1 /* 2 * Xen leaves the responsibility for maintaining p2m mappings to the 3 * guests themselves, but it must also access and update the p2m array 4 * during suspend/resume when all the pages are reallocated. 5 * 6 * The p2m table is logically a flat array, but we implement it as a 7 * three-level tree to allow the address space to be sparse. 8 * 9 * Xen 10 * | 11 * p2m_top p2m_top_mfn 12 * / \ / \ 13 * p2m_mid p2m_mid p2m_mid_mfn p2m_mid_mfn 14 * / \ / \ / / 15 * p2m p2m p2m p2m p2m p2m p2m ... 16 * 17 * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p. 18 * 19 * The p2m_top and p2m_top_mfn levels are limited to 1 page, so the 20 * maximum representable pseudo-physical address space is: 21 * P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages 22 * 23 * P2M_PER_PAGE depends on the architecture, as a mfn is always 24 * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to 25 * 512 and 1024 entries respectively. 26 * 27 * In short, these structures contain the Machine Frame Number (MFN) of the PFN. 28 * 29 * However not all entries are filled with MFNs. Specifically for all other 30 * leaf entries, or for the top root, or middle one, for which there is a void 31 * entry, we assume it is "missing". So (for example) 32 * pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY. 33 * 34 * We also have the possibility of setting 1-1 mappings on certain regions, so 35 * that: 36 * pfn_to_mfn(0xc0000)=0xc0000 37 * 38 * The benefit of this is, that we can assume for non-RAM regions (think 39 * PCI BARs, or ACPI spaces), we can create mappings easily b/c we 40 * get the PFN value to match the MFN. 41 * 42 * For this to work efficiently we have one new page p2m_identity and 43 * allocate (via reserved_brk) any other pages we need to cover the sides 44 * (1GB or 4MB boundary violations). All entries in p2m_identity are set to 45 * INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, 46 * no other fancy value). 47 * 48 * On lookup we spot that the entry points to p2m_identity and return the 49 * identity value instead of dereferencing and returning INVALID_P2M_ENTRY. 50 * If the entry points to an allocated page, we just proceed as before and 51 * return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in 52 * appropriate functions (pfn_to_mfn). 53 * 54 * The reason for having the IDENTITY_FRAME_BIT instead of just returning the 55 * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a 56 * non-identity pfn. To protect ourselves against we elect to set (and get) the 57 * IDENTITY_FRAME_BIT on all identity mapped PFNs. 58 * 59 * This simplistic diagram is used to explain the more subtle piece of code. 60 * There is also a digram of the P2M at the end that can help. 61 * Imagine your E820 looking as so: 62 * 63 * 1GB 2GB 64 * /-------------------+---------\/----\ /----------\ /---+-----\ 65 * | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | 66 * \-------------------+---------/\----/ \----------/ \---+-----/ 67 * ^- 1029MB ^- 2001MB 68 * 69 * [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 70 * 2048MB = 524288 (0x80000)] 71 * 72 * And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB 73 * is actually not present (would have to kick the balloon driver to put it in). 74 * 75 * When we are told to set the PFNs for identity mapping (see patch: "xen/setup: 76 * Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start 77 * of the PFN and the end PFN (263424 and 512256 respectively). The first step 78 * is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page 79 * covers 512^2 of page estate (1GB) and in case the start or end PFN is not 80 * aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn 81 * to end pfn. We reserve_brk top leaf pages if they are missing (means they 82 * point to p2m_mid_missing). 83 * 84 * With the E820 example above, 263424 is not 1GB aligned so we allocate a 85 * reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. 86 * Each entry in the allocate page is "missing" (points to p2m_missing). 