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 logical flat p2m table is mapped to a linear kernel memory area. 7 * For accesses by Xen a three-level tree linked via mfns only is set up to 8 * allow the address space to be sparse. 9 * 10 * Xen 11 * | 12 * p2m_top_mfn 13 * / \ 14 * p2m_mid_mfn p2m_mid_mfn 15 * / / 16 * p2m p2m p2m ... 17 * 18 * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p. 19 * 20 * The p2m_top_mfn level is limited to 1 page, so the maximum representable 21 * pseudo-physical address space is: 22 * P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages 23 * 24 * P2M_PER_PAGE depends on the architecture, as a mfn is always 25 * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to 26 * 512 and 1024 entries respectively. 27 * 28 * In short, these structures contain the Machine Frame Number (MFN) of the PFN. 29 * 30 * However not all entries are filled with MFNs. Specifically for all other 31 * leaf entries, or for the top root, or middle one, for which there is a void 32 * entry, we assume it is "missing". So (for example) 33 * pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY. 34 * We have a dedicated page p2m_missing with all entries being 35 * INVALID_P2M_ENTRY. This page may be referenced multiple times in the p2m 36 * list/tree in case there are multiple areas with P2M_PER_PAGE invalid pfns. 37 * 38 * We also have the possibility of setting 1-1 mappings on certain regions, so 39 * that: 40 * pfn_to_mfn(0xc0000)=0xc0000 41 * 42 * The benefit of this is, that we can assume for non-RAM regions (think 43 * PCI BARs, or ACPI spaces), we can create mappings easily because we 44 * get the PFN value to match the MFN. 45 * 46 * For this to work efficiently we have one new page p2m_identity. All entries 47 * in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only 48 * recognizes that and MFNs, no other fancy value). 49 * 50 * On lookup we spot that the entry points to p2m_identity and return the 51 * identity value instead of dereferencing and returning INVALID_P2M_ENTRY. 52 * If the entry points to an allocated page, we just proceed as before and 53 * return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in 54 * appropriate functions (pfn_to_mfn). 55 * 56 * The reason for having the IDENTITY_FRAME_BIT instead of just returning the 57 * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a 58 * non-identity pfn. To protect ourselves against we elect to set (and get) the 59 * IDENTITY_FRAME_BIT on all identity mapped PFNs. 60 */ 61 62 #include <linux/init.h> 63 #include <linux/module.h> 64 #include <linux/list.h> 65 #include <linux/hash.h> 66 #include <linux/sched.h> 67 #include <linux/seq_file.h> 68 #include <linux/bootmem.h> 69 #include <linux/slab.h> 70 71 #include <asm/cache.h> 72 #include <asm/setup.h> 73 #include <asm/uaccess.h> 74 75 #include <asm/xen/page.h> 76 #include <asm/xen/hypercall.h> 77 #include <asm/xen/hypervisor.h> 78 #include <xen/balloon.h> 79 #include <xen/grant_table.h> 80 81 #include "p2m.h" 82 #include "multicalls.h" 83 #include "xen-ops.h" 84 85 #define PMDS_PER_MID_PAGE (P2M_MID_PER_PAGE / PTRS_PER_PTE) 86 87 static void __init m2p_override_init(void); 88 89 unsigned long *xen_p2m_addr __read_mostly; 90 EXPORT_SYMBOL_GPL(xen_p2m_addr); 91 unsigned long xen_p2m_size __read_mostly; 92 EXPORT_SYMBOL_GPL(xen_p2m_size); 93 unsigned long xen_max_p2m_pfn __read_mostly; 94 EXPORT_SYMBOL_GPL(xen_max_p2m_pfn); 95 96 static DEFINE_SPINLOCK(p2m_update_lock); 97 98 static unsigned long *p2m_mid_missing_mfn; 99 static unsigned long *p2m_top_mfn; 100 static unsigned long **p2m_top_mfn_p; 101 static unsigned long *p2m_missing; 102 static unsigned long *p2m_identity; 103 static pte_t *p2m_missing_pte; 