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 p2m table is logically a flat array, but we implement it as a
   7  * three-level tree to allow the address space to be sparse.
   8  *
   9  *                               Xen
  10  *                                |
  11  *     p2m_top              p2m_top_mfn
  12  *       /  \                   /   \
  13  * p2m_mid p2m_mid      p2m_mid_mfn p2m_mid_mfn
  14  *    / \      / \         /           /
  15  *  p2m p2m p2m p2m p2m p2m p2m ...
  16  *
  17  * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
  18  *
  19  * The p2m_top and p2m_top_mfn levels are limited to 1 page, so the
  20  * maximum representable pseudo-physical address space is:
  21  *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
  22  *
  23  * P2M_PER_PAGE depends on the architecture, as a mfn is always
  24  * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
  25  * 512 and 1024 entries respectively.
  26  *
  27  * In short, these structures contain the Machine Frame Number (MFN) of the PFN.
  28  *
  29  * However not all entries are filled with MFNs. Specifically for all other
  30  * leaf entries, or for the top  root, or middle one, for which there is a void
  31  * entry, we assume it is  "missing". So (for example)
  32  *  pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
  33  *
  34  * We also have the possibility of setting 1-1 mappings on certain regions, so
  35  * that:
  36  *  pfn_to_mfn(0xc0000)=0xc0000
  37  *
  38  * The benefit of this is, that we can assume for non-RAM regions (think
  39  * PCI BARs, or ACPI spaces), we can create mappings easily because we
  40  * get the PFN value to match the MFN.
  41  *
  42  * For this to work efficiently we have one new page p2m_identity and
  43  * allocate (via reserved_brk) any other pages we need to cover the sides
  44  * (1GB or 4MB boundary violations). All entries in p2m_identity are set to
  45  * INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs,
  46  * no other fancy value).
  47  *
  48  * On lookup we spot that the entry points to p2m_identity and return the
  49  * identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
  50  * If the entry points to an allocated page, we just proceed as before and
  51  * return the PFN.  If the PFN has IDENTITY_FRAME_BIT set we unmask that in
  52  * appropriate functions (pfn_to_mfn).
  53  *
  54  * The reason for having the IDENTITY_FRAME_BIT instead of just returning the
  55  * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
  56  * non-identity pfn. To protect ourselves against we elect to set (and get) the
  57  * IDENTITY_FRAME_BIT on all identity mapped PFNs.
  58  *
  59  * This simplistic diagram is used to explain the more subtle piece of code.
  60  * There is also a digram of the P2M at the end that can help.
  61  * Imagine your E820 looking as so:
  62  *
  63  *                    1GB                                           2GB    4GB
  64  * /-------------------+---------\/----\         /----------\    /---+-----\
  65  * | System RAM        | Sys RAM ||ACPI|         | reserved |    | Sys RAM |
  66  * \-------------------+---------/\----/         \----------/    \---+-----/
  67  *                               ^- 1029MB                       ^- 2001MB
  68  *
  69  * [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100),
  70  *  2048MB = 524288 (0x80000)]
  71  *
  72  * And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB
  73  * is actually not present (would have to kick the balloon driver to put it in).
  74  *
  75  * When we are told to set the PFNs for identity mapping (see patch: "xen/setup:
  76  * Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start
  77  * of the PFN and the end PFN (263424 and 512256 respectively). The first step
  78  * is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page
  79  * covers 512^2 of page estate (1GB) and in case the start or end PFN is not
  80  * aligned on 512^2*PAGE_SIZE (1GB) we reserve_brk new middle and leaf pages as
  81  * required to split any existing p2m_mid_missing middle pages.
  82  *
  83  * With the E820 example above, 263424 is not 1GB aligned so we allocate a
  84  * reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000.
  85  * Each entry in the allocate page is "missing" (points to p2m_missing).
  86  *
  87  * Next stage is to determine if we need to do a more granular boundary check
  88  * on the 4MB (or 2MB depending on architecture) off the start and end pfn's.
  89  * We check if the start pfn and end pfn violate that boundary check, and if
  90  * so reserve_brk a (p2m[x][y]) leaf page. This way we have a much finer
  91  * granularity of setting which PFNs are missing and which ones are identity.
  92  * In our example 263424 and 512256 both fail the check so we reserve_brk two
  93  * pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing"
  94  * values) and assign them to p2m[1][2] and p2m[1][488] respectively.
  95  *
  96  * At this point we would at minimum reserve_brk one page, but could be up to
  97  * three. Each call to set_phys_range_identity has at maximum a three page
  98  * cost. If we were to query the P2M at this stage, all those entries from
  99  * start PFN through end PFN (so 1029MB -> 2001MB) would return
 100  * INVALID_P2M_ENTRY ("missing").
 101  *
 102  * The next step is to walk from the start pfn to the end pfn setting
 103  * the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity.
 104  * If we find that the middle entry is pointing to p2m_missing we can swap it
 105  * over to p2m_identity - this way covering 4MB (or 2MB) PFN space (and
 106  * similarly swapping p2m_mid_missing for p2m_mid_identity for larger regions).