87 * 88 * Next stage is to determine if we need to do a more granular boundary check 89 * on the 4MB (or 2MB depending on architecture) off the start and end pfn's. 90 * We check if the start pfn and end pfn violate that boundary check, and if 91 * so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer 92 * granularity of setting which PFNs are missing and which ones are identity. 93 * In our example 263424 and 512256 both fail the check so we reserve_brk two 94 * pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" 95 * values) and assign them to p2m[1][2] and p2m[1][488] respectively. 96 * 97 * At this point we would at minimum reserve_brk one page, but could be up to 98 * three. Each call to set_phys_range_identity has at maximum a three page 99 * cost. If we were to query the P2M at this stage, all those entries from 100 * start PFN through end PFN (so 1029MB -> 2001MB) would return 101 * INVALID_P2M_ENTRY ("missing"). 102 * 103 * The next step is to walk from the start pfn to the end pfn setting 104 * the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity. 105 * If we find that the middle leaf is pointing to p2m_missing we can swap it 106 * over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this 107 * point we do not need to worry about boundary aligment (so no need to 108 * reserve_brk a middle page, figure out which PFNs are "missing" and which 109 * ones are identity), as that has been done earlier. If we find that the 110 * middle leaf is not occupied by p2m_identity or p2m_missing, we dereference 111 * that page (which covers 512 PFNs) and set the appropriate PFN with 112 * IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we 113 * set from p2m[1][2][256->511] and p2m[1][488][0->256] with 114 * IDENTITY_FRAME_BIT set. 115 * 116 * All other regions that are void (or not filled) either point to p2m_missing 117 * (considered missing) or have the default value of INVALID_P2M_ENTRY (also 118 * considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] 119 * contain the INVALID_P2M_ENTRY value and are considered "missing." 120 * 121 * This is what the p2m ends up looking (for the E820 above) with this 122 * fabulous drawing: 123 * 124 * p2m /--------------\ 125 * /-----\ | &mfn_list[0],| /-----------------\ 126 * | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | 127 * |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | 128 * | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | 129 * |-----| \ | [p2m_identity]+\\ | .... | 130 * | 2 |--\ \-------------------->| ... | \\ \----------------/ 131 * |-----| \ \---------------/ \\ 132 * | 3 |\ \ \\ p2m_identity 133 * |-----| \ \-------------------->/---------------\ /-----------------\ 134 * | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | 135 * \-----/ / | [p2m_identity]+-->| ..., ~0 | 136 * / /---------------\ | .... | \-----------------/ 137 * / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | 138 * / | IDENTITY[@256]|<----/ \---------------/ 139 * / | ~0, ~0, .... | 140 * | \---------------/ 141 * | 142 * p2m_missing p2m_missing 143 * /------------------\ /------------\ 144 * | [p2m_mid_missing]+---->| ~0, ~0, ~0 | 145 * | [p2m_mid_missing]+---->| ..., ~0 | 146 * \------------------/ \------------/ 147 * 148 * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) 149 */ 150 151 #include <linux/init.h> 152 #include <linux/module.h> 153 #include <linux/list.h> 154 #include <linux/hash.h> 155 #include <linux/sched.h> 156 #include <linux/seq_file.h> 157 158 #include <asm/cache.h> 159 #include <asm/setup.h> 160 161 #include <asm/xen/page.h> 162 #include <asm/xen/hypercall.h> 163 #include <asm/xen/hypervisor.h> 164 #include <xen/grant_table.h> 165 166 #include "multicalls.h" 167 #include "xen-ops.h" 168 169 static void __init m2p_override_init(void); 170 171 unsigned long xen_max_p2m_pfn __read_mostly; 172 173 #define P2M_PER_PAGE (PAGE_SIZE / sizeof(unsigned long)) 174 #define P2M_MID_PER_PAGE (PAGE_SIZE / sizeof(unsigned long *)) 175 #define P2M_TOP_PER_PAGE (PAGE_SIZE / sizeof(unsigned long **)) 176 177 #define MAX_P2M_PFN (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE) 