104 static pte_t *p2m_identity_pte; 105 106 static inline unsigned p2m_top_index(unsigned long pfn) 107 { 108 BUG_ON(pfn >= MAX_P2M_PFN); 109 return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE); 110 } 111 112 static inline unsigned p2m_mid_index(unsigned long pfn) 113 { 114 return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE; 115 } 116 117 static inline unsigned p2m_index(unsigned long pfn) 118 { 119 return pfn % P2M_PER_PAGE; 120 } 121 122 static void p2m_top_mfn_init(unsigned long *top) 123 { 124 unsigned i; 125 126 for (i = 0; i < P2M_TOP_PER_PAGE; i++) 127 top[i] = virt_to_mfn(p2m_mid_missing_mfn); 128 } 129 130 static void p2m_top_mfn_p_init(unsigned long **top) 131 { 132 unsigned i; 133 134 for (i = 0; i < P2M_TOP_PER_PAGE; i++) 135 top[i] = p2m_mid_missing_mfn; 136 } 137 138 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf) 139 { 140 unsigned i; 141 142 for (i = 0; i < P2M_MID_PER_PAGE; i++) 143 mid[i] = virt_to_mfn(leaf); 144 } 145 146 static void p2m_init(unsigned long *p2m) 147 { 148 unsigned i; 149 150 for (i = 0; i < P2M_PER_PAGE; i++) 151 p2m[i] = INVALID_P2M_ENTRY; 152 } 153 154 static void p2m_init_identity(unsigned long *p2m, unsigned long pfn) 155 { 156 unsigned i; 157 158 for (i = 0; i < P2M_PER_PAGE; i++) 159 p2m[i] = IDENTITY_FRAME(pfn + i); 160 } 161 162 static void * __ref alloc_p2m_page(void) 163 { 164 if (unlikely(!slab_is_available())) 165 return alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE); 166 167 return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT); 168 } 169 170 static void __ref free_p2m_page(void *p) 171 { 172 if (unlikely(!slab_is_available())) { 173 free_bootmem((unsigned long)p, PAGE_SIZE); 174 return; 175 } 176 177 free_page((unsigned long)p); 178 } 179 180 /* 181 * Build the parallel p2m_top_mfn and p2m_mid_mfn structures 182 * 183 * This is called both at boot time, and after resuming from suspend: 184 * - At boot time we're called rather early, and must use alloc_bootmem*() 185 * to allocate memory. 186 * 187 * - After resume we're called from within stop_machine, but the mfn 188 * tree should already be completely allocated. 189 */ 190 void __ref xen_build_mfn_list_list(void) 191 { 192 unsigned long pfn, mfn; 193 pte_t *ptep; 194 unsigned int level, topidx, mididx; 195 unsigned long *mid_mfn_p; 196 197 if (xen_feature(XENFEAT_auto_translated_physmap)) 198 return; 199 200 /* Pre-initialize p2m_top_mfn to be completely missing */ 201 if (p2m_top_mfn == NULL) { 202 p2m_mid_missing_mfn = alloc_p2m_page(); 203 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing); 204 205 p2m_top_mfn_p = alloc_p2m_page(); 206 p2m_top_mfn_p_init(p2m_top_mfn_p); 207 208 p2m_top_mfn = alloc_p2m_page(); 209 p2m_top_mfn_init(p2m_top_mfn); 210 } else { 211 /* Reinitialise, mfn's all change after migration */ 212 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing); 213 } 214 215 for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN; 216 pfn += P2M_PER_PAGE) { 217 topidx = p2m_top_index(pfn); 218 mididx = p2m_mid_index(pfn); 219 220 mid_mfn_p = p2m_top_mfn_p[topidx]; 221 ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), 222 &level); 223 BUG_ON(!ptep || level != PG_LEVEL_4K); 224 mfn = pte_mfn(*ptep); 225 ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1)); 226 227 /* Don't bother allocating any mfn mid levels if 228 * they're just missing, just update the stored mfn, 229 * since all could have changed over a migrate. 