arch/x86/xen/p2m.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
p2m_top_index
p2m_mid_index
p2m_index
p2m_top_mfn_init
p2m_top_mfn_p_init
p2m_mid_mfn_init
p2m_init
p2m_init_identity
alloc_p2m_page
free_p2m_page
xen_build_mfn_list_list
xen_setup_mfn_list_list
xen_build_dynamic_phys_to_machine
xen_p2m_elem_type
xen_rebuild_p2m_list
xen_vmalloc_p2m_tree
get_phys_to_machine
alloc_p2m_pmd
xen_alloc_p2m_entry
set_phys_range_identity
__set_phys_to_machine
set_phys_to_machine
set_foreign_p2m_mapping
clear_foreign_p2m_mapping
p2m_dump_show
p2m_dump_open
xen_p2m_debugfs
   1 // SPDX-License-Identifier: GPL-2.0
   2 
   3 /*
   4  * Xen leaves the responsibility for maintaining p2m mappings to the
   5  * guests themselves, but it must also access and update the p2m array
   6  * during suspend/resume when all the pages are reallocated.
   7  *
   8  * The logical flat p2m table is mapped to a linear kernel memory area.
   9  * For accesses by Xen a three-level tree linked via mfns only is set up to
  10  * allow the address space to be sparse.
  11  *
  12  *               Xen
  13  *                |
  14  *          p2m_top_mfn
  15  *              /   \
  16  * p2m_mid_mfn p2m_mid_mfn
  17  *         /           /
  18  *  p2m p2m p2m ...
  19  *
  20  * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
  21  *
  22  * The p2m_top_mfn level is limited to 1 page, so the maximum representable
  23  * pseudo-physical address space is:
  24  *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
  25  *
  26  * P2M_PER_PAGE depends on the architecture, as a mfn is always
  27  * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
  28  * 512 and 1024 entries respectively.
  29  *
  30  * In short, these structures contain the Machine Frame Number (MFN) of the PFN.
  31  *
  32  * However not all entries are filled with MFNs. Specifically for all other
  33  * leaf entries, or for the top  root, or middle one, for which there is a void
  34  * entry, we assume it is  "missing". So (for example)
  35  *  pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
  36  * We have a dedicated page p2m_missing with all entries being
  37  * INVALID_P2M_ENTRY. This page may be referenced multiple times in the p2m
  38  * list/tree in case there are multiple areas with P2M_PER_PAGE invalid pfns.
  39  *
  40  * We also have the possibility of setting 1-1 mappings on certain regions, so
  41  * that:
  42  *  pfn_to_mfn(0xc0000)=0xc0000
  43  *
  44  * The benefit of this is, that we can assume for non-RAM regions (think
  45  * PCI BARs, or ACPI spaces), we can create mappings easily because we
  46  * get the PFN value to match the MFN.
  47  *
  48  * For this to work efficiently we have one new page p2m_identity. All entries
  49  * in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only
  50  * recognizes that and MFNs, no other fancy value).
  51  *
  52  * On lookup we spot that the entry points to p2m_identity and return the
  53  * identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
  54  * If the entry points to an allocated page, we just proceed as before and
  55  * return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in
  56  * appropriate functions (pfn_to_mfn).
  57  *
  58  * The reason for having the IDENTITY_FRAME_BIT instead of just returning the
  59  * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
  60  * non-identity pfn. To protect ourselves against we elect to set (and get) the
  61  * IDENTITY_FRAME_BIT on all identity mapped PFNs.
