aboutsummaryrefslogtreecommitdiff
path: root/hw/virtio/virtio-balloon.c
blob: ae31f0817acf261004e49472c255305b5ee4d6fa (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
/*
 * Virtio Balloon Device
 *
 * Copyright IBM, Corp. 2008
 * Copyright (C) 2011 Red Hat, Inc.
 * Copyright (C) 2011 Amit Shah <amit.shah@redhat.com>
 *
 * Authors:
 *  Anthony Liguori   <aliguori@us.ibm.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 */

#include "qemu/osdep.h"
#include "qemu/iov.h"
#include "qemu/module.h"
#include "qemu/timer.h"
#include "hw/virtio/virtio.h"
#include "hw/mem/pc-dimm.h"
#include "hw/qdev-properties.h"
#include "sysemu/balloon.h"
#include "hw/virtio/virtio-balloon.h"
#include "exec/address-spaces.h"
#include "qapi/error.h"
#include "qapi/qapi-events-misc.h"
#include "qapi/visitor.h"
#include "trace.h"
#include "qemu/error-report.h"
#include "migration/misc.h"

#include "hw/virtio/virtio-bus.h"
#include "hw/virtio/virtio-access.h"

#define BALLOON_PAGE_SIZE  (1 << VIRTIO_BALLOON_PFN_SHIFT)

typedef struct PartiallyBalloonedPage {
    ram_addr_t base_gpa;
    unsigned long *bitmap;
} PartiallyBalloonedPage;

static void virtio_balloon_pbp_free(PartiallyBalloonedPage *pbp)
{
    if (!pbp->bitmap) {
        return;
    }
    g_free(pbp->bitmap);
    pbp->bitmap = NULL;
}

static void virtio_balloon_pbp_alloc(PartiallyBalloonedPage *pbp,
                                     ram_addr_t base_gpa,
                                     long subpages)
{
    pbp->base_gpa = base_gpa;
    pbp->bitmap = bitmap_new(subpages);
}

static bool virtio_balloon_pbp_matches(PartiallyBalloonedPage *pbp,
                                       ram_addr_t base_gpa)
{
    return pbp->base_gpa == base_gpa;
}

static bool virtio_balloon_inhibited(void)
{
    /* Postcopy cannot deal with concurrent discards, so it's special. */
    return ram_block_discard_is_disabled() || migration_in_incoming_postcopy();
}

static void balloon_inflate_page(VirtIOBalloon *balloon,
                                 MemoryRegion *mr, hwaddr mr_offset,
                                 PartiallyBalloonedPage *pbp)
{
    void *addr = memory_region_get_ram_ptr(mr) + mr_offset;
    ram_addr_t rb_offset, rb_aligned_offset, base_gpa;
    RAMBlock *rb;
    size_t rb_page_size;
    int subpages;

    /* XXX is there a better way to get to the RAMBlock than via a
     * host address? */
    rb = qemu_ram_block_from_host(addr, false, &rb_offset);
    rb_page_size = qemu_ram_pagesize(rb);

    if (rb_page_size == BALLOON_PAGE_SIZE) {
        /* Easy case */

        ram_block_discard_range(rb, rb_offset, rb_page_size);
        /* We ignore errors from ram_block_discard_range(), because it
         * has already reported them, and failing to discard a balloon
         * page is not fatal */
        return;
    }

    /* Hard case
     *
     * We've put a piece of a larger host page into the balloon - we
     * need to keep track until we have a whole host page to
     * discard
     */
    warn_report_once(
"Balloon used with backing page size > 4kiB, this may not be reliable");

    rb_aligned_offset = QEMU_ALIGN_DOWN(rb_offset, rb_page_size);
    subpages = rb_page_size / BALLOON_PAGE_SIZE;
    base_gpa = memory_region_get_ram_addr(mr) + mr_offset -
               (rb_offset - rb_aligned_offset);

    if (pbp->bitmap && !virtio_balloon_pbp_matches(pbp, base_gpa)) {
        /* We've partially ballooned part of a host page, but now
         * we're trying to balloon part of a different one.  Too hard,
         * give up on the old partial page */
        virtio_balloon_pbp_free(pbp);
    }

    if (!pbp->bitmap) {
        virtio_balloon_pbp_alloc(pbp, base_gpa, subpages);
    }

    set_bit((rb_offset - rb_aligned_offset) / BALLOON_PAGE_SIZE,
            pbp->bitmap);

    if (bitmap_full(pbp->bitmap, subpages)) {
        /* We've accumulated a full host page, we can actually discard
         * it now */

        ram_block_discard_range(rb, rb_aligned_offset, rb_page_size);
        /* We ignore errors from ram_block_discard_range(), because it
         * has already reported them, and failing to discard a balloon
         * page is not fatal */
        virtio_balloon_pbp_free(pbp);
    }
}

static void balloon_deflate_page(VirtIOBalloon *balloon,
                                 MemoryRegion *mr, hwaddr mr_offset)
{
    void *addr = memory_region_get_ram_ptr(mr) + mr_offset;
    ram_addr_t rb_offset;
    RAMBlock *rb;
    size_t rb_page_size;
    void *host_addr;
    int ret;

