arch/x86/xen/p2m.c

   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 *ptep, pte_t *pte_pg)
 443 {
 444         pte_t *ptechk;
 445         pte_t *pteret = ptep;
 446         pte_t *pte_newpg[PMDS_PER_MID_PAGE];
 447         pmd_t *pmdp;
 448         unsigned int level;
 449         unsigned long flags;
 450         unsigned long vaddr;
 451         int i;
 452
 453         /* Do all allocations first to bail out in error case. */
 454         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 455                 pte_newpg[i] = alloc_p2m_page();
 456                 if (!pte_newpg[i]) {
 457                         for (i--; i >= 0; i--)
 458                                 free_p2m_page(pte_newpg[i]);
 459
 460                         return NULL;
 461                 }
 462         }
 463
 464         vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);
 465
 466         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 467                 copy_page(pte_newpg[i], pte_pg);
 468                 paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);
 469
 470                 pmdp = lookup_pmd_address(vaddr);
 471                 BUG_ON(!pmdp);
 472
 473                 spin_lock_irqsave(&p2m_update_lock, flags);
 474
 475                 ptechk = lookup_address(vaddr, &level);
 476                 if (ptechk == pte_pg) {
 477                         set_pmd(pmdp,
 478                                 __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
 479                         if (vaddr == (addr & ~(PMD_SIZE - 1)))
 480                                 pteret = pte_offset_kernel(pmdp, addr);
 481                         pte_newpg[i] = NULL;
 482                 }
 483
 484                 spin_unlock_irqrestore(&p2m_update_lock, flags);
 485
 486                 if (pte_newpg[i]) {
 487                         paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
 488                         free_p2m_page(pte_newpg[i]);
 489                 }
 490
 491                 vaddr += PMD_SIZE;
 492         }
 493
 494         return pteret;
 495 }
 496
 497 /*
 498  * Fully allocate the p2m structure for a given pfn.  We need to check
 499  * that both the top and mid levels are allocated, and make sure the
 500  * parallel mfn tree is kept in sync.  We may race with other cpus, so
 501  * the new pages are installed with cmpxchg; if we lose the race then
 502  * simply free the page we allocated and use the one that's there.
 503  */
 504 static bool alloc_p2m(unsigned long pfn)
 505 {
 506         unsigned topidx, mididx;
 507         unsigned long *top_mfn_p, *mid_mfn;
 508         pte_t *ptep, *pte_pg;
 509         unsigned int level;
 510         unsigned long flags;
 511         unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
 512         unsigned long p2m_pfn;
 513
 514         topidx = p2m_top_index(pfn);
 515         mididx = p2m_mid_index(pfn);
 516
 517         ptep = lookup_address(addr, &level);
 518         BUG_ON(!ptep || level != PG_LEVEL_4K);
 519         pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 520
 521         if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
 522                 /* PMD level is missing, allocate a new one */
 523                 ptep = alloc_p2m_pmd(addr, ptep, pte_pg);
 524                 if (!ptep)
 525                         return false;
 526         }
 527
 528         if (p2m_top_mfn) {
 529                 top_mfn_p = &p2m_top_mfn[topidx];
 530                 mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
 531
 532                 BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
 533
 534                 if (mid_mfn == p2m_mid_missing_mfn) {
 535                         /* Separately check the mid mfn level */
 536                         unsigned long missing_mfn;
 537                         unsigned long mid_mfn_mfn;
 538                         unsigned long old_mfn;
 539
 540                         mid_mfn = alloc_p2m_page();
 541                         if (!mid_mfn)
 542                                 return false;
 543
 544                         p2m_mid_mfn_init(mid_mfn, p2m_missing);
 545
 546                         missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
 547                         mid_mfn_mfn = virt_to_mfn(mid_mfn);
 548                         old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
 549                         if (old_mfn != missing_mfn) {
 550                                 free_p2m_page(mid_mfn);
 551                                 mid_mfn = mfn_to_virt(old_mfn);
 552                         } else {
 553                                 p2m_top_mfn_p[topidx] = mid_mfn;
 554                         }
 555                 }
 556         } else {
 557                 mid_mfn = NULL;
 558         }
 559
 560         p2m_pfn = pte_pfn(ACCESS_ONCE(*ptep));
 561         if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
 562             p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
 563                 /* p2m leaf page is missing */
 564                 unsigned long *p2m;
 565
 566                 p2m = alloc_p2m_page();
 567                 if (!p2m)
 568                         return false;
 569
 570                 if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