230 */ 231 if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) { 232 BUG_ON(mididx); 233 BUG_ON(mid_mfn_p != p2m_mid_missing_mfn); 234 p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn); 235 pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE; 236 continue; 237 } 238 239 if (mid_mfn_p == p2m_mid_missing_mfn) { 240 mid_mfn_p = alloc_p2m_page(); 241 p2m_mid_mfn_init(mid_mfn_p, p2m_missing); 242 243 p2m_top_mfn_p[topidx] = mid_mfn_p; 244 } 245 246 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p); 247 mid_mfn_p[mididx] = mfn; 248 } 249 } 250 251 void xen_setup_mfn_list_list(void) 252 { 253 if (xen_feature(XENFEAT_auto_translated_physmap)) 254 return; 255 256 BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info); 257 258 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = 259 virt_to_mfn(p2m_top_mfn); 260 HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn; 261 } 262 263 /* Set up p2m_top to point to the domain-builder provided p2m pages */ 264 void __init xen_build_dynamic_phys_to_machine(void) 265 { 266 unsigned long pfn; 267 268 if (xen_feature(XENFEAT_auto_translated_physmap)) 269 return; 270 271 xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list; 272 xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE); 273 274 for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++) 275 xen_p2m_addr[pfn] = INVALID_P2M_ENTRY; 276 277 xen_max_p2m_pfn = xen_p2m_size; 278 } 279 280 #define P2M_TYPE_IDENTITY 0 281 #define P2M_TYPE_MISSING 1 282 #define P2M_TYPE_PFN 2 283 #define P2M_TYPE_UNKNOWN 3 284 285 static int xen_p2m_elem_type(unsigned long pfn) 286 { 287 unsigned long mfn; 288 289 if (pfn >= xen_p2m_size) 290 return P2M_TYPE_IDENTITY; 291 292 mfn = xen_p2m_addr[pfn]; 293 294 if (mfn == INVALID_P2M_ENTRY) 295 return P2M_TYPE_MISSING; 296 297 if (mfn & IDENTITY_FRAME_BIT) 298 return P2M_TYPE_IDENTITY; 299 300 return P2M_TYPE_PFN; 301 } 302 303 static void __init xen_rebuild_p2m_list(unsigned long *p2m) 304 { 305 unsigned int i, chunk; 306 unsigned long pfn; 307 unsigned long *mfns; 308 pte_t *ptep; 309 pmd_t *pmdp; 310 int type; 311 312 p2m_missing = alloc_p2m_page(); 313 p2m_init(p2m_missing); 314 p2m_identity = alloc_p2m_page(); 315 p2m_init(p2m_identity); 316 317 p2m_missing_pte = alloc_p2m_page(); 318 paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT); 319 p2m_identity_pte = alloc_p2m_page(); 320 paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT); 321 for (i = 0; i < PTRS_PER_PTE; i++) { 322 set_pte(p2m_missing_pte + i, 323 pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO)); 324 set_pte(p2m_identity_pte + i, 325 pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO)); 326 } 327 328 for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) { 329 /* 330 * Try to map missing/identity PMDs or p2m-pages if possible. 331 * We have to respect the structure of the mfn_list_list 332 * which will be built just afterwards. 333 * Chunk size to test is one p2m page if we are in the middle 334 * of a mfn_list_list mid page and the complete mid page area 335 * if we are at index 0 of the mid page. Please note that a 336 * mid page might cover more than one PMD, e.g. on 32 bit PAE 337 * kernels. 338 */ 339 chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ? 340 P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE; 341 342 type = xen_p2m_elem_type(pfn); 343 i = 0; 344 if (type != P2M_TYPE_PFN) 345 for (i = 1; i < chunk; i++) 346 if (xen_p2m_elem_type(pfn + i) != type) 347 break; 348 if (i < chunk) 349 /* Reset to minimal chunk size. */ 350 chunk = P2M_PER_PAGE; 351 352 if (type == P2M_TYPE_PFN || i < chunk) { 353 /* Use initial p2m page contents. */ 354 #ifdef CONFIG_X86_64 355 mfns = alloc_p2m_page(); 356 copy_page(mfns, xen_p2m_addr + pfn); 357 #else 358 mfns = xen_p2m_addr + pfn; 359 #endif 360 ptep = populate_extra_pte((unsigned long)(p2m + pfn)); 361 set_pte(ptep, 362 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL)); 363 continue; 364 } 365 366 if (chunk == P2M_PER_PAGE) { 367 /* Map complete missing or identity p2m-page. */ 368 mfns = (type == P2M_TYPE_MISSING) ? 