arch/x86/xen/p2m.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 /*
   4  * Xen leaves the responsibility for maintaining p2m mappings to the
   5  * guests themselves, but it must also access and update the p2m array
   6  * during suspend/resume when all the pages are reallocated.
   7  *
   8  * The logical flat p2m table is mapped to a linear kernel memory area.
   9  * For accesses by Xen a three-level tree linked via mfns only is set up to
  10  * allow the address space to be sparse.
  11  *
  12  *               Xen
  13  *                |
  14  *          p2m_top_mfn
  15  *              /   \
  16  * p2m_mid_mfn p2m_mid_mfn
  17  *         /           /
  18  *  p2m p2m p2m ...
  19  *
  20  * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
  21  *
  22  * The p2m_top_mfn level is limited to 1 page, so the maximum representable
  23  * pseudo-physical address space is:
  24  *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
  25  *
  26  * P2M_PER_PAGE depends on the architecture, as a mfn is always
  27  * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
  28  * 512 and 1024 entries respectively.
  29  *
  30  * In short, these structures contain the Machine Frame Number (MFN) of the PFN.
  31  *
  32  * However not all entries are filled with MFNs. Specifically for all other
  33  * leaf entries, or for the top  root, or middle one, for which there is a void
  34  * entry, we assume it is  "missing". So (for example)
  35  *  pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
  36  * We have a dedicated page p2m_missing with all entries being
  37  * INVALID_P2M_ENTRY. This page may be referenced multiple times in the p2m
  38  * list/tree in case there are multiple areas with P2M_PER_PAGE invalid pfns.
  39  *
  40  * We also have the possibility of setting 1-1 mappings on certain regions, so
  41  * that:
  42  *  pfn_to_mfn(0xc0000)=0xc0000
  43  *
  44  * The benefit of this is, that we can assume for non-RAM regions (think
  45  * PCI BARs, or ACPI spaces), we can create mappings easily because we
  46  * get the PFN value to match the MFN.
  47  *
  48  * For this to work efficiently we have one new page p2m_identity. All entries
  49  * in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only
  50  * recognizes that and MFNs, no other fancy value).
  51  *
  52  * On lookup we spot that the entry points to p2m_identity and return the
  53  * identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
  54  * If the entry points to an allocated page, we just proceed as before and
  55  * return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in
  56  * appropriate functions (pfn_to_mfn).
  57  *
  58  * The reason for having the IDENTITY_FRAME_BIT instead of just returning the
  59  * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
  60  * non-identity pfn. To protect ourselves against we elect to set (and get) the
  61  * IDENTITY_FRAME_BIT on all identity mapped PFNs.
  62  */
  63
  64 #include <linux/init.h>
  65 #include <linux/export.h>
  66 #include <linux/list.h>
  67 #include <linux/hash.h>
  68 #include <linux/sched.h>
  69 #include <linux/seq_file.h>
  70 #include <linux/memblock.h>
  71 #include <linux/slab.h>
  72 #include <linux/vmalloc.h>
  73
  74 #include <asm/cache.h>
  75 #include <asm/setup.h>
  76 #include <linux/uaccess.h>
  77
  78 #include <asm/xen/page.h>
  79 #include <asm/xen/hypercall.h>
  80 #include <asm/xen/hypervisor.h>
  81 #include <xen/balloon.h>
  82 #include <xen/grant_table.h>
  83
  84 #include "multicalls.h"
  85 #include "xen-ops.h"
  86
  87 #define P2M_MID_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long *))
  88 #define P2M_TOP_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long **))
  89
  90 #define MAX_P2M_PFN     (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
  91
  92 #define PMDS_PER_MID_PAGE       (P2M_MID_PER_PAGE / PTRS_PER_PTE)
  93
  94 unsigned long *xen_p2m_addr __read_mostly;
  95 EXPORT_SYMBOL_GPL(xen_p2m_addr);
  96 unsigned long xen_p2m_size __read_mostly;
  97 EXPORT_SYMBOL_GPL(xen_p2m_size);
  98 unsigned long xen_max_p2m_pfn __read_mostly;
  99 EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
 100
 101 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
 102 #define P2M_LIMIT CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
 103 #else
 104 #define P2M_LIMIT 0
 105 #endif
 106
 107 static DEFINE_SPINLOCK(p2m_update_lock);
 108
 109 static unsigned long *p2m_mid_missing_mfn;
 110 static unsigned long *p2m_top_mfn;
 111 static unsigned long **p2m_top_mfn_p;
 112 static unsigned long *p2m_missing;
 113 static unsigned long *p2m_identity;
 114 static pte_t *p2m_missing_pte;
 115 static pte_t *p2m_identity_pte;
 116
 117 /*
 118  * Hint at last populated PFN.
