1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (c) 2022, Oracle and/or its affiliates. 4 * Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES. All rights reserved 5 */ 6 #include <linux/iova_bitmap.h> 7 #include <linux/mm.h> 8 #include <linux/slab.h> 9 #include <linux/highmem.h> 10 11 #define BITS_PER_PAGE (PAGE_SIZE * BITS_PER_BYTE) 12 13 /* 14 * struct iova_bitmap_map - A bitmap representing an IOVA range 15 * 16 * Main data structure for tracking mapped user pages of bitmap data. 17 * 18 * For example, for something recording dirty IOVAs, it will be provided a 19 * struct iova_bitmap structure, as a general structure for iterating the 20 * total IOVA range. The struct iova_bitmap_map, though, represents the 21 * subset of said IOVA space that is pinned by its parent structure (struct 22 * iova_bitmap). 23 * 24 * The user does not need to exact location of the bits in the bitmap. 25 * From user perspective the only API available is iova_bitmap_set() which 26 * records the IOVA *range* in the bitmap by setting the corresponding 27 * bits. 28 * 29 * The bitmap is an array of u64 whereas each bit represents an IOVA of 30 * range of (1 << pgshift). Thus formula for the bitmap data to be set is: 31 * 32 * data[(iova / page_size) / 64] & (1ULL << (iova % 64)) 33 */ 34 struct iova_bitmap_map { 35 /* base IOVA representing bit 0 of the first page */ 36 unsigned long iova; 37 38 /* page size order that each bit granules to */ 39 unsigned long pgshift; 40 41 /* page offset of the first user page pinned */ 42 unsigned long pgoff; 43 44 /* number of pages pinned */ 45 unsigned long npages; 46 47 /* pinned pages representing the bitmap data */ 48 struct page **pages; 49 }; 50 51 /* 52 * struct iova_bitmap - The IOVA bitmap object 53 * 54 * Main data structure for iterating over the bitmap data. 55 * 56 * Abstracts the pinning work and iterates in IOVA ranges. 57 * It uses a windowing scheme and pins the bitmap in relatively 58 * big ranges e.g. 59 * 60 * The bitmap object uses one base page to store all the pinned pages 61 * pointers related to the bitmap. For sizeof(struct page*) == 8 it stores 62 * 512 struct page pointers which, if the base page size is 4K, it means 63 * 2M of bitmap data is pinned at a time. If the iova_bitmap page size is 64 * also 4K then the range window to iterate is 64G. 65 * 66 * For example iterating on a total IOVA range of 4G..128G, it will walk 67 * through this set of ranges: 68 * 69 * 4G - 68G-1 (64G) 70 * 68G - 128G-1 (64G) 71 * 72 * An example of the APIs on how to use/iterate over the IOVA bitmap: 73 * 74 * bitmap = iova_bitmap_alloc(iova, length, page_size, data); 75 * if (IS_ERR(bitmap)) 76 * return PTR_ERR(bitmap); 77 * 78 * ret = iova_bitmap_for_each(bitmap, arg, dirty_reporter_fn); 79 * 80 * iova_bitmap_free(bitmap); 81 * 82 * Each iteration of the @dirty_reporter_fn is called with a unique @iova 83 * and @length argument, indicating the current range available through the 84 * iova_bitmap. The @dirty_reporter_fn uses iova_bitmap_set() to mark dirty 85 * areas (@iova_length) within that provided range, as following: 86 * 87 * iova_bitmap_set(bitmap, iova, iova_length); 88 * 89 * The internals of the object uses an index @mapped_base_index that indexes 90 * which u64 word of the bitmap is mapped, up to @mapped_total_index. 91 * Those keep being incremented until @mapped_total_index is reached while 92 * mapping up to PAGE_SIZE / sizeof(struct page*) maximum of pages. 