 571                         p2m_init(p2m);
 572                 else
 573                         p2m_init_identity(p2m, pfn);
 574
 575                 spin_lock_irqsave(&p2m_update_lock, flags);
 576
 577                 if (pte_pfn(*ptep) == p2m_pfn) {
 578                         set_pte(ptep,
 579                                 pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
 580                         if (mid_mfn)
 581                                 mid_mfn[mididx] = virt_to_mfn(p2m);
 582                         p2m = NULL;
 583                 }
 584
 585                 spin_unlock_irqrestore(&p2m_update_lock, flags);
 586
 587                 if (p2m)
 588                         free_p2m_page(p2m);
 589         }
 590
 591         return true;
 592 }
 593
 594 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 595                                       unsigned long pfn_e)
 596 {
 597         unsigned long pfn;
 598
 599         if (unlikely(pfn_s >= xen_p2m_size))
 600                 return 0;
 601
 602         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
 603                 return pfn_e - pfn_s;
 604
 605         if (pfn_s > pfn_e)
 606                 return 0;
 607
 608         if (pfn_e > xen_p2m_size)
 609                 pfn_e = xen_p2m_size;
 610
 611         for (pfn = pfn_s; pfn < pfn_e; pfn++)
 612                 xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);
 613
 614         return pfn - pfn_s;
 615 }
 616
 617 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 618 {
 619         pte_t *ptep;
 620         unsigned int level;
 621
 622         /* don't track P2M changes in autotranslate guests */
 623         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
 624                 return true;
 625
 626         if (unlikely(pfn >= xen_p2m_size)) {
 627                 BUG_ON(mfn != INVALID_P2M_ENTRY);
 628                 return true;
 629         }
 630
 631         if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
 632                 return true;
 633
 634         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
 635         BUG_ON(!ptep || level != PG_LEVEL_4K);
 636
 637         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
 638                 return mfn == INVALID_P2M_ENTRY;
 639
 640         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 641                 return mfn == IDENTITY_FRAME(pfn);
 642
 643         return false;
 644 }
 645
 646 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 647 {
 648         if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
 649                 if (!alloc_p2m(pfn))
 650                         return false;
 651
 652                 return __set_phys_to_machine(pfn, mfn);
 653         }
 654
 655         return true;
 656 }
 657
 658 #define M2P_OVERRIDE_HASH_SHIFT 10
 659 #define M2P_OVERRIDE_HASH       (1 << M2P_OVERRIDE_HASH_SHIFT)
 660
 661 static struct list_head *m2p_overrides;
 662 static DEFINE_SPINLOCK(m2p_override_lock);
 663
 664 static void __init m2p_override_init(void)
 665 {
 666         unsigned i;
 667
 668         m2p_overrides = alloc_bootmem_align(
 669                                 sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
 670                                 sizeof(unsigned long));
 671
 672         for (i = 0; i < M2P_OVERRIDE_HASH; i++)
 673                 INIT_LIST_HEAD(&m2p_overrides[i]);
 674 }
 675
 676 static unsigned long mfn_hash(unsigned long mfn)
 677 {
 678         return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
 679 }
 680
 681 /* Add an MFN override for a particular page */
 682 static int m2p_add_override(unsigned long mfn, struct page *page,
 683                             struct gnttab_map_grant_ref *kmap_op)
 684 {
 685         unsigned long flags;
 686         unsigned long pfn;
 687         unsigned long uninitialized_var(address);
 688         unsigned level;
 689         pte_t *ptep = NULL;
 690
 691         pfn = page_to_pfn(page);
 692         if (!PageHighMem(page)) {
 693                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
 694                 ptep = lookup_address(address, &level);
 695                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
 696                          "m2p_add_override: pfn %lx not mapped", pfn))
 697                         return -EINVAL;
 698         }
 699
 700         if (kmap_op != NULL) {
 701                 if (!PageHighMem(page)) {
 702                         struct multicall_space mcs =
 703                                 xen_mc_entry(sizeof(*kmap_op));
 704
 705                         MULTI_grant_table_op(mcs.mc,
 706                                         GNTTABOP_map_grant_ref, kmap_op, 1);
 707
 708                         xen_mc_issue(PARAVIRT_LAZY_MMU);
 709                 }
 710         }
 711         spin_lock_irqsave(&m2p_override_lock, flags);
 712         list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
 713         spin_unlock_irqrestore(&m2p_override_lock, flags);
 714
 715         /* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
 716          * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
 717          * pfn so that the following mfn_to_pfn(mfn) calls will return the
 718          * pfn from the m2p_override (the backend pfn) instead.
