This file is indexed.

/usr/bin/kvm_stat is in linux-tools-host 4.15.0-23.25.

This file is owned by root:root, with mode 0o755.

The actual contents of the file can be viewed below.

   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
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
#!/usr/bin/python
#
# top-like utility for displaying kvm statistics
#
# Copyright 2006-2008 Qumranet Technologies
# Copyright 2008-2011 Red Hat, Inc.
#
# Authors:
#  Avi Kivity <avi@redhat.com>
#
# This work is licensed under the terms of the GNU GPL, version 2.  See
# the COPYING file in the top-level directory.
"""The kvm_stat module outputs statistics about running KVM VMs

Three different ways of output formatting are available:
- as a top-like text ui
- in a key -> value format
- in an all keys, all values format

The data is sampled from the KVM's debugfs entries and its perf events.
"""
from __future__ import print_function

import curses
import sys
import locale
import os
import time
import optparse
import ctypes
import fcntl
import resource
import struct
import re
import subprocess
from collections import defaultdict, namedtuple

VMX_EXIT_REASONS = {
    'EXCEPTION_NMI':        0,
    'EXTERNAL_INTERRUPT':   1,
    'TRIPLE_FAULT':         2,
    'PENDING_INTERRUPT':    7,
    'NMI_WINDOW':           8,
    'TASK_SWITCH':          9,
    'CPUID':                10,
    'HLT':                  12,
    'INVLPG':               14,
    'RDPMC':                15,
    'RDTSC':                16,
    'VMCALL':               18,
    'VMCLEAR':              19,
    'VMLAUNCH':             20,
    'VMPTRLD':              21,
    'VMPTRST':              22,
    'VMREAD':               23,
    'VMRESUME':             24,
    'VMWRITE':              25,
    'VMOFF':                26,
    'VMON':                 27,
    'CR_ACCESS':            28,
    'DR_ACCESS':            29,
    'IO_INSTRUCTION':       30,
    'MSR_READ':             31,
    'MSR_WRITE':            32,
    'INVALID_STATE':        33,
    'MWAIT_INSTRUCTION':    36,
    'MONITOR_INSTRUCTION':  39,
    'PAUSE_INSTRUCTION':    40,
    'MCE_DURING_VMENTRY':   41,
    'TPR_BELOW_THRESHOLD':  43,
    'APIC_ACCESS':          44,
    'EPT_VIOLATION':        48,
    'EPT_MISCONFIG':        49,
    'WBINVD':               54,
    'XSETBV':               55,
    'APIC_WRITE':           56,
    'INVPCID':              58,
}

