kernel/memremap.c

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /* Copyright(c) 2015 Intel Corporation. All rights reserved. */
   3 #include <linux/radix-tree.h>
   4 #include <linux/device.h>
   5 #include <linux/types.h>
   6 #include <linux/pfn_t.h>
   7 #include <linux/io.h>
   8 #include <linux/kasan.h>
   9 #include <linux/mm.h>
  10 #include <linux/memory_hotplug.h>
  11 #include <linux/swap.h>
  12 #include <linux/swapops.h>
  13 #include <linux/wait_bit.h>
  14
  15 static DEFINE_MUTEX(pgmap_lock);
  16 static RADIX_TREE(pgmap_radix, GFP_KERNEL);
  17 #define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
  18 #define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
  19
  20 static unsigned long order_at(struct resource *res, unsigned long pgoff)
  21 {
  22         unsigned long phys_pgoff = PHYS_PFN(res->start) + pgoff;
  23         unsigned long nr_pages, mask;
  24
  25         nr_pages = PHYS_PFN(resource_size(res));
  26         if (nr_pages == pgoff)
  27                 return ULONG_MAX;
  28
  29         /*
  30          * What is the largest aligned power-of-2 range available from
  31          * this resource pgoff to the end of the resource range,
  32          * considering the alignment of the current pgoff?
  33          */
  34         mask = phys_pgoff | rounddown_pow_of_two(nr_pages - pgoff);
  35         if (!mask)
  36                 return ULONG_MAX;
  37
  38         return find_first_bit(&mask, BITS_PER_LONG);
  39 }
  40
  41 #define foreach_order_pgoff(res, order, pgoff) \
  42         for (pgoff = 0, order = order_at((res), pgoff); order < ULONG_MAX; \
  43                         pgoff += 1UL << order, order = order_at((res), pgoff))
  44
  45 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
  46 vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
  47                        unsigned long addr,
  48                        swp_entry_t entry,
  49                        unsigned int flags,
  50                        pmd_t *pmdp)
  51 {
  52         struct page *page = device_private_entry_to_page(entry);
  53
  54         /*
  55          * The page_fault() callback must migrate page back to system memory
  56          * so that CPU can access it. This might fail for various reasons
  57          * (device issue, device was unsafely unplugged, ...). When such
  58          * error conditions happen, the callback must return VM_FAULT_SIGBUS.
  59          *
  60          * Note that because memory cgroup charges are accounted to the device
  61          * memory, this should never fail because of memory restrictions (but
  62          * allocation of regular system page might still fail because we are
  63          * out of memory).
  64          *
  65          * There is a more in-depth description of what that callback can and
  66          * cannot do, in include/linux/memremap.h
  67          */
  68         return page->pgmap->page_fault(vma, addr, page, flags, pmdp);
  69 }
  70 EXPORT_SYMBOL(device_private_entry_fault);
  71 #endif /* CONFIG_DEVICE_PRIVATE */
  72
  73 static void pgmap_radix_release(struct resource *res, unsigned long end_pgoff)
  74 {
  75         unsigned long pgoff, order;
  76
  77         mutex_lock(&pgmap_lock);
  78         foreach_order_pgoff(res, order, pgoff) {
  79                 if (pgoff >= end_pgoff)
  80                         break;
  81                 radix_tree_delete(&pgmap_radix, PHYS_PFN(res->start) + pgoff);
  82         }
  83         mutex_unlock(&pgmap_lock);
  84
  85         synchronize_rcu();
  86 }
  87
  88 static unsigned long pfn_first(struct dev_pagemap *pgmap)
  89 {
  90         const struct resource *res = &pgmap->res;
  91         struct vmem_altmap *altmap = &pgmap->altmap;
  92         unsigned long pfn;
  93
  94         pfn = res->start >> PAGE_SHIFT;
  95         if (pgmap->altmap_valid)
  96                 pfn += vmem_altmap_offset(altmap);
  97         return pfn;
  98 }
  99
 100 static unsigned long pfn_end(struct dev_pagemap *pgmap)
 101 {
 102         const struct resource *res = &pgmap->res;
 103
 104         return (res->start + resource_size(res)) >> PAGE_SHIFT;
 105 }
 106
 107 static unsigned long pfn_next(unsigned long pfn)
 108 {
 109         if (pfn % 1024 == 0)
 110                 cond_resched();
 111         return pfn + 1;
 112 }
 113
 114 #define for_each_device_pfn(pfn, map) \
 115         for (pfn = pfn_first(map); pfn < pfn_end(map); pfn = pfn_next(pfn))
 116
 117 static void devm_memremap_pages_release(void *data)
 118 {
 119         struct dev_pagemap *pgmap = data;
 120         struct device *dev = pgmap->dev;
 121         struct resource *res = &pgmap->res;
 122         resource_size_t align_start, align_size;
 123         unsigned long pfn;
 124
 125         for_each_device_pfn(pfn, pgmap)
 126                 put_page(pfn_to_page(pfn));
 127
 128         if (percpu_ref_tryget_live(pgmap->ref)) {
 129                 dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
 130                 percpu_ref_put(pgmap->ref);
 131         }
 132
 133         /* pages are dead and unused, undo the arch mapping */
 134         align_start = res->start & ~(SECTION_SIZE - 1);
 135         align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
 136                 - align_start;
 137
 138         mem_hotplug_begin();
 139         arch_remove_memory(align_start, align_size, pgmap->altmap_valid ?