 107  * At this point we do not need to worry about boundary aligment (so no need to
 108  * reserve_brk a middle page, figure out which PFNs are "missing" and which
 109  * ones are identity), as that has been done earlier.  If we find that the
 110  * middle leaf is not occupied by p2m_identity or p2m_missing, we dereference
 111  * that page (which covers 512 PFNs) and set the appropriate PFN with
 112  * IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we
 113  * set from p2m[1][2][256->511] and p2m[1][488][0->256] with
 114  * IDENTITY_FRAME_BIT set.
 115  *
 116  * All other regions that are void (or not filled) either point to p2m_missing
 117  * (considered missing) or have the default value of INVALID_P2M_ENTRY (also
 118  * considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511]
 119  * contain the INVALID_P2M_ENTRY value and are considered "missing."
 120  *
 121  * Finally, the region beyond the end of of the E820 (4 GB in this example)
 122  * is set to be identity (in case there are MMIO regions placed here).
 123  *
 124  * This is what the p2m ends up looking (for the E820 above) with this
 125  * fabulous drawing:
 126  *
 127  *    p2m         /--------------\
 128  *  /-----\       | &mfn_list[0],|                           /-----------------\
 129  *  |  0  |------>| &mfn_list[1],|    /---------------\      | ~0, ~0, ..      |
 130  *  |-----|       |  ..., ~0, ~0 |    | ~0, ~0, [x]---+----->| IDENTITY [@256] |
 131  *  |  1  |---\   \--------------/    | [p2m_identity]+\     | IDENTITY [@257] |
 132  *  |-----|    \                      | [p2m_identity]+\\    | ....            |
 133  *  |  2  |--\  \-------------------->|  ...          | \\   \----------------/
 134  *  |-----|   \                       \---------------/  \\
 135  *  |  3  |-\  \                                          \\  p2m_identity [1]
 136  *  |-----|  \  \-------------------->/---------------\   /-----------------\
 137  *  | ..  |\  |                       | [p2m_identity]+-->| ~0, ~0, ~0, ... |
 138  *  \-----/ | |                       | [p2m_identity]+-->| ..., ~0         |
 139  *          | |                       | ....          |   \-----------------/
 140  *          | |                       +-[x], ~0, ~0.. +\
 141  *          | |                       \---------------/ \
 142  *          | |                                          \-> /---------------\
 143  *          | V  p2m_mid_missing       p2m_missing           | IDENTITY[@0]  |
 144  *          | /-----------------\     /------------\         | IDENTITY[@256]|
 145  *          | | [p2m_missing]   +---->| ~0, ~0, ...|         | ~0, ~0, ....  |
 146  *          | | [p2m_missing]   +---->| ..., ~0    |         \---------------/
 147  *          | | ...             |     \------------/
 148  *          | \-----------------/
 149  *          |
 150  *          |     p2m_mid_identity
 151  *          |   /-----------------\
 152  *          \-->| [p2m_identity]  +---->[1]
 153  *              | [p2m_identity]  +---->[1]
 154  *              | ...             |
 155  *              \-----------------/
 156  *
 157  * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
 158  */
 159
 160 #include <linux/init.h>
 161 #include <linux/module.h>
 162 #include <linux/list.h>
 163 #include <linux/hash.h>
 164 #include <linux/sched.h>
 165 #include <linux/seq_file.h>
 166 #include <linux/bootmem.h>
 167 #include <linux/slab.h>
 168
 169 #include <asm/cache.h>
 170 #include <asm/setup.h>
 171
 172 #include <asm/xen/page.h>
 173 #include <asm/xen/hypercall.h>
 174 #include <asm/xen/hypervisor.h>
 175 #include <xen/balloon.h>
 176 #include <xen/grant_table.h>
 177
 178 #include "p2m.h"
 179 #include "multicalls.h"
 180 #include "xen-ops.h"
 181
 182 static void __init m2p_override_init(void);
 183
 184 unsigned long *xen_p2m_addr __read_mostly;
 185 EXPORT_SYMBOL_GPL(xen_p2m_addr);
 186 unsigned long xen_p2m_size __read_mostly;
 187 EXPORT_SYMBOL_GPL(xen_p2m_size);
 188 unsigned long xen_max_p2m_pfn __read_mostly;
 189 EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
 190
 191 static unsigned long *p2m_mid_missing_mfn;
 192 static unsigned long *p2m_top_mfn;
 193 static unsigned long **p2m_top_mfn_p;
 194
 195 /* Placeholders for holes in the address space */
 196 static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
 197 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
 198
 199 static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
 200
 201 static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
 202 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_identity, P2M_MID_PER_PAGE);
 203
 204 RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
 205
 206 static int use_brk = 1;
 207
 208 static inline unsigned p2m_top_index(unsigned long pfn)
 209 {
 210         BUG_ON(pfn >= MAX_P2M_PFN);
 211         return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
 212 }
 213
 214 static inline unsigned p2m_mid_index(unsigned long pfn)
 215 {
 216         return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
 217 }
 218
 219 static inline unsigned p2m_index(unsigned long pfn)
 220 {
 221         return pfn % P2M_PER_PAGE;
 222 }
 223
 224 static void p2m_top_init(unsigned long ***top)
 225 {
 226         unsigned i;
 227
 228         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 229                 top[i] = p2m_mid_missing;
 230 }
 231
 232 static void p2m_top_mfn_init(unsigned long *top)
 233 {
 234         unsigned i;
 235
 236         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 237                 top[i] = virt_to_mfn(p2m_mid_missing_mfn);
 238 }
 239
 240 static void p2m_top_mfn_p_init(unsigned long **top)
 241 {
 242         unsigned i;
 243
 244         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 245                 top[i] = p2m_mid_missing_mfn;
 246 }
 247
 248 static void p2m_mid_init(unsigned long **mid, unsigned long *leaf)