 719          * We need to do this because the pages shared by the frontend
 720          * (xen-blkfront) can be already locked (lock_page, called by
 721          * do_read_cache_page); when the userspace backend tries to use them
 722          * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
 723          * do_blockdev_direct_IO is going to try to lock the same pages
 724          * again resulting in a deadlock.
 725          * As a side effect get_user_pages_fast might not be safe on the
 726          * frontend pages while they are being shared with the backend,
 727          * because mfn_to_pfn (that ends up being called by GUPF) will
 728          * return the backend pfn rather than the frontend pfn. */
 729         pfn = mfn_to_pfn_no_overrides(mfn);
 730         if (__pfn_to_mfn(pfn) == mfn)
 731                 set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
 732
 733         return 0;
 734 }
 735
 736 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 737                             struct gnttab_map_grant_ref *kmap_ops,
 738                             struct page **pages, unsigned int count)
 739 {
 740         int i, ret = 0;
 741         bool lazy = false;
 742         pte_t *pte;
 743
 744         if (xen_feature(XENFEAT_auto_translated_physmap))
 745                 return 0;
 746
 747         if (kmap_ops &&
 748             !in_interrupt() &&
 749             paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
 750                 arch_enter_lazy_mmu_mode();
 751                 lazy = true;
 752         }
 753
 754         for (i = 0; i < count; i++) {
 755                 unsigned long mfn, pfn;
 756
 757                 /* Do not add to override if the map failed. */
 758                 if (map_ops[i].status)
 759                         continue;
 760
 761                 if (map_ops[i].flags & GNTMAP_contains_pte) {
 762                         pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
 763                                 (map_ops[i].host_addr & ~PAGE_MASK));
 764                         mfn = pte_mfn(*pte);
 765                 } else {
 766                         mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 767                 }
 768                 pfn = page_to_pfn(pages[i]);
 769
 770                 WARN_ON(PagePrivate(pages[i]));
 771                 SetPagePrivate(pages[i]);
 772                 set_page_private(pages[i], mfn);
 773                 pages[i]->index = pfn_to_mfn(pfn);
 774
 775                 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
 776                         ret = -ENOMEM;
 777                         goto out;
 778                 }
 779
 780                 if (kmap_ops) {
 781                         ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
 782                         if (ret)
 783                                 goto out;
 784                 }
 785         }
 786
 787 out:
 788         if (lazy)
 789                 arch_leave_lazy_mmu_mode();
 790
 791         return ret;
 792 }
 793 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
 794
 795 static struct page *m2p_find_override(unsigned long mfn)
 796 {
 797         unsigned long flags;
 798         struct list_head *bucket;
 799         struct page *p, *ret;
 800
 801         if (unlikely(!m2p_overrides))
 802                 return NULL;
 803
 804         ret = NULL;
 805         bucket = &m2p_overrides[mfn_hash(mfn)];
 806
 807         spin_lock_irqsave(&m2p_override_lock, flags);
 808
 809         list_for_each_entry(p, bucket, lru) {
 810                 if (page_private(p) == mfn) {
 811                         ret = p;
 812                         break;
 813                 }
 814         }
 815
 816         spin_unlock_irqrestore(&m2p_override_lock, flags);
 817
 818         return ret;
 819 }
 820
 821 static int m2p_remove_override(struct page *page,
