Merge remote-tracking branch 'remotes/dgibson/tags/ppc-for-6.2-20211021' into staging
[qemu.git] / migration / postcopy-ram.c
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/rcu.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
36 /* Arbitrary limit on size of each discard command,
37 * keeps them around ~200 bytes
38 */
39 #define MAX_DISCARDS_PER_COMMAND 12
40
41 struct PostcopyDiscardState {
42 const char *ramblock_name;
43 uint16_t cur_entry;
44 /*
45 * Start and length of a discard range (bytes)
46 */
47 uint64_t start_list[MAX_DISCARDS_PER_COMMAND];
48 uint64_t length_list[MAX_DISCARDS_PER_COMMAND];
49 unsigned int nsentwords;
50 unsigned int nsentcmds;
51 };
52
53 static NotifierWithReturnList postcopy_notifier_list;
54
55 void postcopy_infrastructure_init(void)
56 {
57 notifier_with_return_list_init(&postcopy_notifier_list);
58 }
59
60 void postcopy_add_notifier(NotifierWithReturn *nn)
61 {
62 notifier_with_return_list_add(&postcopy_notifier_list, nn);
63 }
64
65 void postcopy_remove_notifier(NotifierWithReturn *n)
66 {
67 notifier_with_return_remove(n);
68 }
69
70 int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp)
71 {
72 struct PostcopyNotifyData pnd;
73 pnd.reason = reason;
74 pnd.errp = errp;
75
76 return notifier_with_return_list_notify(&postcopy_notifier_list,
77 &pnd);
78 }
79
80 /* Postcopy needs to detect accesses to pages that haven't yet been copied
81 * across, and efficiently map new pages in, the techniques for doing this
82 * are target OS specific.
83 */
84 #if defined(__linux__)
85
86 #include <poll.h>
87 #include <sys/ioctl.h>
88 #include <sys/syscall.h>
89 #include <asm/types.h> /* for __u64 */
90 #endif
91
92 #if defined(__linux__) && defined(__NR_userfaultfd) && defined(CONFIG_EVENTFD)
93 #include <sys/eventfd.h>
94 #include <linux/userfaultfd.h>
95
96 typedef struct PostcopyBlocktimeContext {
97 /* time when page fault initiated per vCPU */
98 uint32_t *page_fault_vcpu_time;
99 /* page address per vCPU */
100 uintptr_t *vcpu_addr;
101 uint32_t total_blocktime;
102 /* blocktime per vCPU */
103 uint32_t *vcpu_blocktime;
104 /* point in time when last page fault was initiated */
105 uint32_t last_begin;
106 /* number of vCPU are suspended */
107 int smp_cpus_down;
108 uint64_t start_time;
109
110 /*
111 * Handler for exit event, necessary for
112 * releasing whole blocktime_ctx
113 */
114 Notifier exit_notifier;
115 } PostcopyBlocktimeContext;
116
117 static void destroy_blocktime_context(struct PostcopyBlocktimeContext *ctx)
118 {
119 g_free(ctx->page_fault_vcpu_time);
120 g_free(ctx->vcpu_addr);
121 g_free(ctx->vcpu_blocktime);
122 g_free(ctx);
123 }
124
125 static void migration_exit_cb(Notifier *n, void *data)
126 {
127 PostcopyBlocktimeContext *ctx = container_of(n, PostcopyBlocktimeContext,
128 exit_notifier);
129 destroy_blocktime_context(ctx);
130 }
131
132 static struct PostcopyBlocktimeContext *blocktime_context_new(void)
133 {
134 MachineState *ms = MACHINE(qdev_get_machine());
135 unsigned int smp_cpus = ms->smp.cpus;
136 PostcopyBlocktimeContext *ctx = g_new0(PostcopyBlocktimeContext, 1);
137 ctx->page_fault_vcpu_time = g_new0(uint32_t, smp_cpus);
138 ctx->vcpu_addr = g_new0(uintptr_t, smp_cpus);
139 ctx->vcpu_blocktime = g_new0(uint32_t, smp_cpus);
140
141 ctx->exit_notifier.notify = migration_exit_cb;
142 ctx->start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
143 qemu_add_exit_notifier(&ctx->exit_notifier);
144 return ctx;
145 }
146
147 static uint32List *get_vcpu_blocktime_list(PostcopyBlocktimeContext *ctx)
148 {
149 MachineState *ms = MACHINE(qdev_get_machine());
150 uint32List *list = NULL;
151 int i;
152
153 for (i = ms->smp.cpus - 1; i >= 0; i--) {
154 QAPI_LIST_PREPEND(list, ctx->vcpu_blocktime[i]);
155 }
156
157 return list;
158 }
159
160 /*
161 * This function just populates MigrationInfo from postcopy's
162 * blocktime context. It will not populate MigrationInfo,
163 * unless postcopy-blocktime capability was set.
164 *
165 * @info: pointer to MigrationInfo to populate
166 */
167 void fill_destination_postcopy_migration_info(MigrationInfo *info)
168 {
169 MigrationIncomingState *mis = migration_incoming_get_current();
170 PostcopyBlocktimeContext *bc = mis->blocktime_ctx;
171
172 if (!bc) {
173 return;
174 }
175
176 info->has_postcopy_blocktime = true;
177 info->postcopy_blocktime = bc->total_blocktime;
178 info->has_postcopy_vcpu_blocktime = true;
179 info->postcopy_vcpu_blocktime = get_vcpu_blocktime_list(bc);
180 }
181
182 static uint32_t get_postcopy_total_blocktime(void)
183 {
184 MigrationIncomingState *mis = migration_incoming_get_current();
185 PostcopyBlocktimeContext *bc = mis->blocktime_ctx;
186
187 if (!bc) {
188 return 0;
189 }
190
191 return bc->total_blocktime;
192 }
193
194 /**
195 * receive_ufd_features: check userfault fd features, to request only supported
196 * features in the future.