 119  *
 120  * Used to set HYPERVISOR_shared_info->arch.max_pfn so the toolstack
 121  * can avoid scanning the whole P2M (which may be sized to account for
 122  * hotplugged memory).
 123  */
 124 static unsigned long xen_p2m_last_pfn;
 125
 126 static inline unsigned p2m_top_index(unsigned long pfn)
 127 {
 128         BUG_ON(pfn >= MAX_P2M_PFN);
 129         return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
 130 }
 131
 132 static inline unsigned p2m_mid_index(unsigned long pfn)
 133 {
 134         return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
 135 }
 136
 137 static inline unsigned p2m_index(unsigned long pfn)
 138 {
 139         return pfn % P2M_PER_PAGE;
 140 }
 141
 142 static void p2m_top_mfn_init(unsigned long *top)
 143 {
 144         unsigned i;
 145
 146         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 147                 top[i] = virt_to_mfn(p2m_mid_missing_mfn);
 148 }
 149
 150 static void p2m_top_mfn_p_init(unsigned long **top)
 151 {
 152         unsigned i;
 153
 154         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 155                 top[i] = p2m_mid_missing_mfn;
 156 }
 157
 158 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
 159 {
 160         unsigned i;
 161
 162         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 163                 mid[i] = virt_to_mfn(leaf);
 164 }
 165
 166 static void p2m_init(unsigned long *p2m)
 167 {
 168         unsigned i;
 169
 170         for (i = 0; i < P2M_PER_PAGE; i++)
 171                 p2m[i] = INVALID_P2M_ENTRY;
 172 }
 173
 174 static void p2m_init_identity(unsigned long *p2m, unsigned long pfn)
 175 {
 176         unsigned i;
 177
 178         for (i = 0; i < P2M_PER_PAGE; i++)
 179                 p2m[i] = IDENTITY_FRAME(pfn + i);
 180 }
 181
 182 static void * __ref alloc_p2m_page(void)
 183 {
 184         if (unlikely(!slab_is_available())) {
 185                 void *ptr = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
 186
 187                 if (!ptr)
 188                         panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
 189                               __func__, PAGE_SIZE, PAGE_SIZE);
 190
 191                 return ptr;
 192         }
 193
 194         return (void *)__get_free_page(GFP_KERNEL);
 195 }
 196
 197 static void __ref free_p2m_page(void *p)
 198 {
 199         if (unlikely(!slab_is_available())) {
 200                 memblock_free((unsigned long)p, PAGE_SIZE);
 201                 return;
 202         }
 203
 204         free_page((unsigned long)p);
 205 }
 206
 207 /*
 208  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
 209  *
 210  * This is called both at boot time, and after resuming from suspend:
 211  * - At boot time we're called rather early, and must use alloc_bootmem*()
 212  *   to allocate memory.
 213  *
 214  * - After resume we're called from within stop_machine, but the mfn
 215  *   tree should already be completely allocated.