369 p2m_missing : p2m_identity; 370 ptep = populate_extra_pte((unsigned long)(p2m + pfn)); 371 set_pte(ptep, 372 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO)); 373 continue; 374 } 375 376 /* Complete missing or identity PMD(s) can be mapped. */ 377 ptep = (type == P2M_TYPE_MISSING) ? 378 p2m_missing_pte : p2m_identity_pte; 379 for (i = 0; i < PMDS_PER_MID_PAGE; i++) { 380 pmdp = populate_extra_pmd( 381 (unsigned long)(p2m + pfn) + i * PMD_SIZE); 382 set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE)); 383 } 384 } 385 } 386 387 void __init xen_vmalloc_p2m_tree(void) 388 { 389 static struct vm_struct vm; 390 391 vm.flags = VM_ALLOC; 392 vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn, 393 PMD_SIZE * PMDS_PER_MID_PAGE); 394 vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE); 395 pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size); 396 397 xen_max_p2m_pfn = vm.size / sizeof(unsigned long); 398 399 xen_rebuild_p2m_list(vm.addr); 400 401 xen_p2m_addr = vm.addr; 402 xen_p2m_size = xen_max_p2m_pfn; 403 404 xen_inv_extra_mem(); 405 406 m2p_override_init(); 407 } 408 409 unsigned long get_phys_to_machine(unsigned long pfn) 410 { 411 pte_t *ptep; 412 unsigned int level; 413 414 if (unlikely(pfn >= xen_p2m_size)) { 415 if (pfn < xen_max_p2m_pfn) 416 return xen_chk_extra_mem(pfn); 417 418 return IDENTITY_FRAME(pfn); 419 } 420 421 ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level); 422 BUG_ON(!ptep || level != PG_LEVEL_4K); 423 424 /* 425 * The INVALID_P2M_ENTRY is filled in both p2m_*identity 426 * and in p2m_*missing, so returning the INVALID_P2M_ENTRY 427 * would be wrong. 428 */ 429 if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity))) 430 return IDENTITY_FRAME(pfn); 431 432 return xen_p2m_addr[pfn]; 433 } 434 EXPORT_SYMBOL_GPL(get_phys_to_machine); 435 436 /* 437 * Allocate new pmd(s). It is checked whether the old pmd is still in place. 438 * If not, nothing is changed. This is okay as the only reason for allocating 439 * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual 440 * pmd. In case of PAE/x86-32 there are multiple pmds to allocate! 441 */ 442 static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg) 443 { 444 pte_t *ptechk; 445 pte_t *pte_newpg[PMDS_PER_MID_PAGE]; 446 pmd_t *pmdp; 447 unsigned int level; 448 unsigned long flags; 449 unsigned long vaddr; 450 int i; 451 452 /* Do all allocations first to bail out in error case. */ 453 for (i = 0; i < PMDS_PER_MID_PAGE; i++) { 454 pte_newpg[i] = alloc_p2m_page(); 455 if (!pte_newpg[i]) { 456 for (i--; i >= 0; i--) 457 free_p2m_page(pte_newpg[i]); 458 459 return NULL; 460 } 461 } 462 463 vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1); 464 465 for (i = 0; i < PMDS_PER_MID_PAGE; i++) { 466 copy_page(pte_newpg[i], pte_pg); 467 paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT); 468 469 pmdp = lookup_pmd_address(vaddr); 470 BUG_ON(!pmdp); 471 472 spin_lock_irqsave(&p2m_update_lock, flags); 473 474 ptechk = lookup_address(vaddr, &level); 475 if (ptechk == pte_pg) { 476 set_pmd(pmdp, 477 __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE)); 478 pte_newpg[i] = NULL; 479 } 480 481 spin_unlock_irqrestore(&p2m_update_lock, flags); 482 483 if (pte_newpg[i]) { 484 paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT); 485 free_p2m_page(pte_newpg[i]); 486 } 487 488 vaddr += PMD_SIZE; 489 } 490 491 return lookup_address(addr, &level); 492 } 493 494 /* 495 * Fully allocate the p2m structure for a given pfn. We need to check 496 * that both the top and mid levels are allocated, and make sure the 497 * parallel mfn tree is kept in sync. We may race with other cpus, so 498 * the new pages are installed with cmpxchg; if we lose the race then 499 * simply free the page we allocated and use the one that's there. 