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 b/c 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
  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 loop on aligned 1GB PFNs from start pfn
  81  * to end pfn.  We reserve_brk top leaf pages if they are missing (means they
  82  * point to p2m_mid_missing).
  83  *
  84  * With the E820 example above, 263424 is not 1GB aligned so we allocate a
  85  * reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000.
  86  * Each entry in the allocate page is "missing" (points to p2m_missing).
  87  *
  88  * Next stage is to determine if we need to do a more granular boundary check
  89  * on the 4MB (or 2MB depending on architecture) off the start and end pfn's.
  90  * We check if the start pfn and end pfn violate that boundary check, and if
  91  * so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer
  92  * granularity of setting which PFNs are missing and which ones are identity.
  93  * In our example 263424 and 512256 both fail the check so we reserve_brk two
  94  * pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing"
  95  * values) and assign them to p2m[1][2] and p2m[1][488] respectively.
  96  *
  97  * At this point we would at minimum reserve_brk one page, but could be up to
  98  * three. Each call to set_phys_range_identity has at maximum a three page
  99  * cost. If we were to query the P2M at this stage, all those entries from
 100  * start PFN through end PFN (so 1029MB -> 2001MB) would return
 101  * INVALID_P2M_ENTRY ("missing").
 102  *
 103  * The next step is to walk from the start pfn to the end pfn setting
 104  * the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity.
 105  * If we find that the middle leaf is pointing to p2m_missing we can swap it
 106  * over to p2m_identity - this way covering 4MB (or 2MB) PFN space.  At this
 107  * 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  * This is what the p2m ends up looking (for the E820 above) with this
 122  * fabulous drawing:
 123  *
 124  *    p2m         /--------------\
 125  *  /-----\       | &mfn_list[0],|                           /-----------------\
 126  *  |  0  |------>| &mfn_list[1],|    /---------------\      | ~0, ~0, ..      |
 127  *  |-----|       |  ..., ~0, ~0 |    | ~0, ~0, [x]---+----->| IDENTITY [@256] |
 128  *  |  1  |---\   \--------------/    | [p2m_identity]+\     | IDENTITY [@257] |
 129  *  |-----|    \                      | [p2m_identity]+\\    | ....            |
 130  *  |  2  |--\  \-------------------->|  ...          | \\   \----------------/
 131  *  |-----|   \                       \---------------/  \\
 132  *  |  3  |\   \                                          \\  p2m_identity
 133  *  |-----| \   \-------------------->/---------------\   /-----------------\
 134  *  | ..  +->+                        | [p2m_identity]+-->| ~0, ~0, ~0, ... |
 135  *  \-----/ /                         | [p2m_identity]+-->| ..., ~0         |
 136  *         / /---------------\        | ....          |   \-----------------/
 137  *        /  | IDENTITY[@0]  |      /-+-[x], ~0, ~0.. |
 138  *       /   | IDENTITY[@256]|<----/  \---------------/
 139  *      /    | ~0, ~0, ....  |
 140  *     |     \---------------/
 141  *     |
 142  *     p2m_missing             p2m_missing
 143  * /------------------\     /------------\
 144  * | [p2m_mid_missing]+---->| ~0, ~0, ~0 |
 145  * | [p2m_mid_missing]+---->| ..., ~0    |
 146  * \------------------/     \------------/
 147  *
 148  * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
 149  */
 150
 151 #include <linux/init.h>
 152 #include <linux/module.h>
 153 #include <linux/list.h>
 154 #include <linux/hash.h>
 155 #include <linux/sched.h>
 156 #include <linux/seq_file.h>
 157
 158 #include <asm/cache.h>
 159 #include <asm/setup.h>
 160
 161 #include <asm/xen/page.h>
 162 #include <asm/xen/hypercall.h>
 163 #include <asm/xen/hypervisor.h>
 164 #include <xen/grant_table.h>
 165
 166 #include "multicalls.h"
 167 #include "xen-ops.h"
 168
 169 static void __init m2p_override_init(void);
 170
 171 unsigned long xen_max_p2m_pfn __read_mostly;
 172
 173 #define P2M_PER_PAGE            (PAGE_SIZE / sizeof(unsigned long))
 174 #define P2M_MID_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long *))
 175 #define P2M_TOP_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long **))
 176
 177 #define MAX_P2M_PFN             (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
 178
 179 /* Placeholders for holes in the address space */
 180 static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
 181 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
 182 static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);
 183
 184 static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
 185 static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);
