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 * Bitmap address to be pinned is calculated via pointer arithmetic 180 * with bitmap u64 word index. 181 */ 182 addr = bitmap->bitmap + bitmap->mapped_base_index; 183 184 /* 185 * We always cap at max number of 'struct page' a base page can fit. 186 * This is, for example, on x86 means 2M of bitmap data max. 187 */ 188 npages = min(npages + !!offset_in_page(addr), 189 PAGE_SIZE / sizeof(struct page *)); 190 191 ret = pin_user_pages_fast((unsigned long)addr, npages, 192 FOLL_WRITE, mapped->pages); 193 if (ret <= 0) 194 return -EFAULT; 195 196 mapped->npages = (unsigned long)ret; 197 /* Base IOVA where @pages point to i.e. bit 0 of the first page */ 198 mapped->iova = iova_bitmap_mapped_iova(bitmap); 199 200 /* 201 * offset of the page where pinned pages bit 0 is located. 202 * This handles the case where the bitmap is not PAGE_SIZE 203 * aligned. 204 */ 205 mapped->pgoff = offset_in_page(addr); 206 return 0; 207 } 208 209 /* 210 * Unpins the bitmap user pages and clears @npages 211 * (un)pinning is abstracted from API user and it's done when advancing 212 * the index or freeing the bitmap. 213 */ 214 static void iova_bitmap_put(struct iova_bitmap *bitmap) 215 { 216 struct iova_bitmap_map *mapped = &bitmap->mapped; 217 218 if (mapped->npages) { 219 unpin_user_pages(mapped->pages, mapped->npages); 220 mapped->npages = 0; 221 } 222 } 223 224 /** 225 * iova_bitmap_alloc() - Allocates an IOVA bitmap object 226 * @iova: Start address of the IOVA range 227 * @length: Length of the IOVA range 228 * @page_size: Page size of the IOVA bitmap. It defines what each bit 229 * granularity represents 230 * @data: Userspace address of the bitmap 231 * 232 * Allocates an IOVA object and initializes all its fields including the 233 * first user pages of @data. 234 * 235 * Return: A pointer to a newly allocated struct iova_bitmap 236 * or ERR_PTR() on error. 237 */ 238 struct iova_bitmap *iova_bitmap_alloc(unsigned long iova, size_t length, 239 unsigned long page_size, u64 __user *data) 240 { 241 struct iova_bitmap_map *mapped; 242 struct iova_bitmap *bitmap; 243 int rc; 244 245 bitmap = kzalloc(sizeof(*bitmap), GFP_KERNEL); 246 if (!bitmap) 247 return ERR_PTR(-ENOMEM); 248 249 mapped = &bitmap->mapped; 250 mapped->pgshift = __ffs(page_size); 251 bitmap->bitmap = (u8 __user *)data; 252 bitmap->mapped_total_index = 253 iova_bitmap_offset_to_index(bitmap, length - 1) + 1; 254 bitmap->iova = iova; 255 bitmap->length = length; 256 mapped->iova = iova; 257 mapped->pages = (struct page **)__get_free_page(GFP_KERNEL); 258 if (!mapped->pages) { 259 rc = -ENOMEM; 260 goto err; 261 } 262 263 rc = iova_bitmap_get(bitmap); 264 if (rc) 265 goto err; 266 return bitmap; 267 268 err: 269 iova_bitmap_free(bitmap); 270 return ERR_PTR(rc); 271 } 272 273 /** 274 * iova_bitmap_free() - Frees an IOVA bitmap object 275 * @bitmap: IOVA bitmap to free 276 * 277 * It unpins and releases pages array memory and clears any leftover 278 * state. 279 */ 280 void iova_bitmap_free(struct iova_bitmap *bitmap) 281 { 282 struct iova_bitmap_map *mapped = &bitmap->mapped; 283 284 iova_bitmap_put(bitmap); 285 286 if (mapped->pages) { 287 free_page((unsigned long)mapped->pages); 288 mapped->pages = NULL; 289 } 290 291 kfree(bitmap); 292 } 293 294 /* 295 * Returns the remaining bitmap indexes from mapped_total_index to process for 296 * the currently pinned bitmap pages. 