 140                         &pgmap->altmap : NULL);
 141         kasan_remove_zero_shadow(__va(align_start), align_size);
 142         mem_hotplug_done();
 143
 144         untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
 145         pgmap_radix_release(res, -1);
 146         dev_WARN_ONCE(dev, pgmap->altmap.alloc,
 147                       "%s: failed to free all reserved pages\n", __func__);
 148 }
 149
 150 /**
 151  * devm_memremap_pages - remap and provide memmap backing for the given resource
 152  * @dev: hosting device for @res
 153  * @pgmap: pointer to a struct dev_pgmap
 154  *
 155  * Notes:
 156  * 1/ At a minimum the res, ref and type members of @pgmap must be initialized
 157  *    by the caller before passing it to this function
 158  *
 159  * 2/ The altmap field may optionally be initialized, in which case altmap_valid
 160  *    must be set to true
 161  *
 162  * 3/ pgmap.ref must be 'live' on entry and 'dead' before devm_memunmap_pages()
 163  *    time (or devm release event). The expected order of events is that ref has
 164  *    been through percpu_ref_kill() before devm_memremap_pages_release(). The
 165  *    wait for the completion of all references being dropped and
 166  *    percpu_ref_exit() must occur after devm_memremap_pages_release().
 167  *
 168  * 4/ res is expected to be a host memory range that could feasibly be
 169  *    treated as a "System RAM" range, i.e. not a device mmio range, but
 170  *    this is not enforced.
 171  */
 172 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 173 {
 174         resource_size_t align_start, align_size, align_end;
 175         struct vmem_altmap *altmap = pgmap->altmap_valid ?
 176                         &pgmap->altmap : NULL;
 177         struct resource *res = &pgmap->res;
 178         unsigned long pfn, pgoff, order;
 179         pgprot_t pgprot = PAGE_KERNEL;
 180         int error, nid, is_ram;
 181         struct dev_pagemap *conflict_pgmap;
 182
 183         align_start = res->start & ~(SECTION_SIZE - 1);
 184         align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
 185                 - align_start;
 186         align_end = align_start + align_size - 1;
 187
 188         conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_start), NULL);
 189         if (conflict_pgmap) {
 190                 dev_WARN(dev, "Conflicting mapping in same section\n");
 191                 put_dev_pagemap(conflict_pgmap);
 192                 return ERR_PTR(-ENOMEM);
 193         }
 194
 195         conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_end), NULL);
 196         if (conflict_pgmap) {
 197                 dev_WARN(dev, "Conflicting mapping in same section\n");
 198                 put_dev_pagemap(conflict_pgmap);
 199                 return ERR_PTR(-ENOMEM);
 200         }
 201
 202         is_ram = region_intersects(align_start, align_size,
 203                 IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
 204
 205         if (is_ram == REGION_MIXED) {
 206                 WARN_ONCE(1, "%s attempted on mixed region %pr\n",
 207                                 __func__, res);
 208                 return ERR_PTR(-ENXIO);
 209         }
 210
 211         if (is_ram == REGION_INTERSECTS)
 212                 return __va(res->start);
 213
 214         if (!pgmap->ref)
 215                 return ERR_PTR(-EINVAL);
 216
 217         pgmap->dev = dev;
 218
 219         mutex_lock(&pgmap_lock);
 220         error = 0;
 221
 222         foreach_order_pgoff(res, order, pgoff) {
 223                 error = __radix_tree_insert(&pgmap_radix,
 224                                 PHYS_PFN(res->start) + pgoff, order, pgmap);
 225                 if (error) {
 226                         dev_err(dev, "%s: failed: %d\n", __func__, error);
 227                         break;
 228                 }
 229         }
 230         mutex_unlock(&pgmap_lock);
 231         if (error)
 232                 goto err_radix;
 233
 234         nid = dev_to_node(dev);
 235         if (nid < 0)
 236                 nid = numa_mem_id();
 237
 238         error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(align_start), 0,
 239                         align_size);
 240         if (error)
 241                 goto err_pfn_remap;
 242
 243         mem_hotplug_begin();
 244         error = kasan_add_zero_shadow(__va(align_start), align_size);
 245         if (error) {
 246                 mem_hotplug_done();
 247                 goto err_kasan;
 248         }
 249
 250         error = arch_add_memory(nid, align_start, align_size, altmap, false);
 251         if (!error)
 252                 move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
 253                                         align_start >> PAGE_SHIFT,
 254                                         align_size >> PAGE_SHIFT, altmap);
 255         mem_hotplug_done();
 256         if (error)
 257                 goto err_add_memory;
 258
 259         for_each_device_pfn(pfn, pgmap) {
 260                 struct page *page = pfn_to_page(pfn);
 261
 262                 /*
 263                  * ZONE_DEVICE pages union ->lru with a ->pgmap back
 264                  * pointer.  It is a bug if a ZONE_DEVICE page is ever
 265                  * freed or placed on a driver-private list.  Seed the
 266                  * storage with LIST_POISON* values.