 186 static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE);
 187
 188 static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
 189
 190 RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
 191 RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
 192
 193 /* We might hit two boundary violations at the start and end, at max each
 194  * boundary violation will require three middle nodes. */
 195 RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3);
 196
 197 static inline unsigned p2m_top_index(unsigned long pfn)
 198 {
 199         BUG_ON(pfn >= MAX_P2M_PFN);
 200         return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
 201 }
 202
 203 static inline unsigned p2m_mid_index(unsigned long pfn)
 204 {
 205         return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
 206 }
 207
 208 static inline unsigned p2m_index(unsigned long pfn)
 209 {
 210         return pfn % P2M_PER_PAGE;
 211 }
 212
 213 static void p2m_top_init(unsigned long ***top)
 214 {
 215         unsigned i;
 216
 217         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 218                 top[i] = p2m_mid_missing;
 219 }
 220
 221 static void p2m_top_mfn_init(unsigned long *top)
 222 {
 223         unsigned i;
 224
 225         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 226                 top[i] = virt_to_mfn(p2m_mid_missing_mfn);
 227 }
 228
 229 static void p2m_top_mfn_p_init(unsigned long **top)
 230 {
 231         unsigned i;
 232
 233         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 234                 top[i] = p2m_mid_missing_mfn;
 235 }
 236
 237 static void p2m_mid_init(unsigned long **mid)
 238 {
 239         unsigned i;
 240
 241         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 242                 mid[i] = p2m_missing;
 243 }
 244
 245 static void p2m_mid_mfn_init(unsigned long *mid)
 246 {
 247         unsigned i;
 248
 249         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 250                 mid[i] = virt_to_mfn(p2m_missing);
 251 }
 252
 253 static void p2m_init(unsigned long *p2m)
 254 {
 255         unsigned i;
 256
 257         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 258                 p2m[i] = INVALID_P2M_ENTRY;
 259 }
 260
 261 /*
 262  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
 263  *
 264  * This is called both at boot time, and after resuming from suspend:
 265  * - At boot time we're called very early, and must use extend_brk()
 266  *   to allocate memory.
 267  *
 268  * - After resume we're called from within stop_machine, but the mfn
 269  *   tree should alreay be completely allocated.
 270  */
 271 void __ref xen_build_mfn_list_list(void)
 272 {
 273         unsigned long pfn;
 274
 275         /* Pre-initialize p2m_top_mfn to be completely missing */
 276         if (p2m_top_mfn == NULL) {
 277                 p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
 278                 p2m_mid_mfn_init(p2m_mid_missing_mfn);
 279
 280                 p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
 281                 p2m_top_mfn_p_init(p2m_top_mfn_p);
 282
 283                 p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
 284                 p2m_top_mfn_init(p2m_top_mfn);
 285         } else {
 286                 /* Reinitialise, mfn's all change after migration */
 287                 p2m_mid_mfn_init(p2m_mid_missing_mfn);
 288         }
 289
 290         for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
 291                 unsigned topidx = p2m_top_index(pfn);
 292                 unsigned mididx = p2m_mid_index(pfn);
 293                 unsigned long **mid;
 294                 unsigned long *mid_mfn_p;
 295
 296                 mid = p2m_top[topidx];
 297                 mid_mfn_p = p2m_top_mfn_p[topidx];
 298
 299                 /* Don't bother allocating any mfn mid levels if
 300                  * they're just missing, just update the stored mfn,
 301                  * since all could have changed over a migrate.
 302                  */
 303                 if (mid == p2m_mid_missing) {
 304                         BUG_ON(mididx);
 305                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 306                         p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
 307                         pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
 308                         continue;
 309                 }
 310
 311                 if (mid_mfn_p == p2m_mid_missing_mfn) {
 312                         /*
 313                          * XXX boot-time only!  We should never find
 314                          * missing parts of the mfn tree after
 315                          * runtime.  extend_brk() will BUG if we call
 316                          * it too late.