178 179 /* Placeholders for holes in the address space */ 180 static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE); 181 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE); 182 static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE); 183 184 static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE); 185 static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE); 186 static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE); 187 188 static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE); 189 190 RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE))); 191 RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE))); 192 193 /* We might hit two boundary violations at the start and end, at max each 194 * boundary violation will require three middle nodes. */ 195 RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3); 196 197 static inline unsigned p2m_top_index(unsigned long pfn) 198 { 199 BUG_ON(pfn >= MAX_P2M_PFN); 200 return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE); 201 } 202 203 static inline unsigned p2m_mid_index(unsigned long pfn) 204 { 205 return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE; 206 } 207 208 static inline unsigned p2m_index(unsigned long pfn) 209 { 210 return pfn % P2M_PER_PAGE; 211 } 212 213 static void p2m_top_init(unsigned long ***top) 214 { 215 unsigned i; 216 217 for (i = 0; i < P2M_TOP_PER_PAGE; i++) 218 top[i] = p2m_mid_missing; 219 } 220 221 static void p2m_top_mfn_init(unsigned long *top) 222 { 223 unsigned i; 224 225 for (i = 0; i < P2M_TOP_PER_PAGE; i++) 226 top[i] = virt_to_mfn(p2m_mid_missing_mfn); 227 } 228 229 static void p2m_top_mfn_p_init(unsigned long **top) 230 { 231 unsigned i; 232 233 for (i = 0; i < P2M_TOP_PER_PAGE; i++) 234 top[i] = p2m_mid_missing_mfn; 235 } 236 237 static void p2m_mid_init(unsigned long **mid) 238 { 239 unsigned i; 240 241 for (i = 0; i < P2M_MID_PER_PAGE; i++) 242 mid[i] = p2m_missing; 243 } 244 245 static void p2m_mid_mfn_init(unsigned long *mid) 246 { 247 unsigned i; 248 249 for (i = 0; i < P2M_MID_PER_PAGE; i++) 250 mid[i] = virt_to_mfn(p2m_missing); 251 } 252 253 static void p2m_init(unsigned long *p2m) 254 { 255 unsigned i; 256 257 for (i = 0; i < P2M_MID_PER_PAGE; i++) 258 p2m[i] = INVALID_P2M_ENTRY; 259 } 260 261 /* 262 * Build the parallel p2m_top_mfn and p2m_mid_mfn structures 263 * 264 * This is called both at boot time, and after resuming from suspend: 265 * - At boot time we're called very early, and must use extend_brk() 266 * to allocate memory. 267 * 268 * - After resume we're called from within stop_machine, but the mfn 269 * tree should alreay be completely allocated. 270 */ 271 void __ref xen_build_mfn_list_list(void) 272 { 273 unsigned long pfn; 274 275 /* Pre-initialize p2m_top_mfn to be completely missing */ 276 if (p2m_top_mfn == NULL) { 277 p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE); 278 p2m_mid_mfn_init(p2m_mid_missing_mfn); 279 280 p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE); 281 p2m_top_mfn_p_init(p2m_top_mfn_p); 282 283 p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE); 284 p2m_top_mfn_init(p2m_top_mfn); 285 } else { 286 /* Reinitialise, mfn's all change after migration */ 287 p2m_mid_mfn_init(p2m_mid_missing_mfn); 288 } 289 290 for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) { 291 unsigned topidx = p2m_top_index(pfn); 292 unsigned mididx = p2m_mid_index(pfn); 293 unsigned long **mid; 294 unsigned long *mid_mfn_p; 295 296 mid = p2m_top[topidx]; 297 mid_mfn_p = p2m_top_mfn_p[topidx]; 298 299 /* Don't bother allocating any mfn mid levels if 300 * they're just missing, just update the stored mfn, 301 * since all could have changed over a migrate. 