exec: remove ram_addr argument from qemu_ram_block_from_host
[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 <glib.h>
21
22 #include "qemu-common.h"
23 #include "migration/migration.h"
24 #include "migration/postcopy-ram.h"
25 #include "sysemu/sysemu.h"
26 #include "sysemu/balloon.h"
27 #include "qemu/error-report.h"
28 #include "trace.h"
29
30 /* Arbitrary limit on size of each discard command,
31 * keeps them around ~200 bytes
32 */
33 #define MAX_DISCARDS_PER_COMMAND 12
34
35 struct PostcopyDiscardState {
36 const char *ramblock_name;
37 uint64_t offset; /* Bitmap entry for the 1st bit of this RAMBlock */
38 uint16_t cur_entry;
39 /*
40 * Start and length of a discard range (bytes)
41 */
42 uint64_t start_list[MAX_DISCARDS_PER_COMMAND];
43 uint64_t length_list[MAX_DISCARDS_PER_COMMAND];
44 unsigned int nsentwords;
45 unsigned int nsentcmds;
46 };
47
48 /* Postcopy needs to detect accesses to pages that haven't yet been copied
49 * across, and efficiently map new pages in, the techniques for doing this
50 * are target OS specific.
51 */
52 #if defined(__linux__)
53
54 #include <poll.h>
55 #include <sys/mman.h>
56 #include <sys/ioctl.h>
57 #include <sys/syscall.h>
58 #include <asm/types.h> /* for __u64 */
59 #endif
60
61 #if defined(__linux__) && defined(__NR_userfaultfd) && defined(CONFIG_EVENTFD)
62 #include <sys/eventfd.h>
63 #include <linux/userfaultfd.h>
64
65 static bool ufd_version_check(int ufd)
66 {
67 struct uffdio_api api_struct;
68 uint64_t ioctl_mask;
69
70 api_struct.api = UFFD_API;
71 api_struct.features = 0;
72 if (ioctl(ufd, UFFDIO_API, &api_struct)) {
73 error_report("postcopy_ram_supported_by_host: UFFDIO_API failed: %s",
74 strerror(errno));
75 return false;
76 }
77
78 ioctl_mask = (__u64)1 << _UFFDIO_REGISTER |
79 (__u64)1 << _UFFDIO_UNREGISTER;
80 if ((api_struct.ioctls & ioctl_mask) != ioctl_mask) {
81 error_report("Missing userfault features: %" PRIx64,
82 (uint64_t)(~api_struct.ioctls & ioctl_mask));
83 return false;
84 }
85
86 return true;
87 }
88
89 /*
90 * Note: This has the side effect of munlock'ing all of RAM, that's
91 * normally fine since if the postcopy succeeds it gets turned back on at the
92 * end.
93 */
94 bool postcopy_ram_supported_by_host(void)
95 {
96 long pagesize = getpagesize();
97 int ufd = -1;
98 bool ret = false; /* Error unless we change it */
99 void *testarea = NULL;
100 struct uffdio_register reg_struct;
101 struct uffdio_range range_struct;
102 uint64_t feature_mask;
103
104 if ((1ul << qemu_target_page_bits()) > pagesize) {
105 error_report("Target page size bigger than host page size");
106 goto out;
107 }
108
109 ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
110 if (ufd == -1) {
111 error_report("%s: userfaultfd not available: %s", __func__,
112 strerror(errno));
113 goto out;
114 }
115
116 /* Version and features check */
117 if (!ufd_version_check(ufd)) {
118 goto out;
119 }
120
121 /*
122 * userfault and mlock don't go together; we'll put it back later if
123 * it was enabled.
124 */
125 if (munlockall()) {
126 error_report("%s: munlockall: %s", __func__, strerror(errno));
127 return -1;
128 }
129
130 /*
131 * We need to check that the ops we need are supported on anon memory
132 * To do that we need to register a chunk and see the flags that
133 * are returned.
