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 /* length of the IOVA range set ahead the pinned pages */ 118 unsigned long set_ahead_length; 119 }; 120 121 /* 122 * Converts a relative IOVA to a bitmap index. 123 * This function provides the index into the u64 array (bitmap::bitmap) 124 * for a given IOVA offset. 125 * Relative IOVA means relative to the bitmap::mapped base IOVA 126 * (stored in mapped::iova). All computations in this file are done using 127 * relative IOVAs and thus avoid an extra subtraction against mapped::iova. 128 * The user API iova_bitmap_set() always uses a regular absolute IOVAs. 129 */ 130 static unsigned long iova_bitmap_offset_to_index(struct iova_bitmap *bitmap, 131 unsigned long iova) 132 { 133 unsigned long pgsize = 1 << bitmap->mapped.pgshift; 134 135 return iova / (BITS_PER_TYPE(*bitmap->bitmap) * pgsize); 136 } 137 138 /* 139 * Converts a bitmap index to a *relative* IOVA. 140 */ 141 static unsigned long iova_bitmap_index_to_offset(struct iova_bitmap *bitmap, 142 unsigned long index) 143 { 144 unsigned long pgshift = bitmap->mapped.pgshift; 145 146 return (index * BITS_PER_TYPE(*bitmap->bitmap)) << pgshift; 147 } 148 149 /* 150 * Returns the base IOVA of the mapped range. 151 */ 152 static unsigned long iova_bitmap_mapped_iova(struct iova_bitmap *bitmap) 153 { 154 unsigned long skip = bitmap->mapped_base_index; 155 156 return bitmap->iova + iova_bitmap_index_to_offset(bitmap, skip); 157 } 158 159 /* 160 * Pins the bitmap user pages for the current range window. 161 * This is internal to IOVA bitmap and called when advancing the 162 * index (@mapped_base_index) or allocating the bitmap. 163 */ 164 static int iova_bitmap_get(struct iova_bitmap *bitmap) 165 { 166 struct iova_bitmap_map *mapped = &bitmap->mapped; 167 unsigned long npages; 168 u8 __user *addr; 169 long ret; 170 171 /* 172 * @mapped_base_index is the index of the currently mapped u64 words 173 * that we have access. Anything before @mapped_base_index is not 174 * mapped. The range @mapped_base_index .. @mapped_total_index-1 is 175 * mapped but capped at a maximum number of pages. 176 */ 177 npages = DIV_ROUND_UP((bitmap->mapped_total_index - 178 bitmap->mapped_base_index) * 179 sizeof(*bitmap->bitmap), PAGE_SIZE); 180 181 /* 182 * Bitmap address to be pinned is calculated via pointer arithmetic 183 * with bitmap u64 word index. 184 */ 185 addr = bitmap->bitmap + bitmap->mapped_base_index; 186 187 /* 188 * We always cap at max number of 'struct page' a base page can fit. 189 * This is, for example, on x86 means 2M of bitmap data max. 190 */ 191 npages = min(npages + !!offset_in_page(addr), 192 PAGE_SIZE / sizeof(struct page *)); 193 194 ret = pin_user_pages_fast((unsigned long)addr, npages, 195 FOLL_WRITE, mapped->pages); 196 if (ret <= 0) 197 return -EFAULT; 198 199 mapped->npages = (unsigned long)ret; 200 /* Base IOVA where @pages point to i.e. bit 0 of the first page */ 201 mapped->iova = iova_bitmap_mapped_iova(bitmap); 202 203 /* 204 * offset of the page where pinned pages bit 0 is located. 205 * This handles the case where the bitmap is not PAGE_SIZE 206 * aligned. 207 */ 208 mapped->pgoff = offset_in_page(addr); 209 return 0; 210 } 211 212 /* 213 * Unpins the bitmap user pages and clears @npages 214 * (un)pinning is abstracted from API user and it's done when advancing 215 * the index or freeing the bitmap. 