// SPDX-License-Identifier: GPL-2.0
  /* Copyright(c) 2016-2019 Intel Corporation. All rights reserved. */
  #include <linux/memremap.h>
  #include <linux/pagemap.h>
  #include <linux/memory.h>
  #include <linux/module.h>
  #include <linux/device.h>
  #include <linux/pfn_t.h>
  #include <linux/slab.h>
  #include <linux/dax.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/mman.h>
  #include "dax-private.h"
  #include "bus.h"
  
  int dev_dax_kmem_probe(struct device *dev)
  {
  	struct dev_dax *dev_dax = to_dev_dax(dev);
  	struct resource *res = &dev_dax->region->res;
  	resource_size_t kmem_start;
  	resource_size_t kmem_size;
  	resource_size_t kmem_end;
  	struct resource *new_res;
  	int numa_node;
  	int rc;
  
  	/*
  	 * Ensure good NUMA information for the persistent memory.
  	 * Without this check, there is a risk that slow memory
  	 * could be mixed in a node with faster memory, causing
  	 * unavoidable performance issues.
  	 */
  	numa_node = dev_dax->target_node;
  	if (numa_node < 0) {
  		dev_warn(dev, "rejecting DAX region %pR with invalid node: %d
  ",
  			 res, numa_node);
  		return -EINVAL;
  	}
  
  	/* Hotplug starting at the beginning of the next block: */
  	kmem_start = ALIGN(res->start, memory_block_size_bytes());
  
  	kmem_size = resource_size(res);
  	/* Adjust the size down to compensate for moving up kmem_start: */
  	kmem_size -= kmem_start - res->start;
  	/* Align the size down to cover only complete blocks: */
  	kmem_size &= ~(memory_block_size_bytes() - 1);
  	kmem_end = kmem_start + kmem_size;
  
  	/* Region is permanently reserved.  Hot-remove not yet implemented. */
  	new_res = request_mem_region(kmem_start, kmem_size, dev_name(dev));
  	if (!new_res) {
  		dev_warn(dev, "could not reserve region [%pa-%pa]
  ",
  			 &kmem_start, &kmem_end);
  		return -EBUSY;
  	}
  
  	/*
  	 * Set flags appropriate for System RAM.  Leave ..._BUSY clear
  	 * so that add_memory() can add a child resource.  Do not
  	 * inherit flags from the parent since it may set new flags
  	 * unknown to us that will break add_memory() below.
  	 */
  	new_res->flags = IORESOURCE_SYSTEM_RAM;
  	new_res->name = dev_name(dev);
  
  	rc = add_memory(numa_node, new_res->start, resource_size(new_res));

  	if (rc) {
  		release_resource(new_res);
  		kfree(new_res);

  		return rc;

  	}

  	dev_dax->dax_kmem_res = new_res;

  
  	return 0;
  }

  #ifdef CONFIG_MEMORY_HOTREMOVE
  static int dev_dax_kmem_remove(struct device *dev)
  {
  	struct dev_dax *dev_dax = to_dev_dax(dev);
  	struct resource *res = dev_dax->dax_kmem_res;
  	resource_size_t kmem_start = res->start;
  	resource_size_t kmem_size = resource_size(res);
  	int rc;
  
  	/*
  	 * We have one shot for removing memory, if some memory blocks were not
  	 * offline prior to calling this function remove_memory() will fail, and
  	 * there is no way to hotremove this memory until reboot because device
  	 * unbind will succeed even if we return failure.
  	 */
  	rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size);
  	if (rc) {
  		dev_err(dev,
  			"DAX region %pR cannot be hotremoved until the next reboot
  ",
  			res);
  		return rc;
  	}
  
  	/* Release and free dax resources */
  	release_resource(res);
  	kfree(res);
  	dev_dax->dax_kmem_res = NULL;
  
  	return 0;
  }
  #else

  static int dev_dax_kmem_remove(struct device *dev)
  {
  	/*

  	 * Without hotremove purposely leak the request_mem_region() for the
  	 * device-dax range and return '0' to ->remove() attempts. The removal
  	 * of the device from the driver always succeeds, but the region is
  	 * permanently pinned as reserved by the unreleased

  	 * request_mem_region().
  	 */
  	return 0;
  }

  #endif /* CONFIG_MEMORY_HOTREMOVE */

  
  static struct dax_device_driver device_dax_kmem_driver = {
  	.drv = {
  		.probe = dev_dax_kmem_probe,
  		.remove = dev_dax_kmem_remove,
  	},
  };
  
  static int __init dax_kmem_init(void)
  {
  	return dax_driver_register(&device_dax_kmem_driver);
  }
  
  static void __exit dax_kmem_exit(void)
  {
  	dax_driver_unregister(&device_dax_kmem_driver);
  }
  
  MODULE_AUTHOR("Intel Corporation");
  MODULE_LICENSE("GPL v2");
  module_init(dax_kmem_init);
  module_exit(dax_kmem_exit);
  MODULE_ALIAS_DAX_DEVICE(0);