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 #include <linux/acpi.h>
  74
  75 #include <asm/cache.h>
  76 #include <asm/setup.h>
  77 #include <linux/uaccess.h>
  78
  79 #include <asm/xen/page.h>
  80 #include <asm/xen/hypercall.h>
  81 #include <asm/xen/hypervisor.h>
  82 #include <xen/balloon.h>
  83 #include <xen/grant_table.h>
  84 #include <xen/hvc-console.h>
  85
  86 #include "xen-ops.h"
  87
  88 #define P2M_MID_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long *))
  89 #define P2M_TOP_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long **))
  90
  91 #define MAX_P2M_PFN     (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
  92
  93 #define PMDS_PER_MID_PAGE       (P2M_MID_PER_PAGE / PTRS_PER_PTE)
  94
  95 unsigned long *xen_p2m_addr __read_mostly;
  96 EXPORT_SYMBOL_GPL(xen_p2m_addr);
  97 unsigned long xen_p2m_size __read_mostly;
  98 EXPORT_SYMBOL_GPL(xen_p2m_size);
  99 unsigned long xen_max_p2m_pfn __read_mostly;
 100 EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
 101
 102 #ifdef CONFIG_XEN_MEMORY_HOTPLUG_LIMIT
 103 #define P2M_LIMIT CONFIG_XEN_MEMORY_HOTPLUG_LIMIT
 104 #else
 105 #define P2M_LIMIT 0
 106 #endif
 107
 108 static DEFINE_SPINLOCK(p2m_update_lock);
 109
 110 static unsigned long *p2m_mid_missing_mfn;
 111 static unsigned long *p2m_top_mfn;
 112 static unsigned long **p2m_top_mfn_p;
 113 static unsigned long *p2m_missing;
 114 static unsigned long *p2m_identity;
 115 static pte_t *p2m_missing_pte;
 116 static pte_t *p2m_identity_pte;
 117
 118 /*
 119  * Hint at last populated PFN.
 120  *
 121  * Used to set HYPERVISOR_shared_info->arch.max_pfn so the toolstack
 122  * can avoid scanning the whole P2M (which may be sized to account for
 123  * hotplugged memory).
 124  */
 125 static unsigned long xen_p2m_last_pfn;
 126
 127 static inline unsigned p2m_top_index(unsigned long pfn)
 128 {
 129         BUG_ON(pfn >= MAX_P2M_PFN);
 130         return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
 131 }
 132
 133 static inline unsigned p2m_mid_index(unsigned long pfn)
 134 {
 135         return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
 136 }
 137
 138 static void p2m_top_mfn_init(unsigned long *top)
 139 {
 140         unsigned i;
 141
 142         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 143                 top[i] = virt_to_mfn(p2m_mid_missing_mfn);
 144 }
 145
 146 static void p2m_top_mfn_p_init(unsigned long **top)
 147 {
 148         unsigned i;
 149
 150         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 151                 top[i] = p2m_mid_missing_mfn;
 152 }
 153
 154 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
 155 {
 156         unsigned i;
 157
 158         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 159                 mid[i] = virt_to_mfn(leaf);
 160 }
 161
 162 static void p2m_init(unsigned long *p2m)
 163 {
 164         unsigned i;
 165
 166         for (i = 0; i < P2M_PER_PAGE; i++)
 167                 p2m[i] = INVALID_P2M_ENTRY;
 168 }
 169
 170 static void p2m_init_identity(unsigned long *p2m, unsigned long pfn)
 171 {
 172         unsigned i;
 173
 174         for (i = 0; i < P2M_PER_PAGE; i++)
 175                 p2m[i] = IDENTITY_FRAME(pfn + i);
 176 }
 177
 178 static void * __ref alloc_p2m_page(void)
 179 {
 180         if (unlikely(!slab_is_available())) {
 181                 void *ptr = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
 182
 183                 if (!ptr)
 184                         panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
 185                               __func__, PAGE_SIZE, PAGE_SIZE);
 186
 187                 return ptr;
 188         }
 189
 190         return (void *)__get_free_page(GFP_KERNEL);
 191 }
 192
 193 static void __ref free_p2m_page(void *p)
 194 {
 195         if (unlikely(!slab_is_available())) {
 196                 memblock_free(p, PAGE_SIZE);
 197                 return;
 198         }
 199
 200         free_page((unsigned long)p);
 201 }
 202
 203 /*
 204  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
 205  *
 206  * This is called both at boot time, and after resuming from suspend:
 207  * - At boot time we're called rather early, and must use alloc_bootmem*()
 208  *   to allocate memory.