197 *
198 * Returns: true on success
199 *
200 * __NR_userfaultfd - should be checked before
201 * @features: out parameter will contain uffdio_api.features provided by kernel
202 * in case of success
203 */
204 static bool receive_ufd_features(uint64_t *features)
205 {
206 struct uffdio_api api_struct = {0};
207 int ufd;
208 bool ret = true;
209
210 /* if we are here __NR_userfaultfd should exists */
211 ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
212 if (ufd == -1) {
213 error_report("%s: syscall __NR_userfaultfd failed: %s", __func__,
214 strerror(errno));
215 return false;
216 }
217
218 /* ask features */
219 api_struct.api = UFFD_API;
220 api_struct.features = 0;
221 if (ioctl(ufd, UFFDIO_API, &api_struct)) {
222 error_report("%s: UFFDIO_API failed: %s", __func__,
223 strerror(errno));
224 ret = false;
225 goto release_ufd;
226 }
227
228 *features = api_struct.features;
229
230 release_ufd:
231 close(ufd);
232 return ret;
233 }
234
235 /**
236 * request_ufd_features: this function should be called only once on a newly
237 * opened ufd, subsequent calls will lead to error.
238 *
239 * Returns: true on success
240 *
241 * @ufd: fd obtained from userfaultfd syscall
242 * @features: bit mask see UFFD_API_FEATURES
243 */
244 static bool request_ufd_features(int ufd, uint64_t features)
245 {
246 struct uffdio_api api_struct = {0};
247 uint64_t ioctl_mask;
248
249 api_struct.api = UFFD_API;
250 api_struct.features = features;
251 if (ioctl(ufd, UFFDIO_API, &api_struct)) {
252 error_report("%s failed: UFFDIO_API failed: %s", __func__,
253 strerror(errno));
254 return false;
255 }
256
257 ioctl_mask = (__u64)1 << _UFFDIO_REGISTER |
258 (__u64)1 << _UFFDIO_UNREGISTER;
259 if ((api_struct.ioctls & ioctl_mask) != ioctl_mask) {
260 error_report("Missing userfault features: %" PRIx64,
261 (uint64_t)(~api_struct.ioctls & ioctl_mask));
262 return false;
263 }
264
265 return true;
266 }
267
268 static bool ufd_check_and_apply(int ufd, MigrationIncomingState *mis)
269 {
270 uint64_t asked_features = 0;
271 static uint64_t supported_features;
272
273 /*
274 * it's not possible to
275 * request UFFD_API twice per one fd
276 * userfault fd features is persistent
277 */
278 if (!supported_features) {
279 if (!receive_ufd_features(&supported_features)) {
280 error_report("%s failed", __func__);
281 return false;
282 }
283 }
284
285 #ifdef UFFD_FEATURE_THREAD_ID
286 if (migrate_postcopy_blocktime() && mis &&
287 UFFD_FEATURE_THREAD_ID & supported_features) {
288 /* kernel supports that feature */
289 /* don't create blocktime_context if it exists */
290 if (!mis->blocktime_ctx) {
291 mis->blocktime_ctx = blocktime_context_new();
292 }
293
294 asked_features |= UFFD_FEATURE_THREAD_ID;
295 }
296 #endif
297
298 /*
299 * request features, even if asked_features is 0, due to
300 * kernel expects UFFD_API before UFFDIO_REGISTER, per
301 * userfault file descriptor
302 */
303 if (!request_ufd_features(ufd, asked_features)) {
304 error_report("%s failed: features %" PRIu64, __func__,
305 asked_features);
306 return false;
307 }
308
309 if (qemu_real_host_page_size != ram_pagesize_summary()) {
310 bool have_hp = false;
311 /* We've got a huge page */
312 #ifdef UFFD_FEATURE_MISSING_HUGETLBFS
313 have_hp = supported_features & UFFD_FEATURE_MISSING_HUGETLBFS;
314 #endif
315 if (!have_hp) {
316 error_report("Userfault on this host does not support huge pages");
317 return false;
318 }
319 }
320 return true;
321 }
322
323 /* Callback from postcopy_ram_supported_by_host block iterator.
324 */
325 static int test_ramblock_postcopiable(RAMBlock *rb, void *opaque)
326 {
327 const char *block_name = qemu_ram_get_idstr(rb);
328 ram_addr_t length = qemu_ram_get_used_length(rb);
329 size_t pagesize = qemu_ram_pagesize(rb);
330
331 if (length % pagesize) {
332 error_report("Postcopy requires RAM blocks to be a page size multiple,"
333 " block %s is 0x" RAM_ADDR_FMT " bytes with a "
334 "page size of 0x%zx", block_name, length, pagesize);
335 return 1;
336 }
337 return 0;
338 }
339
340 /*
341 * Note: This has the side effect of munlock'ing all of RAM, that's
342 * normally fine since if the postcopy succeeds it gets turned back on at the
343 * end.
344 */
345 bool postcopy_ram_supported_by_host(MigrationIncomingState *mis)
346 {
347 long pagesize = qemu_real_host_page_size;
348 int ufd = -1;
349 bool ret = false; /* Error unless we change it */
350 void *testarea = NULL;
351 struct uffdio_register reg_struct;
352 struct uffdio_range range_struct;
353 uint64_t feature_mask;
354 Error *local_err = NULL;
355
356 if (qemu_target_page_size() > pagesize) {
357 error_report("Target page size bigger than host page size");
358 goto out;
359 }
360
361 ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
362 if (ufd == -1) {
363 error_report("%s: userfaultfd not available: %s", __func__,
364 strerror(errno));
365 goto out;
366 }
367
368 /* Give devices a chance to object */
369 if (postcopy_notify(POSTCOPY_NOTIFY_PROBE, &local_err)) {
370 error_report_err(local_err);
371 goto out;
372 }
373
374 /* Version and features check */
375 if (!ufd_check_and_apply(ufd, mis)) {
376 goto out;
377 }
378
379 /* We don't support postcopy with shared RAM yet */
380 if (foreach_not_ignored_block(test_ramblock_postcopiable, NULL)) {
381 goto out;
382 }
383
384 /*
385 * userfault and mlock don't go together; we'll put it back later if
386 * it was enabled.
387 */
388 if (munlockall()) {
389 error_report("%s: munlockall: %s", __func__, strerror(errno));
390 goto out;
391 }
392
393 /*
394 * We need to check that the ops we need are supported on anon memory
395 * To do that we need to register a chunk and see the flags that
396 * are returned.