 317                          */
 318                         mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
 319                         p2m_mid_mfn_init(mid_mfn_p);
 320
 321                         p2m_top_mfn_p[topidx] = mid_mfn_p;
 322                 }
 323
 324                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
 325                 mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
 326         }
 327 }
 328
 329 void xen_setup_mfn_list_list(void)
 330 {
 331         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
 332
 333         HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
 334                 virt_to_mfn(p2m_top_mfn);
 335         HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
 336 }
 337
 338 /* Set up p2m_top to point to the domain-builder provided p2m pages */
 339 void __init xen_build_dynamic_phys_to_machine(void)
 340 {
 341         unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;
 342         unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
 343         unsigned long pfn;
 344
 345         xen_max_p2m_pfn = max_pfn;
 346
 347         p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
 348         p2m_init(p2m_missing);
 349
 350         p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
 351         p2m_mid_init(p2m_mid_missing);
 352
 353         p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
 354         p2m_top_init(p2m_top);
 355
 356         p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
 357         p2m_init(p2m_identity);
 358
 359         /*
 360          * The domain builder gives us a pre-constructed p2m array in
 361          * mfn_list for all the pages initially given to us, so we just
 362          * need to graft that into our tree structure.
 363          */
 364         for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
 365                 unsigned topidx = p2m_top_index(pfn);
 366                 unsigned mididx = p2m_mid_index(pfn);
 367
 368                 if (p2m_top[topidx] == p2m_mid_missing) {
 369                         unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
 370                         p2m_mid_init(mid);
 371
 372                         p2m_top[topidx] = mid;
 373                 }
 374
 375                 /*
 376                  * As long as the mfn_list has enough entries to completely
 377                  * fill a p2m page, pointing into the array is ok. But if
 378                  * not the entries beyond the last pfn will be undefined.
 379                  */
 380                 if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
 381                         unsigned long p2midx;
 382
 383                         p2midx = max_pfn % P2M_PER_PAGE;
 384                         for ( ; p2midx < P2M_PER_PAGE; p2midx++)
 385                                 mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
 386                 }
 387                 p2m_top[topidx][mididx] = &mfn_list[pfn];
 388         }
 389
 390         m2p_override_init();
 391 }
 392
 393 unsigned long get_phys_to_machine(unsigned long pfn)
 394 {
 395         unsigned topidx, mididx, idx;
 396
 397         if (unlikely(pfn >= MAX_P2M_PFN))
 398                 return INVALID_P2M_ENTRY;
 399
 400         topidx = p2m_top_index(pfn);
 401         mididx = p2m_mid_index(pfn);
 402         idx = p2m_index(pfn);
 403
 404         /*
 405          * The INVALID_P2M_ENTRY is filled in both p2m_*identity
 406          * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
 407          * would be wrong.
 408          */
 409         if (p2m_top[topidx][mididx] == p2m_identity)
 410                 return IDENTITY_FRAME(pfn);
 411
 412         return p2m_top[topidx][mididx][idx];
 413 }
 414 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 415
 416 static void *alloc_p2m_page(void)
 417 {
 418         return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
 419 }
 420
 421 static void free_p2m_page(void *p)
 422 {
 423         free_page((unsigned long)p);
 424 }
 425
 426 /*
 427  * Fully allocate the p2m structure for a given pfn.  We need to check
 428  * that both the top and mid levels are allocated, and make sure the
 429  * parallel mfn tree is kept in sync.  We may race with other cpus, so
 430  * the new pages are installed with cmpxchg; if we lose the race then
 431  * simply free the page we allocated and use the one that's there.