 249 {
 250         unsigned i;
 251
 252         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 253                 mid[i] = leaf;
 254 }
 255
 256 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
 257 {
 258         unsigned i;
 259
 260         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 261                 mid[i] = virt_to_mfn(leaf);
 262 }
 263
 264 static void p2m_init(unsigned long *p2m)
 265 {
 266         unsigned i;
 267
 268         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 269                 p2m[i] = INVALID_P2M_ENTRY;
 270 }
 271
 272 static void * __ref alloc_p2m_page(void)
 273 {
 274         if (unlikely(use_brk))
 275                 return extend_brk(PAGE_SIZE, PAGE_SIZE);
 276
 277         if (unlikely(!slab_is_available()))
 278                 return alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
 279
 280         return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
 281 }
 282
 283 /* Only to be called in case of a race for a page just allocated! */
 284 static void free_p2m_page(void *p)
 285 {
 286         BUG_ON(!slab_is_available());
 287         free_page((unsigned long)p);
 288 }
 289
 290 /*
 291  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
 292  *
 293  * This is called both at boot time, and after resuming from suspend:
 294  * - At boot time we're called rather early, and must use alloc_bootmem*()
 295  *   to allocate memory.
 296  *
 297  * - After resume we're called from within stop_machine, but the mfn
 298  *   tree should already be completely allocated.
 299  */
 300 void __ref xen_build_mfn_list_list(void)
 301 {
 302         unsigned long pfn;
 303
 304         if (xen_feature(XENFEAT_auto_translated_physmap))
 305                 return;
 306
 307         /* Pre-initialize p2m_top_mfn to be completely missing */
 308         if (p2m_top_mfn == NULL) {
 309                 p2m_mid_missing_mfn = alloc_p2m_page();
 310                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 311
 312                 p2m_top_mfn_p = alloc_p2m_page();
 313                 p2m_top_mfn_p_init(p2m_top_mfn_p);
 314
 315                 p2m_top_mfn = alloc_p2m_page();
 316                 p2m_top_mfn_init(p2m_top_mfn);
 317         } else {
 318                 /* Reinitialise, mfn's all change after migration */
 319                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 320         }
 321
 322         for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
 323                 unsigned topidx = p2m_top_index(pfn);
 324                 unsigned mididx = p2m_mid_index(pfn);
 325                 unsigned long **mid;
 326                 unsigned long *mid_mfn_p;
 327
 328                 mid = p2m_top[topidx];
 329                 mid_mfn_p = p2m_top_mfn_p[topidx];
 330
 331                 /* Don't bother allocating any mfn mid levels if
 332                  * they're just missing, just update the stored mfn,
 333                  * since all could have changed over a migrate.
 334                  */
 335                 if (mid == p2m_mid_missing) {
 336                         BUG_ON(mididx);
 337                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 338                         p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
 339                         pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
 340                         continue;
 341                 }
 342
 343                 if (mid_mfn_p == p2m_mid_missing_mfn) {
 344                         /*
 345                          * XXX boot-time only!  We should never find
 346                          * missing parts of the mfn tree after
 347                          * runtime.
 348                          */
 349                         mid_mfn_p = alloc_p2m_page();
 350                         p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
 351
 352                         p2m_top_mfn_p[topidx] = mid_mfn_p;
 353                 }
 354
 355                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
 356                 mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
 357         }
 358 }
 359
 360 void xen_setup_mfn_list_list(void)
 361 {
 362         if (xen_feature(XENFEAT_auto_translated_physmap))
 363                 return;
 364
 365         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
 366
 367         HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
 368                 virt_to_mfn(p2m_top_mfn);
 369         HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
 370 }
 371
 372 /* Set up p2m_top to point to the domain-builder provided p2m pages */
 373 void __init xen_build_dynamic_phys_to_machine(void)
 374 {
 375         unsigned long *mfn_list;
 376         unsigned long max_pfn;
 377         unsigned long pfn;
 378
 379          if (xen_feature(XENFEAT_auto_translated_physmap))
 380                 return;
 381
 382         xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
 383         mfn_list = (unsigned long *)xen_start_info->mfn_list;
 384         max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
 385         xen_max_p2m_pfn = max_pfn;
 386         xen_p2m_size = max_pfn;
 387
 388         p2m_missing = alloc_p2m_page();
 389         p2m_init(p2m_missing);
 390         p2m_identity = alloc_p2m_page();
 391         p2m_init(p2m_identity);
 392
 393         p2m_mid_missing = alloc_p2m_page();
 394         p2m_mid_init(p2m_mid_missing, p2m_missing);
 395         p2m_mid_identity = alloc_p2m_page();
 396         p2m_mid_init(p2m_mid_identity, p2m_identity);
 397
 398         p2m_top = alloc_p2m_page();
 399         p2m_top_init(p2m_top);
 400
 401         /*
 402          * The domain builder gives us a pre-constructed p2m array in
 403          * mfn_list for all the pages initially given to us, so we just
 404          * need to graft that into our tree structure.
