drivers/xen/xen-acpi-memhotplug.c - linux/kernel/git/gregkh/usb - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Copyright (C) 2012 Intel Corporation
  *    Author: Liu Jinsong <jinsong.liu@intel.com>
  *    Author: Jiang Yunhong <yunhong.jiang@intel.com>
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/acpi.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_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.address.minimum)) {
 			info->length += address64.address.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.address.minimum;
 	new->length = address64.address.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)
 {
 	struct acpi_device *device = NULL;
 	int result = 0;

 	acpi_scan_lock_acquire();

 	acpi_bus_get_device(handle, &device);
 	if (acpi_device_enumerated(device))
 		goto end;

 	/*
 	 * Now add the notified device.  This creates the acpi_device
 	 * and invokes .add function
 	 */
 	result = acpi_bus_scan(handle);
 	if (result) {
 		pr_warn(PREFIX "ACPI namespace scan failed\n");
 		result = -EINVAL;
 		goto out;
 	}
 	device = NULL;
 	acpi_bus_get_device(handle, &device);
 	if (!acpi_device_enumerated(device)) {
 		pr_warn(PREFIX "Missing device object\n");
 		result = -EINVAL;
 		goto out;
 	}

 end:
 	*mem_device = acpi_driver_data(device);
 	if (!(*mem_device)) {
 		pr_err(PREFIX "driver data not found\n");
 		result = -ENODEV;
 		goto out;
 	}

 out:
 	acpi_scan_lock_release();
 	return result;
 }

 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"));

 		acpi_scan_lock_acquire();
 		if (acpi_bus_get_device(handle, &device)) {
 			acpi_scan_lock_release();
 			pr_err(PREFIX "Device doesn't exist\n");
 			break;
 		}
 		mem_device = acpi_driver_data(device);
 		if (!mem_device) {
 			acpi_scan_lock_release();
 			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);
 		acpi_scan_lock_release();
 		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_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)
 {
 	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");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Copyright (C) 2012 Intel Corporation
	* Author: Liu Jinsong <jinsong.liu@intel.com>
	* Author: Jiang Yunhong <yunhong.jiang@intel.com>
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/types.h>
	#include <linux/acpi.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_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.address.minimum)) {
	info->length += address64.address.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.address.minimum;
	new->length = address64.address.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)
	{
	struct acpi_device *device = NULL;
	int result = 0;

	acpi_scan_lock_acquire();

	acpi_bus_get_device(handle, &device);
	if (acpi_device_enumerated(device))
	goto end;

	/*
	* Now add the notified device. This creates the acpi_device
	* and invokes .add function
	*/
	result = acpi_bus_scan(handle);
	if (result) {
	pr_warn(PREFIX "ACPI namespace scan failed\n");
	result = -EINVAL;
	goto out;
	}
	device = NULL;
	acpi_bus_get_device(handle, &device);
	if (!acpi_device_enumerated(device)) {
	pr_warn(PREFIX "Missing device object\n");
	result = -EINVAL;
	goto out;
	}

	end:
	*mem_device = acpi_driver_data(device);
	if (!(*mem_device)) {
	pr_err(PREFIX "driver data not found\n");
	result = -ENODEV;
	goto out;
	}

	out:
	acpi_scan_lock_release();
	return result;
	}

	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"));

	acpi_scan_lock_acquire();
	if (acpi_bus_get_device(handle, &device)) {
	acpi_scan_lock_release();
	pr_err(PREFIX "Device doesn't exist\n");
	break;
	}
	mem_device = acpi_driver_data(device);
	if (!mem_device) {
	acpi_scan_lock_release();
	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);
	acpi_scan_lock_release();
	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_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)
	{
	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");