1 /* 2 * Postcopy migration for RAM 3 * 4 * Copyright 2013-2015 Red Hat, Inc. and/or its affiliates 5 * 6 * Authors: 7 * Dave Gilbert <dgilbert@redhat.com> 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 * 12 */ 13 14 /* 15 * Postcopy is a migration technique where the execution flips from the 16 * source to the destination before all the data has been copied. 17 */ 18 19 #include "qemu/osdep.h" 20 #include "qemu/madvise.h" 21 #include "exec/target_page.h" 22 #include "migration.h" 23 #include "qemu-file.h" 24 #include "savevm.h" 25 #include "postcopy-ram.h" 26 #include "ram.h" 27 #include "qapi/error.h" 28 #include "qemu/notify.h" 29 #include "qemu/rcu.h" 30 #include "sysemu/sysemu.h" 31 #include "qemu/error-report.h" 32 #include "trace.h" 33 #include "hw/boards.h" 34 #include "exec/ramblock.h" 35 #include "socket.h" 36 #include "yank_functions.h" 37 #include "tls.h" 38 #include "qemu/userfaultfd.h" 39 40 /* Arbitrary limit on size of each discard command, 41 * keeps them around ~200 bytes 42 */ 43 #define MAX_DISCARDS_PER_COMMAND 12 44 45 struct PostcopyDiscardState { 46 const char *ramblock_name; 47 uint16_t cur_entry; 48 /* 49 * Start and length of a discard range (bytes) 50 */ 51 uint64_t start_list[MAX_DISCARDS_PER_COMMAND]; 52 uint64_t length_list[MAX_DISCARDS_PER_COMMAND]; 53 unsigned int nsentwords; 54 unsigned int nsentcmds; 55 }; 56 57 static NotifierWithReturnList postcopy_notifier_list; 58 59 void postcopy_infrastructure_init(void) 60 { 61 notifier_with_return_list_init(&postcopy_notifier_list); 62 } 63 64 void postcopy_add_notifier(NotifierWithReturn *nn) 65 { 66 notifier_with_return_list_add(&postcopy_notifier_list, nn); 67 } 68 69 void postcopy_remove_notifier(NotifierWithReturn *n) 70 { 71 notifier_with_return_remove(n); 72 } 73 74 int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp) 75 { 76 struct PostcopyNotifyData pnd; 77 pnd.reason = reason; 78 pnd.errp = errp; 79 80 return notifier_with_return_list_notify(&postcopy_notifier_list, 81 &pnd); 82 } 83 84 /* 85 * NOTE: this routine is not thread safe, we can't call it concurrently. But it 86 * should be good enough for migration's purposes. 87 */ 88 void postcopy_thread_create(MigrationIncomingState *mis, 89 QemuThread *thread, const char *name, 90 void *(*fn)(void *), int joinable) 91 { 92 qemu_sem_init(&mis->thread_sync_sem, 0); 93 qemu_thread_create(thread, name, fn, mis, joinable); 94 qemu_sem_wait(&mis->thread_sync_sem); 95 qemu_sem_destroy(&mis->thread_sync_sem); 96 } 97 98 /* Postcopy needs to detect accesses to pages that haven't yet been copied 99 * across, and efficiently map new pages in, the techniques for doing this 100 * are target OS specific. 101 */ 102 #if defined(__linux__) 103 104 #include <poll.h> 105 #include <sys/ioctl.h> 106 #include <sys/syscall.h> 107 #include <asm/types.h> /* for __u64 */ 108 #endif 109 110 #if defined(__linux__) && defined(__NR_userfaultfd) && defined(CONFIG_EVENTFD) 111 #include <sys/eventfd.h> 112 #include <linux/userfaultfd.h> 113 114 typedef struct PostcopyBlocktimeContext { 115 /* time when page fault initiated per vCPU */ 116 uint32_t *page_fault_vcpu_time; 117 /* page address per vCPU */ 118 uintptr_t *vcpu_addr; 119 uint32_t total_blocktime; 120 /* blocktime per vCPU */ 121 uint32_t *vcpu_blocktime; 122 /* point in time when last page fault was initiated */ 123 uint32_t last_begin; 124 /* number of vCPU are suspended */ 125 int smp_cpus_down; 126 uint64_t start_time; 127 128 /* 129 * Handler for exit event, necessary for 130 * releasing whole blocktime_ctx 131 */ 132 Notifier exit_notifier; 133 } PostcopyBlocktimeContext; 134 135 static void destroy_blocktime_context(struct PostcopyBlocktimeContext *ctx) 136 { 137 g_free(ctx->page_fault_vcpu_time); 138 g_free(ctx->vcpu_addr); 139 g_free(ctx->vcpu_blocktime); 140 g_free(ctx); 141 } 142 143 static void migration_exit_cb(Notifier *n, void *data) 144 { 145 PostcopyBlocktimeContext *ctx = container_of(n, PostcopyBlocktimeContext, 146 exit_notifier); 147 destroy_blocktime_context(ctx); 148 } 149 150 static struct PostcopyBlocktimeContext *blocktime_context_new(void) 151 { 152 MachineState *ms = MACHINE(qdev_get_machine()); 153 unsigned int smp_cpus = ms->smp.cpus; 154 PostcopyBlocktimeContext *ctx = g_new0(PostcopyBlocktimeContext, 1); 155 ctx->page_fault_vcpu_time = g_new0(uint32_t, smp_cpus); 156 ctx->vcpu_addr = g_new0(uintptr_t, smp_cpus); 157 ctx->vcpu_blocktime = g_new0(uint32_t, smp_cpus); 158 159 ctx->exit_notifier.notify = migration_exit_cb; 160 ctx->start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); 161 qemu_add_exit_notifier(&ctx->exit_notifier); 162 return ctx; 163 } 164 165 static uint32List *get_vcpu_blocktime_list(PostcopyBlocktimeContext *ctx) 166 { 167 MachineState *ms = MACHINE(qdev_get_machine()); 168 uint32List *list = NULL; 169 int i; 170 171 for (i = ms->smp.cpus - 1; i >= 0; i--) { 172 QAPI_LIST_PREPEND(list, ctx->vcpu_blocktime[i]); 173 } 174 175 return list; 176 } 177 178 /* 179 * This function just populates MigrationInfo from postcopy's 180 * blocktime context. It will not populate MigrationInfo, 181 * unless postcopy-blocktime capability was set. 182 * 183 * @info: pointer to MigrationInfo to populate 184 */ 185 void fill_destination_postcopy_migration_info(MigrationInfo *info) 186 { 187 MigrationIncomingState *mis = migration_incoming_get_current(); 188 PostcopyBlocktimeContext *bc = mis->blocktime_ctx; 189 190 if (!bc) { 191 return; 192 } 193 194 info->has_postcopy_blocktime = true; 195 info->postcopy_blocktime = bc->total_blocktime; 196 info->has_postcopy_vcpu_blocktime = true; 197 info->postcopy_vcpu_blocktime = get_vcpu_blocktime_list(bc); 198 } 199 200 static uint32_t get_postcopy_total_blocktime(void) 201 { 202 MigrationIncomingState *mis = migration_incoming_get_current(); 203 PostcopyBlocktimeContext *bc = mis->blocktime_ctx; 204 205 if (!bc) { 206 return 0; 207 } 208 209 return bc->total_blocktime; 210 } 211 212 /** 213 * receive_ufd_features: check userfault fd features, to request only supported 214 * features in the future. 