 209  *
 210  * - After resume we're called from within stop_machine, but the mfn
 211  *   tree should already be completely allocated.
 212  */
 213 void __ref xen_build_mfn_list_list(void)
 214 {
 215         unsigned long pfn, mfn;
 216         pte_t *ptep;
 217         unsigned int level, topidx, mididx;
 218         unsigned long *mid_mfn_p;
 219
 220         if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
 221                 return;
 222
 223         /* Pre-initialize p2m_top_mfn to be completely missing */
 224         if (p2m_top_mfn == NULL) {
 225                 p2m_mid_missing_mfn = alloc_p2m_page();
 226                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 227
 228                 p2m_top_mfn_p = alloc_p2m_page();
 229                 p2m_top_mfn_p_init(p2m_top_mfn_p);
 230
 231                 p2m_top_mfn = alloc_p2m_page();
 232                 p2m_top_mfn_init(p2m_top_mfn);
 233         } else {
 234                 /* Reinitialise, mfn's all change after migration */
 235                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 236         }
 237
 238         for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
 239              pfn += P2M_PER_PAGE) {
 240                 topidx = p2m_top_index(pfn);
 241                 mididx = p2m_mid_index(pfn);
 242
 243                 mid_mfn_p = p2m_top_mfn_p[topidx];
 244                 ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn),
 245                                       &level);
 246                 BUG_ON(!ptep || level != PG_LEVEL_4K);
 247                 mfn = pte_mfn(*ptep);
 248                 ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 249
 250                 /* Don't bother allocating any mfn mid levels if
 251                  * they're just missing, just update the stored mfn,
 252                  * since all could have changed over a migrate.
 253                  */
 254                 if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) {
 255                         BUG_ON(mididx);
 256                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 257                         p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
 258                         pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
 259                         continue;
 260                 }
 261
 262                 if (mid_mfn_p == p2m_mid_missing_mfn) {
 263                         mid_mfn_p = alloc_p2m_page();
 264                         p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
 265
 266                         p2m_top_mfn_p[topidx] = mid_mfn_p;
 267                 }
 268
 269                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
 270                 mid_mfn_p[mididx] = mfn;
 271         }
 272 }
 273
 274 void xen_setup_mfn_list_list(void)
 275 {
 276         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
 277
 278         if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
 279                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = ~0UL;
 280         else
 281                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
 282                         virt_to_mfn(p2m_top_mfn);
 283         HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
 284         HYPERVISOR_shared_info->arch.p2m_generation = 0;
 285         HYPERVISOR_shared_info->arch.p2m_vaddr = (unsigned long)xen_p2m_addr;
 286         HYPERVISOR_shared_info->arch.p2m_cr3 =
 287                 xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
 288 }
 289
 290 /* Set up p2m_top to point to the domain-builder provided p2m pages */
 291 void __init xen_build_dynamic_phys_to_machine(void)
 292 {
 293         unsigned long pfn;
 294
 295         xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
 296         xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE);
 297
 298         for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++)
 299                 xen_p2m_addr[pfn] = INVALID_P2M_ENTRY;
 300
 301         xen_max_p2m_pfn = xen_p2m_size;
 302 }
 303
 304 #define P2M_TYPE_IDENTITY       0
 305 #define P2M_TYPE_MISSING        1
 306 #define P2M_TYPE_PFN            2
 307 #define P2M_TYPE_UNKNOWN        3
 308
 309 static int xen_p2m_elem_type(unsigned long pfn)
 310 {
 311         unsigned long mfn;
 312
 313         if (pfn >= xen_p2m_size)
 314                 return P2M_TYPE_IDENTITY;
 315
 316         mfn = xen_p2m_addr[pfn];
 317
 318         if (mfn == INVALID_P2M_ENTRY)
 319                 return P2M_TYPE_MISSING;
 320
 321         if (mfn & IDENTITY_FRAME_BIT)
 322                 return P2M_TYPE_IDENTITY;
 323
 324         return P2M_TYPE_PFN;
 325 }
 326
 327 static void __init xen_rebuild_p2m_list(unsigned long *p2m)
 328 {
 329         unsigned int i, chunk;
 330         unsigned long pfn;
 331         unsigned long *mfns;
 332         pte_t *ptep;
 333         pmd_t *pmdp;
 334         int type;
 335
 336         p2m_missing = alloc_p2m_page();
 337         p2m_init(p2m_missing);
 338         p2m_identity = alloc_p2m_page();
 339         p2m_init(p2m_identity);
 340
 341         p2m_missing_pte = alloc_p2m_page();
 342         paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
 343         p2m_identity_pte = alloc_p2m_page();
 344         paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
 345         for (i = 0; i < PTRS_PER_PTE; i++) {
 346                 set_pte(p2m_missing_pte + i,
 347                         pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
 348                 set_pte(p2m_identity_pte + i,
 349                         pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
 350         }
 351
 352         for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
 353                 /*
 354                  * Try to map missing/identity PMDs or p2m-pages if possible.
