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TOMOYO Linux Cross Reference
Linux/kernel/memremap.c

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

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