215 * 216 * Returns: true on success 217 * 218 * __NR_userfaultfd - should be checked before 219 * @features: out parameter will contain uffdio_api.features provided by kernel 220 * in case of success 221 */ 222 static bool receive_ufd_features(uint64_t *features) 223 { 224 struct uffdio_api api_struct = {0}; 225 int ufd; 226 bool ret = true; 227 228 ufd = uffd_open(O_CLOEXEC); 229 if (ufd == -1) { 230 error_report("%s: uffd_open() failed: %s", __func__, strerror(errno)); 231 return false; 232 } 233 234 /* ask features */ 235 api_struct.api = UFFD_API; 236 api_struct.features = 0; 237 if (ioctl(ufd, UFFDIO_API, &api_struct)) { 238 error_report("%s: UFFDIO_API failed: %s", __func__, 239 strerror(errno)); 240 ret = false; 241 goto release_ufd; 242 } 243 244 *features = api_struct.features; 245 246 release_ufd: 247 close(ufd); 248 return ret; 249 } 250 251 /** 252 * request_ufd_features: this function should be called only once on a newly 253 * opened ufd, subsequent calls will lead to error. 254 * 255 * Returns: true on success 256 * 257 * @ufd: fd obtained from userfaultfd syscall 258 * @features: bit mask see UFFD_API_FEATURES 259 */ 260 static bool request_ufd_features(int ufd, uint64_t features) 261 { 262 struct uffdio_api api_struct = {0}; 263 uint64_t ioctl_mask; 264 265 api_struct.api = UFFD_API; 266 api_struct.features = features; 267 if (ioctl(ufd, UFFDIO_API, &api_struct)) { 268 error_report("%s failed: UFFDIO_API failed: %s", __func__, 269 strerror(errno)); 270 return false; 271 } 272 273 ioctl_mask = (__u64)1 << _UFFDIO_REGISTER | 274 (__u64)1 << _UFFDIO_UNREGISTER; 275 if ((api_struct.ioctls & ioctl_mask) != ioctl_mask) { 276 error_report("Missing userfault features: %" PRIx64, 277 (uint64_t)(~api_struct.ioctls & ioctl_mask)); 278 return false; 279 } 280 281 return true; 282 } 283 284 static bool ufd_check_and_apply(int ufd, MigrationIncomingState *mis) 285 { 286 uint64_t asked_features = 0; 287 static uint64_t supported_features; 288 289 /* 290 * it's not possible to 291 * request UFFD_API twice per one fd 292 * userfault fd features is persistent 293 */ 294 if (!supported_features) { 295 if (!receive_ufd_features(&supported_features)) { 296 error_report("%s failed", __func__); 297 return false; 298 } 299 } 300 301 #ifdef UFFD_FEATURE_THREAD_ID 302 if (UFFD_FEATURE_THREAD_ID & supported_features) { 303 asked_features |= UFFD_FEATURE_THREAD_ID; 304 if (migrate_postcopy_blocktime()) { 305 if (!mis->blocktime_ctx) { 306 mis->blocktime_ctx = blocktime_context_new(); 307 } 308 } 309 } 310 #endif 311 312 /* 313 * request features, even if asked_features is 0, due to 314 * kernel expects UFFD_API before UFFDIO_REGISTER, per 315 * userfault file descriptor 316 */ 317 if (!request_ufd_features(ufd, asked_features)) { 318 error_report("%s failed: features %" PRIu64, __func__, 319 asked_features); 320 return false; 321 } 322 323 if (qemu_real_host_page_size() != ram_pagesize_summary()) { 324 bool have_hp = false; 325 /* We've got a huge page */ 326 #ifdef UFFD_FEATURE_MISSING_HUGETLBFS 327 have_hp = supported_features & UFFD_FEATURE_MISSING_HUGETLBFS; 328 #endif 329 if (!have_hp) { 330 error_report("Userfault on this host does not support huge pages"); 331 return false; 332 } 333 } 334 return true; 335 } 336 337 /* Callback from postcopy_ram_supported_by_host block iterator. 338 */ 339 static int test_ramblock_postcopiable(RAMBlock *rb, void *opaque) 340 { 341 const char *block_name = qemu_ram_get_idstr(rb); 342 ram_addr_t length = qemu_ram_get_used_length(rb); 343 size_t pagesize = qemu_ram_pagesize(rb); 344 345 if (length % pagesize) { 346 error_report("Postcopy requires RAM blocks to be a page size multiple," 347 " block %s is 0x" RAM_ADDR_FMT " bytes with a " 348 "page size of 0x%zx", block_name, length, pagesize); 349 return 1; 350 } 351 return 0; 352 } 353 354 /* 355 * Note: This has the side effect of munlock'ing all of RAM, that's 356 * normally fine since if the postcopy succeeds it gets turned back on at the 357 * end. 358 */ 359 bool postcopy_ram_supported_by_host(MigrationIncomingState *mis) 360 { 361 long pagesize = qemu_real_host_page_size(); 362 int ufd = -1; 363 bool ret = false; /* Error unless we change it */ 364 void *testarea = NULL; 365 struct uffdio_register reg_struct; 366 struct uffdio_range range_struct; 367 uint64_t feature_mask; 368 Error *local_err = NULL; 369 370 if (qemu_target_page_size() > pagesize) { 371 error_report("Target page size bigger than host page size"); 372 goto out; 373 } 374 375 ufd = uffd_open(O_CLOEXEC); 376 if (ufd == -1) { 377 error_report("%s: userfaultfd not available: %s", __func__, 378 strerror(errno)); 379 goto out; 380 } 381 382 /* Give devices a chance to object */ 383 if (postcopy_notify(POSTCOPY_NOTIFY_PROBE, &local_err)) { 384 error_report_err(local_err); 385 goto out; 386 } 387 388 /* Version and features check */ 389 if (!ufd_check_and_apply(ufd, mis)) { 390 goto out; 391 } 392 393 /* We don't support postcopy with shared RAM yet */ 394 if (foreach_not_ignored_block(test_ramblock_postcopiable, NULL)) { 395 goto out; 396 } 397 398 /* 399 * userfault and mlock don't go together; we'll put it back later if 400 * it was enabled. 401 */ 402 if (munlockall()) { 403 error_report("%s: munlockall: %s", __func__, strerror(errno)); 404 goto out; 405 } 406 407 /* 408 * We need to check that the ops we need are supported on anon memory 409 * To do that we need to register a chunk and see the flags that 410 * are returned. 411 */ 412 testarea = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE | 413 MAP_ANONYMOUS, -1, 0); 414 if (testarea == MAP_FAILED) { 415 error_report("%s: Failed to map test area: %s", __func__, 416 strerror(errno)); 417 goto out; 418 } 419 g_assert(QEMU_PTR_IS_ALIGNED(testarea, pagesize)); 420 421 reg_struct.range.start = (uintptr_t)testarea; 422 reg_struct.range.len = pagesize; 423 reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING; 424 425 if (ioctl(ufd, UFFDIO_REGISTER, ®_struct)) { 426 error_report("%s userfault register: %s", __func__, strerror(errno)); 427 goto out; 428 } 429 430 range_struct.start = (uintptr_t)testarea; 431 range_struct.len = pagesize; 432 if (ioctl(ufd, UFFDIO_UNREGISTER, &range_struct)) { 433 error_report("%s userfault unregister: %s", __func__, strerror(errno)); 434 goto out; 435 } 436 437 feature_mask = (__u64)1 << _UFFDIO_WAKE | 438 (__u64)1 << _UFFDIO_COPY | 439 (__u64)1 << _UFFDIO_ZEROPAGE; 440 if ((reg_struct.ioctls & feature_mask) != feature_mask) { 441 error_report("Missing userfault map features: %" PRIx64, 442 (uint64_t)(~reg_struct.ioctls & feature_mask)); 443 goto out; 444 } 445 446 /* Success! */ 447 ret = true; 448 out: 449 if (testarea) { 450 munmap(testarea, pagesize); 451 } 452 if (ufd != -1) { 453 close(ufd); 454 } 455 return ret; 456 } 457 458 /* 459 * Setup an area of RAM so that it *can* be used for postcopy later; this 460 * must be done right at the start prior to pre-copy. 461 * opaque should be the MIS. 462 */ 463 static int init_range(RAMBlock *rb, void *opaque) 464 { 465 const char *block_name = qemu_ram_get_idstr(rb); 466 void *host_addr = qemu_ram_get_host_addr(rb); 467 ram_addr_t offset = qemu_ram_get_offset(rb); 468 ram_addr_t length = qemu_ram_get_used_length(rb); 469 trace_postcopy_init_range(block_name, host_addr, offset, length); 470 471 /* 472 * Save the used_length before running the guest. In case we have to 473 * resize RAM blocks when syncing RAM block sizes from the source during 474 * precopy, we'll update it manually via the ram block notifier. 