    /* XXX is there a better way to get to the RAMBlock than via a
     * host address? */
    rb = qemu_ram_block_from_host(addr, false, &rb_offset);
    rb_page_size = qemu_ram_pagesize(rb);

    host_addr = (void *)((uintptr_t)addr & ~(rb_page_size - 1));

    /* When a page is deflated, we hint the whole host page it lives
     * on, since we can't do anything smaller */
    ret = qemu_madvise(host_addr, rb_page_size, QEMU_MADV_WILLNEED);
    if (ret != 0) {
        warn_report("Couldn't MADV_WILLNEED on balloon deflate: %s",
                    strerror(errno));
        /* Otherwise ignore, failing to page hint shouldn't be fatal */
    }
}

static const char *balloon_stat_names[] = {
   [VIRTIO_BALLOON_S_SWAP_IN] = "stat-swap-in",
   [VIRTIO_BALLOON_S_SWAP_OUT] = "stat-swap-out",
   [VIRTIO_BALLOON_S_MAJFLT] = "stat-major-faults",
   [VIRTIO_BALLOON_S_MINFLT] = "stat-minor-faults",
   [VIRTIO_BALLOON_S_MEMFREE] = "stat-free-memory",
   [VIRTIO_BALLOON_S_MEMTOT] = "stat-total-memory",
   [VIRTIO_BALLOON_S_AVAIL] = "stat-available-memory",
   [VIRTIO_BALLOON_S_CACHES] = "stat-disk-caches",
   [VIRTIO_BALLOON_S_HTLB_PGALLOC] = "stat-htlb-pgalloc",
   [VIRTIO_BALLOON_S_HTLB_PGFAIL] = "stat-htlb-pgfail",
   [VIRTIO_BALLOON_S_NR] = NULL
};

/*
 * reset_stats - Mark all items in the stats array as unset
 *
 * This function needs to be called at device initialization and before
 * updating to a set of newly-generated stats.  This will ensure that no
 * stale values stick around in case the guest reports a subset of the supported
 * statistics.
 */
static inline void reset_stats(VirtIOBalloon *dev)
{
    int i;
    for (i = 0; i < VIRTIO_BALLOON_S_NR; dev->stats[i++] = -1);
}

static bool balloon_stats_supported(const VirtIOBalloon *s)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(s);
    return virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_STATS_VQ);
}

static bool balloon_stats_enabled(const VirtIOBalloon *s)
{
    return s->stats_poll_interval > 0;
}

static void balloon_stats_destroy_timer(VirtIOBalloon *s)
{
    if (balloon_stats_enabled(s)) {
        timer_del(s->stats_timer);
        timer_free(s->stats_timer);
        s->stats_timer = NULL;
        s->stats_poll_interval = 0;
    }
}

static void balloon_stats_change_timer(VirtIOBalloon *s, int64_t secs)
{
    timer_mod(s->stats_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + secs * 1000);
}

static void balloon_stats_poll_cb(void *opaque)
{
    VirtIOBalloon *s = opaque;
    VirtIODevice *vdev = VIRTIO_DEVICE(s);

    if (s->stats_vq_elem == NULL || !balloon_stats_supported(s)) {
        /* re-schedule */
        balloon_stats_change_timer(s, s->stats_poll_interval);
        return;
    }

    virtqueue_push(s->svq, s->stats_vq_elem, s->stats_vq_offset);
    virtio_notify(vdev, s->svq);
    g_free(s->stats_vq_elem);
    s->stats_vq_elem = NULL;
}

static void balloon_stats_get_all(Object *obj, Visitor *v, const char *name,
                                  void *opaque, Error **errp)
{
    Error *err = NULL;
    VirtIOBalloon *s = opaque;
    int i;

    visit_start_struct(v, name, NULL, 0, &err);
    if (err) {
        goto out;
    }
    visit_type_int(v, "last-update", &s->stats_last_update, &err);
    if (err) {
        goto out_end;
    }