134 */
135 testarea = mmap(NULL, pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE |
136 MAP_ANONYMOUS, -1, 0);
137 if (testarea == MAP_FAILED) {
138 error_report("%s: Failed to map test area: %s", __func__,
139 strerror(errno));
140 goto out;
141 }
142 g_assert(((size_t)testarea & (pagesize-1)) == 0);
143
144 reg_struct.range.start = (uintptr_t)testarea;
145 reg_struct.range.len = pagesize;
146 reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
147
148 if (ioctl(ufd, UFFDIO_REGISTER, &reg_struct)) {
149 error_report("%s userfault register: %s", __func__, strerror(errno));
150 goto out;
151 }
152
153 range_struct.start = (uintptr_t)testarea;
154 range_struct.len = pagesize;
155 if (ioctl(ufd, UFFDIO_UNREGISTER, &range_struct)) {
156 error_report("%s userfault unregister: %s", __func__, strerror(errno));
157 goto out;
158 }
159
160 feature_mask = (__u64)1 << _UFFDIO_WAKE |
161 (__u64)1 << _UFFDIO_COPY |
162 (__u64)1 << _UFFDIO_ZEROPAGE;
163 if ((reg_struct.ioctls & feature_mask) != feature_mask) {
164 error_report("Missing userfault map features: %" PRIx64,
165 (uint64_t)(~reg_struct.ioctls & feature_mask));
166 goto out;
167 }
168
169 /* Success! */
170 ret = true;
171 out:
172 if (testarea) {
173 munmap(testarea, pagesize);
174 }
175 if (ufd != -1) {
176 close(ufd);
177 }
178 return ret;
179 }
180
181 /**
182 * postcopy_ram_discard_range: Discard a range of memory.
183 * We can assume that if we've been called postcopy_ram_hosttest returned true.
184 *
185 * @mis: Current incoming migration state.
186 * @start, @length: range of memory to discard.
187 *
188 * returns: 0 on success.
189 */
190 int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
191 size_t length)
192 {
193 trace_postcopy_ram_discard_range(start, length);
194 if (madvise(start, length, MADV_DONTNEED)) {
195 error_report("%s MADV_DONTNEED: %s", __func__, strerror(errno));
196 return -1;
197 }
198
199 return 0;
200 }
201
202 /*
203 * Setup an area of RAM so that it *can* be used for postcopy later; this
204 * must be done right at the start prior to pre-copy.
205 * opaque should be the MIS.
206 */
207 static int init_range(const char *block_name, void *host_addr,
208 ram_addr_t offset, ram_addr_t length, void *opaque)
209 {
210 MigrationIncomingState *mis = opaque;
211
212 trace_postcopy_init_range(block_name, host_addr, offset, length);
213
214 /*
215 * We need the whole of RAM to be truly empty for postcopy, so things
216 * like ROMs and any data tables built during init must be zero'd
217 * - we're going to get the copy from the source anyway.
218 * (Precopy will just overwrite this data, so doesn't need the discard)
219 */
220 if (postcopy_ram_discard_range(mis, host_addr, length)) {
221 return -1;
222 }
223
224 return 0;
225 }
226
227 /*
228 * At the end of migration, undo the effects of init_range
229 * opaque should be the MIS.
230 */
231 static int cleanup_range(const char *block_name, void *host_addr,
232 ram_addr_t offset, ram_addr_t length, void *opaque)
233 {
234 MigrationIncomingState *mis = opaque;
235 struct uffdio_range range_struct;
236 trace_postcopy_cleanup_range(block_name, host_addr, offset, length);
237
238 /*
239 * We turned off hugepage for the precopy stage with postcopy enabled
240 * we can turn it back on now.
241 */
242 qemu_madvise(host_addr, length, QEMU_MADV_HUGEPAGE);
243
244 /*
245 * We can also turn off userfault now since we should have all the
246 * pages. It can be useful to leave it on to debug postcopy
247 * if you're not sure it's always getting every page.