475 */ 476 rb->postcopy_length = length; 477 478 /* 479 * We need the whole of RAM to be truly empty for postcopy, so things 480 * like ROMs and any data tables built during init must be zero'd 481 * - we're going to get the copy from the source anyway. 482 * (Precopy will just overwrite this data, so doesn't need the discard) 483 */ 484 if (ram_discard_range(block_name, 0, length)) { 485 return -1; 486 } 487 488 return 0; 489 } 490 491 /* 492 * At the end of migration, undo the effects of init_range 493 * opaque should be the MIS. 494 */ 495 static int cleanup_range(RAMBlock *rb, void *opaque) 496 { 497 const char *block_name = qemu_ram_get_idstr(rb); 498 void *host_addr = qemu_ram_get_host_addr(rb); 499 ram_addr_t offset = qemu_ram_get_offset(rb); 500 ram_addr_t length = rb->postcopy_length; 501 MigrationIncomingState *mis = opaque; 502 struct uffdio_range range_struct; 503 trace_postcopy_cleanup_range(block_name, host_addr, offset, length); 504 505 /* 506 * We turned off hugepage for the precopy stage with postcopy enabled 507 * we can turn it back on now. 508 */ 509 qemu_madvise(host_addr, length, QEMU_MADV_HUGEPAGE); 510 511 /* 512 * We can also turn off userfault now since we should have all the 513 * pages. It can be useful to leave it on to debug postcopy 514 * if you're not sure it's always getting every page. 515 */ 516 range_struct.start = (uintptr_t)host_addr; 517 range_struct.len = length; 518 519 if (ioctl(mis->userfault_fd, UFFDIO_UNREGISTER, &range_struct)) { 520 error_report("%s: userfault unregister %s", __func__, strerror(errno)); 521 522 return -1; 523 } 524 525 return 0; 526 } 527 528 /* 529 * Initialise postcopy-ram, setting the RAM to a state where we can go into 530 * postcopy later; must be called prior to any precopy. 531 * called from arch_init's similarly named ram_postcopy_incoming_init 532 */ 533 int postcopy_ram_incoming_init(MigrationIncomingState *mis) 534 { 535 if (foreach_not_ignored_block(init_range, NULL)) { 536 return -1; 537 } 538 539 return 0; 540 } 541 542 static void postcopy_temp_pages_cleanup(MigrationIncomingState *mis) 543 { 544 int i; 545 546 if (mis->postcopy_tmp_pages) { 547 for (i = 0; i < mis->postcopy_channels; i++) { 548 if (mis->postcopy_tmp_pages[i].tmp_huge_page) { 549 munmap(mis->postcopy_tmp_pages[i].tmp_huge_page, 550 mis->largest_page_size); 551 mis->postcopy_tmp_pages[i].tmp_huge_page = NULL; 552 } 553 } 554 g_free(mis->postcopy_tmp_pages); 555 mis->postcopy_tmp_pages = NULL; 556 } 557 558 if (mis->postcopy_tmp_zero_page) { 559 munmap(mis->postcopy_tmp_zero_page, mis->largest_page_size); 560 mis->postcopy_tmp_zero_page = NULL; 561 } 562 } 563 564 /* 565 * At the end of a migration where postcopy_ram_incoming_init was called. 566 */ 567 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis) 568 { 569 trace_postcopy_ram_incoming_cleanup_entry(); 570 571 if (mis->postcopy_prio_thread_created) { 572 qemu_thread_join(&mis->postcopy_prio_thread); 573 mis->postcopy_prio_thread_created = false; 574 } 575 576 if (mis->have_fault_thread) { 577 Error *local_err = NULL; 578 579 /* Let the fault thread quit */ 580 qatomic_set(&mis->fault_thread_quit, 1); 581 postcopy_fault_thread_notify(mis); 582 trace_postcopy_ram_incoming_cleanup_join(); 583 qemu_thread_join(&mis->fault_thread); 584 585 if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_END, &local_err)) { 586 error_report_err(local_err); 587 return -1; 588 } 589 590 if (foreach_not_ignored_block(cleanup_range, mis)) { 591 return -1; 592 } 593 594 trace_postcopy_ram_incoming_cleanup_closeuf(); 595 close(mis->userfault_fd); 596 close(mis->userfault_event_fd); 597 mis->have_fault_thread = false; 598 } 599 600 if (enable_mlock) { 601 if (os_mlock() < 0) { 602 error_report("mlock: %s", strerror(errno)); 603 /* 604 * It doesn't feel right to fail at this point, we have a valid 605 * VM state. 606 */ 607 } 608 } 609 610 postcopy_temp_pages_cleanup(mis); 611 612 trace_postcopy_ram_incoming_cleanup_blocktime( 613 get_postcopy_total_blocktime()); 614 615 trace_postcopy_ram_incoming_cleanup_exit(); 616 return 0; 617 } 618 619 /* 620 * Disable huge pages on an area 621 */ 622 static int nhp_range(RAMBlock *rb, void *opaque) 623 { 624 const char *block_name = qemu_ram_get_idstr(rb); 625 void *host_addr = qemu_ram_get_host_addr(rb); 626 ram_addr_t offset = qemu_ram_get_offset(rb); 627 ram_addr_t length = rb->postcopy_length; 628 trace_postcopy_nhp_range(block_name, host_addr, offset, length); 629 630 /* 631 * Before we do discards we need to ensure those discards really 632 * do delete areas of the page, even if THP thinks a hugepage would 633 * be a good idea, so force hugepages off. 634 */ 635 qemu_madvise(host_addr, length, QEMU_MADV_NOHUGEPAGE); 636 637 return 0; 638 } 639 640 /* 641 * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard 642 * however leaving it until after precopy means that most of the precopy 643 * data is still THPd 644 */ 645 int postcopy_ram_prepare_discard(MigrationIncomingState *mis) 646 { 647 if (foreach_not_ignored_block(nhp_range, mis)) { 648 return -1; 649 } 650 651 postcopy_state_set(POSTCOPY_INCOMING_DISCARD); 652 653 return 0; 654 } 655 656 /* 657 * Mark the given area of RAM as requiring notification to unwritten areas 658 * Used as a callback on foreach_not_ignored_block. 