 405          */
 406         for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
 407                 unsigned topidx = p2m_top_index(pfn);
 408                 unsigned mididx = p2m_mid_index(pfn);
 409
 410                 if (p2m_top[topidx] == p2m_mid_missing) {
 411                         unsigned long **mid = alloc_p2m_page();
 412                         p2m_mid_init(mid, p2m_missing);
 413
 414                         p2m_top[topidx] = mid;
 415                 }
 416
 417                 /*
 418                  * As long as the mfn_list has enough entries to completely
 419                  * fill a p2m page, pointing into the array is ok. But if
 420                  * not the entries beyond the last pfn will be undefined.
 421                  */
 422                 if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
 423                         unsigned long p2midx;
 424
 425                         p2midx = max_pfn % P2M_PER_PAGE;
 426                         for ( ; p2midx < P2M_PER_PAGE; p2midx++)
 427                                 mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
 428                 }
 429                 p2m_top[topidx][mididx] = &mfn_list[pfn];
 430         }
 431 }
 432 #ifdef CONFIG_X86_64
 433 unsigned long __init xen_revector_p2m_tree(void)
 434 {
 435         unsigned long va_start;
 436         unsigned long va_end;
 437         unsigned long pfn;
 438         unsigned long pfn_free = 0;
 439         unsigned long *mfn_list = NULL;
 440         unsigned long size;
 441
 442         use_brk = 0;
 443         va_start = xen_start_info->mfn_list;
 444         /*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long),
 445          * so make sure it is rounded up to that */
 446         size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
 447         va_end = va_start + size;
 448
 449         /* If we were revectored already, don't do it again. */
 450         if (va_start <= __START_KERNEL_map && va_start >= __PAGE_OFFSET)
 451                 return 0;
 452
 453         mfn_list = alloc_bootmem_align(size, PAGE_SIZE);
 454         if (!mfn_list) {
 455                 pr_warn("Could not allocate space for a new P2M tree!\n");
 456                 return xen_start_info->mfn_list;
 457         }
 458         /* Fill it out with INVALID_P2M_ENTRY value */
 459         memset(mfn_list, 0xFF, size);
 460
 461         for (pfn = 0; pfn < ALIGN(MAX_DOMAIN_PAGES, P2M_PER_PAGE); pfn += P2M_PER_PAGE) {
 462                 unsigned topidx = p2m_top_index(pfn);
 463                 unsigned mididx;
 464                 unsigned long *mid_p;
 465
 466                 if (!p2m_top[topidx])
 467                         continue;
 468
 469                 if (p2m_top[topidx] == p2m_mid_missing)
 470                         continue;
 471
 472                 mididx = p2m_mid_index(pfn);
 473                 mid_p = p2m_top[topidx][mididx];
 474                 if (!mid_p)
 475                         continue;
 476                 if ((mid_p == p2m_missing) || (mid_p == p2m_identity))
 477                         continue;
 478
 479                 if ((unsigned long)mid_p == INVALID_P2M_ENTRY)
 480                         continue;
 481
 482                 /* The old va. Rebase it on mfn_list */
 483                 if (mid_p >= (unsigned long *)va_start && mid_p <= (unsigned long *)va_end) {
 484                         unsigned long *new;
 485
 486                         if (pfn_free  > (size / sizeof(unsigned long))) {
 487                                 WARN(1, "Only allocated for %ld pages, but we want %ld!\n",
 488                                      size / sizeof(unsigned long), pfn_free);
 489                                 return 0;
 490                         }
 491                         new = &mfn_list[pfn_free];
 492
 493                         copy_page(new, mid_p);
 494                         p2m_top[topidx][mididx] = &mfn_list[pfn_free];
 495
 496                         pfn_free += P2M_PER_PAGE;
 497
 498                 }
 499                 /* This should be the leafs allocated for identity from _brk. */
 500         }
 501
 502         xen_p2m_size = xen_max_p2m_pfn;
 503         xen_p2m_addr = mfn_list;
 504
 505         xen_inv_extra_mem();
 506
 507         m2p_override_init();
 508         return (unsigned long)mfn_list;
 509 }
 510 #else
 511 unsigned long __init xen_revector_p2m_tree(void)
 512 {
 513         use_brk = 0;
 514         xen_p2m_size = xen_max_p2m_pfn;
 515         xen_inv_extra_mem();
 516         m2p_override_init();
 517         return 0;
 518 }
 519 #endif
 520 unsigned long get_phys_to_machine(unsigned long pfn)
 521 {
 522         unsigned topidx, mididx, idx;
 523
 524         if (unlikely(pfn >= xen_p2m_size)) {
 525                 if (pfn < xen_max_p2m_pfn)
 526                         return xen_chk_extra_mem(pfn);
 527
 528                 return IDENTITY_FRAME(pfn);
 529         }
 530
 531         topidx = p2m_top_index(pfn);
 532         mididx = p2m_mid_index(pfn);
 533         idx = p2m_index(pfn);
 534
 535         /*
 536          * The INVALID_P2M_ENTRY is filled in both p2m_*identity
 537          * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
 538          * would be wrong.