248 */
249 range_struct.start = (uintptr_t)host_addr;
250 range_struct.len = length;
251
252 if (ioctl(mis->userfault_fd, UFFDIO_UNREGISTER, &range_struct)) {
253 error_report("%s: userfault unregister %s", __func__, strerror(errno));
254
255 return -1;
256 }
257
258 return 0;
259 }
260
261 /*
262 * Initialise postcopy-ram, setting the RAM to a state where we can go into
263 * postcopy later; must be called prior to any precopy.
264 * called from arch_init's similarly named ram_postcopy_incoming_init
265 */
266 int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages)
267 {
268 if (qemu_ram_foreach_block(init_range, mis)) {
269 return -1;
270 }
271
272 return 0;
273 }
274
275 /*
276 * At the end of a migration where postcopy_ram_incoming_init was called.
277 */
278 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
279 {
280 trace_postcopy_ram_incoming_cleanup_entry();
281
282 if (mis->have_fault_thread) {
283 uint64_t tmp64;
284
285 if (qemu_ram_foreach_block(cleanup_range, mis)) {
286 return -1;
287 }
288 /*
289 * Tell the fault_thread to exit, it's an eventfd that should
290 * currently be at 0, we're going to increment it to 1
291 */
292 tmp64 = 1;
293 if (write(mis->userfault_quit_fd, &tmp64, 8) == 8) {
294 trace_postcopy_ram_incoming_cleanup_join();
295 qemu_thread_join(&mis->fault_thread);
296 } else {
297 /* Not much we can do here, but may as well report it */
298 error_report("%s: incrementing userfault_quit_fd: %s", __func__,
299 strerror(errno));
300 }
301 trace_postcopy_ram_incoming_cleanup_closeuf();
302 close(mis->userfault_fd);
303 close(mis->userfault_quit_fd);
304 mis->have_fault_thread = false;
305 }
306
307 qemu_balloon_inhibit(false);
308
309 if (enable_mlock) {
310 if (os_mlock() < 0) {
311 error_report("mlock: %s", strerror(errno));
312 /*
313 * It doesn't feel right to fail at this point, we have a valid
314 * VM state.
315 */
316 }
317 }
318
319 postcopy_state_set(POSTCOPY_INCOMING_END);
320 migrate_send_rp_shut(mis, qemu_file_get_error(mis->from_src_file) != 0);
321
322 if (mis->postcopy_tmp_page) {
323 munmap(mis->postcopy_tmp_page, getpagesize());
324 mis->postcopy_tmp_page = NULL;
325 }
326 trace_postcopy_ram_incoming_cleanup_exit();
327 return 0;
328 }
329
330 /*
331 * Disable huge pages on an area
332 */
333 static int nhp_range(const char *block_name, void *host_addr,
334 ram_addr_t offset, ram_addr_t length, void *opaque)
335 {
336 trace_postcopy_nhp_range(block_name, host_addr, offset, length);
337
338 /*
339 * Before we do discards we need to ensure those discards really
340 * do delete areas of the page, even if THP thinks a hugepage would
341 * be a good idea, so force hugepages off.
342 */
343 qemu_madvise(host_addr, length, QEMU_MADV_NOHUGEPAGE);
344
345 return 0;
346 }
347
348 /*
349 * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
350 * however leaving it until after precopy means that most of the precopy
351 * data is still THPd
352 */
353 int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
354 {
355 if (qemu_ram_foreach_block(nhp_range, mis)) {
356 return -1;
357 }
358
359 postcopy_state_set(POSTCOPY_INCOMING_DISCARD);
360
361 return 0;
362 }
363
364 /*
365 * Mark the given area of RAM as requiring notification to unwritten areas
366 * Used as a callback on qemu_ram_foreach_block.