397 */
398 testarea = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE |
399 MAP_ANONYMOUS, -1, 0);
400 if (testarea == MAP_FAILED) {
401 error_report("%s: Failed to map test area: %s", __func__,
402 strerror(errno));
403 goto out;
404 }
405 g_assert(((size_t)testarea & (pagesize - 1)) == 0);
406
407 reg_struct.range.start = (uintptr_t)testarea;
408 reg_struct.range.len = pagesize;
409 reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
410
411 if (ioctl(ufd, UFFDIO_REGISTER, &reg_struct)) {
412 error_report("%s userfault register: %s", __func__, strerror(errno));
413 goto out;
414 }
415
416 range_struct.start = (uintptr_t)testarea;
417 range_struct.len = pagesize;
418 if (ioctl(ufd, UFFDIO_UNREGISTER, &range_struct)) {
419 error_report("%s userfault unregister: %s", __func__, strerror(errno));
420 goto out;
421 }
422
423 feature_mask = (__u64)1 << _UFFDIO_WAKE |
424 (__u64)1 << _UFFDIO_COPY |
425 (__u64)1 << _UFFDIO_ZEROPAGE;
426 if ((reg_struct.ioctls & feature_mask) != feature_mask) {
427 error_report("Missing userfault map features: %" PRIx64,
428 (uint64_t)(~reg_struct.ioctls & feature_mask));
429 goto out;
430 }
431
432 /* Success! */
433 ret = true;
434 out:
435 if (testarea) {
436 munmap(testarea, pagesize);
437 }
438 if (ufd != -1) {
439 close(ufd);
440 }
441 return ret;
442 }
443
444 /*
445 * Setup an area of RAM so that it *can* be used for postcopy later; this
446 * must be done right at the start prior to pre-copy.
447 * opaque should be the MIS.
448 */
449 static int init_range(RAMBlock *rb, void *opaque)
450 {
451 const char *block_name = qemu_ram_get_idstr(rb);
452 void *host_addr = qemu_ram_get_host_addr(rb);
453 ram_addr_t offset = qemu_ram_get_offset(rb);
454 ram_addr_t length = qemu_ram_get_used_length(rb);
455 trace_postcopy_init_range(block_name, host_addr, offset, length);
456
457 /*
458 * Save the used_length before running the guest. In case we have to
459 * resize RAM blocks when syncing RAM block sizes from the source during
460 * precopy, we'll update it manually via the ram block notifier.
461 */
462 rb->postcopy_length = length;
463
464 /*
465 * We need the whole of RAM to be truly empty for postcopy, so things
466 * like ROMs and any data tables built during init must be zero'd
467 * - we're going to get the copy from the source anyway.
468 * (Precopy will just overwrite this data, so doesn't need the discard)
469 */
470 if (ram_discard_range(block_name, 0, length)) {
471 return -1;
472 }
473
474 return 0;
475 }
476
477 /*
478 * At the end of migration, undo the effects of init_range
479 * opaque should be the MIS.
480 */
481 static int cleanup_range(RAMBlock *rb, void *opaque)
482 {
483 const char *block_name = qemu_ram_get_idstr(rb);
484 void *host_addr = qemu_ram_get_host_addr(rb);
485 ram_addr_t offset = qemu_ram_get_offset(rb);
486 ram_addr_t length = rb->postcopy_length;
487 MigrationIncomingState *mis = opaque;
488 struct uffdio_range range_struct;
489 trace_postcopy_cleanup_range(block_name, host_addr, offset, length);
490
491 /*
492 * We turned off hugepage for the precopy stage with postcopy enabled
493 * we can turn it back on now.
494 */
495 qemu_madvise(host_addr, length, QEMU_MADV_HUGEPAGE);
496
497 /*
498 * We can also turn off userfault now since we should have all the
499 * pages. It can be useful to leave it on to debug postcopy
500 * if you're not sure it's always getting every page.
501 */
502 range_struct.start = (uintptr_t)host_addr;
503 range_struct.len = length;
504
505 if (ioctl(mis->userfault_fd, UFFDIO_UNREGISTER, &range_struct)) {
506 error_report("%s: userfault unregister %s", __func__, strerror(errno));
507
508 return -1;
509 }
510
511 return 0;
512 }
513
514 /*
515 * Initialise postcopy-ram, setting the RAM to a state where we can go into
516 * postcopy later; must be called prior to any precopy.
517 * called from arch_init's similarly named ram_postcopy_incoming_init
518 */
519 int postcopy_ram_incoming_init(MigrationIncomingState *mis)
520 {
521 if (foreach_not_ignored_block(init_range, NULL)) {
522 return -1;
523 }
524
525 return 0;
526 }
527
528 /*
529 * At the end of a migration where postcopy_ram_incoming_init was called.
530 */
531 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
532 {
533 trace_postcopy_ram_incoming_cleanup_entry();
534
535 if (mis->have_fault_thread) {
536 Error *local_err = NULL;
537
538 /* Let the fault thread quit */
539 qatomic_set(&mis->fault_thread_quit, 1);
540 postcopy_fault_thread_notify(mis);
541 trace_postcopy_ram_incoming_cleanup_join();
542 qemu_thread_join(&mis->fault_thread);
543
544 if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_END, &local_err)) {
545 error_report_err(local_err);
546 return -1;
547 }
548
549 if (foreach_not_ignored_block(cleanup_range, mis)) {
550 return -1;
551 }
552
553 trace_postcopy_ram_incoming_cleanup_closeuf();
554 close(mis->userfault_fd);
555 close(mis->userfault_event_fd);
556 mis->have_fault_thread = false;
557 }
558
559 if (enable_mlock) {
560 if (os_mlock() < 0) {
561 error_report("mlock: %s", strerror(errno));
562 /*
563 * It doesn't feel right to fail at this point, we have a valid
564 * VM state.
565 */
566 }
567 }
568
569 if (mis->postcopy_tmp_page) {
570 munmap(mis->postcopy_tmp_page, mis->largest_page_size);
571 mis->postcopy_tmp_page = NULL;
572 }
573 if (mis->postcopy_tmp_zero_page) {
574 munmap(mis->postcopy_tmp_zero_page, mis->largest_page_size);
575 mis->postcopy_tmp_zero_page = NULL;
576 }
577 trace_postcopy_ram_incoming_cleanup_blocktime(
578 get_postcopy_total_blocktime());
579
580 trace_postcopy_ram_incoming_cleanup_exit();
581 return 0;
582 }
583
584 /*
585 * Disable huge pages on an area
586 */
587 static int nhp_range(RAMBlock *rb, void *opaque)
588 {
589 const char *block_name = qemu_ram_get_idstr(rb);
590 void *host_addr = qemu_ram_get_host_addr(rb);
591 ram_addr_t offset = qemu_ram_get_offset(rb);
592 ram_addr_t length = rb->postcopy_length;
593 trace_postcopy_nhp_range(block_name, host_addr, offset, length);
594
595 /*
596 * Before we do discards we need to ensure those discards really
597 * do delete areas of the page, even if THP thinks a hugepage would
598 * be a good idea, so force hugepages off.