 539          */
 540         if (p2m_top[topidx][mididx] == p2m_identity)
 541                 return IDENTITY_FRAME(pfn);
 542
 543         return p2m_top[topidx][mididx][idx];
 544 }
 545 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 546
 547 /*
 548  * Fully allocate the p2m structure for a given pfn.  We need to check
 549  * that both the top and mid levels are allocated, and make sure the
 550  * parallel mfn tree is kept in sync.  We may race with other cpus, so
 551  * the new pages are installed with cmpxchg; if we lose the race then
 552  * simply free the page we allocated and use the one that's there.
 553  */
 554 static bool alloc_p2m(unsigned long pfn)
 555 {
 556         unsigned topidx, mididx;
 557         unsigned long ***top_p, **mid;
 558         unsigned long *top_mfn_p, *mid_mfn;
 559         unsigned long *p2m_orig;
 560
 561         topidx = p2m_top_index(pfn);
 562         mididx = p2m_mid_index(pfn);
 563
 564         top_p = &p2m_top[topidx];
 565         mid = ACCESS_ONCE(*top_p);
 566
 567         if (mid == p2m_mid_missing) {
 568                 /* Mid level is missing, allocate a new one */
 569                 mid = alloc_p2m_page();
 570                 if (!mid)
 571                         return false;
 572
 573                 p2m_mid_init(mid, p2m_missing);
 574
 575                 if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
 576                         free_p2m_page(mid);
 577         }
 578
 579         top_mfn_p = &p2m_top_mfn[topidx];
 580         mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
 581
 582         BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
 583
 584         if (mid_mfn == p2m_mid_missing_mfn) {
 585                 /* Separately check the mid mfn level */
 586                 unsigned long missing_mfn;
 587                 unsigned long mid_mfn_mfn;
 588                 unsigned long old_mfn;
 589
 590                 mid_mfn = alloc_p2m_page();
 591                 if (!mid_mfn)
 592                         return false;
 593
 594                 p2m_mid_mfn_init(mid_mfn, p2m_missing);
 595
 596                 missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
 597                 mid_mfn_mfn = virt_to_mfn(mid_mfn);
 598                 old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
 599                 if (old_mfn != missing_mfn) {
 600                         free_p2m_page(mid_mfn);
 601                         mid_mfn = mfn_to_virt(old_mfn);
 602                 } else {
 603                         p2m_top_mfn_p[topidx] = mid_mfn;
 604                 }
 605         }
 606
 607         p2m_orig = ACCESS_ONCE(p2m_top[topidx][mididx]);
 608         if (p2m_orig == p2m_identity || p2m_orig == p2m_missing) {
 609                 /* p2m leaf page is missing */
 610                 unsigned long *p2m;
 611
 612                 p2m = alloc_p2m_page();
 613                 if (!p2m)
 614                         return false;
 615
 616                 p2m_init(p2m);
 617
 618                 if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
 619                         free_p2m_page(p2m);
 620                 else
 621                         mid_mfn[mididx] = virt_to_mfn(p2m);
 622         }
 623
 624         return true;
 625 }
 626
 627 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 628                                       unsigned long pfn_e)
 629 {
 630         unsigned long pfn;
 631
 632         if (unlikely(pfn_s >= xen_p2m_size))
 633                 return 0;
 634
 635         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
 636                 return pfn_e - pfn_s;
 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 /* Try to install p2m mapping; fail if intermediate bits missing */
 651 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 652 {
 653         unsigned topidx, mididx, idx;
 654
 655         /* don't track P2M changes in autotranslate guests */
 656         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
 657                 return true;
 658
 659         if (unlikely(pfn >= xen_p2m_size)) {
 660                 BUG_ON(mfn != INVALID_P2M_ENTRY);
 661                 return true;
 662         }
 663
 664         topidx = p2m_top_index(pfn);
 665         mididx = p2m_mid_index(pfn);
 666         idx = p2m_index(pfn);
 667
 668         /* For sparse holes were the p2m leaf has real PFN along with
 669          * PCI holes, stick in the PFN as the MFN value.
 670          *
 671          * set_phys_range_identity() will have allocated new middle
 672          * and leaf pages as required so an existing p2m_mid_missing
 673          * or p2m_missing mean that whole range will be identity so
 674          * these can be switched to p2m_mid_identity or p2m_identity.