302 */ 303 if (mid == p2m_mid_missing) { 304 BUG_ON(mididx); 305 BUG_ON(mid_mfn_p != p2m_mid_missing_mfn); 306 p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn); 307 pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE; 308 continue; 309 } 310 311 if (mid_mfn_p == p2m_mid_missing_mfn) { 312 /* 313 * XXX boot-time only! We should never find 314 * missing parts of the mfn tree after 315 * runtime. extend_brk() will BUG if we call 316 * it too late. 317 */ 318 mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE); 319 p2m_mid_mfn_init(mid_mfn_p); 320 321 p2m_top_mfn_p[topidx] = mid_mfn_p; 322 } 323 324 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p); 325 mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]); 326 } 327 } 328 329 void xen_setup_mfn_list_list(void) 330 { 331 BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info); 332 333 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = 334 virt_to_mfn(p2m_top_mfn); 335 HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn; 336 } 337 338 /* Set up p2m_top to point to the domain-builder provided p2m pages */ 339 void __init xen_build_dynamic_phys_to_machine(void) 340 { 341 unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list; 342 unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages); 343 unsigned long pfn; 344 345 xen_max_p2m_pfn = max_pfn; 346 347 p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE); 348 p2m_init(p2m_missing); 349 350 p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE); 351 p2m_mid_init(p2m_mid_missing); 352 353 p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE); 354 p2m_top_init(p2m_top); 355 356 p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE); 357 p2m_init(p2m_identity); 358 359 /* 360 * The domain builder gives us a pre-constructed p2m array in 361 * mfn_list for all the pages initially given to us, so we just 362 * need to graft that into our tree structure. 363 */ 364 for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) { 365 unsigned topidx = p2m_top_index(pfn); 366 unsigned mididx = p2m_mid_index(pfn); 367 368 if (p2m_top[topidx] == p2m_mid_missing) { 369 unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE); 370 p2m_mid_init(mid); 371 372 p2m_top[topidx] = mid; 373 } 374 375 /* 376 * As long as the mfn_list has enough entries to completely 377 * fill a p2m page, pointing into the array is ok. But if 378 * not the entries beyond the last pfn will be undefined. 379 */ 380 if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) { 381 unsigned long p2midx; 382 383 p2midx = max_pfn % P2M_PER_PAGE; 384 for ( ; p2midx < P2M_PER_PAGE; p2midx++) 385 mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY; 386 } 387 p2m_top[topidx][mididx] = &mfn_list[pfn]; 388 } 389 390 m2p_override_init(); 391 } 392 393 unsigned long get_phys_to_machine(unsigned long pfn) 394 { 395 unsigned topidx, mididx, idx; 396 397 if (unlikely(pfn >= MAX_P2M_PFN)) 398 return INVALID_P2M_ENTRY; 399 400 topidx = p2m_top_index(pfn); 401 mididx = p2m_mid_index(pfn); 402 idx = p2m_index(pfn); 403 404 /* 405 * The INVALID_P2M_ENTRY is filled in both p2m_*identity 406 * and in p2m_*missing, so returning the INVALID_P2M_ENTRY 407 * would be wrong. 408 */ 409 if (p2m_top[topidx][mididx] == p2m_identity) 410 return IDENTITY_FRAME(pfn); 411 412 return p2m_top[topidx][mididx][idx]; 413 } 414 EXPORT_SYMBOL_GPL(get_phys_to_machine); 415 416 static void *alloc_p2m_page(void) 417 { 418 return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT); 419 } 420 421 static void free_p2m_page(void *p) 422 { 423 free_page((unsigned long)p); 424 } 425 426 /* 427 * Fully allocate the p2m structure for a given pfn. We need to check 428 * that both the top and mid levels are allocated, and make sure the 429 * parallel mfn tree is kept in sync. We may race with other cpus, so 430 * the new pages are installed with cmpxchg; if we lose the race then 431 * simply free the page we allocated and use the one that's there. 