599 */
600 qemu_madvise(host_addr, length, QEMU_MADV_NOHUGEPAGE);
601
602 return 0;
603 }
604
605 /*
606 * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
607 * however leaving it until after precopy means that most of the precopy
608 * data is still THPd
609 */
610 int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
611 {
612 if (foreach_not_ignored_block(nhp_range, mis)) {
613 return -1;
614 }
615
616 postcopy_state_set(POSTCOPY_INCOMING_DISCARD);
617
618 return 0;
619 }
620
621 /*
622 * Mark the given area of RAM as requiring notification to unwritten areas
623 * Used as a callback on foreach_not_ignored_block.
624 * host_addr: Base of area to mark
625 * offset: Offset in the whole ram arena
626 * length: Length of the section
627 * opaque: MigrationIncomingState pointer
628 * Returns 0 on success
629 */
630 static int ram_block_enable_notify(RAMBlock *rb, void *opaque)
631 {
632 MigrationIncomingState *mis = opaque;
633 struct uffdio_register reg_struct;
634
635 reg_struct.range.start = (uintptr_t)qemu_ram_get_host_addr(rb);
636 reg_struct.range.len = rb->postcopy_length;
637 reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
638
639 /* Now tell our userfault_fd that it's responsible for this area */
640 if (ioctl(mis->userfault_fd, UFFDIO_REGISTER, &reg_struct)) {
641 error_report("%s userfault register: %s", __func__, strerror(errno));
642 return -1;
643 }
644 if (!(reg_struct.ioctls & ((__u64)1 << _UFFDIO_COPY))) {
645 error_report("%s userfault: Region doesn't support COPY", __func__);
646 return -1;
647 }
648 if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) {
649 qemu_ram_set_uf_zeroable(rb);
650 }
651
652 return 0;
653 }
654
655 int postcopy_wake_shared(struct PostCopyFD *pcfd,
656 uint64_t client_addr,
657 RAMBlock *rb)
658 {
659 size_t pagesize = qemu_ram_pagesize(rb);
660 struct uffdio_range range;
661 int ret;
662 trace_postcopy_wake_shared(client_addr, qemu_ram_get_idstr(rb));
663 range.start = client_addr & ~(pagesize - 1);
664 range.len = pagesize;
665 ret = ioctl(pcfd->fd, UFFDIO_WAKE, &range);
666 if (ret) {
667 error_report("%s: Failed to wake: %zx in %s (%s)",
668 __func__, (size_t)client_addr, qemu_ram_get_idstr(rb),
669 strerror(errno));
670 }
671 return ret;
672 }
673
674 /*
675 * Callback from shared fault handlers to ask for a page,
676 * the page must be specified by a RAMBlock and an offset in that rb
677 * Note: Only for use by shared fault handlers (in fault thread)
678 */
679 int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
680 uint64_t client_addr, uint64_t rb_offset)
681 {
682 size_t pagesize = qemu_ram_pagesize(rb);
683 uint64_t aligned_rbo = rb_offset & ~(pagesize - 1);
684 MigrationIncomingState *mis = migration_incoming_get_current();
685
686 trace_postcopy_request_shared_page(pcfd->idstr, qemu_ram_get_idstr(rb),
687 rb_offset);
688 if (ramblock_recv_bitmap_test_byte_offset(rb, aligned_rbo)) {
689 trace_postcopy_request_shared_page_present(pcfd->idstr,
690 qemu_ram_get_idstr(rb), rb_offset);
691 return postcopy_wake_shared(pcfd, client_addr, rb);
692 }
693 migrate_send_rp_req_pages(mis, rb, aligned_rbo, client_addr);
694 return 0;
695 }
696
697 static int get_mem_fault_cpu_index(uint32_t pid)
698 {
699 CPUState *cpu_iter;
700
701 CPU_FOREACH(cpu_iter) {
702 if (cpu_iter->thread_id == pid) {
703 trace_get_mem_fault_cpu_index(cpu_iter->cpu_index, pid);
704 return cpu_iter->cpu_index;
705 }
706 }
707 trace_get_mem_fault_cpu_index(-1, pid);
708 return -1;
709 }
710
711 static uint32_t get_low_time_offset(PostcopyBlocktimeContext *dc)
712 {
713 int64_t start_time_offset = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) -
714 dc->start_time;
715 return start_time_offset < 1 ? 1 : start_time_offset & UINT32_MAX;
716 }
717
718 /*
719 * This function is being called when pagefault occurs. It
720 * tracks down vCPU blocking time.
721 *
722 * @addr: faulted host virtual address
723 * @ptid: faulted process thread id
724 * @rb: ramblock appropriate to addr
725 */
726 static void mark_postcopy_blocktime_begin(uintptr_t addr, uint32_t ptid,
727 RAMBlock *rb)
728 {
729 int cpu, already_received;
730 MigrationIncomingState *mis = migration_incoming_get_current();
731 PostcopyBlocktimeContext *dc = mis->blocktime_ctx;
732 uint32_t low_time_offset;
733
734 if (!dc || ptid == 0) {
735 return;
736 }
737 cpu = get_mem_fault_cpu_index(ptid);
738 if (cpu < 0) {
739 return;
740 }
741
742 low_time_offset = get_low_time_offset(dc);
743 if (dc->vcpu_addr[cpu] == 0) {
744 qatomic_inc(&dc->smp_cpus_down);
745 }
746
747 qatomic_xchg(&dc->last_begin, low_time_offset);
748 qatomic_xchg(&dc->page_fault_vcpu_time[cpu], low_time_offset);
749 qatomic_xchg(&dc->vcpu_addr[cpu], addr);
750
751 /*
752 * check it here, not at the beginning of the function,
753 * due to, check could occur early than bitmap_set in
754 * qemu_ufd_copy_ioctl
755 */
756 already_received = ramblock_recv_bitmap_test(rb, (void *)addr);
757 if (already_received) {
758 qatomic_xchg(&dc->vcpu_addr[cpu], 0);
759 qatomic_xchg(&dc->page_fault_vcpu_time[cpu], 0);
760 qatomic_dec(&dc->smp_cpus_down);
761 }
762 trace_mark_postcopy_blocktime_begin(addr, dc, dc->page_fault_vcpu_time[cpu],
763 cpu, already_received);
764 }
765
766 /*
767 * This function just provide calculated blocktime per cpu and trace it.
