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
 167 #include <asm/cache.h>
 168 #include <asm/setup.h>
 169
 170 #include <asm/xen/page.h>
 171 #include <asm/xen/hypercall.h>
 172 #include <asm/xen/hypervisor.h>
 173 #include <xen/balloon.h>
 174 #include <xen/grant_table.h>
 175
 176 #include "multicalls.h"
 177 #include "xen-ops.h"
 178
 179 static void __init m2p_override_init(void);
 180
 181 unsigned long xen_max_p2m_pfn __read_mostly;
 182
 183 #define P2M_PER_PAGE            (PAGE_SIZE / sizeof(unsigned long))
 184 #define P2M_MID_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long *))
 185 #define P2M_TOP_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long **))
 186
 187 #define MAX_P2M_PFN             (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
 188
 189 /* Placeholders for holes in the address space */
 190 static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
 191 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
 192 static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);
 193
 194 static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
 195 static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);
 196 static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE);
 197
 198 static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
 199 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_identity, P2M_MID_PER_PAGE);
 200 static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_identity_mfn, P2M_MID_PER_PAGE);
 201
 202 RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
 203 RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
 204
 205 /* We might hit two boundary violations at the start and end, at max each
 206  * boundary violation will require three middle nodes. */
 207 RESERVE_BRK(p2m_mid_extra, PAGE_SIZE * 2 * 3);
 208
 209 /* When we populate back during bootup, the amount of pages can vary. The
 210  * max we have is seen is 395979, but that does not mean it can't be more.
 211  * Some machines can have 3GB I/O holes even. With early_can_reuse_p2m_middle
 212  * it can re-use Xen provided mfn_list array, so we only need to allocate at
 213  * most three P2M top nodes. */
 214 RESERVE_BRK(p2m_populated, PAGE_SIZE * 3);
 215
 216 static inline unsigned p2m_top_index(unsigned long pfn)
 217 {
 218         BUG_ON(pfn >= MAX_P2M_PFN);
 219         return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
 220 }
 221
 222 static inline unsigned p2m_mid_index(unsigned long pfn)
 223 {
 224         return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
 225 }
 226
 227 static inline unsigned p2m_index(unsigned long pfn)
 228 {
 229         return pfn % P2M_PER_PAGE;
 230 }
 231
 232 static void p2m_top_init(unsigned long ***top)
 233 {
 234         unsigned i;
 235
 236         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 237                 top[i] = p2m_mid_missing;
 238 }
 239
 240 static void p2m_top_mfn_init(unsigned long *top)
 241 {
 242         unsigned i;
 243
 244         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 245                 top[i] = virt_to_mfn(p2m_mid_missing_mfn);
 246 }
 247
 248 static void p2m_top_mfn_p_init(unsigned long **top)
 249 {
 250         unsigned i;
 251
 252         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 253                 top[i] = p2m_mid_missing_mfn;
 254 }
 255
 256 static void p2m_mid_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] = leaf;
 262 }
 263
 264 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
 265 {
 266         unsigned i;
 267
 268         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 269                 mid[i] = virt_to_mfn(leaf);
 270 }
 271
 272 static void p2m_init(unsigned long *p2m)
 273 {
 274         unsigned i;
 275
 276         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 277                 p2m[i] = INVALID_P2M_ENTRY;
 278 }
 279
 280 /*
 281  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
 282  *
 283  * This is called both at boot time, and after resuming from suspend:
 284  * - At boot time we're called very early, and must use extend_brk()
 285  *   to allocate memory.
 286  *
 287  * - After resume we're called from within stop_machine, but the mfn
 288  *   tree should alreay be completely allocated.
 289  */
 290 void __ref xen_build_mfn_list_list(void)
 291 {
 292         unsigned long pfn;
 293
 294         if (xen_feature(XENFEAT_auto_translated_physmap))
 295                 return;
 296
 297         /* Pre-initialize p2m_top_mfn to be completely missing */
 298         if (p2m_top_mfn == NULL) {
 299                 p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
 300                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 301                 p2m_mid_identity_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
 302                 p2m_mid_mfn_init(p2m_mid_identity_mfn, p2m_identity);
 303
 304                 p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
 305                 p2m_top_mfn_p_init(p2m_top_mfn_p);
 306
 307                 p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
 308                 p2m_top_mfn_init(p2m_top_mfn);
 309         } else {
 310                 /* Reinitialise, mfn's all change after migration */
 311                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 312                 p2m_mid_mfn_init(p2m_mid_identity_mfn, p2m_identity);
 313         }
 314
 315         for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
 316                 unsigned topidx = p2m_top_index(pfn);
 317                 unsigned mididx = p2m_mid_index(pfn);
 318                 unsigned long **mid;
 319                 unsigned long *mid_mfn_p;
 320
 321                 mid = p2m_top[topidx];
 322                 mid_mfn_p = p2m_top_mfn_p[topidx];
 323
 324                 /* Don't bother allocating any mfn mid levels if
 325                  * they're just missing, just update the stored mfn,
 326                  * since all could have changed over a migrate.