297 */ 298 static unsigned long iova_bitmap_mapped_remaining(struct iova_bitmap *bitmap) 299 { 300 unsigned long remaining, bytes; 301 302 bytes = (bitmap->mapped.npages << PAGE_SHIFT) - bitmap->mapped.pgoff; 303 304 remaining = bitmap->mapped_total_index - bitmap->mapped_base_index; 305 remaining = min_t(unsigned long, remaining, 306 DIV_ROUND_UP(bytes, sizeof(*bitmap->bitmap))); 307 308 return remaining; 309 } 310 311 /* 312 * Returns the length of the mapped IOVA range. 313 */ 314 static unsigned long iova_bitmap_mapped_length(struct iova_bitmap *bitmap) 315 { 316 unsigned long max_iova = bitmap->iova + bitmap->length - 1; 317 unsigned long iova = iova_bitmap_mapped_iova(bitmap); 318 unsigned long remaining; 319 320 /* 321 * iova_bitmap_mapped_remaining() returns a number of indexes which 322 * when converted to IOVA gives us a max length that the bitmap 323 * pinned data can cover. Afterwards, that is capped to 324 * only cover the IOVA range in @bitmap::iova .. @bitmap::length. 325 */ 326 remaining = iova_bitmap_index_to_offset(bitmap, 327 iova_bitmap_mapped_remaining(bitmap)); 328 329 if (iova + remaining - 1 > max_iova) 330 remaining -= ((iova + remaining - 1) - max_iova); 331 332 return remaining; 333 } 334 335 /* 336 * Returns true if there's not more data to iterate. 337 */ 338 static bool iova_bitmap_done(struct iova_bitmap *bitmap) 339 { 340 return bitmap->mapped_base_index >= bitmap->mapped_total_index; 341 } 342 343 /* 344 * Advances to the next range, releases the current pinned 345 * pages and pins the next set of bitmap pages. 346 * Returns 0 on success or otherwise errno. 347 */ 348 static int iova_bitmap_advance(struct iova_bitmap *bitmap) 349 { 350 unsigned long iova = iova_bitmap_mapped_length(bitmap) - 1; 351 unsigned long count = iova_bitmap_offset_to_index(bitmap, iova) + 1; 352 353 bitmap->mapped_base_index += count; 354 355 iova_bitmap_put(bitmap); 356 if (iova_bitmap_done(bitmap)) 357 return 0; 358 359 /* When advancing the index we pin the next set of bitmap pages */ 360 return iova_bitmap_get(bitmap); 361 } 362 363 /** 364 * iova_bitmap_for_each() - Iterates over the bitmap 365 * @bitmap: IOVA bitmap to iterate 366 * @opaque: Additional argument to pass to the callback 367 * @fn: Function that gets called for each IOVA range 368 * 369 * Helper function to iterate over bitmap data representing a portion of IOVA 370 * space. It hides the complexity of iterating bitmaps and translating the 371 * mapped bitmap user pages into IOVA ranges to process. 372 * 373 * Return: 0 on success, and an error on failure either upon 374 * iteration or when the callback returns an error. 375 */ 376 int iova_bitmap_for_each(struct iova_bitmap *bitmap, void *opaque, 377 iova_bitmap_fn_t fn) 378 { 379 int ret = 0; 380 381 for (; !iova_bitmap_done(bitmap) && !ret; 382 ret = iova_bitmap_advance(bitmap)) { 383 ret = fn(bitmap, iova_bitmap_mapped_iova(bitmap), 384 iova_bitmap_mapped_length(bitmap), opaque); 385 if (ret) 386 break; 387 } 388 389 return ret; 390 } 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 = ((iova - mapped->iova) >> 407 mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE; 408 unsigned long last_bit = (((iova + length - 1) - mapped->iova) >> 409 mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE; 410 unsigned long last_page_idx = mapped->npages - 1; 411 412 do { 413 unsigned int page_idx = cur_bit / BITS_PER_PAGE; 414 unsigned int offset = cur_bit % BITS_PER_PAGE; 415 unsigned int nbits = min(BITS_PER_PAGE - offset, 416 last_bit - cur_bit + 1); 417 void *kaddr; 418 419 if (unlikely(page_idx > last_page_idx)) 420 break; 421 422 kaddr = kmap_local_page(mapped->pages[page_idx]); 423 bitmap_set(kaddr, offset, nbits); 424 kunmap_local(kaddr); 425 cur_bit += nbits; 426 } while (cur_bit <= last_bit); 427 } 428 EXPORT_SYMBOL_GPL(iova_bitmap_set); 429