432 */ 433 static bool alloc_p2m(unsigned long pfn) 434 { 435 unsigned topidx, mididx; 436 unsigned long ***top_p, **mid; 437 unsigned long *top_mfn_p, *mid_mfn; 438 439 topidx = p2m_top_index(pfn); 440 mididx = p2m_mid_index(pfn); 441 442 top_p = &p2m_top[topidx]; 443 mid = *top_p; 444 445 if (mid == p2m_mid_missing) { 446 /* Mid level is missing, allocate a new one */ 447 mid = alloc_p2m_page(); 448 if (!mid) 449 return false; 450 451 p2m_mid_init(mid); 452 453 if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing) 454 free_p2m_page(mid); 455 } 456 457 top_mfn_p = &p2m_top_mfn[topidx]; 458 mid_mfn = p2m_top_mfn_p[topidx]; 459 460 BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p); 461 462 if (mid_mfn == p2m_mid_missing_mfn) { 463 /* Separately check the mid mfn level */ 464 unsigned long missing_mfn; 465 unsigned long mid_mfn_mfn; 466 467 mid_mfn = alloc_p2m_page(); 468 if (!mid_mfn) 469 return false; 470 471 p2m_mid_mfn_init(mid_mfn); 472 473 missing_mfn = virt_to_mfn(p2m_mid_missing_mfn); 474 mid_mfn_mfn = virt_to_mfn(mid_mfn); 475 if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn) 476 free_p2m_page(mid_mfn); 477 else 478 p2m_top_mfn_p[topidx] = mid_mfn; 479 } 480 481 if (p2m_top[topidx][mididx] == p2m_identity || 482 p2m_top[topidx][mididx] == p2m_missing) { 483 /* p2m leaf page is missing */ 484 unsigned long *p2m; 485 unsigned long *p2m_orig = p2m_top[topidx][mididx]; 486 487 p2m = alloc_p2m_page(); 488 if (!p2m) 489 return false; 490 491 p2m_init(p2m); 492 493 if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig) 494 free_p2m_page(p2m); 495 else 496 mid_mfn[mididx] = virt_to_mfn(p2m); 497 } 498 499 return true; 500 } 501 502 static bool __init early_alloc_p2m_middle(unsigned long pfn, bool check_boundary) 503 { 504 unsigned topidx, mididx, idx; 505 unsigned long *p2m; 506 unsigned long *mid_mfn_p; 507 508 topidx = p2m_top_index(pfn); 509 mididx = p2m_mid_index(pfn); 510 idx = p2m_index(pfn); 511 512 /* Pfff.. No boundary cross-over, lets get out. */ 513 if (!idx && check_boundary) 514 return false; 515 516 WARN(p2m_top[topidx][mididx] == p2m_identity, 517 "P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n", 518 topidx, mididx); 519 520 /* 521 * Could be done by xen_build_dynamic_phys_to_machine.. 522 */ 523 if (p2m_top[topidx][mididx] != p2m_missing) 524 return false; 525 526 /* Boundary cross-over for the edges: */ 527 p2m = extend_brk(PAGE_SIZE, PAGE_SIZE); 528 529 p2m_init(p2m); 530 531 p2m_top[topidx][mididx] = p2m; 532 533 /* For save/restore we need to MFN of the P2M saved */ 534 535 mid_mfn_p = p2m_top_mfn_p[topidx]; 536 WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing), 537 "P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n", 538 topidx, mididx); 539 mid_mfn_p[mididx] = virt_to_mfn(p2m); 540 541 return true; 542 } 543 544 static bool __init early_alloc_p2m(unsigned long pfn) 545 { 546 unsigned topidx = p2m_top_index(pfn); 547 unsigned long *mid_mfn_p; 548 unsigned long **mid; 549 550 mid = p2m_top[topidx]; 551 mid_mfn_p = p2m_top_mfn_p[topidx]; 552 if (mid == p2m_mid_missing) { 553 mid = extend_brk(PAGE_SIZE, PAGE_SIZE); 554 555 p2m_mid_init(mid); 556 557 p2m_top[topidx] = mid; 558 559 BUG_ON(mid_mfn_p != p2m_mid_missing_mfn); 560 } 561 /* And the save/restore P2M tables.. */ 562 if (mid_mfn_p == p2m_mid_missing_mfn) { 563 mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE); 564 p2m_mid_mfn_init(mid_mfn_p); 565 566 p2m_top_mfn_p[topidx] = mid_mfn_p; 567 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p); 568 /* Note: we don't set mid_mfn_p[midix] here, 569 * look in early_alloc_p2m_middle */ 570 } 571 return true; 572 } 573 bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn) 574 { 575 if (unlikely(!__set_phys_to_machine(pfn, mfn))) { 576 if (!early_alloc_p2m(pfn)) 577 return false; 578 579 if (!early_alloc_p2m_middle(pfn, false /* boundary crossover OK!*/)) 580 return false; 581 582 if (!__set_phys_to_machine(pfn, mfn)) 583 return false; 584 } 585 586 return true; 587 } 588 unsigned long __init set_phys_range_identity(unsigned long pfn_s, 589 unsigned long pfn_e) 590 { 591 unsigned long pfn; 592 593 if (unlikely(pfn_s >= MAX_P2M_PFN || pfn_e >= MAX_P2M_PFN)) 594 return 0; 595 596 if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) 597 return pfn_e - pfn_s; 598 599 if (pfn_s > pfn_e) 600 return 0; 601 602 for (pfn = (pfn_s & ~(P2M_MID_PER_PAGE * P2M_PER_PAGE - 1)); 603 pfn < ALIGN(pfn_e, (P2M_MID_PER_PAGE * P2M_PER_PAGE)); 604 pfn += P2M_MID_PER_PAGE * P2M_PER_PAGE) 605 { 606 WARN_ON(!early_alloc_p2m(pfn)); 607 } 608 609 early_alloc_p2m_middle(pfn_s, true); 610 early_alloc_p2m_middle(pfn_e, true); 611 612 for (pfn = pfn_s; pfn < pfn_e; pfn++) 613 if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn))) 614 break; 615 616 if (!WARN((pfn - pfn_s) != (pfn_e - pfn_s), 617 "Identity mapping failed. We are %ld short of 1-1 mappings!