 822                                struct gnttab_map_grant_ref *kmap_op,
 823                                unsigned long mfn)
 824 {
 825         unsigned long flags;
 826         unsigned long pfn;
 827         unsigned long uninitialized_var(address);
 828         unsigned level;
 829         pte_t *ptep = NULL;
 830
 831         pfn = page_to_pfn(page);
 832
 833         if (!PageHighMem(page)) {
 834                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
 835                 ptep = lookup_address(address, &level);
 836
 837                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
 838                          "m2p_remove_override: pfn %lx not mapped", pfn))
 839                         return -EINVAL;
 840         }
 841
 842         spin_lock_irqsave(&m2p_override_lock, flags);
 843         list_del(&page->lru);
 844         spin_unlock_irqrestore(&m2p_override_lock, flags);
 845
 846         if (kmap_op != NULL) {
 847                 if (!PageHighMem(page)) {
 848                         struct multicall_space mcs;
 849                         struct gnttab_unmap_and_replace *unmap_op;
 850                         struct page *scratch_page = get_balloon_scratch_page();
 851                         unsigned long scratch_page_address = (unsigned long)
 852                                 __va(page_to_pfn(scratch_page) << PAGE_SHIFT);
 853
 854                         /*
 855                          * It might be that we queued all the m2p grant table
 856                          * hypercalls in a multicall, then m2p_remove_override
 857                          * get called before the multicall has actually been
 858                          * issued. In this case handle is going to -1 because
 859                          * it hasn't been modified yet.
 860                          */
 861                         if (kmap_op->handle == -1)
 862                                 xen_mc_flush();
 863                         /*
 864                          * Now if kmap_op->handle is negative it means that the
 865                          * hypercall actually returned an error.
 866                          */
 867                         if (kmap_op->handle == GNTST_general_error) {
 868                                 pr_warn("m2p_remove_override: pfn %lx mfn %lx, failed to modify kernel mappings",
 869                                         pfn, mfn);
 870                                 put_balloon_scratch_page();
 871                                 return -1;
 872                         }
 873
 874                         xen_mc_batch();
 875
 876                         mcs = __xen_mc_entry(
 877                                 sizeof(struct gnttab_unmap_and_replace));
 878                         unmap_op = mcs.args;
 879                         unmap_op->host_addr = kmap_op->host_addr;
 880                         unmap_op->new_addr = scratch_page_address;
 881                         unmap_op->handle = kmap_op->handle;
 882
 883                         MULTI_grant_table_op(mcs.mc,
 884                                 GNTTABOP_unmap_and_replace, unmap_op, 1);
 885
 886                         mcs = __xen_mc_entry(0);
 887                         MULTI_update_va_mapping(mcs.mc, scratch_page_address,
 888                                         pfn_pte(page_to_pfn(scratch_page),
 889                                         PAGE_KERNEL_RO), 0);
 890
 891                         xen_mc_issue(PARAVIRT_LAZY_MMU);
 892
 893                         kmap_op->host_addr = 0;
 894                         put_balloon_scratch_page();
 895                 }
 896         }
 897
 898         /* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present
 899          * somewhere in this domain, even before being added to the
 900          * m2p_override (see comment above in m2p_add_override).