216 */ 217 static void iova_bitmap_put(struct iova_bitmap *bitmap) 218 { 219 struct iova_bitmap_map *mapped = &bitmap->mapped; 220 221 if (mapped->npages) { 222 unpin_user_pages(mapped->pages, mapped->npages); 223 mapped->npages = 0; 224 } 225 } 226 227 /** 228 * iova_bitmap_alloc() - Allocates an IOVA bitmap object 229 * @iova: Start address of the IOVA range 230 * @length: Length of the IOVA range 231 * @page_size: Page size of the IOVA bitmap. It defines what each bit 232 * granularity represents 233 * @data: Userspace address of the bitmap 234 * 235 * Allocates an IOVA object and initializes all its fields including the 236 * first user pages of @data. 237 * 238 * Return: A pointer to a newly allocated struct iova_bitmap 239 * or ERR_PTR() on error. 240 */ 241 struct iova_bitmap *iova_bitmap_alloc(unsigned long iova, size_t length, 242 unsigned long page_size, u64 __user *data) 243 { 244 struct iova_bitmap_map *mapped; 245 struct iova_bitmap *bitmap; 246 int rc; 247 248 bitmap = kzalloc(sizeof(*bitmap), GFP_KERNEL); 249 if (!bitmap) 250 return ERR_PTR(-ENOMEM); 251 252 mapped = &bitmap->mapped; 253 mapped->pgshift = __ffs(page_size); 254 bitmap->bitmap = (u8 __user *)data; 255 bitmap->mapped_total_index = 256 iova_bitmap_offset_to_index(bitmap, length - 1) + 1; 257 bitmap->iova = iova; 258 bitmap->length = length; 259 mapped->iova = iova; 260 mapped->pages = (struct page **)__get_free_page(GFP_KERNEL); 261 if (!mapped->pages) { 262 rc = -ENOMEM; 263 goto err; 264 } 265 266 rc = iova_bitmap_get(bitmap); 267 if (rc) 268 goto err; 269 return bitmap; 270 271 err: 272 iova_bitmap_free(bitmap); 273 return ERR_PTR(rc); 274 } 275 EXPORT_SYMBOL_NS_GPL(iova_bitmap_alloc, IOMMUFD); 276 277 /** 278 * iova_bitmap_free() - Frees an IOVA bitmap object 279 * @bitmap: IOVA bitmap to free 280 * 281 * It unpins and releases pages array memory and clears any leftover 282 * state. 283 */ 284 void iova_bitmap_free(struct iova_bitmap *bitmap) 285 { 286 struct iova_bitmap_map *mapped = &bitmap->mapped; 287 288 iova_bitmap_put(bitmap); 289 290 if (mapped->pages) { 291 free_page((unsigned long)mapped->pages); 292 mapped->pages = NULL; 293 } 294 295 kfree(bitmap); 296 } 297 EXPORT_SYMBOL_NS_GPL(iova_bitmap_free, IOMMUFD); 298 299 /* 300 * Returns the remaining bitmap indexes from mapped_total_index to process for 301 * the currently pinned bitmap pages. 302 */ 303 static unsigned long iova_bitmap_mapped_remaining(struct iova_bitmap *bitmap) 304 { 305 unsigned long remaining, bytes; 306 307 bytes = (bitmap->mapped.npages << PAGE_SHIFT) - bitmap->mapped.pgoff; 308 309 remaining = bitmap->mapped_total_index - bitmap->mapped_base_index; 310 remaining = min_t(unsigned long, remaining, 311 DIV_ROUND_UP(bytes, sizeof(*bitmap->bitmap))); 312 313 return remaining; 314 } 315 316 /* 317 * Returns the length of the mapped IOVA range. 318 */ 319 static unsigned long iova_bitmap_mapped_length(struct iova_bitmap *bitmap) 320 { 321 unsigned long max_iova = bitmap->iova + bitmap->length - 1; 322 unsigned long iova = iova_bitmap_mapped_iova(bitmap); 323 unsigned long remaining; 324 325 /* 326 * iova_bitmap_mapped_remaining() returns a number of indexes which 327 * when converted to IOVA gives us a max length that the bitmap 328 * pinned data can cover. Afterwards, that is capped to 329 * only cover the IOVA range in @bitmap::iova .. @bitmap::length. 330 */ 331 remaining = iova_bitmap_index_to_offset(bitmap, 332 iova_bitmap_mapped_remaining(bitmap)); 333 334 if (iova + remaining - 1 > max_iova) 335 remaining -= ((iova + remaining - 1) - max_iova); 336 337 return remaining; 338 } 339 340 /* 341 * Returns true if there's not more data to iterate. 