\n", 618 (pfn_e - pfn_s) - (pfn - pfn_s))) 619 printk(KERN_DEBUG "1-1 mapping on %lx->%lx\n", pfn_s, pfn); 620 621 return pfn - pfn_s; 622 } 623 624 /* Try to install p2m mapping; fail if intermediate bits missing */ 625 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn) 626 { 627 unsigned topidx, mididx, idx; 628 629 if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) { 630 BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY); 631 return true; 632 } 633 if (unlikely(pfn >= MAX_P2M_PFN)) { 634 BUG_ON(mfn != INVALID_P2M_ENTRY); 635 return true; 636 } 637 638 topidx = p2m_top_index(pfn); 639 mididx = p2m_mid_index(pfn); 640 idx = p2m_index(pfn); 641 642 /* For sparse holes were the p2m leaf has real PFN along with 643 * PCI holes, stick in the PFN as the MFN value. 644 */ 645 if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) { 646 if (p2m_top[topidx][mididx] == p2m_identity) 647 return true; 648 649 /* Swap over from MISSING to IDENTITY if needed. */ 650 if (p2m_top[topidx][mididx] == p2m_missing) { 651 WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing, 652 p2m_identity) != p2m_missing); 653 return true; 654 } 655 } 656 657 if (p2m_top[topidx][mididx] == p2m_missing) 658 return mfn == INVALID_P2M_ENTRY; 659 660 p2m_top[topidx][mididx][idx] = mfn; 661 662 return true; 663 } 664 665 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn) 666 { 667 if (unlikely(!__set_phys_to_machine(pfn, mfn))) { 668 if (!alloc_p2m(pfn)) 669 return false; 670 671 if (!__set_phys_to_machine(pfn, mfn)) 672 return false; 673 } 674 675 return true; 676 } 677 678 #define M2P_OVERRIDE_HASH_SHIFT 10 679 #define M2P_OVERRIDE_HASH (1 << M2P_OVERRIDE_HASH_SHIFT) 680 681 static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH); 682 static DEFINE_SPINLOCK(m2p_override_lock); 683 684 static void __init m2p_override_init(void) 685 { 686 unsigned i; 687 688 m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH, 689 sizeof(unsigned long)); 690 691 for (i = 0; i < M2P_OVERRIDE_HASH; i++) 692 INIT_LIST_HEAD(&m2p_overrides[i]); 693 } 694 695 static unsigned long mfn_hash(unsigned long mfn) 696 { 697 return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT); 698 } 699 700 /* Add an MFN override for a particular page */ 701 int m2p_add_override(unsigned long mfn, struct page *page, 702 struct gnttab_map_grant_ref *kmap_op) 703 { 704 unsigned long flags; 705 unsigned long pfn; 706 unsigned long uninitialized_var(address); 707 unsigned level; 708 pte_t *ptep = NULL; 709 int ret = 0; 710 711 pfn = page_to_pfn(page); 712 if (!PageHighMem(page)) { 713 address = (unsigned long)__va(pfn << PAGE_SHIFT); 714 ptep = lookup_address(address, &level); 715 if (WARN(ptep == NULL || level != PG_LEVEL_4K, 716 "m2p_add_override: pfn %lx not mapped", pfn)) 717 return -EINVAL; 718 } 719 WARN_ON(PagePrivate(page)); 720 SetPagePrivate(page); 721 set_page_private(page, mfn); 722 page->index = pfn_to_mfn(pfn); 723 724 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) 725 return -ENOMEM; 726 727 if (kmap_op != NULL) { 728 if (!PageHighMem(page)) { 729 struct multicall_space mcs = 730 xen_mc_entry(sizeof(*kmap_op)); 731 732 MULTI_grant_table_op(mcs.mc, 733 GNTTABOP_map_grant_ref, kmap_op, 1); 734 735 xen_mc_issue(PARAVIRT_LAZY_MMU); 736 } 737 /* let's use dev_bus_addr to record the old mfn instead */ 738 kmap_op->dev_bus_addr = page->index; 739 page->index = (unsigned long) kmap_op; 740 } 741 spin_lock_irqsave(&m2p_override_lock, flags); 742 list_add(&page->lru, &m2p_overrides[mfn_hash(mfn)]); 743 spin_unlock_irqrestore(&m2p_override_lock, flags); 744 745 /* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in 746 * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other 747 * pfn so that the following mfn_to_pfn(mfn) calls will return the 748 * pfn from the m2p_override (the backend pfn) instead. 