 327                  */
 328                 if (mid == p2m_mid_missing) {
 329                         BUG_ON(mididx);
 330                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 331                         p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
 332                         pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
 333                         continue;
 334                 }
 335
 336                 if (mid_mfn_p == p2m_mid_missing_mfn) {
 337                         /*
 338                          * XXX boot-time only!  We should never find
 339                          * missing parts of the mfn tree after
 340                          * runtime.  extend_brk() will BUG if we call
 341                          * it too late.
 342                          */
 343                         mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
 344                         p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
 345
 346                         p2m_top_mfn_p[topidx] = mid_mfn_p;
 347                 }
 348
 349                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
 350                 mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
 351         }
 352 }
 353
 354 void xen_setup_mfn_list_list(void)
 355 {
 356         if (xen_feature(XENFEAT_auto_translated_physmap))
 357                 return;
 358
 359         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
 360
 361         HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
 362                 virt_to_mfn(p2m_top_mfn);
 363         HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
 364 }
 365
 366 /* Set up p2m_top to point to the domain-builder provided p2m pages */
 367 void __init xen_build_dynamic_phys_to_machine(void)
 368 {
 369         unsigned long *mfn_list;
 370         unsigned long max_pfn;
 371         unsigned long pfn;
 372
 373          if (xen_feature(XENFEAT_auto_translated_physmap))
 374                 return;
 375
 376         mfn_list = (unsigned long *)xen_start_info->mfn_list;
 377         max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
 378         xen_max_p2m_pfn = max_pfn;
 379
 380         p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
 381         p2m_init(p2m_missing);
 382         p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
 383         p2m_init(p2m_identity);
 384
 385         p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
 386         p2m_mid_init(p2m_mid_missing, p2m_missing);
 387         p2m_mid_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
 388         p2m_mid_init(p2m_mid_identity, p2m_identity);
 389
 390         p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
 391         p2m_top_init(p2m_top);
 392
 393         /*
 394          * The domain builder gives us a pre-constructed p2m array in
 395          * mfn_list for all the pages initially given to us, so we just
 396          * need to graft that into our tree structure.
 397          */
 398         for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
 399                 unsigned topidx = p2m_top_index(pfn);
 400                 unsigned mididx = p2m_mid_index(pfn);
 401
 402                 if (p2m_top[topidx] == p2m_mid_missing) {
 403                         unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
 404                         p2m_mid_init(mid, p2m_missing);
 405
 406                         p2m_top[topidx] = mid;
 407                 }
 408
 409                 /*
 410                  * As long as the mfn_list has enough entries to completely
 411                  * fill a p2m page, pointing into the array is ok. But if
 412                  * not the entries beyond the last pfn will be undefined.
 413                  */
 414                 if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
 415                         unsigned long p2midx;
 416
 417                         p2midx = max_pfn % P2M_PER_PAGE;
 418                         for ( ; p2midx < P2M_PER_PAGE; p2midx++)
 419                                 mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
 420                 }
 421                 p2m_top[topidx][mididx] = &mfn_list[pfn];
 422         }
 423
 424         m2p_override_init();
 425 }
 426 #ifdef CONFIG_X86_64
 427 #include <linux/bootmem.h>
 428 unsigned long __init xen_revector_p2m_tree(void)
 429 {
 430         unsigned long va_start;
 431         unsigned long va_end;
 432         unsigned long pfn;
 433         unsigned long pfn_free = 0;
 434         unsigned long *mfn_list = NULL;
 435         unsigned long size;
 436
 437         va_start = xen_start_info->mfn_list;
 438         /*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long),
 439          * so make sure it is rounded up to that */
 440         size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
 441         va_end = va_start + size;
 442
 443         /* If we were revectored already, don't do it again. */
 444         if (va_start <= __START_KERNEL_map && va_start >= __PAGE_OFFSET)
 445                 return 0;
 446
 447         mfn_list = alloc_bootmem_align(size, PAGE_SIZE);
 448         if (!mfn_list) {
 449                 pr_warn("Could not allocate space for a new P2M tree!\n");
 450                 return xen_start_info->mfn_list;
 451         }
 452         /* Fill it out with INVALID_P2M_ENTRY value */
 453         memset(mfn_list, 0xFF, size);
 454
 455         for (pfn = 0; pfn < ALIGN(MAX_DOMAIN_PAGES, P2M_PER_PAGE); pfn += P2M_PER_PAGE) {
 456                 unsigned topidx = p2m_top_index(pfn);
 457                 unsigned mididx;
 458                 unsigned long *mid_p;
 459
 460                 if (!p2m_top[topidx])
 461                         continue;
 462
 463                 if (p2m_top[topidx] == p2m_mid_missing)
 464                         continue;
 465
 466                 mididx = p2m_mid_index(pfn);
 467                 mid_p = p2m_top[topidx][mididx];
 468                 if (!mid_p)
 469                         continue;
 470                 if ((mid_p == p2m_missing) || (mid_p == p2m_identity))
 471                         continue;
 472
 473                 if ((unsigned long)mid_p == INVALID_P2M_ENTRY)
 474                         continue;
 475
 476                 /* The old va. Rebase it on mfn_list */
 477                 if (mid_p >= (unsigned long *)va_start && mid_p <= (unsigned long *)va_end) {
 478                         unsigned long *new;
 479
 480                         if (pfn_free  > (size / sizeof(unsigned long))) {
 481                                 WARN(1, "Only allocated for %ld pages, but we want %ld!\n",
 482                                      size / sizeof(unsigned long), pfn_free);
 483                                 return 0;
 484                         }
 485                         new = &mfn_list[pfn_free];
 486
 487                         copy_page(new, mid_p);
 488                         p2m_top[topidx][mididx] = &mfn_list[pfn_free];
 489                         p2m_top_mfn_p[topidx][mididx] = virt_to_mfn(&mfn_list[pfn_free]);
 490
 491                         pfn_free += P2M_PER_PAGE;
 492
 493                 }
 494                 /* This should be the leafs allocated for identity from _brk. */
 495         }
 496         return (unsigned long)mfn_list;
 497
 498 }
 499 #else
 500 unsigned long __init xen_revector_p2m_tree(void)
 501 {
 502         return 0;
 503 }
 504 #endif
 505 unsigned long get_phys_to_machine(unsigned long pfn)
 506 {
 507         unsigned topidx, mididx, idx;
 508
 509         if (unlikely(pfn >= MAX_P2M_PFN))
 510                 return IDENTITY_FRAME(pfn);
 511
 512         topidx = p2m_top_index(pfn);
 513         mididx = p2m_mid_index(pfn);
 514         idx = p2m_index(pfn);
 515
 516         /*
 517          * The INVALID_P2M_ENTRY is filled in both p2m_*identity
 518          * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
 519          * would be wrong.