 432  */
 433 static bool alloc_p2m(unsigned long pfn)
 434 {
 435         unsigned topidx, mididx;
 436         unsigned long ***top_p, **mid;
 437         unsigned long *top_mfn_p, *mid_mfn;
 438
 439         topidx = p2m_top_index(pfn);
 440         mididx = p2m_mid_index(pfn);
 441
 442         top_p = &p2m_top[topidx];
 443         mid = *top_p;
 444
 445         if (mid == p2m_mid_missing) {
 446                 /* Mid level is missing, allocate a new one */
 447                 mid = alloc_p2m_page();
 448                 if (!mid)
 449                         return false;
 450
 451                 p2m_mid_init(mid);
 452
 453                 if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
 454                         free_p2m_page(mid);
 455         }
 456
 457         top_mfn_p = &p2m_top_mfn[topidx];
 458         mid_mfn = p2m_top_mfn_p[topidx];
 459
 460         BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
 461
 462         if (mid_mfn == p2m_mid_missing_mfn) {
 463                 /* Separately check the mid mfn level */
 464                 unsigned long missing_mfn;
 465                 unsigned long mid_mfn_mfn;
 466
 467                 mid_mfn = alloc_p2m_page();
 468                 if (!mid_mfn)
 469                         return false;
 470
 471                 p2m_mid_mfn_init(mid_mfn);
 472
 473                 missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
 474                 mid_mfn_mfn = virt_to_mfn(mid_mfn);
 475                 if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)
 476                         free_p2m_page(mid_mfn);
 477                 else
 478                         p2m_top_mfn_p[topidx] = mid_mfn;
 479         }
 480
 481         if (p2m_top[topidx][mididx] == p2m_identity ||
 482             p2m_top[topidx][mididx] == p2m_missing) {
 483                 /* p2m leaf page is missing */
 484                 unsigned long *p2m;
 485                 unsigned long *p2m_orig = p2m_top[topidx][mididx];
 486
 487                 p2m = alloc_p2m_page();
 488                 if (!p2m)
 489                         return false;
 490
 491                 p2m_init(p2m);
 492
 493                 if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
 494                         free_p2m_page(p2m);
 495                 else
 496                         mid_mfn[mididx] = virt_to_mfn(p2m);
 497         }
 498
 499         return true;
 500 }
 501
 502 static bool __init __early_alloc_p2m(unsigned long pfn)
 503 {
 504         unsigned topidx, mididx, idx;
 505
 506         topidx = p2m_top_index(pfn);
 507         mididx = p2m_mid_index(pfn);
 508         idx = p2m_index(pfn);
 509
 510         /* Pfff.. No boundary cross-over, lets get out. */
 511         if (!idx)
 512                 return false;
 513
 514         WARN(p2m_top[topidx][mididx] == p2m_identity,
 515                 "P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
 516                 topidx, mididx);
 517
 518         /*
 519          * Could be done by xen_build_dynamic_phys_to_machine..
 520          */
 521         if (p2m_top[topidx][mididx] != p2m_missing)
 522                 return false;
 523
 524         /* Boundary cross-over for the edges: */
 525         if (idx) {
 526                 unsigned long *p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
 527                 unsigned long *mid_mfn_p;
 528
 529                 p2m_init(p2m);
 530
 531                 p2m_top[topidx][mididx] = p2m;
 532
 533                 /* For save/restore we need to MFN of the P2M saved */
 534
 535                 mid_mfn_p = p2m_top_mfn_p[topidx];
 536                 WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing),
 537                         "P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n",
 538                         topidx, mididx);
 539                 mid_mfn_p[mididx] = virt_to_mfn(p2m);
 540
 541         }
 542         return idx != 0;
 543 }
 544 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 545                                       unsigned long pfn_e)
 546 {
 547         unsigned long pfn;
 548
 549         if (unlikely(pfn_s >= MAX_P2M_PFN || pfn_e >= MAX_P2M_PFN))
 550                 return 0;
 551
 552         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
 553                 return pfn_e - pfn_s;
 554
 555         if (pfn_s > pfn_e)
 556                 return 0;
 557
 558         for (pfn = (pfn_s & ~(P2M_MID_PER_PAGE * P2M_PER_PAGE - 1));
 559                 pfn < ALIGN(pfn_e, (P2M_MID_PER_PAGE * P2M_PER_PAGE));
 560                 pfn += P2M_MID_PER_PAGE * P2M_PER_PAGE)
 561         {
 562                 unsigned topidx = p2m_top_index(pfn);
 563                 unsigned long *mid_mfn_p;
 564                 unsigned long **mid;
 565
 566                 mid = p2m_top[topidx];
 567                 mid_mfn_p = p2m_top_mfn_p[topidx];
 568                 if (mid == p2m_mid_missing) {
 569                         mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
 570
 571                         p2m_mid_init(mid);
 572
 573                         p2m_top[topidx] = mid;
 574
 575                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 576                 }
 577                 /* And the save/restore P2M tables.. */
 578                 if (mid_mfn_p == p2m_mid_missing_mfn) {
 579                         mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
 580                         p2m_mid_mfn_init(mid_mfn_p);
 581
 582                         p2m_top_mfn_p[topidx] = mid_mfn_p;
 583                         p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
 584                         /* Note: we don't set mid_mfn_p[midix] here,
 585                          * look in __early_alloc_p2m */
 586                 }
 587         }
 588
 589         __early_alloc_p2m(pfn_s);
 590         __early_alloc_p2m(pfn_e);
 591
 592         for (pfn = pfn_s; pfn < pfn_e; pfn++)
 593                 if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
 594                         break;
 595
 596         if (!WARN((pfn - pfn_s) != (pfn_e - pfn_s),
 597                 "Identity mapping failed. We are %ld short of 1-1 mappings!\n",
 598                 (pfn_e - pfn_s) - (pfn - pfn_s)))
 599                 printk(KERN_DEBUG "1-1 mapping on %lx->%lx\n", pfn_s, pfn);
 600
 601         return pfn - pfn_s;
 602 }
 603
 604 /* Try to install p2m mapping; fail if intermediate bits missing */
 605 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 606 {
 607         unsigned topidx, mididx, idx;
 608
 609         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {
 610                 BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);
 611                 return true;
 612         }
 613         if (unlikely(pfn >= MAX_P2M_PFN)) {
 614                 BUG_ON(mfn != INVALID_P2M_ENTRY);
 615                 return true;
 616         }
 617
 618         topidx = p2m_top_index(pfn);
 619         mididx = p2m_mid_index(pfn);
 620         idx = p2m_index(pfn);
 621
 622         /* For sparse holes were the p2m leaf has real PFN along with
 623          * PCI holes, stick in the PFN as the MFN value.