    visit_start_struct(v, "stats", NULL, 0, &err);
    if (err) {
        goto out_end;
    }
    for (i = 0; i < VIRTIO_BALLOON_S_NR; i++) {
        visit_type_uint64(v, balloon_stat_names[i], &s->stats[i], &err);
        if (err) {
            goto out_nested;
        }
    }
    visit_check_struct(v, &err);
out_nested:
    visit_end_struct(v, NULL);

    if (!err) {
        visit_check_struct(v, &err);
    }
out_end:
    visit_end_struct(v, NULL);
out:
    error_propagate(errp, err);
}

static void balloon_stats_get_poll_interval(Object *obj, Visitor *v,
                                            const char *name, void *opaque,
                                            Error **errp)
{
    VirtIOBalloon *s = opaque;
    visit_type_int(v, name, &s->stats_poll_interval, errp);
}

static void balloon_stats_set_poll_interval(Object *obj, Visitor *v,
                                            const char *name, void *opaque,
                                            Error **errp)
{
    VirtIOBalloon *s = opaque;
    Error *local_err = NULL;
    int64_t value;

    visit_type_int(v, name, &value, &local_err);
    if (local_err) {
        error_propagate(errp, local_err);
        return;
    }

    if (value < 0) {
        error_setg(errp, "timer value must be greater than zero");
        return;
    }

    if (value > UINT32_MAX) {
        error_setg(errp, "timer value is too big");
        return;
    }

    if (value == s->stats_poll_interval) {
        return;
    }

    if (value == 0) {
        /* timer=0 disables the timer */
        balloon_stats_destroy_timer(s);
        return;
    }

    if (balloon_stats_enabled(s)) {
        /* timer interval change */
        s->stats_poll_interval = value;
        balloon_stats_change_timer(s, value);
        return;
    }

    /* create a new timer */
    g_assert(s->stats_timer == NULL);
    s->stats_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL, balloon_stats_poll_cb, s);
    s->stats_poll_interval = value;
    balloon_stats_change_timer(s, 0);
}

static void virtio_balloon_handle_report(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
    VirtQueueElement *elem;

    while ((elem = virtqueue_pop(vq, sizeof(VirtQueueElement)))) {
        unsigned int i;

        /*
         * When we discard the page it has the effect of removing the page
         * from the hypervisor itself and causing it to be zeroed when it
         * is returned to us. So we must not discard the page if it is
         * accessible by another device or process, or if the guest is
         * expecting it to retain a non-zero value.
         */
        if (virtio_balloon_inhibited() || dev->poison_val) {
            goto skip_element;
        }

        for (i = 0; i < elem->in_num; i++) {
            void *addr = elem->in_sg[i].iov_base;
            size_t size = elem->in_sg[i].iov_len;
            ram_addr_t ram_offset;
            RAMBlock *rb;

            /*
             * There is no need to check the memory section to see if
             * it is ram/readonly/romd like there is for handle_output
             * below. If the region is not meant to be written to then
             * address_space_map will have allocated a bounce buffer
             * and it will be freed in address_space_unmap and trigger
             * and unassigned_mem_write before failing to copy over the
             * buffer. If more than one bad descriptor is provided it
             * will return NULL after the first bounce buffer and fail
             * to map any resources.
             */
            rb = qemu_ram_block_from_host(addr, false, &ram_offset);
            if (!rb) {
                trace_virtio_balloon_bad_addr(elem->in_addr[i]);
                continue;
            }

            /*
             * For now we will simply ignore unaligned memory regions, or
             * regions that overrun the end of the RAMBlock.
             */
            if (!QEMU_IS_ALIGNED(ram_offset | size, qemu_ram_pagesize(rb)) ||
                (ram_offset + size) > qemu_ram_get_used_length(rb)) {
                continue;
            }

            ram_block_discard_range(rb, ram_offset, size);
        }

skip_element:
        virtqueue_push(vq, elem, 0);
        virtio_notify(vdev, vq);
        g_free(elem);
    }
}

static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
    VirtQueueElement *elem;
    MemoryRegionSection section;

    for (;;) {
        PartiallyBalloonedPage pbp = {};
        size_t offset = 0;
        uint32_t pfn;

        elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
        if (!elem) {
            break;
        }

        while (iov_to_buf(elem->out_sg, elem->out_num, offset, &pfn, 4) == 4) {
            unsigned int p = virtio_ldl_p(vdev, &pfn);
            hwaddr pa;