 520          */
 521         if (p2m_top[topidx][mididx] == p2m_identity)
 522                 return IDENTITY_FRAME(pfn);
 523
 524         return p2m_top[topidx][mididx][idx];
 525 }
 526 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 527
 528 static void *alloc_p2m_page(void)
 529 {
 530         return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
 531 }
 532
 533 static void free_p2m_page(void *p)
 534 {
 535         free_page((unsigned long)p);
 536 }
 537
 538 /*
 539  * Fully allocate the p2m structure for a given pfn.  We need to check
 540  * that both the top and mid levels are allocated, and make sure the
 541  * parallel mfn tree is kept in sync.  We may race with other cpus, so
 542  * the new pages are installed with cmpxchg; if we lose the race then
 543  * simply free the page we allocated and use the one that's there.
 544  */
 545 static bool alloc_p2m(unsigned long pfn)
 546 {
 547         unsigned topidx, mididx;
 548         unsigned long ***top_p, **mid;
 549         unsigned long *top_mfn_p, *mid_mfn;
 550
 551         topidx = p2m_top_index(pfn);
 552         mididx = p2m_mid_index(pfn);
 553
 554         top_p = &p2m_top[topidx];
 555         mid = *top_p;
 556
 557         if (mid == p2m_mid_missing) {
 558                 /* Mid level is missing, allocate a new one */
 559                 mid = alloc_p2m_page();
 560                 if (!mid)
 561                         return false;
 562
 563                 p2m_mid_init(mid, p2m_missing);
 564
 565                 if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
 566                         free_p2m_page(mid);
 567         }
 568
 569         top_mfn_p = &p2m_top_mfn[topidx];
 570         mid_mfn = p2m_top_mfn_p[topidx];
 571
 572         BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
 573
 574         if (mid_mfn == p2m_mid_missing_mfn) {
 575                 /* Separately check the mid mfn level */
 576                 unsigned long missing_mfn;
 577                 unsigned long mid_mfn_mfn;
 578
 579                 mid_mfn = alloc_p2m_page();
 580                 if (!mid_mfn)
 581                         return false;
 582
 583                 p2m_mid_mfn_init(mid_mfn, p2m_missing);
 584
 585                 missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
 586                 mid_mfn_mfn = virt_to_mfn(mid_mfn);
 587                 if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)
 588                         free_p2m_page(mid_mfn);
 589                 else
 590                         p2m_top_mfn_p[topidx] = mid_mfn;
 591         }
 592
 593         if (p2m_top[topidx][mididx] == p2m_identity ||
 594             p2m_top[topidx][mididx] == p2m_missing) {
 595                 /* p2m leaf page is missing */
 596                 unsigned long *p2m;
 597                 unsigned long *p2m_orig = p2m_top[topidx][mididx];
 598
 599                 p2m = alloc_p2m_page();
 600                 if (!p2m)
 601                         return false;
 602
 603                 p2m_init(p2m);
 604
 605                 if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
 606                         free_p2m_page(p2m);
 607                 else
 608                         mid_mfn[mididx] = virt_to_mfn(p2m);
 609         }
 610
 611         return true;
 612 }
 613
 614 static bool __init early_alloc_p2m(unsigned long pfn, bool check_boundary)
 615 {
 616         unsigned topidx, mididx, idx;
 617         unsigned long *p2m;
 618         unsigned long *mid_mfn_p;
 619
 620         topidx = p2m_top_index(pfn);
 621         mididx = p2m_mid_index(pfn);
 622         idx = p2m_index(pfn);
 623
 624         /* Pfff.. No boundary cross-over, lets get out. */
 625         if (!idx && check_boundary)
 626                 return false;
 627
 628         WARN(p2m_top[topidx][mididx] == p2m_identity,
 629                 "P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
 630                 topidx, mididx);
 631
 632         /*
 633          * Could be done by xen_build_dynamic_phys_to_machine..