 901          * If there are no other entries in the m2p_override corresponding
 902          * to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for
 903          * the original pfn (the one shared by the frontend): the backend
 904          * cannot do any IO on this page anymore because it has been
 905          * unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of
 906          * the original pfn causes mfn_to_pfn(mfn) to return the frontend
 907          * pfn again. */
 908         mfn &= ~FOREIGN_FRAME_BIT;
 909         pfn = mfn_to_pfn_no_overrides(mfn);
 910         if (__pfn_to_mfn(pfn) == FOREIGN_FRAME(mfn) &&
 911                         m2p_find_override(mfn) == NULL)
 912                 set_phys_to_machine(pfn, mfn);
 913
 914         return 0;
 915 }
 916
 917 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 918                               struct gnttab_map_grant_ref *kmap_ops,
 919                               struct page **pages, unsigned int count)
 920 {
 921         int i, ret = 0;
 922         bool lazy = false;
 923
 924         if (xen_feature(XENFEAT_auto_translated_physmap))
 925                 return 0;
 926
 927         if (kmap_ops &&
 928             !in_interrupt() &&
 929             paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
 930                 arch_enter_lazy_mmu_mode();
 931                 lazy = true;
 932         }
 933
 934         for (i = 0; i < count; i++) {
 935                 unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
 936                 unsigned long pfn = page_to_pfn(pages[i]);
 937
 938                 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
 939                         ret = -EINVAL;
 940                         goto out;
 941                 }
 942
 943                 set_page_private(pages[i], INVALID_P2M_ENTRY);
 944                 WARN_ON(!PagePrivate(pages[i]));
 945                 ClearPagePrivate(pages[i]);
 946                 set_phys_to_machine(pfn, pages[i]->index);
 947
 948                 if (kmap_ops)
 949                         ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
 950                 if (ret)
 951                         goto out;
 952         }
 953
 954 out:
 955         if (lazy)
 956                 arch_leave_lazy_mmu_mode();
 957         return ret;
 958 }
 959 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
 960
 961 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
 962 {
 963         struct page *p = m2p_find_override(mfn);
 964         unsigned long ret = pfn;
 965
 966         if (p)
 967                 ret = page_to_pfn(p);
 968
 969         return ret;
 970 }
 971 EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
 972
 973 #ifdef CONFIG_XEN_DEBUG_FS
 974 #include <linux/debugfs.h>
 975 #include "debugfs.h"
 976 static int p2m_dump_show(struct seq_file *m, void *v)
 977 {
 978         static const char * const type_name[] = {
 979                                 [P2M_TYPE_IDENTITY] = "identity",
 980                                 [P2M_TYPE_MISSING] = "missing",
 981                                 [P2M_TYPE_PFN] = "pfn",
 982                                 [P2M_TYPE_UNKNOWN] = "abnormal"};
 983         unsigned long pfn, first_pfn;
 984         int type, prev_type;
 985
 986         prev_type = xen_p2m_elem_type(0);
 987         first_pfn = 0;
 988
 989         for (pfn = 0; pfn < xen_p2m_size; pfn++) {
 990                 type = xen_p2m_elem_type(pfn);
 991                 if (type != prev_type) {
 992                         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
 993                                    type_name[prev_type]);
 994                         prev_type = type;
 995                         first_pfn = pfn;
 996                 }
 997         }
 998         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
 999                    type_name[prev_type]);
1000         return 0;
1001 }
1002
1003 static int p2m_dump_open(struct inode *inode, struct file *filp)
1004 {
1005         return single_open(filp, p2m_dump_show, NULL);
1006 }
1007
1008 static const struct file_operations p2m_dump_fops = {
1009         .open           = p2m_dump_open,
1010         .read           = seq_read,
1011         .llseek         = seq_lseek,
1012         .release        = single_release,
1013 };
1014
1015 static struct dentry *d_mmu_debug;
1016
1017 static int __init xen_p2m_debugfs(void)
1018 {
1019         struct dentry *d_xen = xen_init_debugfs();
1020
1021         if (d_xen == NULL)
1022                 return -ENOMEM;
1023
1024         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
1025
1026         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
1027         return 0;
1028 }
1029 fs_initcall(xen_p2m_debugfs);
1030 #endif /* CONFIG_XEN_DEBUG_FS */