SVM_EXIT_REASONS = {
    'READ_CR0':       0x000,
    'READ_CR3':       0x003,
    'READ_CR4':       0x004,
    'READ_CR8':       0x008,
    'WRITE_CR0':      0x010,
    'WRITE_CR3':      0x013,
    'WRITE_CR4':      0x014,
    'WRITE_CR8':      0x018,
    'READ_DR0':       0x020,
    'READ_DR1':       0x021,
    'READ_DR2':       0x022,
    'READ_DR3':       0x023,
    'READ_DR4':       0x024,
    'READ_DR5':       0x025,
    'READ_DR6':       0x026,
    'READ_DR7':       0x027,
    'WRITE_DR0':      0x030,
    'WRITE_DR1':      0x031,
    'WRITE_DR2':      0x032,
    'WRITE_DR3':      0x033,
    'WRITE_DR4':      0x034,
    'WRITE_DR5':      0x035,
    'WRITE_DR6':      0x036,
    'WRITE_DR7':      0x037,
    'EXCP_BASE':      0x040,
    'INTR':           0x060,
    'NMI':            0x061,
    'SMI':            0x062,
    'INIT':           0x063,
    'VINTR':          0x064,
    'CR0_SEL_WRITE':  0x065,
    'IDTR_READ':      0x066,
    'GDTR_READ':      0x067,
    'LDTR_READ':      0x068,
    'TR_READ':        0x069,
    'IDTR_WRITE':     0x06a,
    'GDTR_WRITE':     0x06b,
    'LDTR_WRITE':     0x06c,
    'TR_WRITE':       0x06d,
    'RDTSC':          0x06e,
    'RDPMC':          0x06f,
    'PUSHF':          0x070,
    'POPF':           0x071,
    'CPUID':          0x072,
    'RSM':            0x073,
    'IRET':           0x074,
    'SWINT':          0x075,
    'INVD':           0x076,
    'PAUSE':          0x077,
    'HLT':            0x078,
    'INVLPG':         0x079,
    'INVLPGA':        0x07a,
    'IOIO':           0x07b,
    'MSR':            0x07c,
    'TASK_SWITCH':    0x07d,
    'FERR_FREEZE':    0x07e,
    'SHUTDOWN':       0x07f,
    'VMRUN':          0x080,
    'VMMCALL':        0x081,
    'VMLOAD':         0x082,
    'VMSAVE':         0x083,
    'STGI':           0x084,
    'CLGI':           0x085,
    'SKINIT':         0x086,
    'RDTSCP':         0x087,
    'ICEBP':          0x088,
    'WBINVD':         0x089,
    'MONITOR':        0x08a,
    'MWAIT':          0x08b,
    'MWAIT_COND':     0x08c,
    'XSETBV':         0x08d,
    'NPF':            0x400,
}

# EC definition of HSR (from arch/arm64/include/asm/kvm_arm.h)
AARCH64_EXIT_REASONS = {
    'UNKNOWN':      0x00,
    'WFI':          0x01,
    'CP15_32':      0x03,
    'CP15_64':      0x04,
    'CP14_MR':      0x05,
    'CP14_LS':      0x06,
    'FP_ASIMD':     0x07,
    'CP10_ID':      0x08,
    'CP14_64':      0x0C,
    'ILL_ISS':      0x0E,
    'SVC32':        0x11,
    'HVC32':        0x12,
    'SMC32':        0x13,
    'SVC64':        0x15,
    'HVC64':        0x16,
    'SMC64':        0x17,
    'SYS64':        0x18,
    'IABT':         0x20,
    'IABT_HYP':     0x21,
    'PC_ALIGN':     0x22,
    'DABT':         0x24,
    'DABT_HYP':     0x25,
    'SP_ALIGN':     0x26,
    'FP_EXC32':     0x28,
    'FP_EXC64':     0x2C,
    'SERROR':       0x2F,
    'BREAKPT':      0x30,
    'BREAKPT_HYP':  0x31,
    'SOFTSTP':      0x32,
    'SOFTSTP_HYP':  0x33,
    'WATCHPT':      0x34,
    'WATCHPT_HYP':  0x35,
    'BKPT32':       0x38,
    'VECTOR32':     0x3A,
    'BRK64':        0x3C,
}

# From include/uapi/linux/kvm.h, KVM_EXIT_xxx
USERSPACE_EXIT_REASONS = {
    'UNKNOWN':          0,
    'EXCEPTION':        1,
    'IO':               2,
    'HYPERCALL':        3,
    'DEBUG':            4,
    'HLT':              5,
    'MMIO':             6,
    'IRQ_WINDOW_OPEN':  7,
    'SHUTDOWN':         8,
    'FAIL_ENTRY':       9,
    'INTR':             10,
    'SET_TPR':          11,
    'TPR_ACCESS':       12,
    'S390_SIEIC':       13,
    'S390_RESET':       14,
    'DCR':              15,
    'NMI':              16,
    'INTERNAL_ERROR':   17,
    'OSI':              18,
    'PAPR_HCALL':       19,
    'S390_UCONTROL':    20,
    'WATCHDOG':         21,
    'S390_TSCH':        22,
    'EPR':              23,
    'SYSTEM_EVENT':     24,
}

IOCTL_NUMBERS = {
    'SET_FILTER':  0x40082406,
    'ENABLE':      0x00002400,
    'DISABLE':     0x00002401,
    'RESET':       0x00002403,
}

ENCODING = locale.getpreferredencoding(False)
TRACE_FILTER = re.compile(r'^[^\(]*$')


class Arch(object):
    """Encapsulates global architecture specific data.