  62  */
  63 
  64 #include <linux/init.h>
  65 #include <linux/export.h>
  66 #include <linux/list.h>
  67 #include <linux/hash.h>
  68 #include <linux/sched.h>
  69 #include <linux/seq_file.h>
  70 #include <linux/memblock.h>
  71 #include <linux/slab.h>
  72 #include <linux/vmalloc.h>
  73 
  74 #include <asm/cache.h>
  75 #include <asm/setup.h>
  76 #include <linux/uaccess.h>
  77 
  78 #include <asm/xen/page.h>
  79 #include <asm/xen/hypercall.h>
  80 #include <asm/xen/hypervisor.h>
  81 #include <xen/balloon.h>
  82 #include <xen/grant_table.h>
  83 
  84 #include "multicalls.h"
  85 #include "xen-ops.h"
  86 
  87 #define P2M_MID_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long *))
  88 #define P2M_TOP_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long **))
  89 
  90 #define MAX_P2M_PFN     (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
  91 
  92 #define PMDS_PER_MID_PAGE       (P2M_MID_PER_PAGE / PTRS_PER_PTE)
  93 
  94 unsigned long *xen_p2m_addr __read_mostly;
  95 EXPORT_SYMBOL_GPL(xen_p2m_addr);
  96 unsigned long xen_p2m_size __read_mostly;
  97 EXPORT_SYMBOL_GPL(xen_p2m_size);
  98 unsigned long xen_max_p2m_pfn __read_mostly;
  99 EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
 100 
 101 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
 102 #define P2M_LIMIT CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
 103 #else
 104 #define P2M_LIMIT 0
 105 #endif
 106 
 107 static DEFINE_SPINLOCK(p2m_update_lock);
 108 
 109 static unsigned long *p2m_mid_missing_mfn;
 110 static unsigned long *p2m_top_mfn;
 111 static unsigned long **p2m_top_mfn_p;
 112 static unsigned long *p2m_missing;
 113 static unsigned long *p2m_identity;
 114 static pte_t *p2m_missing_pte;
 115 static pte_t *p2m_identity_pte;
 116 
 117 /*
 118  * Hint at last populated PFN.
 119  *
 120  * Used to set HYPERVISOR_shared_info->arch.max_pfn so the toolstack
 121  * can avoid scanning the whole P2M (which may be sized to account for
 122  * hotplugged memory).
 123  */
 124 static unsigned long xen_p2m_last_pfn;
 125 
 126 static inline unsigned p2m_top_index(unsigned long pfn)
 127 {
 128         BUG_ON(pfn >= MAX_P2M_PFN);
 129         return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
 130 }
 131 
 132 static inline unsigned p2m_mid_index(unsigned long pfn)
 133 {
 134         return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
 135 }
 136 
 137 static inline unsigned p2m_index(unsigned long pfn)
 138 {
 139         return pfn % P2M_PER_PAGE;
 140 }
 141 
 142 static void p2m_top_mfn_init(unsigned long *top)
 143 {
 144         unsigned i;
 145 
 146         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 147                 top[i] = virt_to_mfn(p2m_mid_missing_mfn);
 148 }
 149 
 150 static void p2m_top_mfn_p_init(unsigned long **top)
 151 {
 152         unsigned i;
 153 
 154         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
 155                 top[i] = p2m_mid_missing_mfn;
 156 }
 157 
 158 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
 159 {
 160         unsigned i;
 161 
 162         for (i = 0; i < P2M_MID_PER_PAGE; i++)
 163                 mid[i] = virt_to_mfn(leaf);
 164 }
 165 
 166 static void p2m_init(unsigned long *p2m)
 167 {
 168         unsigned i;
 169 
 170         for (i = 0; i < P2M_PER_PAGE; i++)
 171                 p2m[i] = INVALID_P2M_ENTRY;
 172 }
 173 
 174 static void p2m_init_identity(unsigned long *p2m, unsigned long pfn)
 175 {
 176         unsigned i;
 177 
 178         for (i = 0; i < P2M_PER_PAGE; i++)
 179                 p2m[i] = IDENTITY_FRAME(pfn + i);
 180 }
 181 
 182 static void * __ref alloc_p2m_page(void)
 183 {
 184         if (unlikely(!slab_is_available())) {
 185                 void *ptr = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
 186 
 187                 if (!ptr)
 188                         panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
 189                               __func__, PAGE_SIZE, PAGE_SIZE);
 190 
 191                 return ptr;
 192         }
 193 
 194         return (void *)__get_free_page(GFP_KERNEL);
 195 }
 196 
 197 static void __ref free_p2m_page(void *p)
 198 {
 199         if (unlikely(!slab_is_available())) {
 200                 memblock_free((unsigned long)p, PAGE_SIZE);
 201                 return;
 202         }
 203 
 204         free_page((unsigned long)p);
 205 }
 206 
 207 /*
 208  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
 209  *
 210  * This is called both at boot time, and after resuming from suspend:
 211  * - At boot time we're called rather early, and must use alloc_bootmem*()
 212  *   to allocate memory.