367 * host_addr: Base of area to mark
368 * offset: Offset in the whole ram arena
369 * length: Length of the section
370 * opaque: MigrationIncomingState pointer
371 * Returns 0 on success
372 */
373 static int ram_block_enable_notify(const char *block_name, void *host_addr,
374 ram_addr_t offset, ram_addr_t length,
375 void *opaque)
376 {
377 MigrationIncomingState *mis = opaque;
378 struct uffdio_register reg_struct;
379
380 reg_struct.range.start = (uintptr_t)host_addr;
381 reg_struct.range.len = length;
382 reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING;
383
384 /* Now tell our userfault_fd that it's responsible for this area */
385 if (ioctl(mis->userfault_fd, UFFDIO_REGISTER, &reg_struct)) {
386 error_report("%s userfault register: %s", __func__, strerror(errno));
387 return -1;
388 }
389
390 return 0;
391 }
392
393 /*
394 * Handle faults detected by the USERFAULT markings
395 */
396 static void *postcopy_ram_fault_thread(void *opaque)
397 {
398 MigrationIncomingState *mis = opaque;
399 struct uffd_msg msg;
400 int ret;
401 size_t hostpagesize = getpagesize();
402 RAMBlock *rb = NULL;
403 RAMBlock *last_rb = NULL; /* last RAMBlock we sent part of */
404
405 trace_postcopy_ram_fault_thread_entry();
406 qemu_sem_post(&mis->fault_thread_sem);
407
408 while (true) {
409 ram_addr_t rb_offset;
410 struct pollfd pfd[2];
411
412 /*
413 * We're mainly waiting for the kernel to give us a faulting HVA,
414 * however we can be told to quit via userfault_quit_fd which is
415 * an eventfd
416 */
417 pfd[0].fd = mis->userfault_fd;
418 pfd[0].events = POLLIN;
419 pfd[0].revents = 0;
420 pfd[1].fd = mis->userfault_quit_fd;
421 pfd[1].events = POLLIN; /* Waiting for eventfd to go positive */
422 pfd[1].revents = 0;
423
424 if (poll(pfd, 2, -1 /* Wait forever */) == -1) {
425 error_report("%s: userfault poll: %s", __func__, strerror(errno));
426 break;
427 }
428
429 if (pfd[1].revents) {
430 trace_postcopy_ram_fault_thread_quit();
431 break;
432 }
433
434 ret = read(mis->userfault_fd, &msg, sizeof(msg));
435 if (ret != sizeof(msg)) {
436 if (errno == EAGAIN) {
437 /*
438 * if a wake up happens on the other thread just after
439 * the poll, there is nothing to read.
440 */
441 continue;
442 }
443 if (ret < 0) {
444 error_report("%s: Failed to read full userfault message: %s",
445 __func__, strerror(errno));
446 break;
447 } else {
448 error_report("%s: Read %d bytes from userfaultfd expected %zd",
449 __func__, ret, sizeof(msg));
450 break; /* Lost alignment, don't know what we'd read next */
451 }
452 }
453 if (msg.event != UFFD_EVENT_PAGEFAULT) {
454 error_report("%s: Read unexpected event %ud from userfaultfd",
455 __func__, msg.event);
456 continue; /* It's not a page fault, shouldn't happen */
457 }
458
459 rb = qemu_ram_block_from_host(
460 (void *)(uintptr_t)msg.arg.pagefault.address,
461 true, &rb_offset);
462 if (!rb) {
463 error_report("postcopy_ram_fault_thread: Fault outside guest: %"
464 PRIx64, (uint64_t)msg.arg.pagefault.address);
465 break;
466 }
467
468 rb_offset &= ~(hostpagesize - 1);
469 trace_postcopy_ram_fault_thread_request(msg.arg.pagefault.address,
470 qemu_ram_get_idstr(rb),
471 rb_offset);
472
473 /*
474 * Send the request to the source - we want to request one
475 * of our host page sizes (which is >= TPS)
476 */
477 if (rb != last_rb) {
478 last_rb = rb;
479 migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb),
480 rb_offset, hostpagesize);
481 } else {
482 /* Save some space */
483 migrate_send_rp_req_pages(mis, NULL,
484 rb_offset, hostpagesize);
485 }
486 }
487 trace_postcopy_ram_fault_thread_exit();
488 return NULL;
489 }
490
491 int postcopy_ram_enable_notify(MigrationIncomingState *mis)
492 {
493 /* Open the fd for the kernel to give us userfaults */
494 mis->userfault_fd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
495 if (mis->userfault_fd == -1) {
496 error_report("%s: Failed to open userfault fd: %s", __func__,
497 strerror(errno));
498 return -1;
499 }
500
501 /*
502 * Although the host check already tested the API, we need to
503 * do the check again as an ABI handshake on the new fd.