    Contains the performance event open syscall and ioctl numbers, as
    well as the VM exit reasons for the architecture it runs on.

    """
    @staticmethod
    def get_arch():
        machine = os.uname()[4]

        if machine.startswith('ppc'):
            return ArchPPC()
        elif machine.startswith('aarch64'):
            return ArchA64()
        elif machine.startswith('s390'):
            return ArchS390()
        else:
            # X86_64
            for line in open('/proc/cpuinfo'):
                if not line.startswith('flags'):
                    continue

                flags = line.split()
                if 'vmx' in flags:
                    return ArchX86(VMX_EXIT_REASONS)
                if 'svm' in flags:
                    return ArchX86(SVM_EXIT_REASONS)
                return

    def tracepoint_is_child(self, field):
        if (TRACE_FILTER.match(field)):
            return None
        return field.split('(', 1)[0]


class ArchX86(Arch):
    def __init__(self, exit_reasons):
        self.sc_perf_evt_open = 298
        self.ioctl_numbers = IOCTL_NUMBERS
        self.exit_reasons = exit_reasons

    def debugfs_is_child(self, field):
        """ Returns name of parent if 'field' is a child, None otherwise """
        return None


class ArchPPC(Arch):
    def __init__(self):
        self.sc_perf_evt_open = 319
        self.ioctl_numbers = IOCTL_NUMBERS
        self.ioctl_numbers['ENABLE'] = 0x20002400
        self.ioctl_numbers['DISABLE'] = 0x20002401
        self.ioctl_numbers['RESET'] = 0x20002403

        # PPC comes in 32 and 64 bit and some generated ioctl
        # numbers depend on the wordsize.
        char_ptr_size = ctypes.sizeof(ctypes.c_char_p)
        self.ioctl_numbers['SET_FILTER'] = 0x80002406 | char_ptr_size << 16
        self.exit_reasons = {}

    def debugfs_is_child(self, field):
        """ Returns name of parent if 'field' is a child, None otherwise """
        return None


class ArchA64(Arch):
    def __init__(self):
        self.sc_perf_evt_open = 241
        self.ioctl_numbers = IOCTL_NUMBERS
        self.exit_reasons = AARCH64_EXIT_REASONS

    def debugfs_is_child(self, field):
        """ Returns name of parent if 'field' is a child, None otherwise """
        return None


class ArchS390(Arch):
    def __init__(self):
        self.sc_perf_evt_open = 331
        self.ioctl_numbers = IOCTL_NUMBERS
        self.exit_reasons = None

    def debugfs_is_child(self, field):
        """ Returns name of parent if 'field' is a child, None otherwise """
        if field.startswith('instruction_'):
            return 'exit_instruction'


ARCH = Arch.get_arch()


class perf_event_attr(ctypes.Structure):
    """Struct that holds the necessary data to set up a trace event.

    For an extensive explanation see perf_event_open(2) and
    include/uapi/linux/perf_event.h, struct perf_event_attr

    All fields that are not initialized in the constructor are 0.