659 * host_addr: Base of area to mark 660 * offset: Offset in the whole ram arena 661 * length: Length of the section 662 * opaque: MigrationIncomingState pointer 663 * Returns 0 on success 664 */ 665 static int ram_block_enable_notify(RAMBlock *rb, void *opaque) 666 { 667 MigrationIncomingState *mis = opaque; 668 struct uffdio_register reg_struct; 669 670 reg_struct.range.start = (uintptr_t)qemu_ram_get_host_addr(rb); 671 reg_struct.range.len = rb->postcopy_length; 672 reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING; 673 674 /* Now tell our userfault_fd that it's responsible for this area */ 675 if (ioctl(mis->userfault_fd, UFFDIO_REGISTER, ®_struct)) { 676 error_report("%s userfault register: %s", __func__, strerror(errno)); 677 return -1; 678 } 679 if (!(reg_struct.ioctls & ((__u64)1 << _UFFDIO_COPY))) { 680 error_report("%s userfault: Region doesn't support COPY", __func__); 681 return -1; 682 } 683 if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) { 684 qemu_ram_set_uf_zeroable(rb); 685 } 686 687 return 0; 688 } 689 690 int postcopy_wake_shared(struct PostCopyFD *pcfd, 691 uint64_t client_addr, 692 RAMBlock *rb) 693 { 694 size_t pagesize = qemu_ram_pagesize(rb); 695 struct uffdio_range range; 696 int ret; 697 trace_postcopy_wake_shared(client_addr, qemu_ram_get_idstr(rb)); 698 range.start = ROUND_DOWN(client_addr, pagesize); 699 range.len = pagesize; 700 ret = ioctl(pcfd->fd, UFFDIO_WAKE, &range); 701 if (ret) { 702 error_report("%s: Failed to wake: %zx in %s (%s)", 703 __func__, (size_t)client_addr, qemu_ram_get_idstr(rb), 704 strerror(errno)); 705 } 706 return ret; 707 } 708 709 static int postcopy_request_page(MigrationIncomingState *mis, RAMBlock *rb, 710 ram_addr_t start, uint64_t haddr) 711 { 712 void *aligned = (void *)(uintptr_t)ROUND_DOWN(haddr, qemu_ram_pagesize(rb)); 713 714 /* 715 * Discarded pages (via RamDiscardManager) are never migrated. On unlikely 716 * access, place a zeropage, which will also set the relevant bits in the 717 * recv_bitmap accordingly, so we won't try placing a zeropage twice. 718 * 719 * Checking a single bit is sufficient to handle pagesize > TPS as either 720 * all relevant bits are set or not. 721 */ 722 assert(QEMU_IS_ALIGNED(start, qemu_ram_pagesize(rb))); 723 if (ramblock_page_is_discarded(rb, start)) { 724 bool received = ramblock_recv_bitmap_test_byte_offset(rb, start); 725 726 return received ? 0 : postcopy_place_page_zero(mis, aligned, rb); 727 } 728 729 return migrate_send_rp_req_pages(mis, rb, start, haddr); 730 } 731 732 /* 733 * Callback from shared fault handlers to ask for a page, 734 * the page must be specified by a RAMBlock and an offset in that rb 735 * Note: Only for use by shared fault handlers (in fault thread) 736 */ 737 int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb, 738 uint64_t client_addr, uint64_t rb_offset) 739 { 740 uint64_t aligned_rbo = ROUND_DOWN(rb_offset, qemu_ram_pagesize(rb)); 741 MigrationIncomingState *mis = migration_incoming_get_current(); 742 743 trace_postcopy_request_shared_page(pcfd->idstr, qemu_ram_get_idstr(rb), 744 rb_offset); 745 if (ramblock_recv_bitmap_test_byte_offset(rb, aligned_rbo)) { 746 trace_postcopy_request_shared_page_present(pcfd->idstr, 747 qemu_ram_get_idstr(rb), rb_offset); 748 return postcopy_wake_shared(pcfd, client_addr, rb); 749 } 750 postcopy_request_page(mis, rb, aligned_rbo, client_addr); 751 return 0; 752 } 753 754 static int get_mem_fault_cpu_index(uint32_t pid) 755 { 756 CPUState *cpu_iter; 757 758 CPU_FOREACH(cpu_iter) { 759 if (cpu_iter->thread_id == pid) { 760 trace_get_mem_fault_cpu_index(cpu_iter->cpu_index, pid); 761 return cpu_iter->cpu_index; 762 } 763 } 764 trace_get_mem_fault_cpu_index(-1, pid); 765 return -1; 766 } 767 768 static uint32_t get_low_time_offset(PostcopyBlocktimeContext *dc) 769 { 770 int64_t start_time_offset = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - 771 dc->start_time; 772 return start_time_offset < 1 ? 1 : start_time_offset & UINT32_MAX; 773 } 774 775 /* 776 * This function is being called when pagefault occurs. It 777 * tracks down vCPU blocking time. 778 * 779 * @addr: faulted host virtual address 780 * @ptid: faulted process thread id 781 * @rb: ramblock appropriate to addr 782 */ 783 static void mark_postcopy_blocktime_begin(uintptr_t addr, uint32_t ptid, 784 RAMBlock *rb) 785 { 786 int cpu, already_received; 787 MigrationIncomingState *mis = migration_incoming_get_current(); 788 PostcopyBlocktimeContext *dc = mis->blocktime_ctx; 789 uint32_t low_time_offset; 790 791 if (!dc || ptid == 0) { 792 return; 793 } 794 cpu = get_mem_fault_cpu_index(ptid); 795 if (cpu < 0) { 796 return; 797 } 798 799 low_time_offset = get_low_time_offset(dc); 800 if (dc->vcpu_addr[cpu] == 0) { 801 qatomic_inc(&dc->smp_cpus_down); 802 } 803 804 qatomic_xchg(&dc->last_begin, low_time_offset); 805 qatomic_xchg(&dc->page_fault_vcpu_time[cpu], low_time_offset); 806 qatomic_xchg(&dc->vcpu_addr[cpu], addr); 807 808 /* 809 * check it here, not at the beginning of the function, 810 * due to, check could occur early than bitmap_set in 811 * qemu_ufd_copy_ioctl 812 */ 813 already_received = ramblock_recv_bitmap_test(rb, (void *)addr); 814 if (already_received) { 815 qatomic_xchg(&dc->vcpu_addr[cpu], 0); 816 qatomic_xchg(&dc->page_fault_vcpu_time[cpu], 0); 817 qatomic_dec(&dc->smp_cpus_down); 818 } 819 trace_mark_postcopy_blocktime_begin(addr, dc, dc->page_fault_vcpu_time[cpu], 820 cpu, already_received); 821 } 822 823 /* 824 * This function just provide calculated blocktime per cpu and trace it. 825 * Total blocktime is calculated in mark_postcopy_blocktime_end. 826 * 827 * 828 * Assume we have 3 CPU 829 * 830 * S1 E1 S1 E1 831 * -----***********------------xxx***************------------------------> CPU1 832 * 833 * S2 E2 834 * ------------****************xxx---------------------------------------> CPU2 835 * 836 * S3 E3 837 * ------------------------****xxx********-------------------------------> CPU3 838 * 839 * We have sequence S1,S2,E1,S3,S1,E2,E3,E1 840 * S2,E1 - doesn't match condition due to sequence S1,S2,E1 doesn't include CPU3 841 * S3,S1,E2 - sequence includes all CPUs, in this case overlap will be S1,E2 - 842 * it's a part of total blocktime. 