 213  *
 214  * - After resume we're called from within stop_machine, but the mfn
 215  *   tree should already be completely allocated.
 216  */
 217 void __ref xen_build_mfn_list_list(void)
 218 {
 219         unsigned long pfn, mfn;
 220         pte_t *ptep;
 221         unsigned int level, topidx, mididx;
 222         unsigned long *mid_mfn_p;
 223 
 224         if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
 225                 return;
 226 
 227         /* Pre-initialize p2m_top_mfn to be completely missing */
 228         if (p2m_top_mfn == NULL) {
 229                 p2m_mid_missing_mfn = alloc_p2m_page();
 230                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 231 
 232                 p2m_top_mfn_p = alloc_p2m_page();
 233                 p2m_top_mfn_p_init(p2m_top_mfn_p);
 234 
 235                 p2m_top_mfn = alloc_p2m_page();
 236                 p2m_top_mfn_init(p2m_top_mfn);
 237         } else {
 238                 /* Reinitialise, mfn's all change after migration */
 239                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
 240         }
 241 
 242         for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
 243              pfn += P2M_PER_PAGE) {
 244                 topidx = p2m_top_index(pfn);
 245                 mididx = p2m_mid_index(pfn);
 246 
 247                 mid_mfn_p = p2m_top_mfn_p[topidx];
 248                 ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn),
 249                                       &level);
 250                 BUG_ON(!ptep || level != PG_LEVEL_4K);
 251                 mfn = pte_mfn(*ptep);
 252                 ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 253 
 254                 /* Don't bother allocating any mfn mid levels if
 255                  * they're just missing, just update the stored mfn,
 256                  * since all could have changed over a migrate.
 257                  */
 258                 if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) {
 259                         BUG_ON(mididx);
 260                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
 261                         p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
 262                         pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
 263                         continue;
 264                 }
 265 
 266                 if (mid_mfn_p == p2m_mid_missing_mfn) {
 267                         mid_mfn_p = alloc_p2m_page();
 268                         p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
 269 
 270                         p2m_top_mfn_p[topidx] = mid_mfn_p;
 271                 }
 272 
 273                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
 274                 mid_mfn_p[mididx] = mfn;
 275         }
 276 }
 277 
 278 void xen_setup_mfn_list_list(void)
 279 {
 280         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
 281 
 282         if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
 283                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = ~0UL;
 284         else
 285                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
 286                         virt_to_mfn(p2m_top_mfn);
 287         HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
 288         HYPERVISOR_shared_info->arch.p2m_generation = 0;
 289         HYPERVISOR_shared_info->arch.p2m_vaddr = (unsigned long)xen_p2m_addr;
 290         HYPERVISOR_shared_info->arch.p2m_cr3 =
 291                 xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
 292 }
 293 
 294 /* Set up p2m_top to point to the domain-builder provided p2m pages */
 295 void __init xen_build_dynamic_phys_to_machine(void)
 296 {
 297         unsigned long pfn;
 298 
 299         xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
 300         xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE);
 301 
 302         for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++)
 303                 xen_p2m_addr[pfn] = INVALID_P2M_ENTRY;
 304 
 305         xen_max_p2m_pfn = xen_p2m_size;
 306 }
 307 
 308 #define P2M_TYPE_IDENTITY       0
 309 #define P2M_TYPE_MISSING        1
 310 #define P2M_TYPE_PFN            2
 311 #define P2M_TYPE_UNKNOWN        3
 312 
 313 static int xen_p2m_elem_type(unsigned long pfn)
 314 {
 315         unsigned long mfn;
 316 
 317         if (pfn >= xen_p2m_size)
 318                 return P2M_TYPE_IDENTITY;
 319 
 320         mfn = xen_p2m_addr[pfn];
 321 
 322         if (mfn == INVALID_P2M_ENTRY)
 323                 return P2M_TYPE_MISSING;
 324 
 325         if (mfn & IDENTITY_FRAME_BIT)
 326                 return P2M_TYPE_IDENTITY;
 327 
 328         return P2M_TYPE_PFN;
 329 }
 330 
 331 static void __init xen_rebuild_p2m_list(unsigned long *p2m)
 332 {
 333         unsigned int i, chunk;
 334         unsigned long pfn;
 335         unsigned long *mfns;
 336         pte_t *ptep;
 337         pmd_t *pmdp;
 338         int type;
 339 
 340         p2m_missing = alloc_p2m_page();
 341         p2m_init(p2m_missing);
 342         p2m_identity = alloc_p2m_page();
 343         p2m_init(p2m_identity);
 344 
 345         p2m_missing_pte = alloc_p2m_page();
 346         paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
 347         p2m_identity_pte = alloc_p2m_page();
 348         paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
 349         for (i = 0; i < PTRS_PER_PTE; i++) {
 350                 set_pte(p2m_missing_pte + i,
 351                         pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
 352                 set_pte(p2m_identity_pte + i,
 353                         pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
 354         }
 355 
 356         for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
 357                 /*
 358                  * Try to map missing/identity PMDs or p2m-pages if possible.