768 * Total blocktime is calculated in mark_postcopy_blocktime_end.
769 *
770 *
771 * Assume we have 3 CPU
772 *
773 * S1 E1 S1 E1
774 * -----***********------------xxx***************------------------------> CPU1
775 *
776 * S2 E2
777 * ------------****************xxx---------------------------------------> CPU2
778 *
779 * S3 E3
780 * ------------------------****xxx********-------------------------------> CPU3
781 *
782 * We have sequence S1,S2,E1,S3,S1,E2,E3,E1
783 * S2,E1 - doesn't match condition due to sequence S1,S2,E1 doesn't include CPU3
784 * S3,S1,E2 - sequence includes all CPUs, in this case overlap will be S1,E2 -
785 * it's a part of total blocktime.
786 * S1 - here is last_begin
787 * Legend of the picture is following:
788 * * - means blocktime per vCPU
789 * x - means overlapped blocktime (total blocktime)
790 *
791 * @addr: host virtual address
792 */
793 static void mark_postcopy_blocktime_end(uintptr_t addr)
794 {
795 MigrationIncomingState *mis = migration_incoming_get_current();
796 PostcopyBlocktimeContext *dc = mis->blocktime_ctx;
797 MachineState *ms = MACHINE(qdev_get_machine());
798 unsigned int smp_cpus = ms->smp.cpus;
799 int i, affected_cpu = 0;
800 bool vcpu_total_blocktime = false;
801 uint32_t read_vcpu_time, low_time_offset;
802
803 if (!dc) {
804 return;
805 }
806
807 low_time_offset = get_low_time_offset(dc);
808 /* lookup cpu, to clear it,
809 * that algorithm looks straightforward, but it's not
810 * optimal, more optimal algorithm is keeping tree or hash
811 * where key is address value is a list of */
812 for (i = 0; i < smp_cpus; i++) {
813 uint32_t vcpu_blocktime = 0;
814
815 read_vcpu_time = qatomic_fetch_add(&dc->page_fault_vcpu_time[i], 0);
816 if (qatomic_fetch_add(&dc->vcpu_addr[i], 0) != addr ||
817 read_vcpu_time == 0) {
818 continue;
819 }
820 qatomic_xchg(&dc->vcpu_addr[i], 0);
821 vcpu_blocktime = low_time_offset - read_vcpu_time;
822 affected_cpu += 1;
823 /* we need to know is that mark_postcopy_end was due to
824 * faulted page, another possible case it's prefetched
825 * page and in that case we shouldn't be here */
826 if (!vcpu_total_blocktime &&
827 qatomic_fetch_add(&dc->smp_cpus_down, 0) == smp_cpus) {
828 vcpu_total_blocktime = true;
829 }
830 /* continue cycle, due to one page could affect several vCPUs */
831 dc->vcpu_blocktime[i] += vcpu_blocktime;
832 }
833
834 qatomic_sub(&dc->smp_cpus_down, affected_cpu);
835 if (vcpu_total_blocktime) {
836 dc->total_blocktime += low_time_offset - qatomic_fetch_add(
837 &dc->last_begin, 0);
838 }
839 trace_mark_postcopy_blocktime_end(addr, dc, dc->total_blocktime,
840 affected_cpu);
841 }
842
843 static bool postcopy_pause_fault_thread(MigrationIncomingState *mis)
844 {
845 trace_postcopy_pause_fault_thread();
846
847 qemu_sem_wait(&mis->postcopy_pause_sem_fault);
848
849 trace_postcopy_pause_fault_thread_continued();
850
851 return true;
852 }
853
854 /*
855 * Handle faults detected by the USERFAULT markings
856 */
857 static void *postcopy_ram_fault_thread(void *opaque)
858 {
859 MigrationIncomingState *mis = opaque;
860 struct uffd_msg msg;
861 int ret;
862 size_t index;
863 RAMBlock *rb = NULL;
864
865 trace_postcopy_ram_fault_thread_entry();
866 rcu_register_thread();
867 mis->last_rb = NULL; /* last RAMBlock we sent part of */
868 qemu_sem_post(&mis->fault_thread_sem);
869
870 struct pollfd *pfd;
871 size_t pfd_len = 2 + mis->postcopy_remote_fds->len;
872
873 pfd = g_new0(struct pollfd, pfd_len);
874
875 pfd[0].fd = mis->userfault_fd;
876 pfd[0].events = POLLIN;
877 pfd[1].fd = mis->userfault_event_fd;
878 pfd[1].events = POLLIN; /* Waiting for eventfd to go positive */
879 trace_postcopy_ram_fault_thread_fds_core(pfd[0].fd, pfd[1].fd);
880 for (index = 0; index < mis->postcopy_remote_fds->len; index++) {
881 struct PostCopyFD *pcfd = &g_array_index(mis->postcopy_remote_fds,
882 struct PostCopyFD, index);
883 pfd[2 + index].fd = pcfd->fd;
884 pfd[2 + index].events = POLLIN;
885 trace_postcopy_ram_fault_thread_fds_extra(2 + index, pcfd->idstr,
886 pcfd->fd);
887 }
888
889 while (true) {
890 ram_addr_t rb_offset;
891 int poll_result;
892
893 /*
894 * We're mainly waiting for the kernel to give us a faulting HVA,
895 * however we can be told to quit via userfault_quit_fd which is
896 * an eventfd
897 */
898
899 poll_result = poll(pfd, pfd_len, -1 /* Wait forever */);
900 if (poll_result == -1) {
901 error_report("%s: userfault poll: %s", __func__, strerror(errno));
902 break;
903 }
904
905 if (!mis->to_src_file) {
906 /*
907 * Possibly someone tells us that the return path is
908 * broken already using the event. We should hold until
909 * the channel is rebuilt.