843 * S1 - here is last_begin 844 * Legend of the picture is following: 845 * * - means blocktime per vCPU 846 * x - means overlapped blocktime (total blocktime) 847 * 848 * @addr: host virtual address 849 */ 850 static void mark_postcopy_blocktime_end(uintptr_t addr) 851 { 852 MigrationIncomingState *mis = migration_incoming_get_current(); 853 PostcopyBlocktimeContext *dc = mis->blocktime_ctx; 854 MachineState *ms = MACHINE(qdev_get_machine()); 855 unsigned int smp_cpus = ms->smp.cpus; 856 int i, affected_cpu = 0; 857 bool vcpu_total_blocktime = false; 858 uint32_t read_vcpu_time, low_time_offset; 859 860 if (!dc) { 861 return; 862 } 863 864 low_time_offset = get_low_time_offset(dc); 865 /* lookup cpu, to clear it, 866 * that algorithm looks straightforward, but it's not 867 * optimal, more optimal algorithm is keeping tree or hash 868 * where key is address value is a list of */ 869 for (i = 0; i < smp_cpus; i++) { 870 uint32_t vcpu_blocktime = 0; 871 872 read_vcpu_time = qatomic_fetch_add(&dc->page_fault_vcpu_time[i], 0); 873 if (qatomic_fetch_add(&dc->vcpu_addr[i], 0) != addr || 874 read_vcpu_time == 0) { 875 continue; 876 } 877 qatomic_xchg(&dc->vcpu_addr[i], 0); 878 vcpu_blocktime = low_time_offset - read_vcpu_time; 879 affected_cpu += 1; 880 /* we need to know is that mark_postcopy_end was due to 881 * faulted page, another possible case it's prefetched 882 * page and in that case we shouldn't be here */ 883 if (!vcpu_total_blocktime && 884 qatomic_fetch_add(&dc->smp_cpus_down, 0) == smp_cpus) { 885 vcpu_total_blocktime = true; 886 } 887 /* continue cycle, due to one page could affect several vCPUs */ 888 dc->vcpu_blocktime[i] += vcpu_blocktime; 889 } 890 891 qatomic_sub(&dc->smp_cpus_down, affected_cpu); 892 if (vcpu_total_blocktime) { 893 dc->total_blocktime += low_time_offset - qatomic_fetch_add( 894 &dc->last_begin, 0); 895 } 896 trace_mark_postcopy_blocktime_end(addr, dc, dc->total_blocktime, 897 affected_cpu); 898 } 899 900 static void postcopy_pause_fault_thread(MigrationIncomingState *mis) 901 { 902 trace_postcopy_pause_fault_thread(); 903 qemu_sem_wait(&mis->postcopy_pause_sem_fault); 904 trace_postcopy_pause_fault_thread_continued(); 905 } 906 907 /* 908 * Handle faults detected by the USERFAULT markings 909 */ 910 static void *postcopy_ram_fault_thread(void *opaque) 911 { 912 MigrationIncomingState *mis = opaque; 913 struct uffd_msg msg; 914 int ret; 915 size_t index; 916 RAMBlock *rb = NULL; 917 918 trace_postcopy_ram_fault_thread_entry(); 919 rcu_register_thread(); 920 mis->last_rb = NULL; /* last RAMBlock we sent part of */ 921 qemu_sem_post(&mis->thread_sync_sem); 922 923 struct pollfd *pfd; 924 size_t pfd_len = 2 + mis->postcopy_remote_fds->len; 925 926 pfd = g_new0(struct pollfd, pfd_len); 927 928 pfd[0].fd = mis->userfault_fd; 929 pfd[0].events = POLLIN; 930 pfd[1].fd = mis->userfault_event_fd; 931 pfd[1].events = POLLIN; /* Waiting for eventfd to go positive */ 932 trace_postcopy_ram_fault_thread_fds_core(pfd[0].fd, pfd[1].fd); 933 for (index = 0; index < mis->postcopy_remote_fds->len; index++) { 934 struct PostCopyFD *pcfd = &g_array_index(mis->postcopy_remote_fds, 935 struct PostCopyFD, index); 936 pfd[2 + index].fd = pcfd->fd; 937 pfd[2 + index].events = POLLIN; 938 trace_postcopy_ram_fault_thread_fds_extra(2 + index, pcfd->idstr, 939 pcfd->fd); 940 } 941 942 while (true) { 943 ram_addr_t rb_offset; 944 int poll_result; 945 946 /* 947 * We're mainly waiting for the kernel to give us a faulting HVA, 948 * however we can be told to quit via userfault_quit_fd which is 949 * an eventfd 950 */ 951 952 poll_result = poll(pfd, pfd_len, -1 /* Wait forever */); 953 if (poll_result == -1) { 954 error_report("%s: userfault poll: %s", __func__, strerror(errno)); 955 break; 956 } 957 958 if (!mis->to_src_file) { 959 /* 960 * Possibly someone tells us that the return path is 961 * broken already using the event. We should hold until 962 * the channel is rebuilt. 963 */ 964 postcopy_pause_fault_thread(mis); 965 } 966 967 if (pfd[1].revents) { 968 uint64_t tmp64 = 0; 969 970 /* Consume the signal */ 971 if (read(mis->userfault_event_fd, &tmp64, 8) != 8) { 972 /* Nothing obviously nicer than posting this error. */ 973 error_report("%s: read() failed", __func__); 974 } 975 976 if (qatomic_read(&mis->fault_thread_quit)) { 977 trace_postcopy_ram_fault_thread_quit(); 978 break; 979 } 980 } 981 982 if (pfd[0].revents) { 983 poll_result--; 984 ret = read(mis->userfault_fd, &msg, sizeof(msg)); 985 if (ret != sizeof(msg)) { 986 if (errno == EAGAIN) { 987 /* 988 * if a wake up happens on the other thread just after 989 * the poll, there is nothing to read. 990 */ 991 continue; 992 } 993 if (ret < 0) { 994 error_report("%s: Failed to read full userfault " 995 "message: %s", 996 __func__, strerror(errno)); 997 break; 998 } else { 999 error_report("%s: Read %d bytes from userfaultfd " 1000 "expected %zd", 1001 __func__, ret, sizeof(msg)); 1002 break; /* Lost alignment, don't know what we'd read next */ 1003 } 1004 } 1005 if (msg.event != UFFD_EVENT_PAGEFAULT) { 1006 error_report("%s: Read unexpected event %ud from userfaultfd", 1007 __func__, msg.event); 1008 continue; /* It's not a page fault, shouldn't happen */ 1009 } 1010 1011 rb = qemu_ram_block_from_host( 1012 (void *)(uintptr_t)msg.arg.pagefault.address, 1013 true, &rb_offset); 1014 if (!rb) { 1015 error_report("postcopy_ram_fault_thread: Fault outside guest: %" 1016 PRIx64, (uint64_t)msg.arg.pagefault.address); 1017 break; 1018 } 1019 1020 rb_offset = ROUND_DOWN(rb_offset, qemu_ram_pagesize(rb)); 1021 trace_postcopy_ram_fault_thread_request(msg.arg.pagefault.address, 1022 qemu_ram_get_idstr(rb), 1023 rb_offset, 1024 msg.arg.pagefault.feat.ptid); 1025 mark_postcopy_blocktime_begin( 1026 (uintptr_t)(msg.arg.pagefault.address), 1027 msg.arg.pagefault.feat.ptid, rb); 1028 1029 retry: 1030 /* 1031 * Send the request to the source - we want to request one 1032 * of our host page sizes (which is >= TPS) 1033 */ 1034 ret = postcopy_request_page(mis, rb, rb_offset, 1035 msg.arg.pagefault.address); 1036 if (ret) { 1037 /* May be network failure, try to wait for recovery */ 1038 postcopy_pause_fault_thread(mis); 1039 goto retry; 1040 } 1041 } 1042 1043 /* Now handle any requests from external processes on shared memory */ 1044 /* TODO: May need to handle devices deregistering during postcopy */ 1045 for (index = 2; index < pfd_len && poll_result; index++) { 1046 if (pfd[index].revents) { 1047 struct PostCopyFD *pcfd = 1048 &g_array_index(mis->postcopy_remote_fds, 1049 struct PostCopyFD, index - 2); 1050 1051 poll_result--; 1052 if (pfd[index].revents & POLLERR) { 1053 error_report("%s: POLLERR on poll %zd fd=%d", 1054 __func__, index, pcfd->fd); 1055 pfd[index].events = 0; 1056 continue; 1057 } 1058 1059 ret = read(pcfd->fd, &msg, sizeof(msg)); 1060 if (ret != sizeof(msg)) { 1061 if (errno == EAGAIN) { 1062 /* 1063 * if a wake up happens