 634          */
 635         if (p2m_top[topidx][mididx] != p2m_missing)
 636                 return false;
 637
 638         /* Boundary cross-over for the edges: */
 639         p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
 640
 641         p2m_init(p2m);
 642
 643         p2m_top[topidx][mididx] = p2m;
 644
 645         /* For save/restore we need to MFN of the P2M saved */
 646
 647         mid_mfn_p = p2m_top_mfn_p[topidx];
 648         WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing),
 649                 "P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n",
 650                 topidx, mididx);
 651         mid_mfn_p[mididx] = virt_to_mfn(p2m);
 652
 653         return true;
 654 }
 655
 656 static bool __init early_alloc_p2m_middle(unsigned long pfn)
 657 {
 658         unsigned topidx = p2m_top_index(pfn);
 659         unsigned long *mid_mfn_p;
 660         unsigned long **mid;
 661
 662         mid = p2m_top[topidx];
 663         mid_mfn_p = p2m_top_mfn_p[topidx];
 664         if (mid == p2m_mid_missing) {
 665                 mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
 666
 667                 p2m_mid_init(mid, p2m_missing);
 668
 669                 p2m_top[topidx] = mid;
 670
 671                 BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 672         }
 673         /* And the save/restore P2M tables.. */
 674         if (mid_mfn_p == p2m_mid_missing_mfn) {
 675                 mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
 676                 p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
 677
 678                 p2m_top_mfn_p[topidx] = mid_mfn_p;
 679                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
 680                 /* Note: we don't set mid_mfn_p[midix] here,
 681                  * look in early_alloc_p2m() */
 682         }
 683         return true;
 684 }
 685
 686 /*
 687  * Skim over the P2M tree looking at pages that are either filled with
 688  * INVALID_P2M_ENTRY or with 1:1 PFNs. If found, re-use that page and
 689  * replace the P2M leaf with a p2m_missing or p2m_identity.
 690  * Stick the old page in the new P2M tree location.
 691  */
 692 bool __init early_can_reuse_p2m_middle(unsigned long set_pfn, unsigned long set_mfn)
 693 {
 694         unsigned topidx;
 695         unsigned mididx;
 696         unsigned ident_pfns;
 697         unsigned inv_pfns;
 698         unsigned long *p2m;
 699         unsigned long *mid_mfn_p;
 700         unsigned idx;
 701         unsigned long pfn;
 702
 703         /* We only look when this entails a P2M middle layer */
 704         if (p2m_index(set_pfn))
 705                 return false;
 706
 707         for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
 708                 topidx = p2m_top_index(pfn);
 709
 710                 if (!p2m_top[topidx])
 711                         continue;
 712
 713                 if (p2m_top[topidx] == p2m_mid_missing)
 714                         continue;
 715
 716                 mididx = p2m_mid_index(pfn);
 717                 p2m = p2m_top[topidx][mididx];
 718                 if (!p2m)
 719                         continue;
 720
 721                 if ((p2m == p2m_missing) || (p2m == p2m_identity))
 722                         continue;
 723
 724                 if ((unsigned long)p2m == INVALID_P2M_ENTRY)
 725                         continue;
 726
 727                 ident_pfns = 0;
 728                 inv_pfns = 0;
 729                 for (idx = 0; idx < P2M_PER_PAGE; idx++) {
 730                         /* IDENTITY_PFNs are 1:1 */
 731                         if (p2m[idx] == IDENTITY_FRAME(pfn + idx))
 732                                 ident_pfns++;
 733                         else if (p2m[idx] == INVALID_P2M_ENTRY)
 734                                 inv_pfns++;
 735                         else
 736                                 break;
 737                 }
 738                 if ((ident_pfns == P2M_PER_PAGE) || (inv_pfns == P2M_PER_PAGE))
 739                         goto found;
 740         }
 741         return false;
 742 found:
 743         /* Found one, replace old with p2m_identity or p2m_missing */
 744         p2m_top[topidx][mididx] = (ident_pfns ? p2m_identity : p2m_missing);
 745         /* And the other for save/restore.. */
 746         mid_mfn_p = p2m_top_mfn_p[topidx];
 747         /* NOTE: Even if it is a p2m_identity it should still be point to
 748          * a page filled with INVALID_P2M_ENTRY entries. */
 749         mid_mfn_p[mididx] = virt_to_mfn(p2m_missing);
 750
 751         /* Reset where we want to stick the old page in. */
 752         topidx = p2m_top_index(set_pfn);
 753         mididx = p2m_mid_index(set_pfn);
 754
 755         /* This shouldn't happen */
 756         if (WARN_ON(p2m_top[topidx] == p2m_mid_missing))
 757                 early_alloc_p2m_middle(set_pfn);
 758
 759         if (WARN_ON(p2m_top[topidx][mididx] != p2m_missing))
 760                 return false;
 761
 762         p2m_init(p2m);
 763         p2m_top[topidx][mididx] = p2m;
 764         mid_mfn_p = p2m_top_mfn_p[topidx];
 765         mid_mfn_p[mididx] = virt_to_mfn(p2m);
 766
 767         return true;
 768 }
 769 bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 770 {
 771         if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
 772                 if (!early_alloc_p2m_middle(pfn))
 773                         return false;
 774
 775                 if (early_can_reuse_p2m_middle(pfn, mfn))
 776                         return __set_phys_to_machine(pfn, mfn);
 777
 778                 if (!early_alloc_p2m(pfn, false /* boundary crossover OK!*/))
 779                         return false;
 780
 781                 if (!__set_phys_to_machine(pfn, mfn))
 782                         return false;
 783         }
 784
 785         return true;
 786 }
 787
 788 static void __init early_split_p2m(unsigned long pfn)
 789 {
 790         unsigned long mididx, idx;
 791
 792         mididx = p2m_mid_index(pfn);
 793         idx = p2m_index(pfn);
 794
 795         /*
 796          * Allocate new middle and leaf pages if this pfn lies in the
 797          * middle of one.