 675          */
 676         if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
 677                 if (p2m_top[topidx] == p2m_mid_identity)
 678                         return true;
 679
 680                 if (p2m_top[topidx] == p2m_mid_missing) {
 681                         WARN_ON(cmpxchg(&p2m_top[topidx], p2m_mid_missing,
 682                                         p2m_mid_identity) != p2m_mid_missing);
 683                         return true;
 684                 }
 685
 686                 if (p2m_top[topidx][mididx] == p2m_identity)
 687                         return true;
 688
 689                 /* Swap over from MISSING to IDENTITY if needed. */
 690                 if (p2m_top[topidx][mididx] == p2m_missing) {
 691                         WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
 692                                 p2m_identity) != p2m_missing);
 693                         return true;
 694                 }
 695         }
 696
 697         if (p2m_top[topidx][mididx] == p2m_missing)
 698                 return mfn == INVALID_P2M_ENTRY;
 699
 700         p2m_top[topidx][mididx][idx] = mfn;
 701
 702         return true;
 703 }
 704
 705 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 706 {
 707         if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
 708                 if (!alloc_p2m(pfn))
 709                         return false;
 710
 711                 if (!__set_phys_to_machine(pfn, mfn))
 712                         return false;
 713         }
 714
 715         return true;
 716 }
 717
 718 #define M2P_OVERRIDE_HASH_SHIFT 10
 719 #define M2P_OVERRIDE_HASH       (1 << M2P_OVERRIDE_HASH_SHIFT)
 720
 721 static struct list_head *m2p_overrides;
 722 static DEFINE_SPINLOCK(m2p_override_lock);
 723
 724 static void __init m2p_override_init(void)
 725 {
 726         unsigned i;
 727
 728         m2p_overrides = alloc_bootmem_align(
 729                                 sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
 730                                 sizeof(unsigned long));
 731
 732         for (i = 0; i < M2P_OVERRIDE_HASH; i++)
 733                 INIT_LIST_HEAD(&m2p_overrides[i]);
 734 }
 735
 736 static unsigned long mfn_hash(unsigned long mfn)
 737 {
 738         return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
 739 }
 740
 741 /* Add an MFN override for a particular page */
 742 static int m2p_add_override(unsigned long mfn, struct page *page,
 743                             struct gnttab_map_grant_ref *kmap_op)
 744 {
 745         unsigned long flags;
 746         unsigned long pfn;
 747         unsigned long uninitialized_var(address);
 748         unsigned level;
 749         pte_t *ptep = NULL;
 750
 751         pfn = page_to_pfn(page);
 752         if (!PageHighMem(page)) {
 753                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
 754                 ptep = lookup_address(address, &level);
 755                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
 756                          "m2p_add_override: pfn %lx not mapped", pfn))
 757                         return -EINVAL;
 758         }
 759
 760         if (kmap_op != NULL) {
 761                 if (!PageHighMem(page)) {
 762                         struct multicall_space mcs =
 763                                 xen_mc_entry(sizeof(*kmap_op));
 764
 765                         MULTI_grant_table_op(mcs.mc,
 766                                         GNTTABOP_map_grant_ref, kmap_op, 1);
 767
 768                         xen_mc_issue(PARAVIRT_LAZY_MMU);
 769                 }
 770         }
 771         spin_lock_irqsave(&m2p_override_lock, flags);
 772         list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
 773         spin_unlock_irqrestore(&m2p_override_lock, flags);
 774
 775         /* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
 776          * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
 777          * pfn so that the following mfn_to_pfn(mfn) calls will return the
 778          * pfn from the m2p_override (the backend pfn) instead.
 779          * We need to do this because the pages shared by the frontend
 780          * (xen-blkfront) can be already locked (lock_page, called by
 781          * do_read_cache_page); when the userspace backend tries to use them
 782          * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
 783          * do_blockdev_direct_IO is going to try to lock the same pages
 784          * again resulting in a deadlock.
 785          * As a side effect get_user_pages_fast might not be safe on the
 786          * frontend pages while they are being shared with the backend,
 787          * because mfn_to_pfn (that ends up being called by GUPF) will
 788          * return the backend pfn rather than the frontend pfn. */
 789         pfn = mfn_to_pfn_no_overrides(mfn);
 790         if (__pfn_to_mfn(pfn) == mfn)
 791                 set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
 792
 793         return 0;
 794 }
 795
 796 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 797                             struct gnttab_map_grant_ref *kmap_ops,
 798                             struct page **pages, unsigned int count)
 799 {
 800         int i, ret = 0;
 801         bool lazy = false;
 802         pte_t *pte;
 803
 804         if (xen_feature(XENFEAT_auto_translated_physmap))
 805                 return 0;
 806
 807         if (kmap_ops &&
 808             !in_interrupt() &&
 809             paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
 810                 arch_enter_lazy_mmu_mode();
 811                 lazy = true;
 812         }
 813
 814         for (i = 0; i < count; i++) {
 815                 unsigned long mfn, pfn;
 816
 817                 /* Do not add to override if the map failed. */
 818                 if (map_ops[i].status)
 819                         continue;
 820