500 */ 501 static bool alloc_p2m(unsigned long pfn) 502 { 503 unsigned topidx, mididx; 504 unsigned long *top_mfn_p, *mid_mfn; 505 pte_t *ptep, *pte_pg; 506 unsigned int level; 507 unsigned long flags; 508 unsigned long addr = (unsigned long)(xen_p2m_addr + pfn); 509 unsigned long p2m_pfn; 510 511 topidx = p2m_top_index(pfn); 512 mididx = p2m_mid_index(pfn); 513 514 ptep = lookup_address(addr, &level); 515 BUG_ON(!ptep || level != PG_LEVEL_4K); 516 pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1)); 517 518 if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) { 519 /* PMD level is missing, allocate a new one */ 520 ptep = alloc_p2m_pmd(addr, pte_pg); 521 if (!ptep) 522 return false; 523 } 524 525 if (p2m_top_mfn) { 526 top_mfn_p = &p2m_top_mfn[topidx]; 527 mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]); 528 529 BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p); 530 531 if (mid_mfn == p2m_mid_missing_mfn) { 532 /* Separately check the mid mfn level */ 533 unsigned long missing_mfn; 534 unsigned long mid_mfn_mfn; 535 unsigned long old_mfn; 536 537 mid_mfn = alloc_p2m_page(); 538 if (!mid_mfn) 539 return false; 540 541 p2m_mid_mfn_init(mid_mfn, p2m_missing); 542 543 missing_mfn = virt_to_mfn(p2m_mid_missing_mfn); 544 mid_mfn_mfn = virt_to_mfn(mid_mfn); 545 old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn); 546 if (old_mfn != missing_mfn) { 547 free_p2m_page(mid_mfn); 548 mid_mfn = mfn_to_virt(old_mfn); 549 } else { 550 p2m_top_mfn_p[topidx] = mid_mfn; 551 } 552 } 553 } else { 554 mid_mfn = NULL; 555 } 556 557 p2m_pfn = pte_pfn(ACCESS_ONCE(*ptep)); 558 if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) || 559 p2m_pfn == PFN_DOWN(__pa(p2m_missing))) { 560 /* p2m leaf page is missing */ 561 unsigned long *p2m; 562 563 p2m = alloc_p2m_page(); 564 if (!p2m) 565 return false; 566 567 if (p2m_pfn == PFN_DOWN(__pa(p2m_missing))) 568 p2m_init(p2m); 569 else 570 p2m_init_identity(p2m, pfn); 571 572 spin_lock_irqsave(&p2m_update_lock, flags); 573 574 if (pte_pfn(*ptep) == p2m_pfn) { 575 set_pte(ptep, 576 pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL)); 577 if (mid_mfn) 578 mid_mfn[mididx] = virt_to_mfn(p2m); 579 p2m = NULL; 580 } 581 582 spin_unlock_irqrestore(&p2m_update_lock, flags); 583 584 if (p2m) 585 free_p2m_page(p2m); 586 } 587 588 return true; 589 } 590 591 unsigned long __init set_phys_range_identity(unsigned long pfn_s, 592 unsigned long pfn_e) 593 { 594 unsigned long pfn; 595 596 if (unlikely(pfn_s >= xen_p2m_size)) 597 return 0; 598 599 if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) 600 return pfn_e - pfn_s; 601 602 if (pfn_s > pfn_e) 603 return 0; 604 605 if (pfn_e > xen_p2m_size) 606 pfn_e = xen_p2m_size; 607 608 for (pfn = pfn_s; pfn < pfn_e; pfn++) 609 xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn); 610 611 return pfn - pfn_s; 612 } 613 614 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn) 615 { 616 pte_t *ptep; 617 unsigned int level; 618 619 /* don't track P2M changes in autotranslate guests */ 620 if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) 621 return true; 622 623 if (unlikely(pfn >= xen_p2m_size)) { 624 BUG_ON(mfn != INVALID_P2M_ENTRY); 625 return true; 626 } 627 628 if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn))) 629 return true; 630 631 ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level); 632 BUG_ON(!ptep || level != PG_LEVEL_4K); 633 634 if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing))) 635 return mfn == INVALID_P2M_ENTRY; 636 637 if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity))) 638 return mfn == IDENTITY_FRAME(pfn); 639 640 return false; 641 } 642 643 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn) 644 { 645 if (unlikely(!