0x%x]\n", event));
+		/* non-hotplug event; possibly handled by other handler */
+		return;
+	}
+
+	(void) acpi_evaluate_hotplug_ost(handle, event, ost_code, NULL);
+	return;
+}
+
+static int xen_acpi_memory_device_add(struct acpi_device *device)
+{
+	int result;
+	struct acpi_memory_device *mem_device = NULL;
+
+
+	if (!device)
+		return -EINVAL;
+
+	mem_device = kzalloc(sizeof(struct acpi_memory_device), GFP_KERNEL);
+	if (!mem_device)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&mem_device->res_list);
+	mem_device->device = device;
+	sprintf(acpi_device_name(device), "%s", ACPI_MEMORY_DEVICE_NAME);
+	sprintf(acpi_device_class(device), "%s", ACPI_MEMORY_DEVICE_CLASS);
+	device->driver_data = mem_device;
+
+	/* Get the range from the _CRS */
+	result = acpi_memory_get_device_resources(mem_device);
+	if (result) {
+		kfree(mem_device);
+		return result;
+	}
+
+	/*
+	 * For booting existed memory devices, early boot code has recognized
+	 * memory area by EFI/E820. If DSDT shows these memory devices on boot,
+	 * hotplug is not necessary for them.
+	 * For hot-added memory devices during runtime, it need hypercall to
+	 * Xen hypervisor to add memory.
+	 */
+	if (!acpi_hotmem_initialized)
+		return 0;
+
+	if (!acpi_memory_check_device(mem_device))
+		result = xen_acpi_memory_enable_device(mem_device);
+
+	return result;
+}
+
+static int xen_acpi_memory_device_remove(struct acpi_device *device, int type)
+{
+	struct acpi_memory_device *mem_device = NULL;
+
+	if (!device || !acpi_driver_data(device))
+		return -EINVAL;
+
+	mem_device = acpi_driver_data(device);
+	kfree(mem_device);
+
+	return 0;
+}
+
+/*
+ * Helper function to check for memory device
+ */
+static acpi_status is_memory_device(acpi_handle handle)
+{
+	char *hardware_id;
+	acpi_status status;
+	struct acpi_device_info *info;
+
+	status = acpi_get_object_info(handle, &info);
+	if (ACPI_FAILURE(status))
+		return status;
+
+	if (!(info->valid & ACPI_VALID_HID)) {
+		kfree(info);
+		return AE_ERROR;
+	}
+
+	hardware_id = info->hardware_id.string;
+	if ((hardware_id == NULL) ||
+	    (strcmp(hardware_id, ACPI_MEMORY_DEVICE_HID)))
+		status = AE_ERROR;
+
+	kfree(info);
+	return status;
+}
+
+static acpi_status
+acpi_memory_register_notify_handler(acpi_handle handle,
+				    u32 level, void *ctxt, void **retv)
+{
+	acpi_status status;
+
+	status = is_memory_device(handle);
+	if (ACPI_FAILURE(status))
+		return AE_OK;	/* continue */
+
+	status = acpi_install_notify_handler(handle, ACPI_SYSTEM_NOTIFY,
+					     acpi_memory_device_notify, NULL);
+	/* continue */
+	return AE_OK;
+}
+
+static acpi_status
+acpi_memory_deregister_notify_handler(acpi_handle handle,
+				      u32 level, void *ctxt, void **retv)
+{
+	acpi_status status;
+
+	status = is_memory_device(handle);
+	if (ACPI_FAILURE(status))
+		return AE_OK;	/* continue */
+
+	status = acpi_remove_notify_handler(handle,
+					    ACPI_SYSTEM_NOTIFY,
+					    acpi_memory_device_notify);
+
+	return AE_OK;	/* continue */
+}
+
+static const struct acpi_device_id memory_device_ids[] = {
+	{ACPI_MEMORY_DEVICE_HID, 0},
+	{"", 0},
+};
+MODULE_DEVICE_TABLE(acpi, memory_device_ids);
+
+static struct acpi_driver xen_acpi_memory_device_driver = {
+	.name = "acpi_memhotplug",
+	.class = ACPI_MEMORY_DEVICE_CLASS,
+	.ids = memory_device_ids,
+	.ops = {
+		.add = xen_acpi_memory_device_add,
+		.remove = xen_acpi_memory_device_remove,
+		},
+};
+
+static int __init xen_acpi_memory_device_init(void)
+{
+	int result;
+	acpi_status status;
+
+	if (!xen_initial_domain())
+		return -ENODEV;
+
+	/* unregister the stub which only used to reserve driver space */
+	xen_stub_memory_device_exit();
+
+	result = acpi_bus_register_driver(&xen_acpi_memory_device_driver);
+	if (result < 0) {
+		xen_stub_memory_device_init();
+		return -ENODEV;
+	}
+
+	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
+				     ACPI_UINT32_MAX,
+				     acpi_memory_register_notify_handler,
+				     NULL, NULL, NULL);
+
+	if (ACPI_FAILURE(status)) {
+		pr_warn(PREFIX "walk_namespace failed\n");
+		acpi_bus_unregister_driver(&xen_acpi_memory_device_driver);
+		xen_stub_memory_device_init();
+		return -ENODEV;
+	}
+
+	acpi_hotmem_initialized = true;
+	return 0;
+}
+
+static void __exit xen_acpi_memory_device_exit(void)
+{
+	acpi_status status;
+
+	if (!xen_initial_domain())
+		return;
+
+	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
+				     ACPI_UINT32_MAX,
+				     acpi_memory_deregister_notify_handler,
+				     NULL, NULL, NULL);
+	if (ACPI_FAILURE(status))
+		pr_warn(PREFIX "walk_namespace failed\n");
+
+	acpi_bus_unregister_driver(&xen_acpi_memory_device_driver);
+
+	/*
+	 * stub reserve space again to prevent any chance of native
+	 * driver loading.
+	 */
+	xen_stub_memory_device_init();
+	return;
+}
+
+module_init(xen_acpi_memory_device_init);
+module_exit(xen_acpi_memory_device_exit);
+ACPI_MODULE_NAME("xen-acpi-memhotplug");
+MODULE_AUTHOR("Liu Jinsong <jinsong.liu@intel.com>");
+MODULE_DESCRIPTION("Xen Hotplug Mem Driver");
+MODULE_LICENSE("GPL");