910 */
911 if (postcopy_pause_fault_thread(mis)) {
912 /* Continue to read the userfaultfd */
913 } else {
914 error_report("%s: paused but don't allow to continue",
915 __func__);
916 break;
917 }
918 }
919
920 if (pfd[1].revents) {
921 uint64_t tmp64 = 0;
922
923 /* Consume the signal */
924 if (read(mis->userfault_event_fd, &tmp64, 8) != 8) {
925 /* Nothing obviously nicer than posting this error. */
926 error_report("%s: read() failed", __func__);
927 }
928
929 if (qatomic_read(&mis->fault_thread_quit)) {
930 trace_postcopy_ram_fault_thread_quit();
931 break;
932 }
933 }
934
935 if (pfd[0].revents) {
936 poll_result--;
937 ret = read(mis->userfault_fd, &msg, sizeof(msg));
938 if (ret != sizeof(msg)) {
939 if (errno == EAGAIN) {
940 /*
941 * if a wake up happens on the other thread just after
942 * the poll, there is nothing to read.
943 */
944 continue;
945 }
946 if (ret < 0) {
947 error_report("%s: Failed to read full userfault "
948 "message: %s",
949 __func__, strerror(errno));
950 break;
951 } else {
952 error_report("%s: Read %d bytes from userfaultfd "
953 "expected %zd",
954 __func__, ret, sizeof(msg));
955 break; /* Lost alignment, don't know what we'd read next */
956 }
957 }
958 if (msg.event != UFFD_EVENT_PAGEFAULT) {
959 error_report("%s: Read unexpected event %ud from userfaultfd",
960 __func__, msg.event);
961 continue; /* It's not a page fault, shouldn't happen */
962 }
963
964 rb = qemu_ram_block_from_host(
965 (void *)(uintptr_t)msg.arg.pagefault.address,
966 true, &rb_offset);
967 if (!rb) {
968 error_report("postcopy_ram_fault_thread: Fault outside guest: %"
969 PRIx64, (uint64_t)msg.arg.pagefault.address);
970 break;
971 }
972
973 rb_offset &= ~(qemu_ram_pagesize(rb) - 1);
974 trace_postcopy_ram_fault_thread_request(msg.arg.pagefault.address,
975 qemu_ram_get_idstr(rb),
976 rb_offset,
977 msg.arg.pagefault.feat.ptid);
978 mark_postcopy_blocktime_begin(
979 (uintptr_t)(msg.arg.pagefault.address),
980 msg.arg.pagefault.feat.ptid, rb);
981
982 retry:
983 /*
984 * Send the request to the source - we want to request one
985 * of our host page sizes (which is >= TPS)
986 */
987 ret = migrate_send_rp_req_pages(mis, rb, rb_offset,
988 msg.arg.pagefault.address);
989 if (ret) {
990 /* May be network failure, try to wait for recovery */
991 if (ret == -EIO && postcopy_pause_fault_thread(mis)) {
992 /* We got reconnected somehow, try to continue */
993 goto retry;
994 } else {
995 /* This is a unavoidable fault */
996 error_report("%s: migrate_send_rp_req_pages() get %d",
997 __func__, ret);
998 break;
999 }
1000 }
1001 }
1002
1003 /* Now handle any requests from external processes on shared memory */
1004 /* TODO: May need to handle devices deregistering during postcopy */
1005 for (index = 2; index < pfd_len && poll_result; index++) {
1006 if (pfd[index].revents) {
1007 struct PostCopyFD *pcfd =
1008 &g_array_index(mis->postcopy_remote_fds,
1009 struct PostCopyFD, index - 2);
1010
1011 poll_result--;
1012 if (pfd[index].revents & POLLERR) {
1013 error_report("%s: POLLERR on poll %zd fd=%d",
1014 __func__, index, pcfd->fd);
1015 pfd[index].events = 0;
1016 continue;
1017 }
1018
1019 ret = read(pcfd->fd, &msg, sizeof(msg));
1020 if (ret != sizeof(msg)) {
1021 if (errno == EAGAIN) {
1022 /*
1023 * if a wake up happens on the other thread just after
1024 * the poll, there is nothing to read.
1025 */
1026 continue;
1027 }
1028 if (ret < 0) {
1029 error_report("%s: Failed to read full userfault "
1030 "message: %s (shared) revents=%d",
1031 __func__, strerror(errno),
1032 pfd[index].revents);
1033 /*TODO: Could just disable this sharer */
1034 break;
1035 } else {
1036 error_report("%s: Read %d bytes from userfaultfd "
1037 "expected %zd (shared)",
1038 __func__, ret, sizeof(msg));
1039 /*TODO: Could just disable this sharer */
1040 break; /*Lost alignment,don't know what we'd read next*/
1041 }
1042 }
1043 if (msg.event != UFFD_EVENT_PAGEFAULT) {
1044 error_report("%s: Read unexpected event %ud "
1045 "from userfaultfd (shared)",
1046 __func__, msg.event);
1047 continue; /* It's not a page fault, shouldn't happen */
1048 }
1049 /* Call the device handler registered with us */
1050 ret = pcfd->handler(pcfd, &msg);
1051 if (ret) {
1052 error_report("%s: Failed to resolve shared fault on %zd/%s",
1053 __func__, index, pcfd->idstr);
1054 /* TODO: Fail? Disable this sharer? */
1055 }
1056 }
1057 }
1058 }
1059 rcu_unregister_thread();
1060 trace_postcopy_ram_fault_thread_exit();
1061 g_free(pfd);
1062 return NULL;
1063 }
1064
1065 int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
1066 {
1067 /* Open the fd for the kernel to give us userfaults */
1068 mis->userfault_fd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
1069 if (mis->userfault_fd == -1) {
1070 error_report("%s: Failed to open userfault fd: %s", __func__,
1071 strerror(errno));
1072 return -1;
1073 }
1074
1075 /*
1076 * Although the host check already tested the API, we need to
1077 * do the check again as an ABI handshake on the new fd.