 355                  * We have to respect the structure of the mfn_list_list
 356                  * which will be built just afterwards.
 357                  * Chunk size to test is one p2m page if we are in the middle
 358                  * of a mfn_list_list mid page and the complete mid page area
 359                  * if we are at index 0 of the mid page. Please note that a
 360                  * mid page might cover more than one PMD, e.g. on 32 bit PAE
 361                  * kernels.
 362                  */
 363                 chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
 364                         P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;
 365
 366                 type = xen_p2m_elem_type(pfn);
 367                 i = 0;
 368                 if (type != P2M_TYPE_PFN)
 369                         for (i = 1; i < chunk; i++)
 370                                 if (xen_p2m_elem_type(pfn + i) != type)
 371                                         break;
 372                 if (i < chunk)
 373                         /* Reset to minimal chunk size. */
 374                         chunk = P2M_PER_PAGE;
 375
 376                 if (type == P2M_TYPE_PFN || i < chunk) {
 377                         /* Use initial p2m page contents. */
 378                         mfns = alloc_p2m_page();
 379                         copy_page(mfns, xen_p2m_addr + pfn);
 380                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
 381                         set_pte(ptep,
 382                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
 383                         continue;
 384                 }
 385
 386                 if (chunk == P2M_PER_PAGE) {
 387                         /* Map complete missing or identity p2m-page. */
 388                         mfns = (type == P2M_TYPE_MISSING) ?
 389                                 p2m_missing : p2m_identity;
 390                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
 391                         set_pte(ptep,
 392                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
 393                         continue;
 394                 }
 395
 396                 /* Complete missing or identity PMD(s) can be mapped. */
 397                 ptep = (type == P2M_TYPE_MISSING) ?
 398                         p2m_missing_pte : p2m_identity_pte;
 399                 for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 400                         pmdp = populate_extra_pmd(
 401                                 (unsigned long)(p2m + pfn) + i * PMD_SIZE);
 402                         set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
 403                 }
 404         }
 405 }
 406
 407 void __init xen_vmalloc_p2m_tree(void)
 408 {
 409         static struct vm_struct vm;
 410         unsigned long p2m_limit;
 411
 412         xen_p2m_last_pfn = xen_max_p2m_pfn;
 413
 414         p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 / PAGE_SIZE;
 415         vm.flags = VM_ALLOC;
 416         vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn, p2m_limit),
 417                         PMD_SIZE * PMDS_PER_MID_PAGE);
 418         vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
 419         pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
 420
 421         xen_max_p2m_pfn = vm.size / sizeof(unsigned long);
 422
 423         xen_rebuild_p2m_list(vm.addr);
 424
 425         xen_p2m_addr = vm.addr;
 426         xen_p2m_size = xen_max_p2m_pfn;
 427
 428         xen_inv_extra_mem();
 429 }
 430
 431 unsigned long get_phys_to_machine(unsigned long pfn)
 432 {
 433         pte_t *ptep;
 434         unsigned int level;
 435
 436         if (unlikely(pfn >= xen_p2m_size)) {
 437                 if (pfn < xen_max_p2m_pfn)
 438                         return xen_chk_extra_mem(pfn);
 439
 440                 return IDENTITY_FRAME(pfn);
 441         }
 442
 443         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
 444         BUG_ON(!ptep || level != PG_LEVEL_4K);
 445
 446         /*
 447          * The INVALID_P2M_ENTRY is filled in both p2m_*identity
 448          * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
 449          * would be wrong.
 450          */
 451         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 452                 return IDENTITY_FRAME(pfn);
 453
 454         return xen_p2m_addr[pfn];
 455 }
 456 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 457
 458 /*
 459  * Allocate new pmd(s). It is checked whether the old pmd is still in place.
