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 /* mapped length */ 39 unsigned long length; 40 41 /* page size order that each bit granules to */ 42 unsigned long pgshift; 43 44 /* page offset of the first user page pinned */ 45 unsigned long pgoff; 46 47 /* number of pages pinned */ 48 unsigned long npages; 49 50 /* pinned pages representing the bitmap data */ 51 struct page **pages; 52 }; 53 54 /* 55 * struct iova_bitmap - The IOVA bitmap object 56 * 57 * Main data structure for iterating over the bitmap data. 58 * 59 * Abstracts the pinning work and iterates in IOVA ranges. 60 * It uses a windowing scheme and pins the bitmap in relatively 61 * big ranges e.g. 62 * 63 * The bitmap object uses one base page to store all the pinned pages 64 * pointers related to the bitmap. For sizeof(struct page*) == 8 it stores 65 * 512 struct page pointers which, if the base page size is 4K, it means 66 * 2M of bitmap data is pinned at a time. If the iova_bitmap page size is 67 * also 4K then the range window to iterate is 64G. 68 * 69 * For example iterating on a total IOVA range of 4G..128G, it will walk 70 * through this set of ranges: 71 * 72 * 4G - 68G-1 (64G) 73 * 68G - 128G-1 (64G) 74 * 75 * An example of the APIs on how to use/iterate over the IOVA bitmap: 76 * 77 * bitmap = iova_bitmap_alloc(iova, length, page_size, data); 78 * if (IS_ERR(bitmap)) 79 * return PTR_ERR(bitmap); 80 * 81 * ret = iova_bitmap_for_each(bitmap, arg, dirty_reporter_fn); 82 * 83 * iova_bitmap_free(bitmap); 84 * 85 * Each iteration of the @dirty_reporter_fn is called with a unique @iova 86 * and @length argument, indicating the current range available through the 87 * iova_bitmap. The @dirty_reporter_fn uses iova_bitmap_set() to mark dirty 88 * areas (@iova_length) within that provided range, as following: 89 * 90 * iova_bitmap_set(bitmap, iova, iova_length); 91 * 92 * The internals of the object uses an index @mapped_base_index that indexes 93 * which u64 word of the bitmap is mapped, up to @mapped_total_index. 94 * Those keep being incremented until @mapped_total_index is reached while 95 * mapping up to PAGE_SIZE / sizeof(struct page*) maximum of pages. 96 * 97 * The IOVA bitmap is usually located on what tracks DMA mapped ranges or 98 * some form of IOVA range tracking that co-relates to the user passed 99 * bitmap. 100 */ 101 struct iova_bitmap { 102 /* IOVA range representing the currently mapped bitmap data */ 103 struct iova_bitmap_map mapped; 104 105 /* userspace address of the bitmap */ 106 u8 __user *bitmap; 107 108 /* u64 index that @mapped points to */ 109 unsigned long mapped_base_index; 110 111 /* how many u64 can we walk in total */ 112 unsigned long mapped_total_index; 113 114 /* base IOVA of the whole bitmap */ 115 unsigned long iova; 116 117 /* length of the IOVA range for the whole bitmap */ 118 size_t 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 static unsigned long iova_bitmap_mapped_length(struct iova_bitmap *bitmap); 160 161 /* 162 * Pins the bitmap user pages for the current range window. 163 * This is internal to IOVA bitmap and called when advancing the 164 * index (@mapped_base_index) or allocating the bitmap. 165 */ 166 static int iova_bitmap_get(struct iova_bitmap *bitmap) 167 { 168 struct iova_bitmap_map *mapped = &bitmap->mapped; 169 unsigned long npages; 170 u8 __user *addr; 171 long ret; 172 173 /* 174 * @mapped_base_index is the index of the currently mapped u64 words 175 * that we have access. Anything before @mapped_base_index is not 176 * mapped. The range @mapped_base_index .. @mapped_total_index-1 is 177 * mapped but capped at a maximum number of pages. 178 */ 179 npages = DIV_ROUND_UP((bitmap->mapped_total_index - 180 bitmap->mapped_base_index) * 181 sizeof(*bitmap->bitmap), PAGE_SIZE); 182 183 /* 184 * Bitmap address to be pinned is calculated via pointer arithmetic 185 * with bitmap u64 word index. 186 */ 187 addr = bitmap->bitmap + bitmap->mapped_base_index; 188 189 /* 190 * We always cap at max number of 'struct page' a base page can fit. 191 * This is, for example, on x86 means 2M of bitmap data max. 192 */ 193 npages = min(npages + !!offset_in_page(addr), 194 PAGE_SIZE / sizeof(struct page *)); 195 196 ret = pin_user_pages_fast((unsigned long)addr, npages, 197 FOLL_WRITE, mapped->pages); 198 if (ret <= 0) 199 return -EFAULT; 200 201 mapped->npages = (unsigned long)ret; 202 /* Base IOVA where @pages point to i.e. bit 0 of the first page */ 203 mapped->iova = iova_bitmap_mapped_iova(bitmap); 204 205 /* 206 * offset of the page where pinned pages bit 0 is located. 207 * This handles the case where the bitmap is not PAGE_SIZE 208 * aligned. 209 */ 210 mapped->pgoff = offset_in_page(addr); 211 mapped->length = iova_bitmap_mapped_length(bitmap); 212 return 0; 213 } 214 215 /* 216 * Unpins the bitmap user pages and clears @npages 217 * (un)pinning is abstracted from API user and it's done when advancing 218 * the index or freeing the bitmap. 