1078 */
1079 if (!ufd_check_and_apply(mis->userfault_fd, mis)) {
1080 return -1;
1081 }
1082
1083 /* Now an eventfd we use to tell the fault-thread to quit */
1084 mis->userfault_event_fd = eventfd(0, EFD_CLOEXEC);
1085 if (mis->userfault_event_fd == -1) {
1086 error_report("%s: Opening userfault_event_fd: %s", __func__,
1087 strerror(errno));
1088 close(mis->userfault_fd);
1089 return -1;
1090 }
1091
1092 qemu_sem_init(&mis->fault_thread_sem, 0);
1093 qemu_thread_create(&mis->fault_thread, "postcopy/fault",
1094 postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE);
1095 qemu_sem_wait(&mis->fault_thread_sem);
1096 qemu_sem_destroy(&mis->fault_thread_sem);
1097 mis->have_fault_thread = true;
1098
1099 /* Mark so that we get notified of accesses to unwritten areas */
1100 if (foreach_not_ignored_block(ram_block_enable_notify, mis)) {
1101 error_report("ram_block_enable_notify failed");
1102 return -1;
1103 }
1104
1105 mis->postcopy_tmp_page = mmap(NULL, mis->largest_page_size,
1106 PROT_READ | PROT_WRITE, MAP_PRIVATE |
1107 MAP_ANONYMOUS, -1, 0);
1108 if (mis->postcopy_tmp_page == MAP_FAILED) {
1109 mis->postcopy_tmp_page = NULL;
1110 error_report("%s: Failed to map postcopy_tmp_page %s",
1111 __func__, strerror(errno));
1112 return -1;
1113 }
1114
1115 /*
1116 * Map large zero page when kernel can't use UFFDIO_ZEROPAGE for hugepages
1117 */
1118 mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size,
1119 PROT_READ | PROT_WRITE,
1120 MAP_PRIVATE | MAP_ANONYMOUS,
1121 -1, 0);
1122 if (mis->postcopy_tmp_zero_page == MAP_FAILED) {
1123 int e = errno;
1124 mis->postcopy_tmp_zero_page = NULL;
1125 error_report("%s: Failed to map large zero page %s",
1126 __func__, strerror(e));
1127 return -e;
1128 }
1129 memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size);
1130
1131 trace_postcopy_ram_enable_notify();
1132
1133 return 0;
1134 }
1135
1136 static int qemu_ufd_copy_ioctl(MigrationIncomingState *mis, void *host_addr,
1137 void *from_addr, uint64_t pagesize, RAMBlock *rb)
1138 {
1139 int userfault_fd = mis->userfault_fd;
1140 int ret;
1141
1142 if (from_addr) {
1143 struct uffdio_copy copy_struct;
1144 copy_struct.dst = (uint64_t)(uintptr_t)host_addr;
1145 copy_struct.src = (uint64_t)(uintptr_t)from_addr;
1146 copy_struct.len = pagesize;
1147 copy_struct.mode = 0;
1148 ret = ioctl(userfault_fd, UFFDIO_COPY, &copy_struct);
1149 } else {
1150 struct uffdio_zeropage zero_struct;
1151 zero_struct.range.start = (uint64_t)(uintptr_t)host_addr;
1152 zero_struct.range.len = pagesize;
1153 zero_struct.mode = 0;
1154 ret = ioctl(userfault_fd, UFFDIO_ZEROPAGE, &zero_struct);
1155 }
1156 if (!ret) {
1157 qemu_mutex_lock(&mis->page_request_mutex);
1158 ramblock_recv_bitmap_set_range(rb, host_addr,
1159 pagesize / qemu_target_page_size());
1160 /*
1161 * If this page resolves a page fault for a previous recorded faulted
1162 * address, take a special note to maintain the requested page list.
1163 */
1164 if (g_tree_lookup(mis->page_requested, host_addr)) {
1165 g_tree_remove(mis->page_requested, host_addr);
1166 mis->page_requested_count--;
1167 trace_postcopy_page_req_del(host_addr, mis->page_requested_count);
1168 }
1169 qemu_mutex_unlock(&mis->page_request_mutex);
1170 mark_postcopy_blocktime_end((uintptr_t)host_addr);
1171 }
1172 return ret;
1173 }
1174
1175 int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset)
1176 {
1177 int i;
1178 MigrationIncomingState *mis = migration_incoming_get_current();
1179 GArray *pcrfds = mis->postcopy_remote_fds;
1180
1181 for (i = 0; i < pcrfds->len; i++) {
1182 struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i);
1183 int ret = cur->waker(cur, rb, offset);
1184 if (ret) {
1185 return ret;
1186 }
1187 }
1188 return 0;
1189 }
1190
1191 /*
1192 * Place a host page (from) at (host) atomically
1193 * returns 0 on success
1194 */
1195 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
1196 RAMBlock *rb)
1197 {
1198 size_t pagesize = qemu_ram_pagesize(rb);
1199
1200 /* copy also acks to the kernel waking the stalled thread up
1201 * TODO: We can inhibit that ack and only do it if it was requested
1202 * which would be slightly cheaper, but we'd have to be careful
1203 * of the order of updating our page state.