 359                  * We have to respect the structure of the mfn_list_list
 360                  * which will be built just afterwards.
 361                  * Chunk size to test is one p2m page if we are in the middle
 362                  * of a mfn_list_list mid page and the complete mid page area
 363                  * if we are at index 0 of the mid page. Please note that a
 364                  * mid page might cover more than one PMD, e.g. on 32 bit PAE
 365                  * kernels.
 366                  */
 367                 chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
 368                         P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;
 369 
 370                 type = xen_p2m_elem_type(pfn);
 371                 i = 0;
 372                 if (type != P2M_TYPE_PFN)
 373                         for (i = 1; i < chunk; i++)
 374                                 if (xen_p2m_elem_type(pfn + i) != type)
 375                                         break;
 376                 if (i < chunk)
 377                         /* Reset to minimal chunk size. */
 378                         chunk = P2M_PER_PAGE;
 379 
 380                 if (type == P2M_TYPE_PFN || i < chunk) {
 381                         /* Use initial p2m page contents. */
 382 #ifdef CONFIG_X86_64
 383                         mfns = alloc_p2m_page();
 384                         copy_page(mfns, xen_p2m_addr + pfn);
 385 #else
 386                         mfns = xen_p2m_addr + pfn;
 387 #endif
 388                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
 389                         set_pte(ptep,
 390                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
 391                         continue;
 392                 }
 393 
 394                 if (chunk == P2M_PER_PAGE) {
 395                         /* Map complete missing or identity p2m-page. */
 396                         mfns = (type == P2M_TYPE_MISSING) ?
 397                                 p2m_missing : p2m_identity;
 398                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
 399                         set_pte(ptep,
 400                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
 401                         continue;
 402                 }
 403 
 404                 /* Complete missing or identity PMD(s) can be mapped. */
 405                 ptep = (type == P2M_TYPE_MISSING) ?
 406                         p2m_missing_pte : p2m_identity_pte;
 407                 for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 408                         pmdp = populate_extra_pmd(
 409                                 (unsigned long)(p2m + pfn) + i * PMD_SIZE);
 410                         set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
 411                 }
 412         }
 413 }
 414 
 415 void __init xen_vmalloc_p2m_tree(void)
 416 {
 417         static struct vm_struct vm;
 418         unsigned long p2m_limit;
 419 
 420         xen_p2m_last_pfn = xen_max_p2m_pfn;
 421 
 422         p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 / PAGE_SIZE;
 423         vm.flags = VM_ALLOC;
 424         vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn, p2m_limit),
 425                         PMD_SIZE * PMDS_PER_MID_PAGE);
 426         vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
 427         pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
 428 
 429         xen_max_p2m_pfn = vm.size / sizeof(unsigned long);
 430 
 431         xen_rebuild_p2m_list(vm.addr);
 432 
 433         xen_p2m_addr = vm.addr;
 434         xen_p2m_size = xen_max_p2m_pfn;
 435 
 436         xen_inv_extra_mem();
 437 }
 438 
 439 unsigned long get_phys_to_machine(unsigned long pfn)
 440 {
 441         pte_t *ptep;
 442         unsigned int level;
 443 
 444         if (unlikely(pfn >= xen_p2m_size)) {
 445                 if (pfn < xen_max_p2m_pfn)
 446                         return xen_chk_extra_mem(pfn);
 447 
 448                 return IDENTITY_FRAME(pfn);
 449         }
 450 
 451         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
 452         BUG_ON(!ptep || level != PG_LEVEL_4K);
 453 
 454         /*
 455          * The INVALID_P2M_ENTRY is filled in both p2m_*identity
 456          * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
 457          * would be wrong.