on the other thread just after 1064 * the poll, there is nothing to read. 1065 */ 1066 continue; 1067 } 1068 if (ret < 0) { 1069 error_report("%s: Failed to read full userfault " 1070 "message: %s (shared) revents=%d", 1071 __func__, strerror(errno), 1072 pfd[index].revents); 1073 /*TODO: Could just disable this sharer */ 1074 break; 1075 } else { 1076 error_report("%s: Read %d bytes from userfaultfd " 1077 "expected %zd (shared)", 1078 __func__, ret, sizeof(msg)); 1079 /*TODO: Could just disable this sharer */ 1080 break; /*Lost alignment,don't know what we'd read next*/ 1081 } 1082 } 1083 if (msg.event != UFFD_EVENT_PAGEFAULT) { 1084 error_report("%s: Read unexpected event %ud " 1085 "from userfaultfd (shared)", 1086 __func__, msg.event); 1087 continue; /* It's not a page fault, shouldn't happen */ 1088 } 1089 /* Call the device handler registered with us */ 1090 ret = pcfd->handler(pcfd, &msg); 1091 if (ret) { 1092 error_report("%s: Failed to resolve shared fault on %zd/%s", 1093 __func__, index, pcfd->idstr); 1094 /* TODO: Fail? Disable this sharer? */ 1095 } 1096 } 1097 } 1098 } 1099 rcu_unregister_thread(); 1100 trace_postcopy_ram_fault_thread_exit(); 1101 g_free(pfd); 1102 return NULL; 1103 } 1104 1105 static int postcopy_temp_pages_setup(MigrationIncomingState *mis) 1106 { 1107 PostcopyTmpPage *tmp_page; 1108 int err, i, channels; 1109 void *temp_page; 1110 1111 if (migrate_postcopy_preempt()) { 1112 /* If preemption enabled, need extra channel for urgent requests */ 1113 mis->postcopy_channels = RAM_CHANNEL_MAX; 1114 } else { 1115 /* Both precopy/postcopy on the same channel */ 1116 mis->postcopy_channels = 1; 1117 } 1118 1119 channels = mis->postcopy_channels; 1120 mis->postcopy_tmp_pages = g_malloc0_n(sizeof(PostcopyTmpPage), channels); 1121 1122 for (i = 0; i < channels; i++) { 1123 tmp_page = &mis->postcopy_tmp_pages[i]; 1124 temp_page = mmap(NULL, mis->largest_page_size, PROT_READ | PROT_WRITE, 1125 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); 1126 if (temp_page == MAP_FAILED) { 1127 err = errno; 1128 error_report("%s: Failed to map postcopy_tmp_pages[%d]: %s", 1129 __func__, i, strerror(err)); 1130 /* Clean up will be done later */ 1131 return -err; 1132 } 1133 tmp_page->tmp_huge_page = temp_page; 1134 /* Initialize default states for each tmp page */ 1135 postcopy_temp_page_reset(tmp_page); 1136 } 1137 1138 /* 1139 * Map large zero page when kernel can't use UFFDIO_ZEROPAGE for hugepages 1140 */ 1141 mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size, 1142 PROT_READ | PROT_WRITE, 1143 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); 1144 if (mis->postcopy_tmp_zero_page == MAP_FAILED) { 1145 err = errno; 1146 mis->postcopy_tmp_zero_page = NULL; 1147 error_report("%s: Failed to map large zero page %s", 1148 __func__, strerror(err)); 1149 return -err; 1150 } 1151 1152 memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size); 1153 1154 return 0; 1155 } 1156 1157 int postcopy_ram_incoming_setup(MigrationIncomingState *mis) 1158 { 1159 /* Open the fd for the kernel to give us userfaults */ 1160 mis->userfault_fd = uffd_open(O_CLOEXEC | O_NONBLOCK); 1161 if (mis->userfault_fd == -1) { 1162 error_report("%s: Failed to open userfault fd: %s", __func__, 1163 strerror(errno)); 1164 return -1; 1165 } 1166 1167 /* 1168 * Although the host check already tested the API, we need to 1169 * do the check again as an ABI handshake on the new fd. 1170 */ 1171 if (!ufd_check_and_apply(mis->userfault_fd, mis)) { 1172 return -1; 1173 } 1174 1175 /* Now an eventfd we use to tell the fault-thread to quit */ 1176 mis->userfault_event_fd = eventfd(0, EFD_CLOEXEC); 1177 if (mis->userfault_event_fd == -1) { 1178 error_report("%s: Opening userfault_event_fd: %s", __func__, 1179 strerror(errno)); 1180 close(mis->userfault_fd); 1181 return -1; 1182 } 1183 1184 postcopy_thread_create(mis, &mis->fault_thread, "fault-default", 1185 postcopy_ram_fault_thread, QEMU_THREAD_JOINABLE); 1186 mis->have_fault_thread = true; 1187 1188 /* Mark so that we get notified of accesses to unwritten areas */ 1189 if (foreach_not_ignored_block(ram_block_enable_notify, mis)) { 1190 error_report("ram_block_enable_notify failed"); 1191 return -1; 1192 } 1193 1194 if (postcopy_temp_pages_setup(mis)) { 1195 /* Error dumped in the sub-function */ 1196 return -1; 1197 } 1198 1199 if (migrate_postcopy_preempt()) { 1200 /* 1201 * This thread needs to be created after the temp pages because 1202 * it'll fetch RAM_CHANNEL_POSTCOPY PostcopyTmpPage immediately. 1203 */ 1204 postcopy_thread_create(mis, &mis->postcopy_prio_thread, "fault-fast", 1205 postcopy_preempt_thread, QEMU_THREAD_JOINABLE); 1206 mis->postcopy_prio_thread_created = true; 1207 } 1208 1209 trace_postcopy_ram_enable_notify(); 1210 1211 return 0; 1212 } 1213 1214 static int qemu_ufd_copy_ioctl(MigrationIncomingState *mis, void *host_addr, 1215 void *from_addr, uint64_t pagesize, RAMBlock *rb) 1216 { 1217 int userfault_fd = mis->userfault_fd; 1218 int ret; 1219 1220 if (from_addr) { 1221 struct uffdio_copy copy_struct; 1222 copy_struct.dst = (uint64_t)(uintptr_t)host_addr; 1223 copy_struct.src = (uint64_t)(uintptr_t)from_addr; 1224 copy_struct.len = pagesize; 1225 copy_struct.mode = 0; 1226 ret = ioctl(userfault_fd, UFFDIO_COPY, ©_struct); 1227 } else { 1228 struct uffdio_zeropage zero_struct; 1229 zero_struct.range.start = (uint64_t)(uintptr_t)host_addr; 1230 zero_struct.range.len = pagesize; 1231 zero_struct.mode = 0; 1232 ret = ioctl(userfault_fd, UFFDIO_ZEROPAGE, &zero_struct); 1233 } 1234 if (!ret) { 1235 qemu_mutex_lock(&mis->page_request_mutex); 1236 ramblock_recv_bitmap_set_range(rb, host_addr, 1237 pagesize / qemu_target_page_size()); 1238 /* 1239 * If this page resolves a page fault for a previous recorded faulted 1240 * address, take a special note to maintain the requested page list. 1241 */ 1242 if (g_tree_lookup(mis->page_requested, host_addr)) { 1243 g_tree_remove(mis->page_requested, host_addr); 1244 mis->page_requested_count--; 1245 trace_postcopy_page_req_del(host_addr, mis->page_requested_count); 1246 } 1247 qemu_mutex_unlock(&mis->page_request_mutex); 1248 mark_postcopy_blocktime_end((uintptr_t)host_addr); 1249 } 1250 return ret; 1251 } 1252 1253 int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset) 1254 { 1255 int i; 1256 MigrationIncomingState *mis = migration_incoming_get_current(); 1257 GArray *pcrfds = mis->postcopy_remote_fds; 1258 1259 for (i = 0; i < pcrfds->len; i++) { 1260 struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i); 1261 int ret = cur->waker(cur, rb, offset); 1262 if (ret) { 1263 return ret; 1264 } 1265 } 1266 return 0; 1267 } 1268 1269 /* 1270 * Place a host page (from) at (host) atomically 1271 * returns 0 on success 1272 */ 1273 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, 1274 RAMBlock *rb) 1275 { 1276 size_t pagesize = qemu_ram_pagesize(rb); 1277 1278 /* copy also acks to the kernel waking the stalled thread up 1279 * TODO: We can inhibit that ack and only do it if it was requested 1280 * which would be slightly cheaper, but we'd have to be careful 1281 * of the order of updating our page state. 