 216  */
 217 void __ref xen_build_mfn_list_list(void)
 218 {
 219         unsigned long pfn, mfn;
 220         pte_t *ptep;
 221         unsigned int level, topidx, mididx;
 222         unsigned long *mid_mfn_p;
 223
 224         if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
 225                 return;
 226
 227         /* Pre-initialize p2m_top_mfn to be completely missing */
 228         if (p2m_top_mfn == NULL) {
 229                 p2m_mid_missing_mfn = alloc_p2m_page();
 230                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 231
 232                 p2m_top_mfn_p = alloc_p2m_page();
 233                 p2m_top_mfn_p_init(p2m_top_mfn_p);
 234
 235                 p2m_top_mfn = alloc_p2m_page();
 236                 p2m_top_mfn_init(p2m_top_mfn);
 237         } else {
 238                 /* Reinitialise, mfn's all change after migration */
 239                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 240         }
 241
 242         for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
 243              pfn += P2M_PER_PAGE) {
 244                 topidx = p2m_top_index(pfn);
 245                 mididx = p2m_mid_index(pfn);
 246
 247                 mid_mfn_p = p2m_top_mfn_p[topidx];
 248                 ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn),
 249                                       &level);
 250                 BUG_ON(!ptep || level != PG_LEVEL_4K);
 251                 mfn = pte_mfn(*ptep);
 252                 ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 253
 254                 /* Don't bother allocating any mfn mid levels if
 255                  * they're just missing, just update the stored mfn,
 256                  * since all could have changed over a migrate.
 257                  */
 258                 if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) {
 259                         BUG_ON(mididx);
 260                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 261                         p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
 262                         pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
 263                         continue;
 264                 }
 265
 266                 if (mid_mfn_p == p2m_mid_missing_mfn) {
 267                         mid_mfn_p = alloc_p2m_page();
 268                         p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
 269
 270                         p2m_top_mfn_p[topidx] = mid_mfn_p;
 271                 }
 272
 273                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
 274                 mid_mfn_p[mididx] = mfn;
 275         }
 276 }
 277
 278 void xen_setup_mfn_list_list(void)
 279 {
 280         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
 281
 282         if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
 283                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = ~0UL;
 284         else
 285                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
 286                         virt_to_mfn(p2m_top_mfn);
 287         HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
 288         HYPERVISOR_shared_info->arch.p2m_generation = 0;
 289         HYPERVISOR_shared_info->arch.p2m_vaddr = (unsigned long)xen_p2m_addr;
 290         HYPERVISOR_shared_info->arch.p2m_cr3 =
 291                 xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
 292 }
 293
 294 /* Set up p2m_top to point to the domain-builder provided p2m pages */
 295 void __init xen_build_dynamic_phys_to_machine(void)
 296 {
 297         unsigned long pfn;
 298
 299         xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
 300         xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE);
 301
 302         for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++)
 303                 xen_p2m_addr[pfn] = INVALID_P2M_ENTRY;
 304
 305         xen_max_p2m_pfn = xen_p2m_size;
 306 }
 307
 308 #define P2M_TYPE_IDENTITY       0
 309 #define P2M_TYPE_MISSING        1
 310 #define P2M_TYPE_PFN            2
 311 #define P2M_TYPE_UNKNOWN        3
 312
 313 static int xen_p2m_elem_type(unsigned long pfn)
 314 {
 315         unsigned long mfn;
 316
 317         if (pfn >= xen_p2m_size)
 318                 return P2M_TYPE_IDENTITY;
 319
 320         mfn = xen_p2m_addr[pfn];
 321
 322         if (mfn == INVALID_P2M_ENTRY)
 323                 return P2M_TYPE_MISSING;
 324
 325         if (mfn & IDENTITY_FRAME_BIT)
 326                 return P2M_TYPE_IDENTITY;
 327
 328         return P2M_TYPE_PFN;
 329 }
 330
 331 static void __init xen_rebuild_p2m_list(unsigned long *p2m)
 332 {
 333         unsigned int i, chunk;
 334         unsigned long pfn;
 335         unsigned long *mfns;
 336         pte_t *ptep;
 337         pmd_t *pmdp;
 338         int type;
 339
 340         p2m_missing = alloc_p2m_page();
 341         p2m_init(p2m_missing);
 342         p2m_identity = alloc_p2m_page();
 343         p2m_init(p2m_identity);
 344
 345         p2m_missing_pte = alloc_p2m_page();
 346         paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
 347         p2m_identity_pte = alloc_p2m_page();
 348         paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
 349         for (i = 0; i < PTRS_PER_PTE; i++) {
 350                 set_pte(p2m_missing_pte + i,
 351                         pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
 352                 set_pte(p2m_identity_pte + i,
 353                         pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
 354         }
 355
 356         for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
 357                 /*
 358                  * Try to map missing/identity PMDs or p2m-pages if possible.