749 * We need to do this because the pages shared by the frontend 750 * (xen-blkfront) can be already locked (lock_page, called by 751 * do_read_cache_page); when the userspace backend tries to use them 752 * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so 753 * do_blockdev_direct_IO is going to try to lock the same pages 754 * again resulting in a deadlock. 755 * As a side effect get_user_pages_fast might not be safe on the 756 * frontend pages while they are being shared with the backend, 757 * because mfn_to_pfn (that ends up being called by GUPF) will 758 * return the backend pfn rather than the frontend pfn. */ 759 ret = __get_user(pfn, &machine_to_phys_mapping[mfn]); 760 if (ret == 0 && get_phys_to_machine(pfn) == mfn) 761 set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)); 762 763 return 0; 764 } 765 EXPORT_SYMBOL_GPL(m2p_add_override); 766 int m2p_remove_override(struct page *page, bool clear_pte) 767 { 768 unsigned long flags; 769 unsigned long mfn; 770 unsigned long pfn; 771 unsigned long uninitialized_var(address); 772 unsigned level; 773 pte_t *ptep = NULL; 774 int ret = 0; 775 776 pfn = page_to_pfn(page); 777 mfn = get_phys_to_machine(pfn); 778 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) 779 return -EINVAL; 780 781 if (!PageHighMem(page)) { 782 address = (unsigned long)__va(pfn << PAGE_SHIFT); 783 ptep = lookup_address(address, &level); 784 785 if (WARN(ptep == NULL || level != PG_LEVEL_4K, 786 "m2p_remove_override: pfn %lx not mapped", pfn)) 787 return -EINVAL; 788 } 789 790 spin_lock_irqsave(&m2p_override_lock, flags); 791 list_del(&page->lru); 792 spin_unlock_irqrestore(&m2p_override_lock, flags); 793 WARN_ON(!PagePrivate(page)); 794 ClearPagePrivate(page); 795 796 if (clear_pte) { 797 struct gnttab_map_grant_ref *map_op = 798 (struct gnttab_map_grant_ref *) page->index; 799 set_phys_to_machine(pfn, map_op->dev_bus_addr); 800 if (!PageHighMem(page)) { 801 struct multicall_space mcs; 802 struct gnttab_unmap_grant_ref *unmap_op; 803 804 /* 805 * It might be that we queued all the m2p grant table 806 * hypercalls in a multicall, then m2p_remove_override 807 * get called before the multicall has actually been 808 * issued. In this case handle is going to -1 because 809 * it hasn't been modified yet. 810 */ 811 if (map_op->handle == -1) 812 xen_mc_flush(); 813 /* 814 * Now if map_op->handle is negative it means that the 815 * hypercall actually returned an error. 816 */ 817 if (map_op->handle == GNTST_general_error) { 818 printk(KERN_WARNING "m2p_remove_override: " 819 "pfn %lx mfn %lx, failed to modify kernel mappings", 820 pfn, mfn); 821 return -1; 822 } 823 824 mcs = xen_mc_entry( 825 sizeof(struct gnttab_unmap_grant_ref)); 826 unmap_op = mcs.args; 827 unmap_op->host_addr = map_op->host_addr; 828 unmap_op->handle = map_op->handle; 829 unmap_op->dev_bus_addr = 0; 830 831 MULTI_grant_table_op(mcs.mc, 832 GNTTABOP_unmap_grant_ref, unmap_op, 1); 833 834 xen_mc_issue(PARAVIRT_LAZY_MMU); 835 836 set_pte_at(&init_mm, address, ptep, 837 pfn_pte(pfn, PAGE_KERNEL)); 838 __flush_tlb_single(address); 839 map_op->host_addr = 0; 840 } 841 } else 842 set_phys_to_machine(pfn, page->index); 843 844 /* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present 845 * somewhere in this domain, even before being added to the 846 * m2p_override (see comment above in m2p_add_override). 