 798          */
 799         if (mididx || idx)
 800                 early_alloc_p2m_middle(pfn);
 801         if (idx)
 802                 early_alloc_p2m(pfn, false);
 803 }
 804
 805 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 806                                       unsigned long pfn_e)
 807 {
 808         unsigned long pfn;
 809
 810         if (unlikely(pfn_s >= MAX_P2M_PFN))
 811                 return 0;
 812
 813         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
 814                 return pfn_e - pfn_s;
 815
 816         if (pfn_s > pfn_e)
 817                 return 0;
 818
 819         if (pfn_e > MAX_P2M_PFN)
 820                 pfn_e = MAX_P2M_PFN;
 821
 822         early_split_p2m(pfn_s);
 823         early_split_p2m(pfn_e);
 824
 825         for (pfn = pfn_s; pfn < pfn_e;) {
 826                 unsigned topidx = p2m_top_index(pfn);
 827                 unsigned mididx = p2m_mid_index(pfn);
 828
 829                 if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
 830                         break;
 831                 pfn++;
 832
 833                 /*
 834                  * If the PFN was set to a middle or leaf identity
 835                  * page the remainder must also be identity, so skip
 836                  * ahead to the next middle or leaf entry.
 837                  */
 838                 if (p2m_top[topidx] == p2m_mid_identity)
 839                         pfn = ALIGN(pfn, P2M_MID_PER_PAGE * P2M_PER_PAGE);
 840                 else if (p2m_top[topidx][mididx] == p2m_identity)
 841                         pfn = ALIGN(pfn, P2M_PER_PAGE);
 842         }
 843
 844         if (!WARN((pfn - pfn_s) != (pfn_e - pfn_s),
 845                 "Identity mapping failed. We are %ld short of 1-1 mappings!\n",
 846                 (pfn_e - pfn_s) - (pfn - pfn_s)))
 847                 printk(KERN_DEBUG "1-1 mapping on %lx->%lx\n", pfn_s, pfn);
 848
 849         return pfn - pfn_s;
 850 }
 851
 852 /* Try to install p2m mapping; fail if intermediate bits missing */
 853 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 854 {
 855         unsigned topidx, mididx, idx;
 856
 857         /* don't track P2M changes in autotranslate guests */
 858         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
 859                 return true;
 860
 861         if (unlikely(pfn >= MAX_P2M_PFN)) {
 862                 BUG_ON(mfn != INVALID_P2M_ENTRY);
 863                 return true;
 864         }
 865
 866         topidx = p2m_top_index(pfn);
 867         mididx = p2m_mid_index(pfn);
 868         idx = p2m_index(pfn);
 869
 870         /* For sparse holes were the p2m leaf has real PFN along with
 871          * PCI holes, stick in the PFN as the MFN value.
 872          *
 873          * set_phys_range_identity() will have allocated new middle
 874          * and leaf pages as required so an existing p2m_mid_missing
 875          * or p2m_missing mean that whole range will be identity so
 876          * these can be switched to p2m_mid_identity or p2m_identity.