 624          */
 625         if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
 626                 if (p2m_top[topidx][mididx] == p2m_identity)
 627                         return true;
 628
 629                 /* Swap over from MISSING to IDENTITY if needed. */
 630                 if (p2m_top[topidx][mididx] == p2m_missing) {
 631                         WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
 632                                 p2m_identity) != p2m_missing);
 633                         return true;
 634                 }
 635         }
 636
 637         if (p2m_top[topidx][mididx] == p2m_missing)
 638                 return mfn == INVALID_P2M_ENTRY;
 639
 640         p2m_top[topidx][mididx][idx] = mfn;
 641
 642         return true;
 643 }
 644
 645 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 646 {
 647         if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
 648                 if (!alloc_p2m(pfn))
 649                         return false;
 650
 651                 if (!__set_phys_to_machine(pfn, mfn))
 652                         return false;
 653         }
 654
 655         return true;
 656 }
 657
 658 #define M2P_OVERRIDE_HASH_SHIFT 10
 659 #define M2P_OVERRIDE_HASH       (1 << M2P_OVERRIDE_HASH_SHIFT)
 660
 661 static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);
 662 static DEFINE_SPINLOCK(m2p_override_lock);
 663
 664 static void __init m2p_override_init(void)
 665 {
 666         unsigned i;
 667
 668         m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
 669                                    sizeof(unsigned long));
 670
 671         for (i = 0; i < M2P_OVERRIDE_HASH; i++)
 672                 INIT_LIST_HEAD(&m2p_overrides[i]);
 673 }
 674
 675 static unsigned long mfn_hash(unsigned long mfn)
 676 {
 677         return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
 678 }
 679
 680 /* Add an MFN override for a particular page */
 681 int m2p_add_override(unsigned long mfn, struct page *page,
 682                 struct gnttab_map_grant_ref *kmap_op)
 683 {
 684         unsigned long flags;
 685         unsigned long pfn;
 686         unsigned long uninitialized_var(address);
 687         unsigned level;
 688         pte_t *ptep = NULL;
 689
 690         pfn = page_to_pfn(page);
 691         if (!PageHighMem(page)) {
 692                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
 693                 ptep = lookup_address(address, &level);
 694                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
 695                                         "m2p_add_override: pfn %lx not mapped", pfn))
 696                         return -EINVAL;
 697         }
 698         WARN_ON(PagePrivate(page));
 699         SetPagePrivate(page);
 700         set_page_private(page, mfn);
 701         page->index = pfn_to_mfn(pfn);
 702
 703         if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
 704                 return -ENOMEM;
 705
 706         if (kmap_op != NULL) {
 707                 if (!PageHighMem(page)) {
 708                         struct multicall_space mcs =
 709                                 xen_mc_entry(sizeof(*kmap_op));
 710
 711                         MULTI_grant_table_op(mcs.mc,
 712                                         GNTTABOP_map_grant_ref, kmap_op, 1);
 713
 714                         xen_mc_issue(PARAVIRT_LAZY_MMU);
 715                 }
 716                 /* let's use dev_bus_addr to record the old mfn instead */
 717                 kmap_op->dev_bus_addr = page->index;
 718                 page->index = (unsigned long) kmap_op;
 719         }
 720         spin_lock_irqsave(&m2p_override_lock, flags);
 721         list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
 722         spin_unlock_irqrestore(&m2p_override_lock, flags);
 723
 724         return 0;
 725 }
 726 EXPORT_SYMBOL_GPL(m2p_add_override);
 727 int m2p_remove_override(struct page *page, bool clear_pte)
 728 {
 729         unsigned long flags;
 730         unsigned long mfn;
 731         unsigned long pfn;
 732         unsigned long uninitialized_var(address);
 733         unsigned level;
 734         pte_t *ptep = NULL;
 735
 736         pfn = page_to_pfn(page);
 737         mfn = get_phys_to_machine(pfn);
 738         if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT))
 739                 return -EINVAL;
 740
 741         if (!PageHighMem(page)) {