            pa = (hwaddr) p << VIRTIO_BALLOON_PFN_SHIFT;
            offset += 4;

            section = memory_region_find(get_system_memory(), pa,
                                         BALLOON_PAGE_SIZE);
            if (!section.mr) {
                trace_virtio_balloon_bad_addr(pa);
                continue;
            }
            if (!memory_region_is_ram(section.mr) ||
                memory_region_is_rom(section.mr) ||
                memory_region_is_romd(section.mr)) {
                trace_virtio_balloon_bad_addr(pa);
                memory_region_unref(section.mr);
                continue;
            }

            trace_virtio_balloon_handle_output(memory_region_name(section.mr),
                                               pa);
            if (!virtio_balloon_inhibited()) {
                if (vq == s->ivq) {
                    balloon_inflate_page(s, section.mr,
                                         section.offset_within_region, &pbp);
                } else if (vq == s->dvq) {
                    balloon_deflate_page(s, section.mr, section.offset_within_region);
                } else {
                    g_assert_not_reached();
                }
            }
            memory_region_unref(section.mr);
        }

        virtqueue_push(vq, elem, offset);
        virtio_notify(vdev, vq);
        g_free(elem);
        virtio_balloon_pbp_free(&pbp);
    }
}

static void virtio_balloon_receive_stats(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
    VirtQueueElement *elem;
    VirtIOBalloonStat stat;
    size_t offset = 0;
    qemu_timeval tv;

    elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
    if (!elem) {
        goto out;
    }

    if (s->stats_vq_elem != NULL) {
        /* This should never happen if the driver follows the spec. */
        virtqueue_push(vq, s->stats_vq_elem, 0);
        virtio_notify(vdev, vq);
        g_free(s->stats_vq_elem);
    }

    s->stats_vq_elem = elem;

    /* Initialize the stats to get rid of any stale values.  This is only
     * needed to handle the case where a guest supports fewer stats than it
     * used to (ie. it has booted into an old kernel).
     */
    reset_stats(s);

    while (iov_to_buf(elem->out_sg, elem->out_num, offset, &stat, sizeof(stat))
           == sizeof(stat)) {
        uint16_t tag = virtio_tswap16(vdev, stat.tag);
        uint64_t val = virtio_tswap64(vdev, stat.val);

        offset += sizeof(stat);
        if (tag < VIRTIO_BALLOON_S_NR)
            s->stats[tag] = val;
    }
    s->stats_vq_offset = offset;

    if (qemu_gettimeofday(&tv) < 0) {
        warn_report("%s: failed to get time of day", __func__);
        goto out;
    }

    s->stats_last_update = tv.tv_sec;

out:
    if (balloon_stats_enabled(s)) {
        balloon_stats_change_timer(s, s->stats_poll_interval);
    }
}

static void virtio_balloon_handle_free_page_vq(VirtIODevice *vdev,
                                               VirtQueue *vq)
{
    VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
    qemu_bh_schedule(s->free_page_bh);
}

static bool get_free_page_hints(VirtIOBalloon *dev)
{
    VirtQueueElement *elem;
    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    VirtQueue *vq = dev->free_page_vq;
    bool ret = true;

    while (dev->block_iothread) {
        qemu_cond_wait(&dev->free_page_cond, &dev->free_page_lock);
    }

    elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
    if (!elem) {
        return false;
    }

    if (elem->out_num) {
        uint32_t id;
        size_t size = iov_to_buf(elem->out_sg, elem->out_num, 0,
                                 &id, sizeof(id));

        virtio_tswap32s(vdev, &id);
        if (unlikely(size != sizeof(id))) {
            virtio_error(vdev, "received an incorrect cmd id");
            ret = false;
            goto out;
        }
        if (id == dev->free_page_report_cmd_id) {
            dev->free_page_report_status = FREE_PAGE_REPORT_S_START;
        } else {
            /*
             * Stop the optimization only when it has started. This
             * avoids a stale stop sign for the previous command.
             */
            if (dev->free_page_report_status == FREE_PAGE_REPORT_S_START) {
                dev->free_page_report_status = FREE_PAGE_REPORT_S_STOP;
            }
        }
    }

    if (elem->in_num) {
        if (dev->free_page_report_status == FREE_PAGE_REPORT_S_START) {
            qemu_guest_free_page_hint(elem->in_sg[0].iov_base,
                                      elem->in_sg[0].iov_len);
        }
    }