1282 */ 1283 if (qemu_ufd_copy_ioctl(mis, host, from, pagesize, rb)) { 1284 int e = errno; 1285 error_report("%s: %s copy host: %p from: %p (size: %zd)", 1286 __func__, strerror(e), host, from, pagesize); 1287 1288 return -e; 1289 } 1290 1291 trace_postcopy_place_page(host); 1292 return postcopy_notify_shared_wake(rb, 1293 qemu_ram_block_host_offset(rb, host)); 1294 } 1295 1296 /* 1297 * Place a zero page at (host) atomically 1298 * returns 0 on success 1299 */ 1300 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, 1301 RAMBlock *rb) 1302 { 1303 size_t pagesize = qemu_ram_pagesize(rb); 1304 trace_postcopy_place_page_zero(host); 1305 1306 /* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE 1307 * but it's not available for everything (e.g. hugetlbpages) 1308 */ 1309 if (qemu_ram_is_uf_zeroable(rb)) { 1310 if (qemu_ufd_copy_ioctl(mis, host, NULL, pagesize, rb)) { 1311 int e = errno; 1312 error_report("%s: %s zero host: %p", 1313 __func__, strerror(e), host); 1314 1315 return -e; 1316 } 1317 return postcopy_notify_shared_wake(rb, 1318 qemu_ram_block_host_offset(rb, 1319 host)); 1320 } else { 1321 return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page, rb); 1322 } 1323 } 1324 1325 #else 1326 /* No target OS support, stubs just fail */ 1327 void fill_destination_postcopy_migration_info(MigrationInfo *info) 1328 { 1329 } 1330 1331 bool postcopy_ram_supported_by_host(MigrationIncomingState *mis) 1332 { 1333 error_report("%s: No OS support", __func__); 1334 return false; 1335 } 1336 1337 int postcopy_ram_incoming_init(MigrationIncomingState *mis) 1338 { 1339 error_report("postcopy_ram_incoming_init: No OS support"); 1340 return -1; 1341 } 1342 1343 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis) 1344 { 1345 assert(0); 1346 return -1; 1347 } 1348 1349 int postcopy_ram_prepare_discard(MigrationIncomingState *mis) 1350 { 1351 assert(0); 1352 return -1; 1353 } 1354 1355 int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb, 1356 uint64_t client_addr, uint64_t rb_offset) 1357 { 1358 assert(0); 1359 return -1; 1360 } 1361 1362 int postcopy_ram_incoming_setup(MigrationIncomingState *mis) 1363 { 1364 assert(0); 1365 return -1; 1366 } 1367 1368 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, 1369 RAMBlock *rb) 1370 { 1371 assert(0); 1372 return -1; 1373 } 1374 1375 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, 1376 RAMBlock *rb) 1377 { 1378 assert(0); 1379 return -1; 1380 } 1381 1382 int postcopy_wake_shared(struct PostCopyFD *pcfd, 1383 uint64_t client_addr, 1384 RAMBlock *rb) 1385 { 1386 assert(0); 1387 return -1; 1388 } 1389 #endif 1390 1391 /* ------------------------------------------------------------------------- */ 1392 void postcopy_temp_page_reset(PostcopyTmpPage *tmp_page) 1393 { 1394 tmp_page->target_pages = 0; 1395 tmp_page->host_addr = NULL; 1396 /* 1397 * This is set to true when reset, and cleared as long as we received any 1398 * of the non-zero small page within this huge page. 1399 */ 1400 tmp_page->all_zero = true; 1401 } 1402 1403 void postcopy_fault_thread_notify(MigrationIncomingState *mis) 1404 { 1405 uint64_t tmp64 = 1; 1406 1407 /* 1408 * Wakeup the fault_thread. It's an eventfd that should currently 1409 * be at 0, we're going to increment it to 1 1410 */ 1411 if (write(mis->userfault_event_fd, &tmp64, 8) != 8) { 1412 /* Not much we can do here, but may as well report it */ 1413 error_report("%s: incrementing failed: %s", __func__, 1414 strerror(errno)); 1415 } 1416 } 1417 1418 /** 1419 * postcopy_discard_send_init: Called at the start of each RAMBlock before 1420 * asking to discard individual ranges. 1421 * 1422 * @ms: The current migration state. 1423 * @offset: the bitmap offset of the named RAMBlock in the migration bitmap. 1424 * @name: RAMBlock that discards will operate on. 1425 */ 1426 static PostcopyDiscardState pds = {0}; 1427 void postcopy_discard_send_init(MigrationState *ms, const char *name) 1428 { 1429 pds.ramblock_name = name; 1430 pds.cur_entry = 0; 1431 pds.nsentwords = 0; 1432 pds.nsentcmds = 0; 1433 } 1434 1435 /** 1436 * postcopy_discard_send_range: Called by the bitmap code for each chunk to 1437 * discard. May send a discard message, may just leave it queued to 1438 * be sent later. 1439 * 1440 * @ms: Current migration state. 1441 * @start,@length: a range of pages in the migration bitmap in the 1442 * RAM block passed to postcopy_discard_send_init() (length=1 is one page) 1443 */ 1444 void postcopy_discard_send_range(MigrationState *ms, unsigned long start, 1445 unsigned long length) 1446 { 1447 size_t tp_size = qemu_target_page_size(); 1448 /* Convert to byte offsets within the RAM block */ 1449 pds.start_list[pds.cur_entry] = start * tp_size; 1450 pds.length_list[pds.cur_entry] = length * tp_size; 1451 trace_postcopy_discard_send_range(pds.ramblock_name, start, length); 1452 pds.cur_entry++; 1453 pds.nsentwords++; 1454 1455 if (pds.cur_entry == MAX_DISCARDS_PER_COMMAND) { 1456 /* Full set, ship it! */ 1457 qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file, 1458 pds.ramblock_name, 1459 pds.cur_entry, 1460 pds.start_list, 1461 pds.length_list); 1462 pds.nsentcmds++; 1463 pds.cur_entry = 0; 1464 } 1465 } 1466 1467 /** 1468 * postcopy_discard_send_finish: Called at the end of each RAMBlock by the 1469 * bitmap code. Sends any outstanding discard messages, frees the PDS 1470 * 1471 * @ms: Current migration state. 