__set_phys_to_machine(pfn, mfn))) { 646 if (!alloc_p2m(pfn)) 647 return false; 648 649 return __set_phys_to_machine(pfn, mfn); 650 } 651 652 return true; 653 } 654 655 #define M2P_OVERRIDE_HASH_SHIFT 10 656 #define M2P_OVERRIDE_HASH (1 << M2P_OVERRIDE_HASH_SHIFT) 657 658 static struct list_head *m2p_overrides; 659 static DEFINE_SPINLOCK(m2p_override_lock); 660 661 static void __init m2p_override_init(void) 662 { 663 unsigned i; 664 665 m2p_overrides = alloc_bootmem_align( 666 sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH, 667 sizeof(unsigned long)); 668 669 for (i = 0; i < M2P_OVERRIDE_HASH; i++) 670 INIT_LIST_HEAD(&m2p_overrides[i]); 671 } 672 673 static unsigned long mfn_hash(unsigned long mfn) 674 { 675 return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT); 676 } 677 678 /* Add an MFN override for a particular page */ 679 static int m2p_add_override(unsigned long mfn, struct page *page, 680 struct gnttab_map_grant_ref *kmap_op) 681 { 682 unsigned long flags; 683 unsigned long pfn; 684 unsigned long uninitialized_var(address); 685 unsigned level; 686 pte_t *ptep = NULL; 687 688 pfn = page_to_pfn(page); 689 if (!PageHighMem(page)) { 690 address = (unsigned long)__va(pfn << PAGE_SHIFT); 691 ptep = lookup_address(address, &level); 692 if (WARN(ptep == NULL || level != PG_LEVEL_4K, 693 "m2p_add_override: pfn %lx not mapped", pfn)) 694 return -EINVAL; 695 } 696 697 if (kmap_op != NULL) { 698 if (!PageHighMem(page)) { 699 struct multicall_space mcs = 700 xen_mc_entry(sizeof(*kmap_op)); 701 702 MULTI_grant_table_op(mcs.mc, 703 GNTTABOP_map_grant_ref, kmap_op, 1); 704 705 xen_mc_issue(PARAVIRT_LAZY_MMU); 706 } 707 } 708 spin_lock_irqsave(&m2p_override_lock, flags); 709 list_add(&page->lru, &m2p_overrides[mfn_hash(mfn)]); 710 spin_unlock_irqrestore(&m2p_override_lock, flags); 711 712 /* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in 713 * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other 714 * pfn so that the following mfn_to_pfn(mfn) calls will return the 715 * pfn from the m2p_override (the backend pfn) instead. 716 * We need to do this because the pages shared by the frontend 717 * (xen-blkfront) can be already locked (lock_page, called by 718 * do_read_cache_page); when the userspace backend tries to use them 719 * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so 720 * do_blockdev_direct_IO is going to try to lock the same pages 721 * again resulting in a deadlock. 722 * As a side effect get_user_pages_fast might not be safe on the 723 * frontend pages while they are being shared with the backend, 724 * because mfn_to_pfn (that ends up being called by GUPF) will 725 * return the backend pfn rather than the frontend pfn. */ 726 pfn = mfn_to_pfn_no_overrides(mfn); 727 if (__pfn_to_mfn(pfn) == mfn) 728 set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)); 729 730 return 0; 731 } 732 733 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops, 734 struct gnttab_map_grant_ref *kmap_ops, 735 struct page **pages, unsigned int count) 736 { 737 int i, ret = 0; 738 bool lazy = false; 739 pte_t *pte; 740 741 if (xen_feature(XENFEAT_auto_translated_physmap)) 742 return 0; 743 744 if (kmap_ops && 745 !in_interrupt() && 746 paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) { 747 arch_enter_lazy_mmu_mode(); 748 lazy = true; 749 } 750 751 for (i = 0; i < count; i++) { 752 unsigned long mfn, pfn; 753 754 /* Do not add to override if the map failed. */ 755 if (map_ops[i].status) 756 continue; 757 758 if (map_ops[i].flags & GNTMAP_contains_pte) { 759 pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) + 760 (map_ops[i].host_addr & ~PAGE_MASK)); 761 mfn = pte_mfn(*pte); 762 } else { 763 mfn = PFN_DOWN(map_ops[i].dev_bus_addr); 764 } 765 pfn = page_to_pfn(pages[i]); 766 767 WARN_ON(PagePrivate(pages[i])); 768 SetPagePrivate(pages[i]); 769 set_page_private(pages[i], mfn); 770 pages[i]->index = pfn_to_mfn(pfn); 771 772 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) { 773 ret = -ENOMEM; 774 goto out; 775 } 776 777 if (kmap_ops) { 778 ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]); 779 if (ret) 780 goto out; 781 } 782 } 783 784 out: 785 if (lazy) 786 arch_leave_lazy_mmu_mode(); 787 788 return ret; 789 } 790 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping); 791 792 static struct page *m2p_find_override(unsigned long mfn) 793 { 794 unsigned long flags; 795 struct list_head *bucket; 796 struct page *p, *ret; 797 798 if (unlikely(!m2p_overrides)) 799 return NULL; 800 801 ret = NULL; 802 bucket = &m2p_overrides[mfn_hash(mfn)]; 803 804 spin_lock_irqsave(&m2p_override_lock, flags); 805 806 list_for_each_entry(p, bucket, lru) { 807 if (page_private(p) == mfn) { 808 ret = p; 809 break; 810 } 811 } 812 813 spin_unlock_irqrestore(&m2p_override_lock, flags); 814 815 return ret; 816 } 817 818 static int m2p_remove_override(struct page *page, 819 struct gnttab_map_grant_ref *kmap_op, 820 unsigned long mfn) 821 { 822 unsigned long flags; 823 unsigned long pfn; 824 unsigned long uninitialized_var(address); 825 unsigned level; 826 pte_t *ptep = NULL; 827 828 pfn = page_to_pfn(page); 829 830 if (!PageHighMem(page)) { 831 address = (unsigned long)__va(pfn << PAGE_SHIFT); 832 ptep = lookup_address(address, &level); 833 834 if (WARN(ptep == NULL || level != PG_LEVEL_4K, 835 "m2p_remove_override: pfn %lx not mapped", pfn)) 836 return -EINVAL; 837 } 838 839 spin_lock_irqsave(&m2p_override_lock, flags); 840 list_del(&page->lru); 841 spin_unlock_irqrestore(&m2p_override_lock, flags); 842 843 if (kmap_op != NULL) { 844 if (!PageHighMem(page)) { 845 struct multicall_space mcs; 846 struct gnttab_unmap_and_replace *unmap_op; 847 struct page *scratch_page = get_balloon_scratch_page(); 848 unsigned long scratch_page_address = (unsigned long) 849 __va(page_to_pfn(scratch_page) << PAGE_SHIFT); 850 851 /* 852 * It might be that we queued all the m2p grant table 853 * hypercalls in a multicall, then m2p_remove_override 854 * get called before the multicall has actually been 855 * issued. In this case handle is going to -1 because 856 * it hasn't been modified yet. 857 */ 858 if (kmap_op->handle == -1) 859 xen_mc_flush(); 860 /* 861 * Now if kmap_op->handle is negative it means that the 862 * hypercall actually returned an error. 863 */ 864 if (kmap_op->handle == GNTST_general_error) { 865 pr_warn("m2p_remove_override: pfn %lx mfn %lx, failed to modify kernel mappings", 866 pfn, mfn); 867 put_balloon_scratch_page(); 868 return -1; 869 } 870 871 xen_mc_batch(); 872 873 mcs = __xen_mc_entry( 874 sizeof(struct gnttab_unmap_and_replace)); 875 unmap_op = mcs.args; 876 unmap_op->host_addr = kmap_op->host_addr; 877 unmap_op->new_addr = scratch_page_address; 878 unmap_op->handle = kmap_op->handle; 879 880 MULTI_grant_table_op(mcs.mc, 881 GNTTABOP_unmap_and_replace, unmap_op, 1); 882 883 mcs = __xen_mc_entry(0); 884 MULTI_update_va_mapping(mcs.mc, scratch_page_address, 885 pfn_pte(page_to_pfn(scratch_page), 886 PAGE_KERNEL_RO), 0); 887 888 xen_mc_issue(PARAVIRT_LAZY_MMU); 889 890 kmap_op->host_addr = 0; 891 put_balloon_scratch_page(); 892 } 893 } 894 895 /* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present 896 * somewhere in this domain, even before being added to the 897 * m2p_override (see comment above in m2p_add_override). 