 460  * If not, nothing is changed. This is okay as the only reason for allocating
 461  * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
 462  * pmd.
 463  */
 464 static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
 465 {
 466         pte_t *ptechk;
 467         pte_t *pte_newpg[PMDS_PER_MID_PAGE];
 468         pmd_t *pmdp;
 469         unsigned int level;
 470         unsigned long flags;
 471         unsigned long vaddr;
 472         int i;
 473
 474         /* Do all allocations first to bail out in error case. */
 475         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 476                 pte_newpg[i] = alloc_p2m_page();
 477                 if (!pte_newpg[i]) {
 478                         for (i--; i >= 0; i--)
 479                                 free_p2m_page(pte_newpg[i]);
 480
 481                         return NULL;
 482                 }
 483         }
 484
 485         vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);
 486
 487         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 488                 copy_page(pte_newpg[i], pte_pg);
 489                 paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);
 490
 491                 pmdp = lookup_pmd_address(vaddr);
 492                 BUG_ON(!pmdp);
 493
 494                 spin_lock_irqsave(&p2m_update_lock, flags);
 495
 496                 ptechk = lookup_address(vaddr, &level);
 497                 if (ptechk == pte_pg) {
 498                         HYPERVISOR_shared_info->arch.p2m_generation++;
 499                         wmb(); /* Tools are synchronizing via p2m_generation. */
 500                         set_pmd(pmdp,
 501                                 __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
 502                         wmb(); /* Tools are synchronizing via p2m_generation. */
 503                         HYPERVISOR_shared_info->arch.p2m_generation++;
 504                         pte_newpg[i] = NULL;
 505                 }
 506
 507                 spin_unlock_irqrestore(&p2m_update_lock, flags);
 508
 509                 if (pte_newpg[i]) {
 510                         paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
 511                         free_p2m_page(pte_newpg[i]);
 512                 }
 513
 514                 vaddr += PMD_SIZE;
 515         }
 516
 517         return lookup_address(addr, &level);
 518 }
 519
 520 /*
 521  * Fully allocate the p2m structure for a given pfn.  We need to check
 522  * that both the top and mid levels are allocated, and make sure the
 523  * parallel mfn tree is kept in sync.  We may race with other cpus, so
 524  * the new pages are installed with cmpxchg; if we lose the race then
 525  * simply free the page we allocated and use the one that's there.
 526  */
 527 int xen_alloc_p2m_entry(unsigned long pfn)
 528 {
 529         unsigned topidx;
 530         unsigned long *top_mfn_p, *mid_mfn;
 531         pte_t *ptep, *pte_pg;
 532         unsigned int level;
 533         unsigned long flags;
 534         unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
 535         unsigned long p2m_pfn;
 536
 537         ptep = lookup_address(addr, &level);
 538         BUG_ON(!ptep || level != PG_LEVEL_4K);
 539         pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 540
 541         if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
 542                 /* PMD level is missing, allocate a new one */
 543                 ptep = alloc_p2m_pmd(addr, pte_pg);
 544                 if (!ptep)
 545                         return -ENOMEM;
 546         }
 547
 548         if (p2m_top_mfn && pfn < MAX_P2M_PFN) {
 549                 topidx = p2m_top_index(pfn);
 550                 top_mfn_p = &p2m_top_mfn[topidx];
 551                 mid_mfn = READ_ONCE(p2m_top_mfn_p[topidx]);
 552
 553                 BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
 554
 555                 if (mid_mfn == p2m_mid_missing_mfn) {
 556                         /* Separately check the mid mfn level */
 557                         unsigned long missing_mfn;
 558                         unsigned long mid_mfn_mfn;
 559
 560                         mid_mfn = alloc_p2m_page();
 561                         if (!mid_mfn)
 562                                 return -ENOMEM;
 563
 564                         p2m_mid_mfn_init(mid_mfn, p2m_missing);
 565
 566                         missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
 567                         mid_mfn_mfn = virt_to_mfn(mid_mfn);
 568                         /* try_cmpxchg() updates missing_mfn on failure. */
 569                         if (try_cmpxchg(top_mfn_p, &missing_mfn, mid_mfn_mfn)) {
 570                                 p2m_top_mfn_p[topidx] = mid_mfn;
 571                         } else {
 572                                 free_p2m_page(mid_mfn);
 573                                 mid_mfn = mfn_to_virt(missing_mfn);
 574                         }
 575                 }
 576         } else {
 577                 mid_mfn = NULL;
 578         }
 579
 580         p2m_pfn = pte_pfn(READ_ONCE(*ptep));
 581         if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
 582             p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
 583                 /* p2m leaf page is missing */
 584                 unsigned long *p2m;
 585
 586                 p2m = alloc_p2m_page();
 587                 if (!p2m)