 359                  * We have to respect the structure of the mfn_list_list
 360                  * which will be built just afterwards.
 361                  * Chunk size to test is one p2m page if we are in the middle
 362                  * of a mfn_list_list mid page and the complete mid page area
 363                  * if we are at index 0 of the mid page. Please note that a
 364                  * mid page might cover more than one PMD, e.g. on 32 bit PAE
 365                  * kernels.
 366                  */
 367                 chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
 368                         P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;
 369
 370                 type = xen_p2m_elem_type(pfn);
 371                 i = 0;
 372                 if (type != P2M_TYPE_PFN)
 373                         for (i = 1; i < chunk; i++)
 374                                 if (xen_p2m_elem_type(pfn + i) != type)
 375                                         break;
 376                 if (i < chunk)
 377                         /* Reset to minimal chunk size. */
 378                         chunk = P2M_PER_PAGE;
 379
 380                 if (type == P2M_TYPE_PFN || i < chunk) {
 381                         /* Use initial p2m page contents. */
 382                         mfns = alloc_p2m_page();
 383                         copy_page(mfns, xen_p2m_addr + pfn);
 384                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
 385                         set_pte(ptep,
 386                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
 387                         continue;
 388                 }
 389
 390                 if (chunk == P2M_PER_PAGE) {
 391                         /* Map complete missing or identity p2m-page. */
 392                         mfns = (type == P2M_TYPE_MISSING) ?
 393                                 p2m_missing : p2m_identity;
 394                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
 395                         set_pte(ptep,
 396                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
 397                         continue;
 398                 }
 399
 400                 /* Complete missing or identity PMD(s) can be mapped. */
 401                 ptep = (type == P2M_TYPE_MISSING) ?
 402                         p2m_missing_pte : p2m_identity_pte;
 403                 for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 404                         pmdp = populate_extra_pmd(
 405                                 (unsigned long)(p2m + pfn) + i * PMD_SIZE);
 406                         set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
 407                 }
 408         }
 409 }
 410
 411 void __init xen_vmalloc_p2m_tree(void)
 412 {
 413         static struct vm_struct vm;
 414         unsigned long p2m_limit;
 415
 416         xen_p2m_last_pfn = xen_max_p2m_pfn;
 417
 418         p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 / PAGE_SIZE;
 419         vm.flags = VM_ALLOC;
 420         vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn, p2m_limit),
 421                         PMD_SIZE * PMDS_PER_MID_PAGE);
 422         vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
 423         pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
 424
 425         xen_max_p2m_pfn = vm.size / sizeof(unsigned long);
 426
 427         xen_rebuild_p2m_list(vm.addr);
 428
 429         xen_p2m_addr = vm.addr;
 430         xen_p2m_size = xen_max_p2m_pfn;
 431
 432         xen_inv_extra_mem();
 433 }
 434
 435 unsigned long get_phys_to_machine(unsigned long pfn)
 436 {
 437         pte_t *ptep;
 438         unsigned int level;
 439
 440         if (unlikely(pfn >= xen_p2m_size)) {
 441                 if (pfn < xen_max_p2m_pfn)
 442                         return xen_chk_extra_mem(pfn);
 443
 444                 return IDENTITY_FRAME(pfn);
 445         }
 446
 447         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
 448         BUG_ON(!ptep || level != PG_LEVEL_4K);
 449
 450         /*
 451          * The INVALID_P2M_ENTRY is filled in both p2m_*identity
 452          * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
 453          * would be wrong.