504 */
505 if (!ufd_version_check(mis->userfault_fd)) {
506 return -1;
507 }
508
509 /* Now an eventfd we use to tell the fault-thread to quit */
510 mis->userfault_quit_fd = eventfd(0, EFD_CLOEXEC);
511 if (mis->userfault_quit_fd == -1) {
512 error_report("%s: Opening userfault_quit_fd: %s", __func__,
513 strerror(errno));
514 close(mis->userfault_fd);
515 return -1;
516 }
517
518 qemu_sem_init(&mis->fault_thread_sem, 0);
519 qemu_thread_create(&mis->fault_thread, "postcopy/fault",
520 postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE);
521 qemu_sem_wait(&mis->fault_thread_sem);
522 qemu_sem_destroy(&mis->fault_thread_sem);
523 mis->have_fault_thread = true;
524
525 /* Mark so that we get notified of accesses to unwritten areas */
526 if (qemu_ram_foreach_block(ram_block_enable_notify, mis)) {
527 return -1;
528 }
529
530 /*
531 * Ballooning can mark pages as absent while we're postcopying
532 * that would cause false userfaults.
533 */
534 qemu_balloon_inhibit(true);
535
536 trace_postcopy_ram_enable_notify();
537
538 return 0;
539 }
540
541 /*
542 * Place a host page (from) at (host) atomically
543 * returns 0 on success
544 */
545 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
546 {
547 struct uffdio_copy copy_struct;
548
549 copy_struct.dst = (uint64_t)(uintptr_t)host;
550 copy_struct.src = (uint64_t)(uintptr_t)from;
551 copy_struct.len = getpagesize();
552 copy_struct.mode = 0;
553
554 /* copy also acks to the kernel waking the stalled thread up
555 * TODO: We can inhibit that ack and only do it if it was requested
556 * which would be slightly cheaper, but we'd have to be careful
557 * of the order of updating our page state.
558 */
559 if (ioctl(mis->userfault_fd, UFFDIO_COPY, &copy_struct)) {
560 int e = errno;
561 error_report("%s: %s copy host: %p from: %p",
562 __func__, strerror(e), host, from);
563
564 return -e;
565 }
566
567 trace_postcopy_place_page(host);
568 return 0;
569 }
570
571 /*
572 * Place a zero page at (host) atomically
573 * returns 0 on success
574 */
575 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
576 {
577 struct uffdio_zeropage zero_struct;
578
579 zero_struct.range.start = (uint64_t)(uintptr_t)host;
580 zero_struct.range.len = getpagesize();
581 zero_struct.mode = 0;
582
583 if (ioctl(mis->userfault_fd, UFFDIO_ZEROPAGE, &zero_struct)) {
584 int e = errno;
585 error_report("%s: %s zero host: %p",
586 __func__, strerror(e), host);
587
588 return -e;
589 }
590
591 trace_postcopy_place_page_zero(host);
592 return 0;
593 }
594
595 /*
596 * Returns a target page of memory that can be mapped at a later point in time
597 * using postcopy_place_page
598 * The same address is used repeatedly, postcopy_place_page just takes the
599 * backing page away.