 588                         return -ENOMEM;
 589
 590                 if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
 591                         p2m_init(p2m);
 592                 else
 593                         p2m_init_identity(p2m, pfn & ~(P2M_PER_PAGE - 1));
 594
 595                 spin_lock_irqsave(&p2m_update_lock, flags);
 596
 597                 if (pte_pfn(*ptep) == p2m_pfn) {
 598                         HYPERVISOR_shared_info->arch.p2m_generation++;
 599                         wmb(); /* Tools are synchronizing via p2m_generation. */
 600                         set_pte(ptep,
 601                                 pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
 602                         wmb(); /* Tools are synchronizing via p2m_generation. */
 603                         HYPERVISOR_shared_info->arch.p2m_generation++;
 604                         if (mid_mfn)
 605                                 mid_mfn[p2m_mid_index(pfn)] = virt_to_mfn(p2m);
 606                         p2m = NULL;
 607                 }
 608
 609                 spin_unlock_irqrestore(&p2m_update_lock, flags);
 610
 611                 if (p2m)
 612                         free_p2m_page(p2m);
 613         }
 614
 615         /* Expanded the p2m? */
 616         if (pfn >= xen_p2m_last_pfn) {
 617                 xen_p2m_last_pfn = ALIGN(pfn + 1, P2M_PER_PAGE);
 618                 HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
 619         }
 620
 621         return 0;
 622 }
 623 EXPORT_SYMBOL(xen_alloc_p2m_entry);
 624
 625 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 626                                       unsigned long pfn_e)
 627 {
 628         unsigned long pfn;
 629
 630         if (unlikely(pfn_s >= xen_p2m_size))
 631                 return 0;
 632
 633         if (pfn_s > pfn_e)
 634                 return 0;
 635
 636         if (pfn_e > xen_p2m_size)
 637                 pfn_e = xen_p2m_size;
 638
 639         for (pfn = pfn_s; pfn < pfn_e; pfn++)
 640                 xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);
 641
 642         return pfn - pfn_s;
 643 }
 644
 645 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 646 {
 647         pte_t *ptep;
 648         unsigned int level;
 649
 650         /* Only invalid entries allowed above the highest p2m covered frame. */
 651         if (unlikely(pfn >= xen_p2m_size))
 652                 return mfn == INVALID_P2M_ENTRY;
 653
 654         /*
 655          * The interface requires atomic updates on p2m elements.
 656          * xen_safe_write_ulong() is using an atomic store via asm().
 657          */
 658         if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
 659                 return true;
 660
 661         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
 662         BUG_ON(!ptep || level != PG_LEVEL_4K);
 663
 664         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
 665                 return mfn == INVALID_P2M_ENTRY;
 666
 667         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 668                 return mfn == IDENTITY_FRAME(pfn);
 669
 670         return false;
 671 }
 672
 673 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 674 {
 675         if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
 676                 int ret;
 677
 678                 ret = xen_alloc_p2m_entry(pfn);
 679                 if (ret < 0)
 680                         return false;
 681
 682                 return __set_phys_to_machine(pfn, mfn);
 683         }
 684
 685         return true;
 686 }
 687
 688 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 689                             struct gnttab_map_grant_ref *kmap_ops,
 690                             struct page **pages, unsigned int count)
 691 {
 692         int i, ret = 0;
 693         pte_t *pte;
 694
 695         if (xen_feature(XENFEAT_auto_translated_physmap))
 696                 return 0;
 697
 698         if (kmap_ops) {
 699                 ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
 700                                                 kmap_ops, count);
 701                 if (ret)
 702                         goto out;
 703         }
 704
 705         for (i = 0; i < count; i++) {
 706                 unsigned long mfn, pfn;
 707                 struct gnttab_unmap_grant_ref unmap[2];
 708                 int rc;
 709
 710                 /* Do not add to override if the map failed. */
 711                 if (map_ops[i].status != GNTST_okay ||
 712                     (kmap_ops && kmap_ops[i].status != GNTST_okay))
 713                         continue;
 714
 715                 if (map_ops[i].flags & GNTMAP_contains_pte) {
 716                         pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
 717                                 (map_ops[i].host_addr & ~PAGE_MASK));
 718                         mfn = pte_mfn(*pte);
 719                 } else {
 720                         mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 721                 }
 722                 pfn = page_to_pfn(pages[i]);
 723
 724                 WARN(pfn_to_mfn(pfn) != INVALID_P2M_ENTRY, "page must be ballooned");
 725
 726                 if (likely(set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
 727                         continue;
 728
 729                 /*
 730                  * Signal an error for this slot. This in turn requires
 731                  * immediate unmapping.