out:
    virtqueue_push(vq, elem, 1);
    g_free(elem);
    return ret;
}

static void virtio_ballloon_get_free_page_hints(void *opaque)
{
    VirtIOBalloon *dev = opaque;
    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    VirtQueue *vq = dev->free_page_vq;
    bool continue_to_get_hints;

    do {
        qemu_mutex_lock(&dev->free_page_lock);
        virtio_queue_set_notification(vq, 0);
        continue_to_get_hints = get_free_page_hints(dev);
        qemu_mutex_unlock(&dev->free_page_lock);
        virtio_notify(vdev, vq);
      /*
       * Start to poll the vq once the reporting started. Otherwise, continue
       * only when there are entries on the vq, which need to be given back.
       */
    } while (continue_to_get_hints ||
             dev->free_page_report_status == FREE_PAGE_REPORT_S_START);
    virtio_queue_set_notification(vq, 1);
}

static bool virtio_balloon_free_page_support(void *opaque)
{
    VirtIOBalloon *s = opaque;
    VirtIODevice *vdev = VIRTIO_DEVICE(s);

    return virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT);
}

static void virtio_balloon_free_page_start(VirtIOBalloon *s)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(s);

    /* For the stop and copy phase, we don't need to start the optimization */
    if (!vdev->vm_running) {
        return;
    }

    if (s->free_page_report_cmd_id == UINT_MAX) {
        s->free_page_report_cmd_id =
                       VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN;
    } else {
        s->free_page_report_cmd_id++;
    }

    s->free_page_report_status = FREE_PAGE_REPORT_S_REQUESTED;
    virtio_notify_config(vdev);
}

static void virtio_balloon_free_page_stop(VirtIOBalloon *s)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(s);

    if (s->free_page_report_status != FREE_PAGE_REPORT_S_STOP) {
        /*
         * The lock also guarantees us that the
         * virtio_ballloon_get_free_page_hints exits after the
         * free_page_report_status is set to S_STOP.
         */
        qemu_mutex_lock(&s->free_page_lock);
        /*
         * The guest hasn't done the reporting, so host sends a notification
         * to the guest to actively stop the reporting.
         */
        s->free_page_report_status = FREE_PAGE_REPORT_S_STOP;
        qemu_mutex_unlock(&s->free_page_lock);
        virtio_notify_config(vdev);
    }
}

static void virtio_balloon_free_page_done(VirtIOBalloon *s)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(s);

    if (s->free_page_report_status != FREE_PAGE_REPORT_S_DONE) {
        /* See virtio_balloon_free_page_stop() */
        qemu_mutex_lock(&s->free_page_lock);
        s->free_page_report_status = FREE_PAGE_REPORT_S_DONE;
        qemu_mutex_unlock(&s->free_page_lock);
        virtio_notify_config(vdev);
    }
}

static int
virtio_balloon_free_page_report_notify(NotifierWithReturn *n, void *data)
{
    VirtIOBalloon *dev = container_of(n, VirtIOBalloon,
                                      free_page_report_notify);
    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    PrecopyNotifyData *pnd = data;

    if (!virtio_balloon_free_page_support(dev)) {
        /*
         * This is an optimization provided to migration, so just return 0 to
         * have the normal migration process not affected when this feature is
         * not supported.
         */
        return 0;
    }

    switch (pnd->reason) {
    case PRECOPY_NOTIFY_SETUP:
        precopy_enable_free_page_optimization();
        break;
    case PRECOPY_NOTIFY_BEFORE_BITMAP_SYNC:
        virtio_balloon_free_page_stop(dev);
        break;
    case PRECOPY_NOTIFY_AFTER_BITMAP_SYNC:
        if (vdev->vm_running) {
            virtio_balloon_free_page_start(dev);
            break;
        }
        /*
         * Set S_DONE before migrating the vmstate, so the guest will reuse
         * all hinted pages once running on the destination. Fall through.
         */
    case PRECOPY_NOTIFY_CLEANUP:
        /*
         * Especially, if something goes wrong during precopy or if migration
         * is canceled, we have to properly communicate S_DONE to the VM.
         */
        virtio_balloon_free_page_done(dev);
        break;
    case PRECOPY_NOTIFY_COMPLETE:
        break;
    default:
        virtio_error(vdev, "%s: %d reason unknown", __func__, pnd->reason);
    }

    return 0;
}

static size_t virtio_balloon_config_size(VirtIOBalloon *s)
{
    uint64_t features = s->host_features;