 458          */
 459         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 460                 return IDENTITY_FRAME(pfn);
 461 
 462         return xen_p2m_addr[pfn];
 463 }
 464 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 465 
 466 /*
 467  * Allocate new pmd(s). It is checked whether the old pmd is still in place.
 468  * If not, nothing is changed. This is okay as the only reason for allocating
 469  * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
 470  * pmd. In case of PAE/x86-32 there are multiple pmds to allocate!
 471  */
 472 static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
 473 {
 474         pte_t *ptechk;
 475         pte_t *pte_newpg[PMDS_PER_MID_PAGE];
 476         pmd_t *pmdp;
 477         unsigned int level;
 478         unsigned long flags;
 479         unsigned long vaddr;
 480         int i;
 481 
 482         /* Do all allocations first to bail out in error case. */
 483         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 484                 pte_newpg[i] = alloc_p2m_page();
 485                 if (!pte_newpg[i]) {
 486                         for (i--; i >= 0; i--)
 487                                 free_p2m_page(pte_newpg[i]);
 488 
 489                         return NULL;
 490                 }
 491         }
 492 
 493         vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);
 494 
 495         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
 496                 copy_page(pte_newpg[i], pte_pg);
 497                 paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);
 498 
 499                 pmdp = lookup_pmd_address(vaddr);
 500                 BUG_ON(!pmdp);
 501 
 502                 spin_lock_irqsave(&p2m_update_lock, flags);
 503 
 504                 ptechk = lookup_address(vaddr, &level);
 505                 if (ptechk == pte_pg) {
 506                         HYPERVISOR_shared_info->arch.p2m_generation++;
 507                         wmb(); /* Tools are synchronizing via p2m_generation. */
 508                         set_pmd(pmdp,
 509                                 __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
 510                         wmb(); /* Tools are synchronizing via p2m_generation. */
 511                         HYPERVISOR_shared_info->arch.p2m_generation++;
 512                         pte_newpg[i] = NULL;
 513                 }
 514 
 515                 spin_unlock_irqrestore(&p2m_update_lock, flags);
 516 
 517                 if (pte_newpg[i]) {
 518                         paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
 519                         free_p2m_page(pte_newpg[i]);
 520                 }
 521 
 522                 vaddr += PMD_SIZE;
 523         }
 524 
 525         return lookup_address(addr, &level);
 526 }
 527 
 528 /*
 529  * Fully allocate the p2m structure for a given pfn.  We need to check
 530  * that both the top and mid levels are allocated, and make sure the
 531  * parallel mfn tree is kept in sync.  We may race with other cpus, so
 532  * the new pages are installed with cmpxchg; if we lose the race then
 533  * simply free the page we allocated and use the one that's there.