 732                  */
 733                 map_ops[i].status = GNTST_general_error;
 734                 unmap[0].host_addr = map_ops[i].host_addr;
 735                 unmap[0].handle = map_ops[i].handle;
 736                 map_ops[i].handle = INVALID_GRANT_HANDLE;
 737                 if (map_ops[i].flags & GNTMAP_device_map)
 738                         unmap[0].dev_bus_addr = map_ops[i].dev_bus_addr;
 739                 else
 740                         unmap[0].dev_bus_addr = 0;
 741
 742                 if (kmap_ops) {
 743                         kmap_ops[i].status = GNTST_general_error;
 744                         unmap[1].host_addr = kmap_ops[i].host_addr;
 745                         unmap[1].handle = kmap_ops[i].handle;
 746                         kmap_ops[i].handle = INVALID_GRANT_HANDLE;
 747                         if (kmap_ops[i].flags & GNTMAP_device_map)
 748                                 unmap[1].dev_bus_addr = kmap_ops[i].dev_bus_addr;
 749                         else
 750                                 unmap[1].dev_bus_addr = 0;
 751                 }
 752
 753                 /*
 754                  * Pre-populate both status fields, to be recognizable in
 755                  * the log message below.
 756                  */
 757                 unmap[0].status = 1;
 758                 unmap[1].status = 1;
 759
 760                 rc = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
 761                                                unmap, 1 + !!kmap_ops);
 762                 if (rc || unmap[0].status != GNTST_okay ||
 763                     unmap[1].status != GNTST_okay)
 764                         pr_err_once("gnttab unmap failed: rc=%d st0=%d st1=%d\n",
 765                                     rc, unmap[0].status, unmap[1].status);
 766         }
 767
 768 out:
 769         return ret;
 770 }
 771
 772 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 773                               struct gnttab_unmap_grant_ref *kunmap_ops,
 774                               struct page **pages, unsigned int count)
 775 {
 776         int i, ret = 0;
 777
 778         if (xen_feature(XENFEAT_auto_translated_physmap))
 779                 return 0;
 780
 781         for (i = 0; i < count; i++) {
 782                 unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
 783                 unsigned long pfn = page_to_pfn(pages[i]);
 784
 785                 if (mfn != INVALID_P2M_ENTRY && (mfn & FOREIGN_FRAME_BIT))
 786                         set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 787                 else
 788                         ret = -EINVAL;
 789         }
 790         if (kunmap_ops)
 791                 ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
 792                                                 kunmap_ops, count) ?: ret;
 793
 794         return ret;
 795 }
 796
 797 /* Remapped non-RAM areas */
 798 #define NR_NONRAM_REMAP 4
 799 static struct nonram_remap {
 800         phys_addr_t maddr;
 801         phys_addr_t paddr;
 802         size_t size;
 803 } xen_nonram_remap[NR_NONRAM_REMAP] __ro_after_init;
 804 static unsigned int nr_nonram_remap __ro_after_init;
 805
 806 /*
 807  * Do the real remapping of non-RAM regions as specified in the
 808  * xen_nonram_remap[] array.
 809  * In case of an error just crash the system.