93 * 94 * The IOVA bitmap is usually located on what tracks DMA mapped ranges or 95 * some form of IOVA range tracking that co-relates to the user passed 96 * bitmap. 97 */ 98 struct iova_bitmap { 99 /* IOVA range representing the currently mapped bitmap data */ 100 struct iova_bitmap_map mapped; 101 102 /* userspace address of the bitmap */ 103 u8 __user *bitmap; 104 105 /* u64 index that @mapped points to */ 106 unsigned long mapped_base_index; 107 108 /* how many u64 can we walk in total */ 109 unsigned long mapped_total_index; 110 111 /* base IOVA of the whole bitmap */ 112 unsigned long iova; 113 114 /* length of the IOVA range for the whole bitmap */ 115 size_t length; 116 }; 117 118 /* 119 * Converts a relative IOVA to a bitmap index. 120 * This function provides the index into the u64 array (bitmap::bitmap) 121 * for a given IOVA offset. 122 * Relative IOVA means relative to the bitmap::mapped base IOVA 123 * (stored in mapped::iova). All computations in this file are done using 124 * relative IOVAs and thus avoid an extra subtraction against mapped::iova. 125 * The user API iova_bitmap_set() always uses a regular absolute IOVAs. 126 */ 127 static unsigned long iova_bitmap_offset_to_index(struct iova_bitmap *bitmap, 128 unsigned long iova) 129 { 130 unsigned long pgsize = 1 << bitmap->mapped.pgshift; 131 132 return iova / (BITS_PER_TYPE(*bitmap->bitmap) * pgsize); 133 } 134 135 /* 136 * Converts a bitmap index to a *relative* IOVA. 137 */ 138 static unsigned long iova_bitmap_index_to_offset(struct iova_bitmap *bitmap, 139 unsigned long index) 140 { 141 unsigned long pgshift = bitmap->mapped.pgshift; 142 143 return (index * BITS_PER_TYPE(*bitmap->bitmap)) << pgshift; 144 } 145 146 /* 147 * Returns the base IOVA of the mapped range. 148 */ 149 static unsigned long iova_bitmap_mapped_iova(struct iova_bitmap *bitmap) 150 { 151 unsigned long skip = bitmap->mapped_base_index; 152 153 return bitmap->iova + iova_bitmap_index_to_offset(bitmap, skip); 154 } 155 156 /* 157 * Pins the bitmap user pages for the current range window. 158 * This is internal to IOVA bitmap and called when advancing the 159 * index (@mapped_base_index) or allocating the bitmap. 160 */ 161 static int iova_bitmap_get(struct iova_bitmap *bitmap) 162 { 163 struct iova_bitmap_map *mapped = &bitmap->mapped; 164 unsigned long npages; 165 u8 __user *addr; 166 long ret; 167 168 /* 169 * @mapped_base_index is the index of the currently mapped u64 words 170 * that we have access. Anything before @mapped_base_index is not 171 * mapped. The range @mapped_base_index .. @mapped_total_index-1 is 172 * mapped but capped at a maximum number of pages. 173 */ 174 npages = DIV_ROUND_UP((bitmap->mapped_total_index - 175 bitmap->mapped_base_index) * 176 sizeof(*bitmap->bitmap), PAGE_SIZE); 177 178 /* 179 * We always cap at max number of 'struct page' a base page can fit. 180 * This is, for example, on x86 means 2M of bitmap data max. 181 */ 182 npages = min(npages, PAGE_SIZE / sizeof(struct page *)); 183 184 /* 185 * Bitmap address to be pinned is calculated via pointer arithmetic 186 * with bitmap u64 word index. 187 */ 188 addr = bitmap->bitmap + bitmap->mapped_base_index; 189 190 ret = pin_user_pages_fast((unsigned long)addr, npages, 191 FOLL_WRITE, mapped->pages); 192 if (ret <= 0) 193 return -EFAULT; 194 195 mapped->npages = (unsigned long)ret; 196 /* Base IOVA where @pages point to i.e. bit 0 of the first page */ 197 mapped->iova = iova_bitmap_mapped_iova(bitmap); 198 199 /* 200 * offset of the page where pinned pages bit 0 is located. 