    if (s->qemu_4_0_config_size) {
        return sizeof(struct virtio_balloon_config);
    }
    if (virtio_has_feature(features, VIRTIO_BALLOON_F_PAGE_POISON)) {
        return sizeof(struct virtio_balloon_config);
    }
    if (virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
        return offsetof(struct virtio_balloon_config, poison_val);
    }
    return offsetof(struct virtio_balloon_config, free_page_report_cmd_id);
}

static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
{
    VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
    struct virtio_balloon_config config = {};

    config.num_pages = cpu_to_le32(dev->num_pages);
    config.actual = cpu_to_le32(dev->actual);
    config.poison_val = cpu_to_le32(dev->poison_val);

    if (dev->free_page_report_status == FREE_PAGE_REPORT_S_REQUESTED) {
        config.free_page_report_cmd_id =
                       cpu_to_le32(dev->free_page_report_cmd_id);
    } else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_STOP) {
        config.free_page_report_cmd_id =
                       cpu_to_le32(VIRTIO_BALLOON_CMD_ID_STOP);
    } else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_DONE) {
        config.free_page_report_cmd_id =
                       cpu_to_le32(VIRTIO_BALLOON_CMD_ID_DONE);
    }

    trace_virtio_balloon_get_config(config.num_pages, config.actual);
    memcpy(config_data, &config, virtio_balloon_config_size(dev));
}

static int build_dimm_list(Object *obj, void *opaque)
{
    GSList **list = opaque;

    if (object_dynamic_cast(obj, TYPE_PC_DIMM)) {
        DeviceState *dev = DEVICE(obj);
        if (dev->realized) { /* only realized DIMMs matter */
            *list = g_slist_prepend(*list, dev);
        }
    }

    object_child_foreach(obj, build_dimm_list, opaque);
    return 0;
}

static ram_addr_t get_current_ram_size(void)
{
    GSList *list = NULL, *item;
    ram_addr_t size = ram_size;

    build_dimm_list(qdev_get_machine(), &list);
    for (item = list; item; item = g_slist_next(item)) {
        Object *obj = OBJECT(item->data);
        if (!strcmp(object_get_typename(obj), TYPE_PC_DIMM)) {
            size += object_property_get_int(obj, PC_DIMM_SIZE_PROP,
                                            &error_abort);
        }
    }
    g_slist_free(list);

    return size;
}

static bool virtio_balloon_page_poison_support(void *opaque)
{
    VirtIOBalloon *s = opaque;
    VirtIODevice *vdev = VIRTIO_DEVICE(s);

    return virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
}

static void virtio_balloon_set_config(VirtIODevice *vdev,
                                      const uint8_t *config_data)
{
    VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
    struct virtio_balloon_config config;
    uint32_t oldactual = dev->actual;
    ram_addr_t vm_ram_size = get_current_ram_size();

    memcpy(&config, config_data, virtio_balloon_config_size(dev));
    dev->actual = le32_to_cpu(config.actual);
    if (dev->actual != oldactual) {
        qapi_event_send_balloon_change(vm_ram_size -
                        ((ram_addr_t) dev->actual << VIRTIO_BALLOON_PFN_SHIFT));
    }
    dev->poison_val = 0;
    if (virtio_balloon_page_poison_support(dev)) {
        dev->poison_val = le32_to_cpu(config.poison_val);
    }
    trace_virtio_balloon_set_config(dev->actual, oldactual);
}

static uint64_t virtio_balloon_get_features(VirtIODevice *vdev, uint64_t f,
                                            Error **errp)
{
    VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
    f |= dev->host_features;
    virtio_add_feature(&f, VIRTIO_BALLOON_F_STATS_VQ);

    return f;
}

static void virtio_balloon_stat(void *opaque, BalloonInfo *info)
{
    VirtIOBalloon *dev = opaque;
    info->actual = get_current_ram_size() - ((uint64_t) dev->actual <<
                                             VIRTIO_BALLOON_PFN_SHIFT);
}

static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
{
    VirtIOBalloon *dev = VIRTIO_BALLOON(opaque);
    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    ram_addr_t vm_ram_size = get_current_ram_size();

    if (target > vm_ram_size) {
        target = vm_ram_size;
    }
    if (target) {
        dev->num_pages = (vm_ram_size - target) >> VIRTIO_BALLOON_PFN_SHIFT;
        virtio_notify_config(vdev);
    }
    trace_virtio_balloon_to_target(target, dev->num_pages);
}

static int virtio_balloon_post_load_device(void *opaque, int version_id)
{
    VirtIOBalloon *s = VIRTIO_BALLOON(opaque);