 454          */
 455         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 456                 return IDENTITY_FRAME(pfn);
 457
 458         return xen_p2m_addr[pfn];
 459 }
 460 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 461
 462 /*
 463  * Allocate new pmd(s). It is checked whether the old pmd is still in place.
 464  * If not, nothing is changed. This is okay as the only reason for allocating
 465  * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
 466  * pmd.
 467  */
 468 static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
 469 {
 470         pte_t *ptechk;
 471         pte_t *pte_newpg[PMDS_PER_MID_PAGE];
 472         pmd_t *pmdp;
 473         unsigned int level;
 474         unsigned long flags;
 475         unsigned long vaddr;
 476         int i;
 477
 478         /* Do all allocations first to bail out in error case. */
 479         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 480                 pte_newpg[i] = alloc_p2m_page();
 481                 if (!pte_newpg[i]) {
 482                         for (i--; i >= 0; i--)
 483                                 free_p2m_page(pte_newpg[i]);
 484
 485                         return NULL;
 486                 }
 487         }
 488
 489         vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);
 490
 491         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 492                 copy_page(pte_newpg[i], pte_pg);
 493                 paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);
 494
 495                 pmdp = lookup_pmd_address(vaddr);
 496                 BUG_ON(!pmdp);
 497
 498                 spin_lock_irqsave(&p2m_update_lock, flags);
 499
 500                 ptechk = lookup_address(vaddr, &level);
 501                 if (ptechk == pte_pg) {
 502                         HYPERVISOR_shared_info->arch.p2m_generation++;
 503                         wmb(); /* Tools are synchronizing via p2m_generation. */
 504                         set_pmd(pmdp,
 505                                 __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
 506                         wmb(); /* Tools are synchronizing via p2m_generation. */
 507                         HYPERVISOR_shared_info->arch.p2m_generation++;
 508                         pte_newpg[i] = NULL;
 509                 }
 510
 511                 spin_unlock_irqrestore(&p2m_update_lock, flags);
 512
 513                 if (pte_newpg[i]) {
 514                         paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
 515                         free_p2m_page(pte_newpg[i]);
 516                 }
 517
 518                 vaddr += PMD_SIZE;
 519         }
 520
 521         return lookup_address(addr, &level);
 522 }
 523
 524 /*
 525  * Fully allocate the p2m structure for a given pfn.  We need to check
 526  * that both the top and mid levels are allocated, and make sure the
 527  * parallel mfn tree is kept in sync.  We may race with other cpus, so
 528  * the new pages are installed with cmpxchg; if we lose the race then
 529  * simply free the page we allocated and use the one that's there.
 530  */
 531 int xen_alloc_p2m_entry(unsigned long pfn)
 532 {
 533         unsigned topidx;
 534         unsigned long *top_mfn_p, *mid_mfn;
 535         pte_t *ptep, *pte_pg;
 536         unsigned int level;
 537         unsigned long flags;
 538         unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
 539         unsigned long p2m_pfn;
 540
 541         ptep = lookup_address(addr, &level);
 542         BUG_ON(!ptep || level != PG_LEVEL_4K);
 543         pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 544
 545         if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
 546                 /* PMD level is missing, allocate a new one */
 547                 ptep = alloc_p2m_pmd(addr, pte_pg);
 548                 if (!ptep)
 549                         return -ENOMEM;
 550         }
 551
 552         if (p2m_top_mfn && pfn < MAX_P2M_PFN) {
 553                 topidx = p2m_top_index(pfn);
 554                 top_mfn_p = &p2m_top_mfn[topidx];
 555                 mid_mfn = READ_ONCE(p2m_top_mfn_p[topidx]);
 556