201 * This handles the case where the bitmap is not PAGE_SIZE 202 * aligned. 203 */ 204 mapped->pgoff = offset_in_page(addr); 205 return 0; 206 } 207 208 /* 209 * Unpins the bitmap user pages and clears @npages 210 * (un)pinning is abstracted from API user and it's done when advancing 211 * the index or freeing the bitmap. 212 */ 213 static void iova_bitmap_put(struct iova_bitmap *bitmap) 214 { 215 struct iova_bitmap_map *mapped = &bitmap->mapped; 216 217 if (mapped->npages) { 218 unpin_user_pages(mapped->pages, mapped->npages); 219 mapped->npages = 0; 220 } 221 } 222 223 /** 224 * iova_bitmap_alloc() - Allocates an IOVA bitmap object 225 * @iova: Start address of the IOVA range 226 * @length: Length of the IOVA range 227 * @page_size: Page size of the IOVA bitmap. It defines what each bit 228 * granularity represents 229 * @data: Userspace address of the bitmap 230 * 231 * Allocates an IOVA object and initializes all its fields including the 232 * first user pages of @data. 233 * 234 * Return: A pointer to a newly allocated struct iova_bitmap 235 * or ERR_PTR() on error. 236 */ 237 struct iova_bitmap *iova_bitmap_alloc(unsigned long iova, size_t length, 238 unsigned long page_size, u64 __user *data) 239 { 240 struct iova_bitmap_map *mapped; 241 struct iova_bitmap *bitmap; 242 int rc; 243 244 bitmap = kzalloc(sizeof(*bitmap), GFP_KERNEL); 245 if (!bitmap) 246 return ERR_PTR(-ENOMEM); 247 248 mapped = &bitmap->mapped; 249 mapped->pgshift = __ffs(page_size); 250 bitmap->bitmap = (u8 __user *)data; 251 bitmap->mapped_total_index = 252 iova_bitmap_offset_to_index(bitmap, length - 1) + 1; 253 bitmap->iova = iova; 254 bitmap->length = length; 255 mapped->iova = iova; 256 mapped->pages = (struct page **)__get_free_page(GFP_KERNEL); 257 if (!mapped->pages) { 258 rc = -ENOMEM; 259 goto err; 260 } 261 262 rc = iova_bitmap_get(bitmap); 263 if (rc) 264 goto err; 265 return bitmap; 266 267 err: 268 iova_bitmap_free(bitmap); 269 return ERR_PTR(rc); 270 } 271 272 /** 273 * iova_bitmap_free() - Frees an IOVA bitmap object 274 * @bitmap: IOVA bitmap to free 275 * 276 * It unpins and releases pages array memory and clears any leftover 277 * state. 278 */ 279 void iova_bitmap_free(struct iova_bitmap *bitmap) 280 { 281 struct iova_bitmap_map *mapped = &bitmap->mapped; 282 283 iova_bitmap_put(bitmap); 284 285 if (mapped->pages) { 286 free_page((unsigned long)mapped->pages); 287 mapped->pages = NULL; 288 } 289 290 kfree(bitmap); 291 } 292 293 /* 294 * Returns the remaining bitmap indexes from mapped_total_index to process for 295 * the currently pinned bitmap pages. 296 */ 297 static unsigned long iova_bitmap_mapped_remaining(struct iova_bitmap *bitmap) 298 { 299 unsigned long remaining, bytes; 300 301 bytes = (bitmap->mapped.npages << PAGE_SHIFT) - bitmap->mapped.pgoff; 302 303 remaining = bitmap->mapped_total_index - bitmap->mapped_base_index; 304 remaining = min_t(unsigned long, remaining, 305 DIV_ROUND_UP(bytes, sizeof(*bitmap->bitmap))); 306 307 return remaining; 308 } 309 310 /* 311 * Returns the length of the mapped IOVA range. 312 */ 313 static unsigned long iova_bitmap_mapped_length(struct iova_bitmap *bitmap) 314 { 315 unsigned long max_iova = bitmap->iova + bitmap->length - 1; 316 unsigned long iova = iova_bitmap_mapped_iova(bitmap); 317 unsigned long remaining; 318 319 /* 320 * iova_bitmap_mapped_remaining() returns a number of indexes which 321 * when converted to IOVA gives us a max length that the bitmap 322 * pinned data can cover. Afterwards, that is capped to 323 * only cover the IOVA range in @bitmap::iova .. @bitmap::length. 