 877          */
 878         if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
 879                 if (p2m_top[topidx] == p2m_mid_identity)
 880                         return true;
 881
 882                 if (p2m_top[topidx] == p2m_mid_missing) {
 883                         WARN_ON(cmpxchg(&p2m_top[topidx], p2m_mid_missing,
 884                                         p2m_mid_identity) != p2m_mid_missing);
 885                         return true;
 886                 }
 887
 888                 if (p2m_top[topidx][mididx] == p2m_identity)
 889                         return true;
 890
 891                 /* Swap over from MISSING to IDENTITY if needed. */
 892                 if (p2m_top[topidx][mididx] == p2m_missing) {
 893                         WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
 894                                 p2m_identity) != p2m_missing);
 895                         return true;
 896                 }
 897         }
 898
 899         if (p2m_top[topidx][mididx] == p2m_missing)
 900                 return mfn == INVALID_P2M_ENTRY;
 901
 902         p2m_top[topidx][mididx][idx] = mfn;
 903
 904         return true;
 905 }
 906
 907 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 908 {
 909         if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
 910                 if (!alloc_p2m(pfn))
 911                         return false;
 912
 913                 if (!__set_phys_to_machine(pfn, mfn))
 914                         return false;
 915         }
 916
 917         return true;
 918 }
 919
 920 #define M2P_OVERRIDE_HASH_SHIFT 10
 921 #define M2P_OVERRIDE_HASH       (1 << M2P_OVERRIDE_HASH_SHIFT)
 922
 923 static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);
 924 static DEFINE_SPINLOCK(m2p_override_lock);
 925
 926 static void __init m2p_override_init(void)
 927 {
 928         unsigned i;
 929
 930         m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
 931                                    sizeof(unsigned long));
 932
 933         for (i = 0; i < M2P_OVERRIDE_HASH; i++)
 934                 INIT_LIST_HEAD(&m2p_overrides[i]);
 935 }
 936
 937 static unsigned long mfn_hash(unsigned long mfn)
 938 {
 939         return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
 940 }
 941
 942 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 943                             struct gnttab_map_grant_ref *kmap_ops,
 944                             struct page **pages, unsigned int count)
 945 {
 946         int i, ret = 0;
 947         bool lazy = false;
 948         pte_t *pte;
 949
 950         if (xen_feature(XENFEAT_auto_translated_physmap))
 951                 return 0;
 952
 953         if (kmap_ops &&
 954             !in_interrupt() &&
 955             paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
 956                 arch_enter_lazy_mmu_mode();
 957                 lazy = true;
 958         }
 959
 960         for (i = 0; i < count; i++) {
 961                 unsigned long mfn, pfn;
 962
 963                 /* Do not add to override if the map failed. */
 964                 if (map_ops[i].status)
 965                         continue;
 966
 967                 if (map_ops[i].flags & GNTMAP_contains_pte) {
 968                         pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
 969                                 (map_ops[i].host_addr & ~PAGE_MASK));
 970                         mfn = pte_mfn(*pte);
 971                 } else {
 972                         mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 973                 }
 974                 pfn = page_to_pfn(pages[i]);
 975
 976                 WARN_ON(PagePrivate(pages[i]));
 977                 SetPagePrivate(pages[i]);
 978                 set_page_private(pages[i], mfn);
 979                 pages[i]->index = pfn_to_mfn(pfn);
 980
 981                 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
 982                         ret = -ENOMEM;
 983                         goto out;
 984                 }
 985
 986                 if (kmap_ops) {
 987                         ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
 988                         if (ret)
 989                                 goto out;
 990                 }
 991         }
 992
 993 out:
 994         if (lazy)
 995                 arch_leave_lazy_mmu_mode();
 996
 997         return ret;
 998 }
 999 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
1000
1001 /* Add an MFN override for a particular page */
1002 int m2p_add_override(unsigned long mfn, struct page *page,
1003                 struct gnttab_map_grant_ref *kmap_op)
1004 {
1005         unsigned long flags;
1006         unsigned long pfn;
1007         unsigned long uninitialized_var(address);
1008         unsigned level;
1009         pte_t *ptep = NULL;
1010
1011         pfn = page_to_pfn(page);
1012         if (!PageHighMem(page)) {
1013                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
1014                 ptep = lookup_address(address, &level);
1015                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
1016                                         "m2p_add_override: pfn %lx not mapped", pfn))
1017                         return -EINVAL;
1018         }
1019
1020         if (kmap_op != NULL) {
1021                 if (!PageHighMem(page)) {
1022                         struct multicall_space mcs =
1023                                 xen_mc_entry(sizeof(*kmap_op));
1024
1025                         MULTI_grant_table_op(mcs.mc,
1026                                         GNTTABOP_map_grant_ref, kmap_op, 1);
1027
1028                         xen_mc_issue(PARAVIRT_LAZY_MMU);
1029                 }
1030         }
1031         spin_lock_irqsave(&m2p_override_lock, flags);
1032         list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
1033         spin_unlock_irqrestore(&m2p_override_lock, flags);
1034
1035         /* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
1036          * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
1037          * pfn so that the following mfn_to_pfn(mfn) calls will return the
1038          * pfn from the m2p_override (the backend pfn) instead.
1039          * We need to do this because the pages shared by the frontend
1040          * (xen-blkfront) can be already locked (lock_page, called by
1041          * do_read_cache_page); when the userspace backend tries to use them
1042          * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
1043          * do_blockdev_direct_IO is going to try to lock the same pages
1044          * again resulting in a deadlock.