    if (balloon_stats_enabled(s)) {
        balloon_stats_change_timer(s, s->stats_poll_interval);
    }
    return 0;
}

static const VMStateDescription vmstate_virtio_balloon_free_page_report = {
    .name = "virtio-balloon-device/free-page-report",
    .version_id = 1,
    .minimum_version_id = 1,
    .needed = virtio_balloon_free_page_support,
    .fields = (VMStateField[]) {
        VMSTATE_UINT32(free_page_report_cmd_id, VirtIOBalloon),
        VMSTATE_UINT32(free_page_report_status, VirtIOBalloon),
        VMSTATE_END_OF_LIST()
    }
};

static const VMStateDescription vmstate_virtio_balloon_page_poison = {
    .name = "vitio-balloon-device/page-poison",
    .version_id = 1,
    .minimum_version_id = 1,
    .needed = virtio_balloon_page_poison_support,
    .fields = (VMStateField[]) {
        VMSTATE_UINT32(poison_val, VirtIOBalloon),
        VMSTATE_END_OF_LIST()
    }
};

static const VMStateDescription vmstate_virtio_balloon_device = {
    .name = "virtio-balloon-device",
    .version_id = 1,
    .minimum_version_id = 1,
    .post_load = virtio_balloon_post_load_device,
    .fields = (VMStateField[]) {
        VMSTATE_UINT32(num_pages, VirtIOBalloon),
        VMSTATE_UINT32(actual, VirtIOBalloon),
        VMSTATE_END_OF_LIST()
    },
    .subsections = (const VMStateDescription * []) {
        &vmstate_virtio_balloon_free_page_report,
        &vmstate_virtio_balloon_page_poison,
        NULL
    }
};

static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    VirtIOBalloon *s = VIRTIO_BALLOON(dev);
    int ret;

    virtio_init(vdev, "virtio-balloon", VIRTIO_ID_BALLOON,
                virtio_balloon_config_size(s));

    ret = qemu_add_balloon_handler(virtio_balloon_to_target,
                                   virtio_balloon_stat, s);

    if (ret < 0) {
        error_setg(errp, "Only one balloon device is supported");
        virtio_cleanup(vdev);
        return;
    }

    if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_FREE_PAGE_HINT) &&
        !s->iothread) {
        error_setg(errp, "'free-page-hint' requires 'iothread' to be set");
        virtio_cleanup(vdev);
        return;
    }

    s->ivq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
    s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
    s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);

    if (virtio_has_feature(s->host_features,
                           VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
        s->free_page_vq = virtio_add_queue(vdev, VIRTQUEUE_MAX_SIZE,
                                           virtio_balloon_handle_free_page_vq);
        precopy_add_notifier(&s->free_page_report_notify);

        object_ref(OBJECT(s->iothread));
        s->free_page_bh = aio_bh_new(iothread_get_aio_context(s->iothread),
                                     virtio_ballloon_get_free_page_hints, s);
    }

    if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_REPORTING)) {
        s->reporting_vq = virtio_add_queue(vdev, 32,
                                           virtio_balloon_handle_report);
    }

    reset_stats(s);
}

static void virtio_balloon_device_unrealize(DeviceState *dev)
{
    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
    VirtIOBalloon *s = VIRTIO_BALLOON(dev);

    if (s->free_page_bh) {
        qemu_bh_delete(s->free_page_bh);
        object_unref(OBJECT(s->iothread));
        virtio_balloon_free_page_stop(s);
        precopy_remove_notifier(&s->free_page_report_notify);
    }
    balloon_stats_destroy_timer(s);
    qemu_remove_balloon_handler(s);

    virtio_delete_queue(s->ivq);
    virtio_delete_queue(s->dvq);
    virtio_delete_queue(s->svq);
    if (s->free_page_vq) {
        virtio_delete_queue(s->free_page_vq);
    }
    if (s->reporting_vq) {
        virtio_delete_queue(s->reporting_vq);
    }
    virtio_cleanup(vdev);
}

static void virtio_balloon_device_reset(VirtIODevice *vdev)
{
    VirtIOBalloon *s = VIRTIO_BALLOON(vdev);

    if (virtio_balloon_free_page_support(s)) {
        virtio_balloon_free_page_stop(s);
    }

    if (s->stats_vq_elem != NULL) {
        virtqueue_unpop(s->svq, s->stats_vq_elem, 0);
        g_free(s->stats_vq_elem);
        s->stats_vq_elem = NULL;
    }