 267                  */
 268                 list_del(&page->lru);
 269                 page->pgmap = pgmap;
 270                 percpu_ref_get(pgmap->ref);
 271         }
 272
 273         devm_add_action(dev, devm_memremap_pages_release, pgmap);
 274
 275         return __va(res->start);
 276
 277  err_add_memory:
 278         kasan_remove_zero_shadow(__va(align_start), align_size);
 279  err_kasan:
 280         untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
 281  err_pfn_remap:
 282  err_radix:
 283         pgmap_radix_release(res, pgoff);
 284         return ERR_PTR(error);
 285 }
 286 EXPORT_SYMBOL(devm_memremap_pages);
 287
 288 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
 289 {
 290         /* number of pfns from base where pfn_to_page() is valid */
 291         return altmap->reserve + altmap->free;
 292 }
 293
 294 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
 295 {
 296         altmap->alloc -= nr_pfns;
 297 }
 298
 299 /**
 300  * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
 301  * @pfn: page frame number to lookup page_map
 302  * @pgmap: optional known pgmap that already has a reference
 303  *
 304  * If @pgmap is non-NULL and covers @pfn it will be returned as-is.  If @pgmap
 305  * is non-NULL but does not cover @pfn the reference to it will be released.
 306  */
 307 struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 308                 struct dev_pagemap *pgmap)
 309 {
 310         resource_size_t phys = PFN_PHYS(pfn);
 311
 312         /*
 313          * In the cached case we're already holding a live reference.
 314          */
 315         if (pgmap) {
 316                 if (phys >= pgmap->res.start && phys <= pgmap->res.end)
 317                         return pgmap;
 318                 put_dev_pagemap(pgmap);
 319         }
 320
 321         /* fall back to slow path lookup */
 322         rcu_read_lock();
 323         pgmap = radix_tree_lookup(&pgmap_radix, PHYS_PFN(phys));
 324         if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
 325                 pgmap = NULL;
 326         rcu_read_unlock();
 327
 328         return pgmap;
 329 }
 330 EXPORT_SYMBOL_GPL(get_dev_pagemap);
 331
 332 #ifdef CONFIG_DEV_PAGEMAP_OPS
 333 DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
 334 EXPORT_SYMBOL(devmap_managed_key);
 335 static atomic_t devmap_enable;
 336
 337 /*
 338  * Toggle the static key for ->page_free() callbacks when dev_pagemap
 339  * pages go idle.
 340  */
 341 void dev_pagemap_get_ops(void)
 342 {
 343         if (atomic_inc_return(&devmap_enable) == 1)
 344                 static_branch_enable(&devmap_managed_key);
 345 }
 346 EXPORT_SYMBOL_GPL(dev_pagemap_get_ops);
 347
 348 void dev_pagemap_put_ops(void)
 349 {
 350         if (atomic_dec_and_test(&devmap_enable))
 351                 static_branch_disable(&devmap_managed_key);
 352 }
 353 EXPORT_SYMBOL_GPL(dev_pagemap_put_ops);
 354
 355 void __put_devmap_managed_page(struct page *page)
 356 {
 357         int count = page_ref_dec_return(page);
 358
 359         /*
 360          * If refcount is 1 then page is freed and refcount is stable as nobody
 361          * holds a reference on the page.
 362          */
 363         if (count == 1) {
 364                 /* Clear Active bit in case of parallel mark_page_accessed */
 365                 __ClearPageActive(page);
 366                 __ClearPageWaiters(page);
 367
 368                 mem_cgroup_uncharge(page);
 369
 370                 page->pgmap->page_free(page, page->pgmap->data);
 371         } else if (!count)
 372                 __put_page(page);
 373 }
 374 EXPORT_SYMBOL(__put_devmap_managed_page);
 375 #endif /* CONFIG_DEV_PAGEMAP_OPS */