847 * If there are no other entries in the m2p_override corresponding 848 * to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for 849 * the original pfn (the one shared by the frontend): the backend 850 * cannot do any IO on this page anymore because it has been 851 * unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of 852 * the original pfn causes mfn_to_pfn(mfn) to return the frontend 853 * pfn again. */ 854 mfn &= ~FOREIGN_FRAME_BIT; 855 ret = __get_user(pfn, &machine_to_phys_mapping[mfn]); 856 if (ret == 0 && get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) && 857 m2p_find_override(mfn) == NULL) 858 set_phys_to_machine(pfn, mfn); 859 860 return 0; 861 } 862 EXPORT_SYMBOL_GPL(m2p_remove_override); 863 864 struct page *m2p_find_override(unsigned long mfn) 865 { 866 unsigned long flags; 867 struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)]; 868 struct page *p, *ret; 869 870 ret = NULL; 871 872 spin_lock_irqsave(&m2p_override_lock, flags); 873 874 list_for_each_entry(p, bucket, lru) { 875 if (page_private(p) == mfn) { 876 ret = p; 877 break; 878 } 879 } 880 881 spin_unlock_irqrestore(&m2p_override_lock, flags); 882 883 return ret; 884 } 885 886 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn) 887 { 888 struct page *p = m2p_find_override(mfn); 889 unsigned long ret = pfn; 890 891 if (p) 892 ret = page_to_pfn(p); 893 894 return ret; 895 } 896 EXPORT_SYMBOL_GPL(m2p_find_override_pfn); 897 898 #ifdef CONFIG_XEN_DEBUG_FS 899 #include <linux/debugfs.h> 900 #include "debugfs.h" 901 static int p2m_dump_show(struct seq_file *m, void *v) 902 { 903 static const char * const level_name[] = { "top", "middle", 904 "entry", "abnormal", "error"}; 905 #define TYPE_IDENTITY 0 906 #define TYPE_MISSING 1 907 #define TYPE_PFN 2 908 #define TYPE_UNKNOWN 3 909 static const char * const type_name[] = { 910 [TYPE_IDENTITY] = "identity", 911 [TYPE_MISSING] = "missing", 912 [TYPE_PFN] = "pfn", 913 [TYPE_UNKNOWN] = "abnormal"}; 914 unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0; 915 unsigned int uninitialized_var(prev_level); 916 unsigned int uninitialized_var(prev_type); 917 918 if (!p2m_top) 919 return 0; 920 921 for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) { 922 unsigned topidx = p2m_top_index(pfn); 923 unsigned mididx = p2m_mid_index(pfn); 924 unsigned idx = p2m_index(pfn); 925 unsigned lvl, type; 926 927 lvl = 4; 928 type = TYPE_UNKNOWN; 929 if (p2m_top[topidx] == p2m_mid_missing) { 930 lvl = 0; type = TYPE_MISSING; 931 } else if (p2m_top[topidx] == NULL) { 932 lvl = 0; type = TYPE_UNKNOWN; 933 } else if (p2m_top[topidx][mididx] == NULL) { 934 lvl = 1; type = TYPE_UNKNOWN; 935 } else if (p2m_top[topidx][mididx] == p2m_identity) { 936 lvl = 1; type = TYPE_IDENTITY; 937 } else if (p2m_top[topidx][mididx] == p2m_missing) { 938 lvl = 1; type = TYPE_MISSING; 939 } else if (p2m_top[topidx][mididx][idx] == 0) { 940 lvl = 2; type = TYPE_UNKNOWN; 941 } else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) { 942 lvl = 2; type = TYPE_IDENTITY; 943 } else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) { 944 lvl = 2; type = TYPE_MISSING; 945 } else if (p2m_top[topidx][mididx][idx] == pfn) { 946 lvl = 2; type = TYPE_PFN; 947 } else if (p2m_top[topidx][mididx][idx] != pfn) { 948 lvl = 2; type = TYPE_PFN; 949 } 950 if (pfn == 0) { 951 prev_level = lvl; 952 prev_type = type; 953 } 954 if (pfn == MAX_DOMAIN_PAGES-1) { 955 lvl = 3; 956 type = TYPE_UNKNOWN; 957 } 958 if (prev_type != type) { 959 seq_printf(m, " [0x%lx->0x%lx] %s\n", 960 prev_pfn_type, pfn, type_name[prev_type]); 961 prev_pfn_type = pfn; 962 prev_type = type; 963 } 964 if (prev_level != lvl) { 965 seq_printf(m, " [0x%lx->0x%lx] level %s\n", 966 prev_pfn_level, pfn, level_name[prev_level]); 967 prev_pfn_level = pfn; 968 prev_level = lvl; 969 } 970 } 971 return 0; 972 #undef TYPE_IDENTITY 973 #undef TYPE_MISSING 974 #undef TYPE_PFN 975 #undef TYPE_UNKNOWN 976 } 977 978 static int p2m_dump_open(struct inode *inode, struct file *filp) 979 { 980 return single_open(filp, p2m_dump_show, NULL); 981 } 982 983 static const struct file_operations p2m_dump_fops = { 984 .open = p2m_dump_open, 985 .read = seq_read, 986 .llseek = seq_lseek, 987 .release = single_release, 988 }; 989 990 static struct dentry *d_mmu_debug; 991 992 static int __init xen_p2m_debugfs(void) 993 { 994 struct dentry *d_xen = xen_init_debugfs(); 995 996 if (d_xen == NULL) 997 return -ENOMEM; 998 999 d_mmu_debug = debugfs_create_dir("mmu", d_xen); 1000 1001 debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops); 1002 return 0; 1003 } 1004 fs_initcall(xen_p2m_debugfs); 1005 #endif /* CONFIG_XEN_DEBUG_FS */ 1006