    s->poison_val = 0;
}

static void virtio_balloon_set_status(VirtIODevice *vdev, uint8_t status)
{
    VirtIOBalloon *s = VIRTIO_BALLOON(vdev);

    if (!s->stats_vq_elem && vdev->vm_running &&
        (status & VIRTIO_CONFIG_S_DRIVER_OK) && virtqueue_rewind(s->svq, 1)) {
        /* poll stats queue for the element we have discarded when the VM
         * was stopped */
        virtio_balloon_receive_stats(vdev, s->svq);
    }

    if (virtio_balloon_free_page_support(s)) {
        /*
         * The VM is woken up and the iothread was blocked, so signal it to
         * continue.
         */
        if (vdev->vm_running && s->block_iothread) {
            qemu_mutex_lock(&s->free_page_lock);
            s->block_iothread = false;
            qemu_cond_signal(&s->free_page_cond);
            qemu_mutex_unlock(&s->free_page_lock);
        }

        /* The VM is stopped, block the iothread. */
        if (!vdev->vm_running) {
            qemu_mutex_lock(&s->free_page_lock);
            s->block_iothread = true;
            qemu_mutex_unlock(&s->free_page_lock);
        }
    }
}

static void virtio_balloon_instance_init(Object *obj)
{
    VirtIOBalloon *s = VIRTIO_BALLOON(obj);

    qemu_mutex_init(&s->free_page_lock);
    qemu_cond_init(&s->free_page_cond);
    s->free_page_report_cmd_id = VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN;
    s->free_page_report_notify.notify = virtio_balloon_free_page_report_notify;

    object_property_add(obj, "guest-stats", "guest statistics",
                        balloon_stats_get_all, NULL, NULL, s);

    object_property_add(obj, "guest-stats-polling-interval", "int",
                        balloon_stats_get_poll_interval,
                        balloon_stats_set_poll_interval,
                        NULL, s);
}

static const VMStateDescription vmstate_virtio_balloon = {
    .name = "virtio-balloon",
    .minimum_version_id = 1,
    .version_id = 1,
    .fields = (VMStateField[]) {
        VMSTATE_VIRTIO_DEVICE,
        VMSTATE_END_OF_LIST()
    },
};

static Property virtio_balloon_properties[] = {
    DEFINE_PROP_BIT("deflate-on-oom", VirtIOBalloon, host_features,
                    VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false),
    DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features,
                    VIRTIO_BALLOON_F_FREE_PAGE_HINT, false),
    DEFINE_PROP_BIT("page-poison", VirtIOBalloon, host_features,
                    VIRTIO_BALLOON_F_PAGE_POISON, true),
    DEFINE_PROP_BIT("free-page-reporting", VirtIOBalloon, host_features,
                    VIRTIO_BALLOON_F_REPORTING, false),
    /* QEMU 4.0 accidentally changed the config size even when free-page-hint
     * is disabled, resulting in QEMU 3.1 migration incompatibility.  This
     * property retains this quirk for QEMU 4.1 machine types.
     */
    DEFINE_PROP_BOOL("qemu-4-0-config-size", VirtIOBalloon,
                     qemu_4_0_config_size, false),
    DEFINE_PROP_LINK("iothread", VirtIOBalloon, iothread, TYPE_IOTHREAD,
                     IOThread *),
    DEFINE_PROP_END_OF_LIST(),
};

static void virtio_balloon_class_init(ObjectClass *klass, void *data)
{
    DeviceClass *dc = DEVICE_CLASS(klass);
    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);

    device_class_set_props(dc, virtio_balloon_properties);
    dc->vmsd = &vmstate_virtio_balloon;
    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
    vdc->realize = virtio_balloon_device_realize;
    vdc->unrealize = virtio_balloon_device_unrealize;
    vdc->reset = virtio_balloon_device_reset;
    vdc->get_config = virtio_balloon_get_config;
    vdc->set_config = virtio_balloon_set_config;
    vdc->get_features = virtio_balloon_get_features;
    vdc->set_status = virtio_balloon_set_status;
    vdc->vmsd = &vmstate_virtio_balloon_device;
}

static const TypeInfo virtio_balloon_info = {
    .name = TYPE_VIRTIO_BALLOON,
    .parent = TYPE_VIRTIO_DEVICE,
    .instance_size = sizeof(VirtIOBalloon),
    .instance_init = virtio_balloon_instance_init,
    .class_init = virtio_balloon_class_init,
};

static void virtio_register_types(void)
{
    type_register_static(&virtio_balloon_info);
}

type_init(virtio_register_types)