898 * If there are no other entries in the m2p_override corresponding 899 * to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for 900 * the original pfn (the one shared by the frontend): the backend 901 * cannot do any IO on this page anymore because it has been 902 * unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of 903 * the original pfn causes mfn_to_pfn(mfn) to return the frontend 904 * pfn again. */ 905 mfn &= ~FOREIGN_FRAME_BIT; 906 pfn = mfn_to_pfn_no_overrides(mfn); 907 if (__pfn_to_mfn(pfn) == FOREIGN_FRAME(mfn) && 908 m2p_find_override(mfn) == NULL) 909 set_phys_to_machine(pfn, mfn); 910 911 return 0; 912 } 913 914 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops, 915 struct gnttab_map_grant_ref *kmap_ops, 916 struct page **pages, unsigned int count) 917 { 918 int i, ret = 0; 919 bool lazy = false; 920 921 if (xen_feature(XENFEAT_auto_translated_physmap)) 922 return 0; 923 924 if (kmap_ops && 925 !in_interrupt() && 926 paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) { 927 arch_enter_lazy_mmu_mode(); 928 lazy = true; 929 } 930 931 for (i = 0; i < count; i++) { 932 unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i])); 933 unsigned long pfn = page_to_pfn(pages[i]); 934 935 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) { 936 ret = -EINVAL; 937 goto out; 938 } 939 940 set_page_private(pages[i], INVALID_P2M_ENTRY); 941 WARN_ON(!PagePrivate(pages[i])); 942 ClearPagePrivate(pages[i]); 943 set_phys_to_machine(pfn, pages[i]->index); 944 945 if (kmap_ops) 946 ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn); 947 if (ret) 948 goto out; 949 } 950 951 out: 952 if (lazy) 953 arch_leave_lazy_mmu_mode(); 954 return ret; 955 } 956 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping); 957 958 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn) 959 { 960 struct page *p = m2p_find_override(mfn); 961 unsigned long ret = pfn; 962 963 if (p) 964 ret = page_to_pfn(p); 965 966 return ret; 967 } 968 EXPORT_SYMBOL_GPL(m2p_find_override_pfn); 969 970 #ifdef CONFIG_XEN_DEBUG_FS 971 #include <linux/debugfs.h> 972 #include "debugfs.h" 973 static int p2m_dump_show(struct seq_file *m, void *v) 974 { 975 static const char * const type_name[] = { 976 [P2M_TYPE_IDENTITY] = "identity", 977 [P2M_TYPE_MISSING] = "missing", 978 [P2M_TYPE_PFN] = "pfn", 979 [P2M_TYPE_UNKNOWN] = "abnormal"}; 980 unsigned long pfn, first_pfn; 981 int type, prev_type; 982 983 prev_type = xen_p2m_elem_type(0); 984 first_pfn = 0; 985 986 for (pfn = 0; pfn < xen_p2m_size; pfn++) { 987 type = xen_p2m_elem_type(pfn); 988 if (type != prev_type) { 989 seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn, 990 type_name[prev_type]); 991 prev_type = type; 992 first_pfn = pfn; 993 } 994 } 995 seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn, 996 type_name[prev_type]); 997 return 0; 998 } 999 1000 static int p2m_dump_open(struct inode *inode, struct file *filp) 1001 { 1002 return single_open(filp, p2m_dump_show, NULL); 1003 } 1004 1005 static const struct file_operations p2m_dump_fops = { 1006 .open = p2m_dump_open, 1007 .read = seq_read, 1008 .llseek = seq_lseek, 1009 .release = single_release, 1010 }; 1011 1012 static struct dentry *d_mmu_debug; 1013 1014 static int __init xen_p2m_debugfs(void) 1015 { 1016 struct dentry *d_xen = xen_init_debugfs(); 1017 1018 if (d_xen == NULL) 1019 return -ENOMEM; 1020 1021 d_mmu_debug = debugfs_create_dir("mmu", d_xen); 1022 1023 debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops); 1024 return 0; 1025 } 1026 fs_initcall(xen_p2m_debugfs); 1027 #endif /* CONFIG_XEN_DEBUG_FS */ 1028