1045          * As a side effect get_user_pages_fast might not be safe on the
1046          * frontend pages while they are being shared with the backend,
1047          * because mfn_to_pfn (that ends up being called by GUPF) will
1048          * return the backend pfn rather than the frontend pfn. */
1049         pfn = mfn_to_pfn_no_overrides(mfn);
1050         if (get_phys_to_machine(pfn) == mfn)
1051                 set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
1052
1053         return 0;
1054 }
1055 EXPORT_SYMBOL_GPL(m2p_add_override);
1056
1057 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
1058                               struct gnttab_map_grant_ref *kmap_ops,
1059                               struct page **pages, unsigned int count)
1060 {
1061         int i, ret = 0;
1062         bool lazy = false;
1063
1064         if (xen_feature(XENFEAT_auto_translated_physmap))
1065                 return 0;
1066
1067         if (kmap_ops &&
1068             !in_interrupt() &&
1069             paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
1070                 arch_enter_lazy_mmu_mode();
1071                 lazy = true;
1072         }
1073
1074         for (i = 0; i < count; i++) {
1075                 unsigned long mfn = get_phys_to_machine(page_to_pfn(pages[i]));
1076                 unsigned long pfn = page_to_pfn(pages[i]);
1077
1078                 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
1079                         ret = -EINVAL;
1080                         goto out;
1081                 }
1082
1083                 set_page_private(pages[i], INVALID_P2M_ENTRY);
1084                 WARN_ON(!PagePrivate(pages[i]));
1085                 ClearPagePrivate(pages[i]);
1086                 set_phys_to_machine(pfn, pages[i]->index);
1087
1088                 if (kmap_ops)
1089                         ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
1090                 if (ret)
1091                         goto out;
1092         }
1093
1094 out:
1095         if (lazy)
1096                 arch_leave_lazy_mmu_mode();
1097         return ret;
1098 }
1099 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
1100
1101 int m2p_remove_override(struct page *page,
1102                         struct gnttab_map_grant_ref *kmap_op,
1103                         unsigned long mfn)
1104 {
1105         unsigned long flags;
1106         unsigned long pfn;
1107         unsigned long uninitialized_var(address);
1108         unsigned level;
1109         pte_t *ptep = NULL;
1110
1111         pfn = page_to_pfn(page);
1112
1113         if (!PageHighMem(page)) {
1114                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
1115                 ptep = lookup_address(address, &level);
1116
1117                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
1118                                         "m2p_remove_override: pfn %lx not mapped", pfn))
1119                         return -EINVAL;
1120         }
1121
1122         spin_lock_irqsave(&m2p_override_lock, flags);
1123         list_del(&page->lru);
1124         spin_unlock_irqrestore(&m2p_override_lock, flags);
1125
1126         if (kmap_op != NULL) {
1127                 if (!PageHighMem(page)) {
1128                         struct multicall_space mcs;
1129                         struct gnttab_unmap_and_replace *unmap_op;
1130                         struct page *scratch_page = get_balloon_scratch_page();
1131                         unsigned long scratch_page_address = (unsigned long)
1132                                 __va(page_to_pfn(scratch_page) << PAGE_SHIFT);
1133
1134                         /*
1135                          * It might be that we queued all the m2p grant table
1136                          * hypercalls in a multicall, then m2p_remove_override
1137                          * get called before the multicall has actually been
1138                          * issued. In this case handle is going to -1 because
1139                          * it hasn't been modified yet.
1140                          */
1141                         if (kmap_op->handle == -1)
1142                                 xen_mc_flush();
1143                         /*
1144                          * Now if kmap_op->handle is negative it means that the
1145                          * hypercall actually returned an error.
1146                          */
1147                         if (kmap_op->handle == GNTST_general_error) {
1148                                 printk(KERN_WARNING "m2p_remove_override: "
1149                                                 "pfn %lx mfn %lx, failed to modify kernel mappings",
1150                                                 pfn, mfn);
1151                                 put_balloon_scratch_page();
1152                                 return -1;
1153                         }
1154
1155                         xen_mc_batch();
1156
1157                         mcs = __xen_mc_entry(
1158                                         sizeof(struct gnttab_unmap_and_replace));
1159                         unmap_op = mcs.args;
1160                         unmap_op->host_addr = kmap_op->host_addr;
1161                         unmap_op->new_addr = scratch_page_address;
1162                         unmap_op->handle = kmap_op->handle;
1163
1164                         MULTI_grant_table_op(mcs.mc,
1165                                         GNTTABOP_unmap_and_replace, unmap_op, 1);
1166
1167                         mcs = __xen_mc_entry(0);
1168                         MULTI_update_va_mapping(mcs.mc, scratch_page_address,
1169                                         pfn_pte(page_to_pfn(scratch_page),
1170                                         PAGE_KERNEL_RO), 0);
1171
1172                         xen_mc_issue(PARAVIRT_LAZY_MMU);
1173
1174                         kmap_op->host_addr = 0;
1175                         put_balloon_scratch_page();
1176                 }
1177         }
1178
1179         /* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present
1180          * somewhere in this domain, even before being added to the
1181          * m2p_override (see comment above in m2p_add_override).