324 */ 325 remaining = iova_bitmap_index_to_offset(bitmap, 326 iova_bitmap_mapped_remaining(bitmap)); 327 328 if (iova + remaining - 1 > max_iova) 329 remaining -= ((iova + remaining - 1) - max_iova); 330 331 return remaining; 332 } 333 334 /* 335 * Returns true if there's not more data to iterate. 336 */ 337 static bool iova_bitmap_done(struct iova_bitmap *bitmap) 338 { 339 return bitmap->mapped_base_index >= bitmap->mapped_total_index; 340 } 341 342 /* 343 * Advances to the next range, releases the current pinned 344 * pages and pins the next set of bitmap pages. 345 * Returns 0 on success or otherwise errno. 346 */ 347 static int iova_bitmap_advance(struct iova_bitmap *bitmap) 348 { 349 unsigned long iova = iova_bitmap_mapped_length(bitmap) - 1; 350 unsigned long count = iova_bitmap_offset_to_index(bitmap, iova) + 1; 351 352 bitmap->mapped_base_index += count; 353 354 iova_bitmap_put(bitmap); 355 if (iova_bitmap_done(bitmap)) 356 return 0; 357 358 /* When advancing the index we pin the next set of bitmap pages */ 359 return iova_bitmap_get(bitmap); 360 } 361 362 /** 363 * iova_bitmap_for_each() - Iterates over the bitmap 364 * @bitmap: IOVA bitmap to iterate 365 * @opaque: Additional argument to pass to the callback 366 * @fn: Function that gets called for each IOVA range 367 * 368 * Helper function to iterate over bitmap data representing a portion of IOVA 369 * space. It hides the complexity of iterating bitmaps and translating the 370 * mapped bitmap user pages into IOVA ranges to process. 371 * 372 * Return: 0 on success, and an error on failure either upon 373 * iteration or when the callback returns an error. 374 */ 375 int iova_bitmap_for_each(struct iova_bitmap *bitmap, void *opaque, 376 iova_bitmap_fn_t fn) 377 { 378 int ret = 0; 379 380 for (; !iova_bitmap_done(bitmap) && !ret; 381 ret = iova_bitmap_advance(bitmap)) { 382 ret = fn(bitmap, iova_bitmap_mapped_iova(bitmap), 383 iova_bitmap_mapped_length(bitmap), opaque); 384 if (ret) 385 break; 386 } 387 388 return ret; 389 } 390 391 /** 392 * iova_bitmap_set() - Records an IOVA range in bitmap 393 * @bitmap: IOVA bitmap 394 * @iova: IOVA to start 395 * @length: IOVA range length 396 * 397 * Set the bits corresponding to the range [iova .. iova+length-1] in 398 * the user bitmap. 399 * 400 */ 401 void iova_bitmap_set(struct iova_bitmap *bitmap, 402 unsigned long iova, size_t length) 403 { 404 struct iova_bitmap_map *mapped = &bitmap->mapped; 405 unsigned long cur_bit = ((iova - mapped->iova) >> 406 mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE; 407 unsigned long last_bit = (((iova + length - 1) - mapped->iova) >> 408 mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE; 409 unsigned long last_page_idx = mapped->npages - 1; 410 411 do { 412 unsigned int page_idx = cur_bit / BITS_PER_PAGE; 413 unsigned int offset = cur_bit % BITS_PER_PAGE; 414 unsigned int nbits = min(BITS_PER_PAGE - offset, 415 last_bit - cur_bit + 1); 416 void *kaddr; 417 418 if (unlikely(page_idx > last_page_idx)) 419 break; 420 421 kaddr = kmap_local_page(mapped->pages[page_idx]); 422 bitmap_set(kaddr, offset, nbits); 423 kunmap_local(kaddr); 424 cur_bit += nbits; 425 } while (cur_bit <= last_bit); 426 } 427 EXPORT_SYMBOL_GPL(iova_bitmap_set); 428