 810  */
 811 void __init xen_do_remap_nonram(void)
 812 {
 813         unsigned int i;
 814         unsigned int remapped = 0;
 815         const struct nonram_remap *remap = xen_nonram_remap;
 816         unsigned long pfn, mfn, end_pfn;
 817
 818         for (i = 0; i < nr_nonram_remap; i++) {
 819                 end_pfn = PFN_UP(remap->paddr + remap->size);
 820                 pfn = PFN_DOWN(remap->paddr);
 821                 mfn = PFN_DOWN(remap->maddr);
 822                 while (pfn < end_pfn) {
 823                         if (!set_phys_to_machine(pfn, mfn))
 824                                 panic("Failed to set p2m mapping for pfn=%lx mfn=%lx\n",
 825                                        pfn, mfn);
 826
 827                         pfn++;
 828                         mfn++;
 829                         remapped++;
 830                 }
 831
 832                 remap++;
 833         }
 834
 835         pr_info("Remapped %u non-RAM page(s)\n", remapped);
 836 }
 837
 838 #ifdef CONFIG_ACPI
 839 /*
 840  * Xen variant of acpi_os_ioremap() taking potentially remapped non-RAM
 841  * regions into account.
 842  * Any attempt to map an area crossing a remap boundary will produce a
 843  * WARN() splat.
 844  * phys is related to remap->maddr on input and will be rebased to remap->paddr.
 845  */
 846 static void __iomem *xen_acpi_os_ioremap(acpi_physical_address phys,
 847                                          acpi_size size)
 848 {
 849         unsigned int i;
 850         const struct nonram_remap *remap = xen_nonram_remap;
 851
 852         for (i = 0; i < nr_nonram_remap; i++) {
 853                 if (phys + size > remap->maddr &&
 854                     phys < remap->maddr + remap->size) {
 855                         WARN_ON(phys < remap->maddr ||
 856                                 phys + size > remap->maddr + remap->size);
 857                         phys += remap->paddr - remap->maddr;
 858                         break;
 859                 }
 860         }
 861
 862         return x86_acpi_os_ioremap(phys, size);
 863 }
 864 #endif /* CONFIG_ACPI */
 865
 866 /*
 867  * Add a new non-RAM remap entry.
 868  * In case of no free entry found, just crash the system.
 869  */
 870 void __init xen_add_remap_nonram(phys_addr_t maddr, phys_addr_t paddr,
 871                                  unsigned long size)
 872 {
 873         BUG_ON((maddr & ~PAGE_MASK) != (paddr & ~PAGE_MASK));
 874
 875         if (nr_nonram_remap == NR_NONRAM_REMAP) {
 876                 xen_raw_console_write("Number of required E820 entry remapping actions exceed maximum value\n");
 877                 BUG();
 878         }
 879
 880 #ifdef CONFIG_ACPI
 881         /* Switch to the Xen acpi_os_ioremap() variant. */
 882         if (nr_nonram_remap == 0)
 883                 acpi_os_ioremap = xen_acpi_os_ioremap;
 884 #endif
 885
 886         xen_nonram_remap[nr_nonram_remap].maddr = maddr;
 887         xen_nonram_remap[nr_nonram_remap].paddr = paddr;
 888         xen_nonram_remap[nr_nonram_remap].size = size;
 889
 890         nr_nonram_remap++;
 891 }
 892
 893 #ifdef CONFIG_XEN_DEBUG_FS
 894 #include <linux/debugfs.h>
 895 static int p2m_dump_show(struct seq_file *m, void *v)
 896 {
 897         static const char * const type_name[] = {
 898                                 [P2M_TYPE_IDENTITY] = "identity",
 899                                 [P2M_TYPE_MISSING] = "missing",
 900                                 [P2M_TYPE_PFN] = "pfn",
 901                                 [P2M_TYPE_UNKNOWN] = "abnormal"};
 902         unsigned long pfn, first_pfn;
 903         int type, prev_type;
 904
 905         prev_type = xen_p2m_elem_type(0);
 906         first_pfn = 0;
 907
 908         for (pfn = 0; pfn < xen_p2m_size; pfn++) {
 909                 type = xen_p2m_elem_type(pfn);
 910                 if (type != prev_type) {
 911                         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
 912                                    type_name[prev_type]);
 913                         prev_type = type;
 914                         first_pfn = pfn;
 915                 }
 916         }
 917         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
 918                    type_name[prev_type]);
 919         return 0;
 920 }
 921
 922 DEFINE_SHOW_ATTRIBUTE(p2m_dump);
 923
 924 static struct dentry *d_mmu_debug;
 925
 926 static int __init xen_p2m_debugfs(void)
 927 {
 928         struct dentry *d_xen = xen_init_debugfs();
 929
 930         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
 931
 932         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
 933         return 0;
 934 }
 935 fs_initcall(xen_p2m_debugfs);
 936 #endif /* CONFIG_XEN_DEBUG_FS */