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 /* Memory resource name used for add_memory_driver_managed(). */ 18 static const char *kmem_name; 19 /* Set if any memory will remain added when the driver will be unloaded. */ 20 static bool any_hotremove_failed; 21 22 int dev_dax_kmem_probe(struct device *dev) 23 { 24 struct dev_dax *dev_dax = to_dev_dax(dev); 25 struct resource *res = &dev_dax->region->res; 26 resource_size_t kmem_start; 27 resource_size_t kmem_size; 28 resource_size_t kmem_end; 29 struct resource *new_res; 30 const char *new_res_name; 31 int numa_node; 32 int rc; 33 34 /* 35 * Ensure good NUMA information for the persistent memory. 36 * Without this check, there is a risk that slow memory 37 * could be mixed in a node with faster memory, causing 38 * unavoidable performance issues. 39 */ 40 numa_node = dev_dax->target_node; 41 if (numa_node < 0) { 42 dev_warn(dev, "rejecting DAX region %pR with invalid node: %d\n", 43 res, numa_node); 44 return -EINVAL; 45 } 46 47 /* Hotplug starting at the beginning of the next block: */ 48 kmem_start = ALIGN(res->start, memory_block_size_bytes()); 49 50 kmem_size = resource_size(res); 51 /* Adjust the size down to compensate for moving up kmem_start: */ 52 kmem_size -= kmem_start - res->start; 53 /* Align the size down to cover only complete blocks: */ 54 kmem_size &= ~(memory_block_size_bytes() - 1); 55 kmem_end = kmem_start + kmem_size; 56 57 new_res_name = kstrdup(dev_name(dev), GFP_KERNEL); 58 if (!new_res_name) 59 return -ENOMEM; 60 61 /* Region is permanently reserved if hotremove fails. */ 62 new_res = request_mem_region(kmem_start, kmem_size, new_res_name); 63 if (!new_res) { 64 dev_warn(dev, "could not reserve region [%pa-%pa]\n", 65 &kmem_start, &kmem_end); 66 kfree(new_res_name); 67 return -EBUSY; 68 } 69 70 /* 71 * Set flags appropriate for System RAM. Leave ..._BUSY clear 72 * so that add_memory() can add a child resource. Do not 73 * inherit flags from the parent since it may set new flags 74 * unknown to us that will break add_memory() below. 75 */ 76 new_res->flags = IORESOURCE_SYSTEM_RAM; 77 78 /* 79 * Ensure that future kexec'd kernels will not treat this as RAM 80 * automatically. 81 */ 82 rc = add_memory_driver_managed(numa_node, new_res->start, 83 resource_size(new_res), kmem_name); 84 if (rc) { 85 release_resource(new_res); 86 kfree(new_res); 87 kfree(new_res_name); 88 return rc; 89 } 90 dev_dax->dax_kmem_res = new_res; 91 92 return 0; 93 } 94 95 #ifdef CONFIG_MEMORY_HOTREMOVE 96 static int dev_dax_kmem_remove(struct device *dev) 97 { 98 struct dev_dax *dev_dax = to_dev_dax(dev); 99 struct resource *res = dev_dax->dax_kmem_res; 100 resource_size_t kmem_start = res->start; 101 resource_size_t kmem_size = resource_size(res); 102 const char *res_name = res->name; 103 int rc; 104 105 /* 106 * We have one shot for removing memory, if some memory blocks were not 107 * offline prior to calling this function remove_memory() will fail, and 108 * there is no way to hotremove this memory until reboot because device 109 * unbind will succeed even if we return failure. 110 */ 111 rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size); 112 if (rc) { 113 any_hotremove_failed = true; 114 dev_err(dev, 115 "DAX region %pR cannot be hotremoved until the next reboot\n", 116 res); 117 return rc; 118 } 119 120 /* Release and free dax resources */ 121 release_resource(res); 122 kfree(res); 123 kfree(res_name); 124 dev_dax->dax_kmem_res = NULL; 125 126 return 0; 127 } 128 #else 129 static int dev_dax_kmem_remove(struct device *dev) 130 { 131 /* 132 * Without hotremove purposely leak the request_mem_region() for the 133 * device-dax range and return '0' to ->remove() attempts. The removal 134 * of the device from the driver always succeeds, but the region is 135 * permanently pinned as reserved by the unreleased 136 * request_mem_region(). 137 */ 138 any_hotremove_failed = true; 139 return 0; 140 } 141 #endif /* CONFIG_MEMORY_HOTREMOVE */ 142 143 static struct dax_device_driver device_dax_kmem_driver = { 144 .drv = { 145 .probe = dev_dax_kmem_probe, 146 .remove = dev_dax_kmem_remove, 147 }, 148 }; 149 150 static int __init dax_kmem_init(void) 151 { 152 int rc; 153 154 /* Resource name is permanently allocated if any hotremove fails. */ 155 kmem_name = kstrdup_const("System RAM (kmem)", GFP_KERNEL); 156 if (!kmem_name) 157 return -ENOMEM; 158 159 rc = dax_driver_register(&device_dax_kmem_driver); 160 if (rc) 161 kfree_const(kmem_name); 162 return rc; 163 } 164 165 static void __exit dax_kmem_exit(void) 166 { 167 dax_driver_unregister(&device_dax_kmem_driver); 168 if (!any_hotremove_failed) 169 kfree_const(kmem_name); 170 } 171 172 MODULE_AUTHOR("Intel Corporation"); 173 MODULE_LICENSE("GPL v2"); 174 module_init(dax_kmem_init); 175 module_exit(dax_kmem_exit); 176 MODULE_ALIAS_DAX_DEVICE(0); 177