1472 */ 1473 void postcopy_discard_send_finish(MigrationState *ms) 1474 { 1475 /* Anything unsent? */ 1476 if (pds.cur_entry) { 1477 qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file, 1478 pds.ramblock_name, 1479 pds.cur_entry, 1480 pds.start_list, 1481 pds.length_list); 1482 pds.nsentcmds++; 1483 } 1484 1485 trace_postcopy_discard_send_finish(pds.ramblock_name, pds.nsentwords, 1486 pds.nsentcmds); 1487 } 1488 1489 /* 1490 * Current state of incoming postcopy; note this is not part of 1491 * MigrationIncomingState since it's state is used during cleanup 1492 * at the end as MIS is being freed. 1493 */ 1494 static PostcopyState incoming_postcopy_state; 1495 1496 PostcopyState postcopy_state_get(void) 1497 { 1498 return qatomic_mb_read(&incoming_postcopy_state); 1499 } 1500 1501 /* Set the state and return the old state */ 1502 PostcopyState postcopy_state_set(PostcopyState new_state) 1503 { 1504 return qatomic_xchg(&incoming_postcopy_state, new_state); 1505 } 1506 1507 /* Register a handler for external shared memory postcopy 1508 * called on the destination. 1509 */ 1510 void postcopy_register_shared_ufd(struct PostCopyFD *pcfd) 1511 { 1512 MigrationIncomingState *mis = migration_incoming_get_current(); 1513 1514 mis->postcopy_remote_fds = g_array_append_val(mis->postcopy_remote_fds, 1515 *pcfd); 1516 } 1517 1518 /* Unregister a handler for external shared memory postcopy 1519 */ 1520 void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd) 1521 { 1522 guint i; 1523 MigrationIncomingState *mis = migration_incoming_get_current(); 1524 GArray *pcrfds = mis->postcopy_remote_fds; 1525 1526 if (!pcrfds) { 1527 /* migration has already finished and freed the array */ 1528 return; 1529 } 1530 for (i = 0; i < pcrfds->len; i++) { 1531 struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i); 1532 if (cur->fd == pcfd->fd) { 1533 mis->postcopy_remote_fds = g_array_remove_index(pcrfds, i); 1534 return; 1535 } 1536 } 1537 } 1538 1539 void postcopy_preempt_new_channel(MigrationIncomingState *mis, QEMUFile *file) 1540 { 1541 /* 1542 * The new loading channel has its own threads, so it needs to be 1543 * blocked too. It's by default true, just be explicit. 1544 */ 1545 qemu_file_set_blocking(file, true); 1546 mis->postcopy_qemufile_dst = file; 1547 qemu_sem_post(&mis->postcopy_qemufile_dst_done); 1548 trace_postcopy_preempt_new_channel(); 1549 } 1550 1551 /* 1552 * Setup the postcopy preempt channel with the IOC. If ERROR is specified, 1553 * setup the error instead. This helper will free the ERROR if specified. 1554 */ 1555 static void 1556 postcopy_preempt_send_channel_done(MigrationState *s, 1557 QIOChannel *ioc, Error *local_err) 1558 { 1559 if (local_err) { 1560 migrate_set_error(s, local_err); 1561 error_free(local_err); 1562 } else { 1563 migration_ioc_register_yank(ioc); 1564 s->postcopy_qemufile_src = qemu_file_new_output(ioc); 1565 trace_postcopy_preempt_new_channel(); 1566 } 1567 1568 /* 1569 * Kick the waiter in all cases. The waiter should check upon 1570 * postcopy_qemufile_src to know whether it failed or not. 1571 */ 1572 qemu_sem_post(&s->postcopy_qemufile_src_sem); 1573 } 1574 1575 static void 1576 postcopy_preempt_tls_handshake(QIOTask *task, gpointer opaque) 1577 { 1578 g_autoptr(QIOChannel) ioc = QIO_CHANNEL(qio_task_get_source(task)); 1579 MigrationState *s = opaque; 1580 Error *local_err = NULL; 1581 1582 qio_task_propagate_error(task, &local_err); 1583 postcopy_preempt_send_channel_done(s, ioc, local_err); 1584 } 1585 1586 static void 1587 postcopy_preempt_send_channel_new(QIOTask *task, gpointer opaque) 1588 { 1589 g_autoptr(QIOChannel) ioc = QIO_CHANNEL(qio_task_get_source(task)); 1590 MigrationState *s = opaque; 1591 QIOChannelTLS *tioc; 1592 Error *local_err = NULL; 1593 1594 if (qio_task_propagate_error(task, &local_err)) { 1595 goto out; 1596 } 1597 1598 if (migrate_channel_requires_tls_upgrade(ioc)) { 1599 tioc = migration_tls_client_create(s, ioc, s->hostname, &local_err); 1600 if (!tioc) { 1601 goto out; 1602 } 1603 trace_postcopy_preempt_tls_handshake(); 1604 qio_channel_set_name(QIO_CHANNEL(tioc), "migration-tls-preempt"); 1605 qio_channel_tls_handshake(tioc, postcopy_preempt_tls_handshake, 1606 s, NULL, NULL); 1607 /* Setup the channel until TLS handshake finished */ 1608 return; 1609 } 1610 1611 out: 1612 /* This handles both good and error cases */ 1613 postcopy_preempt_send_channel_done(s, ioc, local_err); 1614 } 1615 1616 /* 1617 * This function will kick off an async task to establish the preempt 1618 * channel, and wait until the connection setup completed. Returns 0 if 1619 * channel established, -1 for error. 1620 */ 1621 int postcopy_preempt_establish_channel(MigrationState *s) 1622 { 1623 /* If preempt not enabled, no need to wait */ 1624 if (!migrate_postcopy_preempt()) { 1625 return 0; 1626 } 1627 1628 /* Kick off async task to establish preempt channel */ 1629 postcopy_preempt_setup(s); 1630 1631 /* 1632 * We need the postcopy preempt channel to be established before 1633 * starting doing anything. 1634 */ 1635 qemu_sem_wait(&s->postcopy_qemufile_src_sem); 1636 1637 return s->postcopy_qemufile_src ? 0 : -1; 1638 } 1639 1640 void postcopy_preempt_setup(MigrationState *s) 1641 { 1642 /* Kick an async task to connect */ 1643 socket_send_channel_create(postcopy_preempt_send_channel_new, s); 1644 } 1645 1646 static void postcopy_pause_ram_fast_load(MigrationIncomingState *mis) 1647 { 1648 trace_postcopy_pause_fast_load(); 1649 qemu_mutex_unlock(&mis->postcopy_prio_thread_mutex); 1650 qemu_sem_wait(&mis->postcopy_pause_sem_fast_load); 1651 qemu_mutex_lock(&mis->postcopy_prio_thread_mutex); 1652 trace_postcopy_pause_fast_load_continued(); 1653 } 1654 1655 void *postcopy_preempt_thread(void *opaque) 1656 { 1657 MigrationIncomingState *mis = opaque; 1658 int ret; 1659 1660 trace_postcopy_preempt_thread_entry(); 1661 1662 rcu_register_thread(); 1663 1664 qemu_sem_post(&mis->thread_sync_sem); 1665 1666 /* 1667 * The preempt channel is established in asynchronous way. Wait 1668 * for its completion. 1669 */ 1670 qemu_sem_wait(&mis->postcopy_qemufile_dst_done); 1671 1672 /* Sending RAM_SAVE_FLAG_EOS to terminate this thread */ 1673 qemu_mutex_lock(&mis->postcopy_prio_thread_mutex); 1674 while (1) { 1675 ret = ram_load_postcopy(mis->postcopy_qemufile_dst, 1676 RAM_CHANNEL_POSTCOPY); 1677 /* If error happened, go into recovery routine */ 1678 if (ret) { 1679 postcopy_pause_ram_fast_load(mis); 1680 } else { 1681 /* We're done */ 1682 break; 1683 } 1684 } 1685 qemu_mutex_unlock(&mis->postcopy_prio_thread_mutex); 1686 1687 rcu_unregister_thread(); 1688 1689 trace_postcopy_preempt_thread_exit(); 1690 1691 return NULL; 1692 } 1693