 557                 BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
 558
 559                 if (mid_mfn == p2m_mid_missing_mfn) {
 560                         /* Separately check the mid mfn level */
 561                         unsigned long missing_mfn;
 562                         unsigned long mid_mfn_mfn;
 563                         unsigned long old_mfn;
 564
 565                         mid_mfn = alloc_p2m_page();
 566                         if (!mid_mfn)
 567                                 return -ENOMEM;
 568
 569                         p2m_mid_mfn_init(mid_mfn, p2m_missing);
 570
 571                         missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
 572                         mid_mfn_mfn = virt_to_mfn(mid_mfn);
 573                         old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
 574                         if (old_mfn != missing_mfn) {
 575                                 free_p2m_page(mid_mfn);
 576                                 mid_mfn = mfn_to_virt(old_mfn);
 577                         } else {
 578                                 p2m_top_mfn_p[topidx] = mid_mfn;
 579                         }
 580                 }
 581         } else {
 582                 mid_mfn = NULL;
 583         }
 584
 585         p2m_pfn = pte_pfn(READ_ONCE(*ptep));
 586         if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
 587             p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
 588                 /* p2m leaf page is missing */
 589                 unsigned long *p2m;
 590
 591                 p2m = alloc_p2m_page();
 592                 if (!p2m)
 593                         return -ENOMEM;
 594
 595                 if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
 596                         p2m_init(p2m);
 597                 else
 598                         p2m_init_identity(p2m, pfn & ~(P2M_PER_PAGE - 1));
 599
 600                 spin_lock_irqsave(&p2m_update_lock, flags);
 601
 602                 if (pte_pfn(*ptep) == p2m_pfn) {
 603                         HYPERVISOR_shared_info->arch.p2m_generation++;
 604                         wmb(); /* Tools are synchronizing via p2m_generation. */
 605                         set_pte(ptep,
 606                                 pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
 607                         wmb(); /* Tools are synchronizing via p2m_generation. */
 608                         HYPERVISOR_shared_info->arch.p2m_generation++;
 609                         if (mid_mfn)
 610                                 mid_mfn[p2m_mid_index(pfn)] = virt_to_mfn(p2m);
 611                         p2m = NULL;
 612                 }
 613
 614                 spin_unlock_irqrestore(&p2m_update_lock, flags);
 615
 616                 if (p2m)
 617                         free_p2m_page(p2m);
 618         }
 619
 620         /* Expanded the p2m? */
 621         if (pfn > xen_p2m_last_pfn) {
 622                 xen_p2m_last_pfn = pfn;
 623                 HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
 624         }
 625
 626         return 0;
 627 }
 628 EXPORT_SYMBOL(xen_alloc_p2m_entry);
 629
 630 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 631                                       unsigned long pfn_e)
 632 {
 633         unsigned long pfn;
 634
 635         if (unlikely(pfn_s >= xen_p2m_size))
 636                 return 0;
 637
 638         if (pfn_s > pfn_e)
 639                 return 0;
 640
 641         if (pfn_e > xen_p2m_size)
 642                 pfn_e = xen_p2m_size;
 643
 644         for (pfn = pfn_s; pfn < pfn_e; pfn++)
 645                 xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);
 646
 647         return pfn - pfn_s;
 648 }
 649
 650 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 651 {
 652         pte_t *ptep;
 653         unsigned int level;
 654
 655         if (unlikely(pfn >= xen_p2m_size)) {
 656                 BUG_ON(mfn != INVALID_P2M_ENTRY);
 657                 return true;
 658         }
 659
 660         /*
 661          * The interface requires atomic updates on p2m elements.
 662          * xen_safe_write_ulong() is using an atomic store via asm().