 821                 if (map_ops[i].flags & GNTMAP_contains_pte) {
 822                         pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
 823                                 (map_ops[i].host_addr & ~PAGE_MASK));
 824                         mfn = pte_mfn(*pte);
 825                 } else {
 826                         mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 827                 }
 828                 pfn = page_to_pfn(pages[i]);
 829
 830                 WARN_ON(PagePrivate(pages[i]));
 831                 SetPagePrivate(pages[i]);
 832                 set_page_private(pages[i], mfn);
 833                 pages[i]->index = pfn_to_mfn(pfn);
 834
 835                 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
 836                         ret = -ENOMEM;
 837                         goto out;
 838                 }
 839
 840                 if (kmap_ops) {
 841                         ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
 842                         if (ret)
 843                                 goto out;
 844                 }
 845         }
 846
 847 out:
 848         if (lazy)
 849                 arch_leave_lazy_mmu_mode();
 850
 851         return ret;
 852 }
 853 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
 854
 855 static struct page *m2p_find_override(unsigned long mfn)
 856 {
 857         unsigned long flags;
 858         struct list_head *bucket;
 859         struct page *p, *ret;
 860
 861         if (unlikely(!m2p_overrides))
 862                 return NULL;
 863
 864         ret = NULL;
 865         bucket = &m2p_overrides[mfn_hash(mfn)];
 866
 867         spin_lock_irqsave(&m2p_override_lock, flags);
 868
 869         list_for_each_entry(p, bucket, lru) {
 870                 if (page_private(p) == mfn) {
 871                         ret = p;
 872                         break;
 873                 }
 874         }
 875
 876         spin_unlock_irqrestore(&m2p_override_lock, flags);
 877
 878         return ret;
 879 }
 880
 881 static int m2p_remove_override(struct page *page,
 882                                struct gnttab_map_grant_ref *kmap_op,
 883                                unsigned long mfn)
 884 {
 885         unsigned long flags;
 886         unsigned long pfn;
 887         unsigned long uninitialized_var(address);
 888         unsigned level;
 889         pte_t *ptep = NULL;
 890
 891         pfn = page_to_pfn(page);
 892
 893         if (!PageHighMem(page)) {
 894                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
 895                 ptep = lookup_address(address, &level);
 896
 897                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
 898                          "m2p_remove_override: pfn %lx not mapped", pfn))
 899                         return -EINVAL;
 900         }
 901
 902         spin_lock_irqsave(&m2p_override_lock, flags);
 903         list_del(&page->lru);
 904         spin_unlock_irqrestore(&m2p_override_lock, flags);
 905
 906         if (kmap_op != NULL) {
 907                 if (!PageHighMem(page)) {
 908                         struct multicall_space mcs;
 909                         struct gnttab_unmap_and_replace *unmap_op;
 910                         struct page *scratch_page = get_balloon_scratch_page();
 911                         unsigned long scratch_page_address = (unsigned long)
 912                                 __va(page_to_pfn(scratch_page) << PAGE_SHIFT);
 913
 914                         /*
 915                          * It might be that we queued all the m2p grant table
 916                          * hypercalls in a multicall, then m2p_remove_override
 917                          * get called before the multicall has actually been
 918                          * issued. In this case handle is going to -1 because
 919                          * it hasn't been modified yet.
 920                          */
 921                         if (kmap_op->handle == -1)
 922                                 xen_mc_flush();
 923                         /*
 924                          * Now if kmap_op->handle is negative it means that the
 925                          * hypercall actually returned an error.
 926                          */
 927                         if (kmap_op->handle == GNTST_general_error) {
 928                                 pr_warn("m2p_remove_override: pfn %lx mfn %lx, failed to modify kernel mappings",
 929                                         pfn, mfn);
 930                                 put_balloon_scratch_page();
 931                                 return -1;
 932                         }
 933
 934                         xen_mc_batch();
 935
 936                         mcs = __xen_mc_entry(
 937                                 sizeof(struct gnttab_unmap_and_replace));
 938                         unmap_op = mcs.args;
 939                         unmap_op->host_addr = kmap_op->host_addr;
 940                         unmap_op->new_addr = scratch_page_address;
 941                         unmap_op->handle = kmap_op->handle;
 942
 943                         MULTI_grant_table_op(mcs.mc,
 944                                 GNTTABOP_unmap_and_replace, unmap_op, 1);
 945
 946                         mcs = __xen_mc_entry(0);
 947                         MULTI_update_va_mapping(mcs.mc, scratch_page_address,
 948                                         pfn_pte(page_to_pfn(scratch_page),
 949                                         PAGE_KERNEL_RO), 0);
 950
 951                         xen_mc_issue(PARAVIRT_LAZY_MMU);
 952
 953                         kmap_op->host_addr = 0;
 954                         put_balloon_scratch_page();
 955                 }
 956         }
 957
 958         /* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present
 959          * somewhere in this domain, even before being added to the
 960          * m2p_override (see comment above in m2p_add_override).