 742                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
 743                 ptep = lookup_address(address, &level);
 744
 745                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
 746                                         "m2p_remove_override: pfn %lx not mapped", pfn))
 747                         return -EINVAL;
 748         }
 749
 750         spin_lock_irqsave(&m2p_override_lock, flags);
 751         list_del(&page->lru);
 752         spin_unlock_irqrestore(&m2p_override_lock, flags);
 753         WARN_ON(!PagePrivate(page));
 754         ClearPagePrivate(page);
 755
 756         if (clear_pte) {
 757                 struct gnttab_map_grant_ref *map_op =
 758                         (struct gnttab_map_grant_ref *) page->index;
 759                 set_phys_to_machine(pfn, map_op->dev_bus_addr);
 760                 if (!PageHighMem(page)) {
 761                         struct multicall_space mcs;
 762                         struct gnttab_unmap_grant_ref *unmap_op;
 763
 764                         /*
 765                          * It might be that we queued all the m2p grant table
 766                          * hypercalls in a multicall, then m2p_remove_override
 767                          * get called before the multicall has actually been
 768                          * issued. In this case handle is going to -1 because
 769                          * it hasn't been modified yet.
 770                          */
 771                         if (map_op->handle == -1)
 772                                 xen_mc_flush();
 773                         /*
 774                          * Now if map_op->handle is negative it means that the
 775                          * hypercall actually returned an error.
 776                          */
 777                         if (map_op->handle == GNTST_general_error) {
 778                                 printk(KERN_WARNING "m2p_remove_override: "
 779                                                 "pfn %lx mfn %lx, failed to modify kernel mappings",
 780                                                 pfn, mfn);
 781                                 return -1;
 782                         }
 783
 784                         mcs = xen_mc_entry(
 785                                         sizeof(struct gnttab_unmap_grant_ref));
 786                         unmap_op = mcs.args;
 787                         unmap_op->host_addr = map_op->host_addr;
 788                         unmap_op->handle = map_op->handle;
 789                         unmap_op->dev_bus_addr = 0;
 790
 791                         MULTI_grant_table_op(mcs.mc,
 792                                         GNTTABOP_unmap_grant_ref, unmap_op, 1);
 793
 794                         xen_mc_issue(PARAVIRT_LAZY_MMU);
 795
 796                         set_pte_at(&init_mm, address, ptep,
 797                                         pfn_pte(pfn, PAGE_KERNEL));
 798                         __flush_tlb_single(address);
 799                         map_op->host_addr = 0;
 800                 }
 801         } else
 802                 set_phys_to_machine(pfn, page->index);
 803
 804         return 0;
 805 }
 806 EXPORT_SYMBOL_GPL(m2p_remove_override);
 807
 808 struct page *m2p_find_override(unsigned long mfn)
 809 {
 810         unsigned long flags;
 811         struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
 812         struct page *p, *ret;
 813
 814         ret = NULL;
 815
 816         spin_lock_irqsave(&m2p_override_lock, flags);
 817
 818         list_for_each_entry(p, bucket, lru) {
 819                 if (page_private(p) == mfn) {
 820                         ret = p;
 821                         break;
 822                 }
 823         }
 824
 825         spin_unlock_irqrestore(&m2p_override_lock, flags);
 826
 827         return ret;
 828 }
 829
 830 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
 831 {
 832         struct page *p = m2p_find_override(mfn);
 833         unsigned long ret = pfn;
 834
 835         if (p)
 836                 ret = page_to_pfn(p);
 837
 838         return ret;
 839 }
 840 EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
 841
 842 #ifdef CONFIG_XEN_DEBUG_FS
 843 #include <linux/debugfs.h>
 844 #include "debugfs.h"
 845 static int p2m_dump_show(struct seq_file *m, void *v)
 846 {
 847         static const char * const level_name[] = { "top", "middle",
