drivers/dax/kmem.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright(c) 2016-2019 Intel Corporation. All rights reserved. */
   3 #include <linux/memremap.h>
   4 #include <linux/pagemap.h>
   5 #include <linux/memory.h>
   6 #include <linux/module.h>
   7 #include <linux/device.h>
   8 #include <linux/pfn_t.h>
   9 #include <linux/slab.h>
  10 #include <linux/dax.h>
  11 #include <linux/fs.h>
  12 #include <linux/mm.h>
  13 #include <linux/mman.h>
  14 #include "dax-private.h"
  15 #include "bus.h"
  16
  17 int dev_dax_kmem_probe(struct device *dev)
  18 {
  19         struct dev_dax *dev_dax = to_dev_dax(dev);
  20         struct resource *res = &dev_dax->region->res;
  21         resource_size_t kmem_start;
  22         resource_size_t kmem_size;
  23         resource_size_t kmem_end;
  24         struct resource *new_res;
  25         int numa_node;
  26         int rc;
  27
  28         /*
  29          * Ensure good NUMA information for the persistent memory.
  30          * Without this check, there is a risk that slow memory
  31          * could be mixed in a node with faster memory, causing
  32          * unavoidable performance issues.
  33          */
  34         numa_node = dev_dax->target_node;
  35         if (numa_node < 0) {
  36                 dev_warn(dev, "rejecting DAX region %pR with invalid node: %d\n",
  37                          res, numa_node);
  38                 return -EINVAL;
  39         }
  40
  41         /* Hotplug starting at the beginning of the next block: */
  42         kmem_start = ALIGN(res->start, memory_block_size_bytes());
  43
  44         kmem_size = resource_size(res);
  45         /* Adjust the size down to compensate for moving up kmem_start: */
  46         kmem_size -= kmem_start - res->start;
  47         /* Align the size down to cover only complete blocks: */
  48         kmem_size &= ~(memory_block_size_bytes() - 1);
  49         kmem_end = kmem_start + kmem_size;
  50
  51         /* Region is permanently reserved.  Hot-remove not yet implemented. */
  52         new_res = request_mem_region(kmem_start, kmem_size, dev_name(dev));
  53         if (!new_res) {
  54                 dev_warn(dev, "could not reserve region [%pa-%pa]\n",
  55                          &kmem_start, &kmem_end);
  56                 return -EBUSY;
  57         }
  58
  59         /*
  60          * Set flags appropriate for System RAM.  Leave ..._BUSY clear
  61          * so that add_memory() can add a child resource.  Do not
  62          * inherit flags from the parent since it may set new flags
  63          * unknown to us that will break add_memory() below.
  64          */
  65         new_res->flags = IORESOURCE_SYSTEM_RAM;
  66         new_res->name = dev_name(dev);
  67
  68         rc = add_memory(numa_node, new_res->start, resource_size(new_res));
  69         if (rc) {
  70                 release_resource(new_res);
  71                 kfree(new_res);
  72                 return rc;
  73         }
  74         dev_dax->dax_kmem_res = new_res;
  75
  76         return 0;
  77 }
  78
  79 #ifdef CONFIG_MEMORY_HOTREMOVE
  80 static int dev_dax_kmem_remove(struct device *dev)
  81 {
  82         struct dev_dax *dev_dax = to_dev_dax(dev);
  83         struct resource *res = dev_dax->dax_kmem_res;
  84         resource_size_t kmem_start = res->start;
  85         resource_size_t kmem_size = resource_size(res);
  86         int rc;
  87
  88         /*
  89          * We have one shot for removing memory, if some memory blocks were not
  90          * offline prior to calling this function remove_memory() will fail, and
  91          * there is no way to hotremove this memory until reboot because device
  92          * unbind will succeed even if we return failure.
  93          */
  94         rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size);
  95         if (rc) {
  96                 dev_err(dev,
  97                         "DAX region %pR cannot be hotremoved until the next reboot\n",
  98                         res);
  99                 return rc;
 100         }
 101
 102         /* Release and free dax resources */
 103         release_resource(res);
 104         kfree(res);
 105         dev_dax->dax_kmem_res = NULL;
 106
 107         return 0;
 108 }
 109 #else
 110 static int dev_dax_kmem_remove(struct device *dev)
 111 {
 112         /*
 113          * Without hotremove purposely leak the request_mem_region() for the
 114          * device-dax range and return '0' to ->remove() attempts. The removal
 115          * of the device from the driver always succeeds, but the region is
 116          * permanently pinned as reserved by the unreleased
 117          * request_mem_region().
 118          */
 119         return 0;
 120 }
 121 #endif /* CONFIG_MEMORY_HOTREMOVE */
 122
 123 static struct dax_device_driver device_dax_kmem_driver = {
 124         .drv = {
 125                 .probe = dev_dax_kmem_probe,
 126                 .remove = dev_dax_kmem_remove,
 127         },
 128 };
 129
 130 static int __init dax_kmem_init(void)
 131 {
 132         return dax_driver_register(&device_dax_kmem_driver);
 133 }
 134
 135 static void __exit dax_kmem_exit(void)
 136 {
 137         dax_driver_unregister(&device_dax_kmem_driver);
 138 }
 139
 140 MODULE_AUTHOR("Intel Corporation");
 141 MODULE_LICENSE("GPL v2");
 142 module_init(dax_kmem_init);
 143 module_exit(dax_kmem_exit);
 144 MODULE_ALIAS_DAX_DEVICE(0);