342 */ 343 static bool iova_bitmap_done(struct iova_bitmap *bitmap) 344 { 345 return bitmap->mapped_base_index >= bitmap->mapped_total_index; 346 } 347 348 static int iova_bitmap_set_ahead(struct iova_bitmap *bitmap, 349 size_t set_ahead_length) 350 { 351 int ret = 0; 352 353 while (set_ahead_length > 0 && !iova_bitmap_done(bitmap)) { 354 unsigned long length = iova_bitmap_mapped_length(bitmap); 355 unsigned long iova = iova_bitmap_mapped_iova(bitmap); 356 357 ret = iova_bitmap_get(bitmap); 358 if (ret) 359 break; 360 361 length = min(length, set_ahead_length); 362 iova_bitmap_set(bitmap, iova, length); 363 364 set_ahead_length -= length; 365 bitmap->mapped_base_index += 366 iova_bitmap_offset_to_index(bitmap, length - 1) + 1; 367 iova_bitmap_put(bitmap); 368 } 369 370 bitmap->set_ahead_length = 0; 371 return ret; 372 } 373 374 /* 375 * Advances to the next range, releases the current pinned 376 * pages and pins the next set of bitmap pages. 377 * Returns 0 on success or otherwise errno. 378 */ 379 static int iova_bitmap_advance(struct iova_bitmap *bitmap) 380 { 381 unsigned long iova = iova_bitmap_mapped_length(bitmap) - 1; 382 unsigned long count = iova_bitmap_offset_to_index(bitmap, iova) + 1; 383 384 bitmap->mapped_base_index += count; 385 386 iova_bitmap_put(bitmap); 387 if (iova_bitmap_done(bitmap)) 388 return 0; 389 390 /* Iterate, set and skip any bits requested for next iteration */ 391 if (bitmap->set_ahead_length) { 392 int ret; 393 394 ret = iova_bitmap_set_ahead(bitmap, bitmap->set_ahead_length); 395 if (ret) 396 return ret; 397 } 398 399 /* When advancing the index we pin the next set of bitmap pages */ 400 return iova_bitmap_get(bitmap); 401 } 402 403 /** 404 * iova_bitmap_for_each() - Iterates over the bitmap 405 * @bitmap: IOVA bitmap to iterate 406 * @opaque: Additional argument to pass to the callback 407 * @fn: Function that gets called for each IOVA range 408 * 409 * Helper function to iterate over bitmap data representing a portion of IOVA 410 * space. It hides the complexity of iterating bitmaps and translating the 411 * mapped bitmap user pages into IOVA ranges to process. 412 * 413 * Return: 0 on success, and an error on failure either upon 414 * iteration or when the callback returns an error. 415 */ 416 int iova_bitmap_for_each(struct iova_bitmap *bitmap, void *opaque, 417 iova_bitmap_fn_t fn) 418 { 419 int ret = 0; 420 421 for (; !iova_bitmap_done(bitmap) && !ret; 422 ret = iova_bitmap_advance(bitmap)) { 423 ret = fn(bitmap, iova_bitmap_mapped_iova(bitmap), 424 iova_bitmap_mapped_length(bitmap), opaque); 425 if (ret) 426 break; 427 } 428 429 return ret; 430 } 431 EXPORT_SYMBOL_NS_GPL(iova_bitmap_for_each, IOMMUFD); 432 433 /** 434 * iova_bitmap_set() - Records an IOVA range in bitmap 435 * @bitmap: IOVA bitmap 436 * @iova: IOVA to start 437 * @length: IOVA range length 438 * 439 * Set the bits corresponding to the range [iova .. iova+length-1] in 440 * the user bitmap. 441 * 442 */ 443 void iova_bitmap_set(struct iova_bitmap *bitmap, 444 unsigned long iova, size_t length) 445 { 446 struct iova_bitmap_map *mapped = &bitmap->mapped; 447 unsigned long cur_bit = ((iova - mapped->iova) >> 448 mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE; 449 unsigned long last_bit = (((iova + length - 1) - mapped->iova) >> 450 mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE; 451 unsigned long last_page_idx = mapped->npages - 1; 452 453 do { 454 unsigned int page_idx = cur_bit / BITS_PER_PAGE; 455 unsigned int offset = cur_bit % BITS_PER_PAGE; 456 unsigned int nbits = min(BITS_PER_PAGE - offset, 457 last_bit - cur_bit + 1); 458 void *kaddr; 459 460 if (unlikely(page_idx > last_page_idx)) 461 break; 462 463 kaddr = kmap_local_page(mapped->pages[page_idx]); 464 bitmap_set(kaddr, offset, nbits); 465 kunmap_local(kaddr); 466 cur_bit += nbits; 467 } while (cur_bit <= last_bit); 468 469 if (unlikely(cur_bit <= last_bit)) { 470 bitmap->set_ahead_length = 471 ((last_bit - cur_bit + 1) << bitmap->mapped.pgshift); 472 } 473 } 474 EXPORT_SYMBOL_NS_GPL(iova_bitmap_set, IOMMUFD); 475