 534  */
 535 int xen_alloc_p2m_entry(unsigned long pfn)
 536 {
 537         unsigned topidx;
 538         unsigned long *top_mfn_p, *mid_mfn;
 539         pte_t *ptep, *pte_pg;
 540         unsigned int level;
 541         unsigned long flags;
 542         unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
 543         unsigned long p2m_pfn;
 544 
 545         ptep = lookup_address(addr, &level);
 546         BUG_ON(!ptep || level != PG_LEVEL_4K);
 547         pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
 548 
 549         if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
 550                 /* PMD level is missing, allocate a new one */
 551                 ptep = alloc_p2m_pmd(addr, pte_pg);
 552                 if (!ptep)
 553                         return -ENOMEM;
 554         }
 555 
 556         if (p2m_top_mfn && pfn < MAX_P2M_PFN) {
 557                 topidx = p2m_top_index(pfn);
 558                 top_mfn_p = &p2m_top_mfn[topidx];
 559                 mid_mfn = READ_ONCE(p2m_top_mfn_p[topidx]);
 560 
 561                 BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
 562 
 563                 if (mid_mfn == p2m_mid_missing_mfn) {
 564                         /* Separately check the mid mfn level */
 565                         unsigned long missing_mfn;
 566                         unsigned long mid_mfn_mfn;
 567                         unsigned long old_mfn;
 568 
 569                         mid_mfn = alloc_p2m_page();
 570                         if (!mid_mfn)
 571                                 return -ENOMEM;
 572 
 573                         p2m_mid_mfn_init(mid_mfn, p2m_missing);
 574 
 575                         missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
 576                         mid_mfn_mfn = virt_to_mfn(mid_mfn);
 577                         old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
 578                         if (old_mfn != missing_mfn) {
 579                                 free_p2m_page(mid_mfn);
 580                                 mid_mfn = mfn_to_virt(old_mfn);
 581                         } else {
 582                                 p2m_top_mfn_p[topidx] = mid_mfn;
 583                         }
 584                 }
 585         } else {
 586                 mid_mfn = NULL;
 587         }
 588 
 589         p2m_pfn = pte_pfn(READ_ONCE(*ptep));
 590         if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
 591             p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
 592                 /* p2m leaf page is missing */
 593                 unsigned long *p2m;
 594 
 595                 p2m = alloc_p2m_page();
 596                 if (!p2m)
 597                         return -ENOMEM;
 598 
 599                 if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
 600                         p2m_init(p2m);
 601                 else
 602                         p2m_init_identity(p2m, pfn & ~(P2M_PER_PAGE - 1));
 603 
 604                 spin_lock_irqsave(&p2m_update_lock, flags);
 605 
 606                 if (pte_pfn(*ptep) == p2m_pfn) {
 607                         HYPERVISOR_shared_info->arch.p2m_generation++;
 608                         wmb(); /* Tools are synchronizing via p2m_generation. */
 609                         set_pte(ptep,
 610                                 pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
 611                         wmb(); /* Tools are synchronizing via p2m_generation. */
 612                         HYPERVISOR_shared_info->arch.p2m_generation++;
 613                         if (mid_mfn)
 614                                 mid_mfn[p2m_mid_index(pfn)] = virt_to_mfn(p2m);
 615                         p2m = NULL;
 616                 }
 617 
 618                 spin_unlock_irqrestore(&p2m_update_lock, flags);
 619 
 620                 if (p2m)
 621                         free_p2m_page(p2m);
 622         }
 623 
 624         /* Expanded the p2m? */
 625         if (pfn > xen_p2m_last_pfn) {
 626                 xen_p2m_last_pfn = pfn;
 627                 HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
 628         }
 629 
 630         return 0;
 631 }
 632 EXPORT_SYMBOL(xen_alloc_p2m_entry);
 633 
 634 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 635                                       unsigned long pfn_e)
 636 {
 637         unsigned long pfn;
 638 
 639         if (unlikely(pfn_s >= xen_p2m_size))
 640                 return 0;
 641 
 642         if (pfn_s > pfn_e)
 643                 return 0;
 644 
 645         if (pfn_e > xen_p2m_size)
 646                 pfn_e = xen_p2m_size;
 647 
 648         for (pfn = pfn_s; pfn < pfn_e; pfn++)
 649                 xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);
 650 
 651         return pfn - pfn_s;
 652 }
 653 
 654 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 655 {
 656         pte_t *ptep;
 657         unsigned int level;
 658 
 659         if (unlikely(pfn >= xen_p2m_size)) {
 660                 BUG_ON(mfn != INVALID_P2M_ENTRY);
 661                 return true;
 662         }
 663 
 664         /*
 665          * The interface requires atomic updates on p2m elements.
 666          * xen_safe_write_ulong() is using an atomic store via asm().