1182          * If there are no other entries in the m2p_override corresponding
1183          * to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for
1184          * the original pfn (the one shared by the frontend): the backend
1185          * cannot do any IO on this page anymore because it has been
1186          * unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of
1187          * the original pfn causes mfn_to_pfn(mfn) to return the frontend
1188          * pfn again. */
1189         mfn &= ~FOREIGN_FRAME_BIT;
1190         pfn = mfn_to_pfn_no_overrides(mfn);
1191         if (get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) &&
1192                         m2p_find_override(mfn) == NULL)
1193                 set_phys_to_machine(pfn, mfn);
1194
1195         return 0;
1196 }
1197 EXPORT_SYMBOL_GPL(m2p_remove_override);
1198
1199 struct page *m2p_find_override(unsigned long mfn)
1200 {
1201         unsigned long flags;
1202         struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
1203         struct page *p, *ret;
1204
1205         ret = NULL;
1206
1207         spin_lock_irqsave(&m2p_override_lock, flags);
1208
1209         list_for_each_entry(p, bucket, lru) {
1210                 if (page_private(p) == mfn) {
1211                         ret = p;
1212                         break;
1213                 }
1214         }
1215
1216         spin_unlock_irqrestore(&m2p_override_lock, flags);
1217
1218         return ret;
1219 }
1220
1221 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
1222 {
1223         struct page *p = m2p_find_override(mfn);
1224         unsigned long ret = pfn;
1225
1226         if (p)
1227                 ret = page_to_pfn(p);
1228
1229         return ret;
1230 }
1231 EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
1232
1233 #ifdef CONFIG_XEN_DEBUG_FS
1234 #include <linux/debugfs.h>
1235 #include "debugfs.h"
1236 static int p2m_dump_show(struct seq_file *m, void *v)
1237 {
1238         static const char * const level_name[] = { "top", "middle",
1239                                                 "entry", "abnormal", "error"};
1240 #define TYPE_IDENTITY 0
1241 #define TYPE_MISSING 1
1242 #define TYPE_PFN 2
1243 #define TYPE_UNKNOWN 3
1244         static const char * const type_name[] = {
1245                                 [TYPE_IDENTITY] = "identity",
1246                                 [TYPE_MISSING] = "missing",
1247                                 [TYPE_PFN] = "pfn",
1248                                 [TYPE_UNKNOWN] = "abnormal"};
1249         unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
1250         unsigned int uninitialized_var(prev_level);
1251         unsigned int uninitialized_var(prev_type);
1252
1253         if (!p2m_top)
1254                 return 0;
1255
1256         for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
1257                 unsigned topidx = p2m_top_index(pfn);
1258                 unsigned mididx = p2m_mid_index(pfn);
1259                 unsigned idx = p2m_index(pfn);
1260                 unsigned lvl, type;
1261
1262                 lvl = 4;
1263                 type = TYPE_UNKNOWN;
1264                 if (p2m_top[topidx] == p2m_mid_missing) {
1265                         lvl = 0; type = TYPE_MISSING;
1266                 } else if (p2m_top[topidx] == NULL) {
1267                         lvl = 0; type = TYPE_UNKNOWN;
1268                 } else if (p2m_top[topidx][mididx] == NULL) {
1269                         lvl = 1; type = TYPE_UNKNOWN;
1270                 } else if (p2m_top[topidx][mididx] == p2m_identity) {
1271                         lvl = 1; type = TYPE_IDENTITY;
1272                 } else if (p2m_top[topidx][mididx] == p2m_missing) {
1273                         lvl = 1; type = TYPE_MISSING;
1274                 } else if (p2m_top[topidx][mididx][idx] == 0) {
1275                         lvl = 2; type = TYPE_UNKNOWN;
1276                 } else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
1277                         lvl = 2; type = TYPE_IDENTITY;
1278                 } else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
1279                         lvl = 2; type = TYPE_MISSING;
1280                 } else if (p2m_top[topidx][mididx][idx] == pfn) {
1281                         lvl = 2; type = TYPE_PFN;
1282                 } else if (p2m_top[topidx][mididx][idx] != pfn) {
1283                         lvl = 2; type = TYPE_PFN;
1284                 }
1285                 if (pfn == 0) {
1286                         prev_level = lvl;
1287                         prev_type = type;
1288                 }
1289                 if (pfn == MAX_DOMAIN_PAGES-1) {
1290                         lvl = 3;
1291                         type = TYPE_UNKNOWN;
1292                 }
1293                 if (prev_type != type) {
1294                         seq_printf(m, " [0x%lx->0x%lx] %s\n",
1295                                 prev_pfn_type, pfn, type_name[prev_type]);
1296                         prev_pfn_type = pfn;
1297                         prev_type = type;
1298                 }
1299                 if (prev_level != lvl) {
1300                         seq_printf(m, " [0x%lx->0x%lx] level %s\n",
1301                                 prev_pfn_level, pfn, level_name[prev_level]);
1302                         prev_pfn_level = pfn;
1303                         prev_level = lvl;
1304                 }
1305         }
1306         return 0;
1307 #undef TYPE_IDENTITY
1308 #undef TYPE_MISSING
1309 #undef TYPE_PFN
1310 #undef TYPE_UNKNOWN
1311 }
1312
1313 static int p2m_dump_open(struct inode *inode, struct file *filp)
1314 {
1315         return single_open(filp, p2m_dump_show, NULL);
1316 }
1317
1318 static const struct file_operations p2m_dump_fops = {
1319         .open           = p2m_dump_open,
1320         .read           = seq_read,
1321         .llseek         = seq_lseek,
1322         .release        = single_release,
1323 };
1324
1325 static struct dentry *d_mmu_debug;
1326
1327 static int __init xen_p2m_debugfs(void)
1328 {
1329         struct dentry *d_xen = xen_init_debugfs();
1330
1331         if (d_xen == NULL)
1332                 return -ENOMEM;
1333
1334         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
1335
1336         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
1337         return 0;
1338 }
1339 fs_initcall(xen_p2m_debugfs);
1340 #endif /* CONFIG_XEN_DEBUG_FS */