 961          * If there are no other entries in the m2p_override corresponding
 962          * to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for
 963          * the original pfn (the one shared by the frontend): the backend
 964          * cannot do any IO on this page anymore because it has been
 965          * unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of
 966          * the original pfn causes mfn_to_pfn(mfn) to return the frontend
 967          * pfn again. */
 968         mfn &= ~FOREIGN_FRAME_BIT;
 969         pfn = mfn_to_pfn_no_overrides(mfn);
 970         if (__pfn_to_mfn(pfn) == FOREIGN_FRAME(mfn) &&
 971                         m2p_find_override(mfn) == NULL)
 972                 set_phys_to_machine(pfn, mfn);
 973
 974         return 0;
 975 }
 976
 977 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 978                               struct gnttab_map_grant_ref *kmap_ops,
 979                               struct page **pages, unsigned int count)
 980 {
 981         int i, ret = 0;
 982         bool lazy = false;
 983
 984         if (xen_feature(XENFEAT_auto_translated_physmap))
 985                 return 0;
 986
 987         if (kmap_ops &&
 988             !in_interrupt() &&
 989             paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
 990                 arch_enter_lazy_mmu_mode();
 991                 lazy = true;
 992         }
 993
 994         for (i = 0; i < count; i++) {
 995                 unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
 996                 unsigned long pfn = page_to_pfn(pages[i]);
 997
 998                 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
 999                         ret = -EINVAL;
1000                         goto out;
1001                 }
1002
1003                 set_page_private(pages[i], INVALID_P2M_ENTRY);
1004                 WARN_ON(!PagePrivate(pages[i]));
1005                 ClearPagePrivate(pages[i]);
1006                 set_phys_to_machine(pfn, pages[i]->index);
1007
1008                 if (kmap_ops)
1009                         ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
1010                 if (ret)
1011                         goto out;
1012         }
1013
1014 out:
1015         if (lazy)
1016                 arch_leave_lazy_mmu_mode();
1017         return ret;
1018 }
1019 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
1020
1021 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
1022 {
1023         struct page *p = m2p_find_override(mfn);
1024         unsigned long ret = pfn;
1025
1026         if (p)
1027                 ret = page_to_pfn(p);
1028
1029         return ret;
1030 }
1031 EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
1032
1033 #ifdef CONFIG_XEN_DEBUG_FS
1034 #include <linux/debugfs.h>
1035 #include "debugfs.h"
1036 static int p2m_dump_show(struct seq_file *m, void *v)
1037 {
1038         static const char * const level_name[] = { "top", "middle",
1039                                                 "entry", "abnormal", "error"};
1040 #define TYPE_IDENTITY 0
1041 #define TYPE_MISSING 1
1042 #define TYPE_PFN 2
1043 #define TYPE_UNKNOWN 3
1044         static const char * const type_name[] = {
1045                                 [TYPE_IDENTITY] = "identity",
1046                                 [TYPE_MISSING] = "missing",
1047                                 [TYPE_PFN] = "pfn",
1048                                 [TYPE_UNKNOWN] = "abnormal"};
1049         unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
1050         unsigned int uninitialized_var(prev_level);
1051         unsigned int uninitialized_var(prev_type);
1052
1053         if (!p2m_top)
1054                 return 0;
1055
1056         for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
1057                 unsigned topidx = p2m_top_index(pfn);
1058                 unsigned mididx = p2m_mid_index(pfn);
1059                 unsigned idx = p2m_index(pfn);
1060                 unsigned lvl, type;
1061
1062                 lvl = 4;
1063                 type = TYPE_UNKNOWN;
1064                 if (p2m_top[topidx] == p2m_mid_missing) {
1065                         lvl = 0; type = TYPE_MISSING;
1066                 } else if (p2m_top[topidx] == NULL) {
1067                         lvl = 0; type = TYPE_UNKNOWN;
1068                 } else if (p2m_top[topidx][mididx] == NULL) {
1069                         lvl = 1; type = TYPE_UNKNOWN;
1070                 } else if (p2m_top[topidx][mididx] == p2m_identity) {
1071                         lvl = 1; type = TYPE_IDENTITY;
1072                 } else if (p2m_top[topidx][mididx] == p2m_missing) {
1073                         lvl = 1; type = TYPE_MISSING;
1074                 } else if (p2m_top[topidx][mididx][idx] == 0) {
1075                         lvl = 2; type = TYPE_UNKNOWN;
1076                 } else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
1077                         lvl = 2; type = TYPE_IDENTITY;
1078                 } else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
1079                         lvl = 2; type = TYPE_MISSING;
1080                 } else if (p2m_top[topidx][mididx][idx] == pfn) {
1081                         lvl = 2; type = TYPE_PFN;
1082                 } else if (p2m_top[topidx][mididx][idx] != pfn) {
1083                         lvl = 2; type = TYPE_PFN;
1084                 }
1085                 if (pfn == 0) {
1086                         prev_level = lvl;
1087                         prev_type = type;
1088                 }
1089                 if (pfn == MAX_DOMAIN_PAGES-1) {
1090                         lvl = 3;
1091                         type = TYPE_UNKNOWN;
1092                 }
1093                 if (prev_type != type) {
1094                         seq_printf(m, " [0x%lx->0x%lx] %s\n",
1095                                 prev_pfn_type, pfn, type_name[prev_type]);
1096                         prev_pfn_type = pfn;
1097                         prev_type = type;
1098                 }
1099                 if (prev_level != lvl) {
1100                         seq_printf(m, " [0x%lx->0x%lx] level %s\n",
1101                                 prev_pfn_level, pfn, level_name[prev_level]);
1102                         prev_pfn_level = pfn;
1103                         prev_level = lvl;
1104                 }
1105         }
1106         return 0;
1107 #undef TYPE_IDENTITY
1108 #undef TYPE_MISSING
1109 #undef TYPE_PFN
1110 #undef TYPE_UNKNOWN
1111 }
1112
1113 static int p2m_dump_open(struct inode *inode, struct file *filp)
1114 {
1115         return single_open(filp, p2m_dump_show, NULL);
1116 }
1117
1118 static const struct file_operations p2m_dump_fops = {
1119         .open           = p2m_dump_open,
1120         .read           = seq_read,
1121         .llseek         = seq_lseek,
1122         .release        = single_release,
1123 };
1124
1125 static struct dentry *d_mmu_debug;
1126
1127 static int __init xen_p2m_debugfs(void)
1128 {
1129         struct dentry *d_xen = xen_init_debugfs();
1130
1131         if (d_xen == NULL)
1132                 return -ENOMEM;
1133
1134         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
1135
1136         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
1137         return 0;
1138 }
1139 fs_initcall(xen_p2m_debugfs);
1140 #endif /* CONFIG_XEN_DEBUG_FS */