 667          */
 668         if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
 669                 return true;
 670 
 671         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
 672         BUG_ON(!ptep || level != PG_LEVEL_4K);
 673 
 674         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
 675                 return mfn == INVALID_P2M_ENTRY;
 676 
 677         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
 678                 return mfn == IDENTITY_FRAME(pfn);
 679 
 680         return false;
 681 }
 682 
 683 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 684 {
 685         if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
 686                 int ret;
 687 
 688                 ret = xen_alloc_p2m_entry(pfn);
 689                 if (ret < 0)
 690                         return false;
 691 
 692                 return __set_phys_to_machine(pfn, mfn);
 693         }
 694 
 695         return true;
 696 }
 697 
 698 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 699                             struct gnttab_map_grant_ref *kmap_ops,
 700                             struct page **pages, unsigned int count)
 701 {
 702         int i, ret = 0;
 703         pte_t *pte;
 704 
 705         if (xen_feature(XENFEAT_auto_translated_physmap))
 706                 return 0;
 707 
 708         if (kmap_ops) {
 709                 ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
 710                                                 kmap_ops, count);
 711                 if (ret)
 712                         goto out;
 713         }
 714 
 715         for (i = 0; i < count; i++) {
 716                 unsigned long mfn, pfn;
 717 
 718                 /* Do not add to override if the map failed. */
 719                 if (map_ops[i].status)
 720                         continue;
 721 
 722                 if (map_ops[i].flags & GNTMAP_contains_pte) {
 723                         pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
 724                                 (map_ops[i].host_addr & ~PAGE_MASK));
 725                         mfn = pte_mfn(*pte);
 726                 } else {
 727                         mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 728                 }
 729                 pfn = page_to_pfn(pages[i]);
 730 
 731                 WARN(pfn_to_mfn(pfn) != INVALID_P2M_ENTRY, "page must be ballooned");
 732 
 733                 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
 734                         ret = -ENOMEM;
 735                         goto out;
 736                 }
 737         }
 738 
 739 out:
 740         return ret;
 741 }
 742 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
 743 
 744 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 745                               struct gnttab_unmap_grant_ref *kunmap_ops,
 746                               struct page **pages, unsigned int count)
 747 {
 748         int i, ret = 0;
 749 
 750         if (xen_feature(XENFEAT_auto_translated_physmap))
 751                 return 0;
 752 
 753         for (i = 0; i < count; i++) {
 754                 unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
 755                 unsigned long pfn = page_to_pfn(pages[i]);
 756 
 757                 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
 758                         ret = -EINVAL;
 759                         goto out;
 760                 }
 761 
 762                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 763         }
 764         if (kunmap_ops)
 765                 ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
 766                                                 kunmap_ops, count);
 767 out:
 768         return ret;
 769 }
 770 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
 771 
 772 #ifdef CONFIG_XEN_DEBUG_FS
 773 #include <linux/debugfs.h>
 774 #include "debugfs.h"
 775 static int p2m_dump_show(struct seq_file *m, void *v)
 776 {
 777         static const char * const type_name[] = {
 778                                 [P2M_TYPE_IDENTITY] = "identity",
 779                                 [P2M_TYPE_MISSING] = "missing",
 780                                 [P2M_TYPE_PFN] = "pfn",
 781                                 [P2M_TYPE_UNKNOWN] = "abnormal"};
 782         unsigned long pfn, first_pfn;
 783         int type, prev_type;
 784 
 785         prev_type = xen_p2m_elem_type(0);
 786         first_pfn = 0;
 787 
 788         for (pfn = 0; pfn < xen_p2m_size; pfn++) {
 789                 type = xen_p2m_elem_type(pfn);
 790                 if (type != prev_type) {
 791                         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
 792                                    type_name[prev_type]);
 793                         prev_type = type;
 794                         first_pfn = pfn;
 795                 }
 796         }
 797         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
 798                    type_name[prev_type]);
 799         return 0;
 800 }
 801 
 802 static int p2m_dump_open(struct inode *inode, struct file *filp)
 803 {
 804         return single_open(filp, p2m_dump_show, NULL);
 805 }
 806 
 807 static const struct file_operations p2m_dump_fops = {
 808         .open           = p2m_dump_open,
 809         .read           = seq_read,
 810         .llseek         = seq_lseek,
 811         .release        = single_release,
 812 };
 813 
 814 static struct dentry *d_mmu_debug;
 815 
 816 static int __init xen_p2m_debugfs(void)
 817 {
 818         struct dentry *d_xen = xen_init_debugfs();
 819 
 820         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
 821 
 822         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
 823         return 0;
 824 }
 825 fs_initcall(xen_p2m_debugfs);
 826 #endif /* CONFIG_XEN_DEBUG_FS */
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root/arch/x86/xen/p2m.c

DEFINITIONS