219 */ 220 static void iova_bitmap_put(struct iova_bitmap *bitmap) 221 { 222 struct iova_bitmap_map *mapped = &bitmap->mapped; 223 224 if (mapped->npages) { 225 unpin_user_pages(mapped->pages, mapped->npages); 226 mapped->npages = 0; 227 } 228 } 229 230 /** 231 * iova_bitmap_alloc() - Allocates an IOVA bitmap object 232 * @iova: Start address of the IOVA range 233 * @length: Length of the IOVA range 234 * @page_size: Page size of the IOVA bitmap. It defines what each bit 235 * granularity represents 236 * @data: Userspace address of the bitmap 237 * 238 * Allocates an IOVA object and initializes all its fields including the 239 * first user pages of @data. 240 * 241 * Return: A pointer to a newly allocated struct iova_bitmap 242 * or ERR_PTR() on error. 243 */ 244 struct iova_bitmap *iova_bitmap_alloc(unsigned long iova, size_t length, 245 unsigned long page_size, u64 __user *data) 246 { 247 struct iova_bitmap_map *mapped; 248 struct iova_bitmap *bitmap; 249 int rc; 250 251 bitmap = kzalloc(sizeof(*bitmap), GFP_KERNEL); 252 if (!bitmap) 253 return ERR_PTR(-ENOMEM); 254 255 mapped = &bitmap->mapped; 256 mapped->pgshift = __ffs(page_size); 257 bitmap->bitmap = (u8 __user *)data; 258 bitmap->mapped_total_index = 259 iova_bitmap_offset_to_index(bitmap, length - 1) + 1; 260 bitmap->iova = iova; 261 bitmap->length = length; 262 mapped->iova = iova; 263 mapped->pages = (struct page **)__get_free_page(GFP_KERNEL); 264 if (!mapped->pages) { 265 rc = -ENOMEM; 266 goto err; 267 } 268 269 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 [@iova..@iova+@length-1] is part of the mapped IOVA range. 342 */ 343 static bool iova_bitmap_mapped_range(struct iova_bitmap_map *mapped, 344 unsigned long iova, size_t length) 345 { 346 return mapped->npages && 347 (iova >= mapped->iova && 348 (iova + length - 1) <= (mapped->iova + mapped->length - 1)); 349 } 350 351 /* 352 * Advances to a selected range, releases the current pinned 353 * pages and pins the next set of bitmap pages. 354 * Returns 0 on success or otherwise errno. 355 */ 356 static int iova_bitmap_advance_to(struct iova_bitmap *bitmap, 357 unsigned long iova) 358 { 359 unsigned long index; 360 361 index = iova_bitmap_offset_to_index(bitmap, iova - bitmap->iova); 362 if (index >= bitmap->mapped_total_index) 363 return -EINVAL; 364 bitmap->mapped_base_index = index; 365 366 iova_bitmap_put(bitmap); 367 368 /* Pin the next set of bitmap pages */ 369 return iova_bitmap_get(bitmap); 370 } 371 372 /** 373 * iova_bitmap_for_each() - Iterates over the bitmap 374 * @bitmap: IOVA bitmap to iterate 375 * @opaque: Additional argument to pass to the callback 376 * @fn: Function that gets called for each IOVA range 377 * 378 * Helper function to iterate over bitmap data representing a portion of IOVA 379 * space. It hides the complexity of iterating bitmaps and translating the 380 * mapped bitmap user pages into IOVA ranges to process. 381 * 382 * Return: 0 on success, and an error on failure either upon 383 * iteration or when the callback returns an error. 384 */ 385 int iova_bitmap_for_each(struct iova_bitmap *bitmap, void *opaque, 386 iova_bitmap_fn_t fn) 387 { 388 return fn(bitmap, bitmap->iova, bitmap->length, opaque); 389 } 390 EXPORT_SYMBOL_NS_GPL(iova_bitmap_for_each, IOMMUFD); 391 392 /** 393 * iova_bitmap_set() - Records an IOVA range in bitmap 394 * @bitmap: IOVA bitmap 395 * @iova: IOVA to start 396 * @length: IOVA range length 397 * 398 * Set the bits corresponding to the range [iova .. iova+length-1] in 399 * the user bitmap. 400 * 401 */ 402 void iova_bitmap_set(struct iova_bitmap *bitmap, 403 unsigned long iova, size_t length) 404 { 405 struct iova_bitmap_map *mapped = &bitmap->mapped; 406 unsigned long cur_bit, last_bit, last_page_idx; 407 408 update_indexes: 409 if (unlikely(!iova_bitmap_mapped_range(mapped, iova, length))) { 410 411 /* 412 * The attempt to advance the base index to @iova 413 * may fail if it's out of bounds, or pinning the pages 414 * returns an error. 415 */ 416 if (iova_bitmap_advance_to(bitmap, iova)) 417 return; 418 } 419 420 last_page_idx = mapped->npages - 1; 421 cur_bit = ((iova - mapped->iova) >> 422 mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE; 423 last_bit = (((iova + length - 1) - mapped->iova) >> 424 mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE; 425 426 do { 427 unsigned int page_idx = cur_bit / BITS_PER_PAGE; 428 unsigned int offset = cur_bit % BITS_PER_PAGE; 429 unsigned int nbits = min(BITS_PER_PAGE - offset, 430 last_bit - cur_bit + 1); 431 void *kaddr; 432 433 if (unlikely(page_idx > last_page_idx)) { 434 unsigned long left = 435 ((last_bit - cur_bit + 1) << mapped->pgshift); 436 437 iova += (length - left); 438 length = left; 439 goto update_indexes; 440 } 441 442 kaddr = kmap_local_page(mapped->pages[page_idx]); 443 bitmap_set(kaddr, offset, nbits); 444 kunmap_local(kaddr); 445 cur_bit += nbits; 446 } while (cur_bit <= last_bit); 447 } 448 EXPORT_SYMBOL_NS_GPL(iova_bitmap_set, IOMMUFD); 449