600 * Returns: Pointer to allocated page
601 *
602 */
603 void *postcopy_get_tmp_page(MigrationIncomingState *mis)
604 {
605 if (!mis->postcopy_tmp_page) {
606 mis->postcopy_tmp_page = mmap(NULL, getpagesize(),
607 PROT_READ | PROT_WRITE, MAP_PRIVATE |
608 MAP_ANONYMOUS, -1, 0);
609 if (!mis->postcopy_tmp_page) {
610 error_report("%s: %s", __func__, strerror(errno));
611 return NULL;
612 }
613 }
614
615 return mis->postcopy_tmp_page;
616 }
617
618 #else
619 /* No target OS support, stubs just fail */
620 bool postcopy_ram_supported_by_host(void)
621 {
622 error_report("%s: No OS support", __func__);
623 return false;
624 }
625
626 int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages)
627 {
628 error_report("postcopy_ram_incoming_init: No OS support");
629 return -1;
630 }
631
632 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
633 {
634 assert(0);
635 return -1;
636 }
637
638 int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
639 size_t length)
640 {
641 assert(0);
642 return -1;
643 }
644
645 int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
646 {
647 assert(0);
648 return -1;
649 }
650
651 int postcopy_ram_enable_notify(MigrationIncomingState *mis)
652 {
653 assert(0);
654 return -1;
655 }
656
657 int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
658 {
659 assert(0);
660 return -1;
661 }
662
663 int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
664 {
665 assert(0);
666 return -1;
667 }
668
669 void *postcopy_get_tmp_page(MigrationIncomingState *mis)
670 {
671 assert(0);
672 return NULL;
673 }
674
675 #endif
676
677 /* ------------------------------------------------------------------------- */
678
679 /**
680 * postcopy_discard_send_init: Called at the start of each RAMBlock before
681 * asking to discard individual ranges.
682 *
683 * @ms: The current migration state.
684 * @offset: the bitmap offset of the named RAMBlock in the migration
685 * bitmap.
686 * @name: RAMBlock that discards will operate on.
687 *
688 * returns: a new PDS.
689 */
690 PostcopyDiscardState *postcopy_discard_send_init(MigrationState *ms,
691 unsigned long offset,
692 const char *name)
693 {
694 PostcopyDiscardState *res = g_malloc0(sizeof(PostcopyDiscardState));
695
696 if (res) {
697 res->ramblock_name = name;
698 res->offset = offset;
699 }
700
701 return res;
702 }
703
704 /**
705 * postcopy_discard_send_range: Called by the bitmap code for each chunk to
706 * discard. May send a discard message, may just leave it queued to
707 * be sent later.
708 *
709 * @ms: Current migration state.
710 * @pds: Structure initialised by postcopy_discard_send_init().
711 * @start,@length: a range of pages in the migration bitmap in the
712 * RAM block passed to postcopy_discard_send_init() (length=1 is one page)
713 */
714 void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState *pds,
715 unsigned long start, unsigned long length)
716 {
717 size_t tp_bits = qemu_target_page_bits();
718 /* Convert to byte offsets within the RAM block */
719 pds->start_list[pds->cur_entry] = (start - pds->offset) << tp_bits;
720 pds->length_list[pds->cur_entry] = length << tp_bits;
721 trace_postcopy_discard_send_range(pds->ramblock_name, start, length);
722 pds->cur_entry++;
723 pds->nsentwords++;
724
725 if (pds->cur_entry == MAX_DISCARDS_PER_COMMAND) {
726 /* Full set, ship it! */
727 qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
728 pds->ramblock_name,
729 pds->cur_entry,
730 pds->start_list,
731 pds->length_list);
732 pds->nsentcmds++;
733 pds->cur_entry = 0;
734 }
735 }
736
737 /**
738 * postcopy_discard_send_finish: Called at the end of each RAMBlock by the
739 * bitmap code. Sends any outstanding discard messages, frees the PDS
740 *
741 * @ms: Current migration state.
742 * @pds: Structure initialised by postcopy_discard_send_init().
743 */
744 void postcopy_discard_send_finish(MigrationState *ms, PostcopyDiscardState *pds)
745 {
746 /* Anything unsent? */
747 if (pds->cur_entry) {
748 qemu_savevm_send_postcopy_ram_discard(ms->to_dst_file,
749 pds->ramblock_name,
750 pds->cur_entry,
751 pds->start_list,
752 pds->length_list);
753 pds->nsentcmds++;
754 }
755
756 trace_postcopy_discard_send_finish(pds->ramblock_name, pds->nsentwords,
757 pds->nsentcmds);
758
759 g_free(pds);
760 }