1204 */
1205 if (qemu_ufd_copy_ioctl(mis, host, from, pagesize, rb)) {
1206 int e = errno;
1207 error_report("%s: %s copy host: %p from: %p (size: %zd)",
1208 __func__, strerror(e), host, from, pagesize);
1209
1210 return -e;
1211 }
1212
1213 trace_postcopy_place_page(host);
1214 return postcopy_notify_shared_wake(rb,
1215 qemu_ram_block_host_offset(rb, host));
1216 }
1217
1218 /*
1219 * Place a zero page at (host) atomically
1220 * returns 0 on success
1221 */
1222 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
1223 RAMBlock *rb)
1224 {
1225 size_t pagesize = qemu_ram_pagesize(rb);
1226 trace_postcopy_place_page_zero(host);
1227
1228 /* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE
1229 * but it's not available for everything (e.g. hugetlbpages)
1230 */
1231 if (qemu_ram_is_uf_zeroable(rb)) {
1232 if (qemu_ufd_copy_ioctl(mis, host, NULL, pagesize, rb)) {
1233 int e = errno;
1234 error_report("%s: %s zero host: %p",
1235 __func__, strerror(e), host);
1236
1237 return -e;
1238 }
1239 return postcopy_notify_shared_wake(rb,
1240 qemu_ram_block_host_offset(rb,
1241 host));
1242 } else {
1243 return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page, rb);
1244 }
1245 }
1246
1247 #else
1248 /* No target OS support, stubs just fail */
1249 void fill_destination_postcopy_migration_info(MigrationInfo *info)
1250 {
1251 }
1252
1253 bool postcopy_ram_supported_by_host(MigrationIncomingState *mis)
1254 {
1255 error_report("%s: No OS support", __func__);
1256 return false;
1257 }
1258
1259 int postcopy_ram_incoming_init(MigrationIncomingState *mis)
1260 {
1261 error_report("postcopy_ram_incoming_init: No OS support");
1262 return -1;
1263 }
1264
1265 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
1266 {
1267 assert(0);
1268 return -1;
1269 }
1270
1271 int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
1272 {
1273 assert(0);
1274 return -1;
1275 }
1276
1277 int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb,
1278 uint64_t client_addr, uint64_t rb_offset)
1279 {
1280 assert(0);
1281 return -1;
1282 }
1283
1284 int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
1285 {
1286 assert(0);
1287 return -1;
1288 }
1289
1290 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
1291 RAMBlock *rb)
1292 {
1293 assert(0);
1294 return -1;
1295 }
1296
1297 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
1298 RAMBlock *rb)
1299 {
1300 assert(0);
1301 return -1;
1302 }
1303
1304 int postcopy_wake_shared(struct PostCopyFD *pcfd,
1305 uint64_t client_addr,
1306 RAMBlock *rb)
1307 {
1308 assert(0);
1309 return -1;
1310 }
1311 #endif
1312
1313 /* ------------------------------------------------------------------------- */
1314
1315 void postcopy_fault_thread_notify(MigrationIncomingState *mis)
1316 {
1317 uint64_t tmp64 = 1;
1318
1319 /*
1320 * Wakeup the fault_thread. It's an eventfd that should currently
1321 * be at 0, we're going to increment it to 1
1322 */
1323 if (write(mis->userfault_event_fd, &tmp64, 8) != 8) {
1324 /* Not much we can do here, but may as well report it */
1325 error_report("%s: incrementing failed: %s", __func__,
1326 strerror(errno));
1327 }
1328 }
1329
1330 /**
1331 * postcopy_discard_send_init: Called at the start of each RAMBlock before
1332 * asking to discard individual ranges.
1333 *
1334 * @ms: The current migration state.
1335 * @offset: the bitmap offset of the named RAMBlock in the migration bitmap.
1336 * @name: RAMBlock that discards will operate on.
1337 */
1338 static PostcopyDiscardState pds = {0};
1339 void postcopy_discard_send_init(MigrationState *ms, const char *name)
1340 {
1341 pds.ramblock_name = name;
1342 pds.cur_entry = 0;
1343 pds.nsentwords = 0;
1344 pds.nsentcmds = 0;
1345 }
1346
1347 /**
1348 * postcopy_discard_send_range: Called by the bitmap code for each chunk to
1349 * discard. May send a discard message, may just leave it queued to
1350 * be sent later.
1351 *
1352 * @ms: Current migration state.
1353 * @start,@length: a range of pages in the migration bitmap in the
1354 * RAM block passed to postcopy_discard_send_init() (length=1 is one page)
1355 */
1356 void postcopy_discard_send_range(MigrationState *ms, unsigned long start,
1357 unsigned long length)
1358 {
1359 size_t tp_size = qemu_target_page_size();
1360 /* Convert to byte offsets within the RAM block */
1361 pds.start_list[pds.cur_entry] = start * tp_size;
1362 pds.length_list[pds.cur_entry] = length * tp_size;
1363 trace_postcopy_discard_send_range(pds.ramblock_name, start, length);
1364 pds.cur_entry++;
1365 pds.nsentwords++;
1366
1367 if (pds.cur_entry == MAX_DISCARDS_PER_COMMAND) {
1368 /* Full set, ship it! */
1369 qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
1370 pds.ramblock_name,
1371 pds.cur_entry,
1372 pds.start_list,
1373 pds.length_list);
1374 pds.nsentcmds++;
1375 pds.cur_entry = 0;
1376 }
1377 }
1378
1379 /**
1380 * postcopy_discard_send_finish: Called at the end of each RAMBlock by the
1381 * bitmap code. Sends any outstanding discard messages, frees the PDS
1382 *
1383 * @ms: Current migration state.
1384 */
1385 void postcopy_discard_send_finish(MigrationState *ms)
1386 {
1387 /* Anything unsent? */
1388 if (pds.cur_entry) {
1389 qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
1390 pds.ramblock_name,
1391 pds.cur_entry,
1392 pds.start_list,
1393 pds.length_list);
1394 pds.nsentcmds++;
1395 }
1396
1397 trace_postcopy_discard_send_finish(pds.ramblock_name, pds.nsentwords,
1398 pds.nsentcmds);
1399 }
1400
1401 /*
1402 * Current state of incoming postcopy; note this is not part of
1403 * MigrationIncomingState since it's state is used during cleanup
1404 * at the end as MIS is being freed.
1405 */
1406 static PostcopyState incoming_postcopy_state;
1407
1408 PostcopyState postcopy_state_get(void)
1409 {
1410 return qatomic_mb_read(&incoming_postcopy_state);
1411 }
1412
1413 /* Set the state and return the old state */
1414 PostcopyState postcopy_state_set(PostcopyState new_state)
1415 {
1416 return qatomic_xchg(&incoming_postcopy_state, new_state);
1417 }
1418
1419 /* Register a handler for external shared memory postcopy
1420 * called on the destination.
1421 */
1422 void postcopy_register_shared_ufd(struct PostCopyFD *pcfd)
1423 {
1424 MigrationIncomingState *mis = migration_incoming_get_current();
1425
1426 mis->postcopy_remote_fds = g_array_append_val(mis->postcopy_remote_fds,
1427 *pcfd);
1428 }
1429
1430 /* Unregister a handler for external shared memory postcopy
1431 */
1432 void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd)
1433 {
1434 guint i;
1435 MigrationIncomingState *mis = migration_incoming_get_current();
1436 GArray *pcrfds = mis->postcopy_remote_fds;
1437
1438 for (i = 0; i < pcrfds->len; i++) {
1439 struct PostCopyFD *cur = &g_array_index(pcrfds, struct PostCopyFD, i);
1440 if (cur->fd == pcfd->fd) {
1441 mis->postcopy_remote_fds = g_array_remove_index(pcrfds, i);
1442 return;
1443 }
1444 }
1445 }