 663          */
 664         if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
 665                 return true;
 666
 667         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
 668         BUG_ON(!ptep || level != PG_LEVEL_4K);
 669
 670         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
 671                 return mfn == INVALID_P2M_ENTRY;
 672
 673         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 674                 return mfn == IDENTITY_FRAME(pfn);
 675
 676         return false;
 677 }
 678
 679 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 680 {
 681         if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
 682                 int ret;
 683
 684                 ret = xen_alloc_p2m_entry(pfn);
 685                 if (ret < 0)
 686                         return false;
 687
 688                 return __set_phys_to_machine(pfn, mfn);
 689         }
 690
 691         return true;
 692 }
 693
 694 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 695                             struct gnttab_map_grant_ref *kmap_ops,
 696                             struct page **pages, unsigned int count)
 697 {
 698         int i, ret = 0;
 699         pte_t *pte;
 700
 701         if (xen_feature(XENFEAT_auto_translated_physmap))
 702                 return 0;
 703
 704         if (kmap_ops) {
 705                 ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
 706                                                 kmap_ops, count);
 707                 if (ret)
 708                         goto out;
 709         }
 710
 711         for (i = 0; i < count; i++) {
 712                 unsigned long mfn, pfn;
 713
 714                 /* Do not add to override if the map failed. */
 715                 if (map_ops[i].status)
 716                         continue;
 717
 718                 if (map_ops[i].flags & GNTMAP_contains_pte) {
 719                         pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
 720                                 (map_ops[i].host_addr & ~PAGE_MASK));
 721                         mfn = pte_mfn(*pte);
 722                 } else {
 723                         mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 724                 }
 725                 pfn = page_to_pfn(pages[i]);
 726
 727                 WARN(pfn_to_mfn(pfn) != INVALID_P2M_ENTRY, "page must be ballooned");
 728
 729                 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
 730                         ret = -ENOMEM;
 731                         goto out;
 732                 }
 733         }
 734
 735 out:
 736         return ret;
 737 }
 738 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
 739
 740 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 741                               struct gnttab_unmap_grant_ref *kunmap_ops,
 742                               struct page **pages, unsigned int count)
 743 {
 744         int i, ret = 0;
 745
 746         if (xen_feature(XENFEAT_auto_translated_physmap))
 747                 return 0;
 748
 749         for (i = 0; i < count; i++) {
 750                 unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
 751                 unsigned long pfn = page_to_pfn(pages[i]);
 752
 753                 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
 754                         ret = -EINVAL;
 755                         goto out;
 756                 }
 757
 758                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 759         }
 760         if (kunmap_ops)
 761                 ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
 762                                                 kunmap_ops, count);
 763 out:
 764         return ret;
 765 }
 766 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
 767
 768 #ifdef CONFIG_XEN_DEBUG_FS
 769 #include <linux/debugfs.h>
 770 #include "debugfs.h"
 771 static int p2m_dump_show(struct seq_file *m, void *v)
 772 {
 773         static const char * const type_name[] = {
 774                                 [P2M_TYPE_IDENTITY] = "identity",
 775                                 [P2M_TYPE_MISSING] = "missing",
 776                                 [P2M_TYPE_PFN] = "pfn",
 777                                 [P2M_TYPE_UNKNOWN] = "abnormal"};
 778         unsigned long pfn, first_pfn;
 779         int type, prev_type;
 780
 781         prev_type = xen_p2m_elem_type(0);
 782         first_pfn = 0;
 783
 784         for (pfn = 0; pfn < xen_p2m_size; pfn++) {
 785                 type = xen_p2m_elem_type(pfn);
 786                 if (type != prev_type) {
 787                         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
 788                                    type_name[prev_type]);
 789                         prev_type = type;
 790                         first_pfn = pfn;
 791                 }
 792         }
 793         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
 794                    type_name[prev_type]);
 795         return 0;
 796 }
 797
 798 static int p2m_dump_open(struct inode *inode, struct file *filp)
 799 {
 800         return single_open(filp, p2m_dump_show, NULL);
 801 }
 802
 803 static const struct file_operations p2m_dump_fops = {
 804         .open           = p2m_dump_open,
 805         .read           = seq_read,
 806         .llseek         = seq_lseek,
 807         .release        = single_release,
 808 };
 809
 810 static struct dentry *d_mmu_debug;
 811
 812 static int __init xen_p2m_debugfs(void)
 813 {
 814         struct dentry *d_xen = xen_init_debugfs();
 815
 816         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
 817
 818         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
 819         return 0;
 820 }
 821 fs_initcall(xen_p2m_debugfs);
 822 #endif /* CONFIG_XEN_DEBUG_FS */