 848                                                 "entry", "abnormal", "error"};
 849 #define TYPE_IDENTITY 0
 850 #define TYPE_MISSING 1
 851 #define TYPE_PFN 2
 852 #define TYPE_UNKNOWN 3
 853         static const char * const type_name[] = {
 854                                 [TYPE_IDENTITY] = "identity",
 855                                 [TYPE_MISSING] = "missing",
 856                                 [TYPE_PFN] = "pfn",
 857                                 [TYPE_UNKNOWN] = "abnormal"};
 858         unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
 859         unsigned int uninitialized_var(prev_level);
 860         unsigned int uninitialized_var(prev_type);
 861
 862         if (!p2m_top)
 863                 return 0;
 864
 865         for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
 866                 unsigned topidx = p2m_top_index(pfn);
 867                 unsigned mididx = p2m_mid_index(pfn);
 868                 unsigned idx = p2m_index(pfn);
 869                 unsigned lvl, type;
 870
 871                 lvl = 4;
 872                 type = TYPE_UNKNOWN;
 873                 if (p2m_top[topidx] == p2m_mid_missing) {
 874                         lvl = 0; type = TYPE_MISSING;
 875                 } else if (p2m_top[topidx] == NULL) {
 876                         lvl = 0; type = TYPE_UNKNOWN;
 877                 } else if (p2m_top[topidx][mididx] == NULL) {
 878                         lvl = 1; type = TYPE_UNKNOWN;
 879                 } else if (p2m_top[topidx][mididx] == p2m_identity) {
 880                         lvl = 1; type = TYPE_IDENTITY;
 881                 } else if (p2m_top[topidx][mididx] == p2m_missing) {
 882                         lvl = 1; type = TYPE_MISSING;
 883                 } else if (p2m_top[topidx][mididx][idx] == 0) {
 884                         lvl = 2; type = TYPE_UNKNOWN;
 885                 } else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
 886                         lvl = 2; type = TYPE_IDENTITY;
 887                 } else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
 888                         lvl = 2; type = TYPE_MISSING;
 889                 } else if (p2m_top[topidx][mididx][idx] == pfn) {
 890                         lvl = 2; type = TYPE_PFN;
 891                 } else if (p2m_top[topidx][mididx][idx] != pfn) {
 892                         lvl = 2; type = TYPE_PFN;
 893                 }
 894                 if (pfn == 0) {
 895                         prev_level = lvl;
 896                         prev_type = type;
 897                 }
 898                 if (pfn == MAX_DOMAIN_PAGES-1) {
 899                         lvl = 3;
 900                         type = TYPE_UNKNOWN;
 901                 }
 902                 if (prev_type != type) {
 903                         seq_printf(m, " [0x%lx->0x%lx] %s\n",
 904                                 prev_pfn_type, pfn, type_name[prev_type]);
 905                         prev_pfn_type = pfn;
 906                         prev_type = type;
 907                 }
 908                 if (prev_level != lvl) {
 909                         seq_printf(m, " [0x%lx->0x%lx] level %s\n",
 910                                 prev_pfn_level, pfn, level_name[prev_level]);
 911                         prev_pfn_level = pfn;
 912                         prev_level = lvl;
 913                 }
 914         }
 915         return 0;
 916 #undef TYPE_IDENTITY
 917 #undef TYPE_MISSING
 918 #undef TYPE_PFN
 919 #undef TYPE_UNKNOWN
 920 }
 921
 922 static int p2m_dump_open(struct inode *inode, struct file *filp)
 923 {
 924         return single_open(filp, p2m_dump_show, NULL);
 925 }
 926
 927 static const struct file_operations p2m_dump_fops = {
 928         .open           = p2m_dump_open,
 929         .read           = seq_read,
 930         .llseek         = seq_lseek,
 931         .release        = single_release,
 932 };
 933
 934 static struct dentry *d_mmu_debug;
 935
 936 static int __init xen_p2m_debugfs(void)
 937 {
 938         struct dentry *d_xen = xen_init_debugfs();
 939
 940         if (d_xen == NULL)
 941                 return -ENOMEM;
 942
 943         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
 944
 945         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
 946         return 0;
 947 }
 948 fs_initcall(xen_p2m_debugfs);
 949 #endif /* CONFIG_XEN_DEBUG_FS */