    """
    _fields_ = [('type', ctypes.c_uint32),
                ('size', ctypes.c_uint32),
                ('config', ctypes.c_uint64),
                ('sample_freq', ctypes.c_uint64),
                ('sample_type', ctypes.c_uint64),
                ('read_format', ctypes.c_uint64),
                ('flags', ctypes.c_uint64),
                ('wakeup_events', ctypes.c_uint32),
                ('bp_type', ctypes.c_uint32),
                ('bp_addr', ctypes.c_uint64),
                ('bp_len', ctypes.c_uint64),
                ]

    def __init__(self):
        super(self.__class__, self).__init__()
        self.type = PERF_TYPE_TRACEPOINT
        self.size = ctypes.sizeof(self)
        self.read_format = PERF_FORMAT_GROUP


PERF_TYPE_TRACEPOINT = 2
PERF_FORMAT_GROUP = 1 << 3


class Group(object):
    """Represents a perf event group."""

    def __init__(self):
        self.events = []

    def add_event(self, event):
        self.events.append(event)

    def read(self):
        """Returns a dict with 'event name: value' for all events in the
        group.

        Values are read by reading from the file descriptor of the
        event that is the group leader. See perf_event_open(2) for
        details.

        Read format for the used event configuration is:
        struct read_format {
            u64 nr; /* The number of events */
            struct {
                u64 value; /* The value of the event */
            } values[nr];
        };

        """
        length = 8 * (1 + len(self.events))
        read_format = 'xxxxxxxx' + 'Q' * len(self.events)
        return dict(zip([event.name for event in self.events],
                        struct.unpack(read_format,
                                      os.read(self.events[0].fd, length))))


class Event(object):
    """Represents a performance event and manages its life cycle."""
    def __init__(self, name, group, trace_cpu, trace_pid, trace_point,
                 trace_filter, trace_set='kvm'):
        self.libc = ctypes.CDLL('libc.so.6', use_errno=True)
        self.syscall = self.libc.syscall
        self.name = name
        self.fd = None
        self._setup_event(group, trace_cpu, trace_pid, trace_point,
                          trace_filter, trace_set)

    def __del__(self):
        """Closes the event's file descriptor.

        As no python file object was created for the file descriptor,
        python will not reference count the descriptor and will not
        close it itself automatically, so we do it.

        """
        if self.fd:
            os.close(self.fd)

    def _perf_event_open(self, attr, pid, cpu, group_fd, flags):
        """Wrapper for the sys_perf_evt_open() syscall.

        Used to set up performance events, returns a file descriptor or -1
        on error.

        Attributes are:
        - syscall number
        - struct perf_event_attr *
        - pid or -1 to monitor all pids
        - cpu number or -1 to monitor all cpus
        - The file descriptor of the group leader or -1 to create a group.
        - flags

        """
        return self.syscall(ARCH.sc_perf_evt_open, ctypes.pointer(attr),
                            ctypes.c_int(pid), ctypes.c_int(cpu),
                            ctypes.c_int(group_fd), ctypes.c_long(flags))

    def _setup_event_attribute(self, trace_set, trace_point):
        """Returns an initialized ctype perf_event_attr struct."""

        id_path = os.path.join(PATH_DEBUGFS_TRACING, 'events', trace_set,
                               trace_point, 'id')

        event_attr = perf_event_attr()
        event_attr.config = int(open(id_path).read())
        return event_attr

    def _setup_event(self, group, trace_cpu, trace_pid, trace_point,
                     trace_filter, trace_set):
        """Sets up the perf event in Linux.

        Issues the syscall to register the event in the kernel and
        then sets the optional filter.

        """

        event_attr = self._setup_event_attribute(trace_set, trace_point)

        # First event will be group leader.
        group_leader = -1

        # All others have to pass the leader's descriptor instead.
        if group.events:
            group_leader = group.events[0].fd

        fd = self._perf_event_open(event_attr, trace_pid,
                                   trace_cpu, group_leader, 0)
        if fd == -1:
            err = ctypes.get_errno()
            raise OSError(err, os.strerror(err),
                          'while calling sys_perf_event_open().')

        if trace_filter:
            fcntl.ioctl(fd, ARCH.ioctl_numbers['SET_FILTER'],
                        trace_filter)

        self.fd = fd

    def enable(self):
        """Enables the trace event in the kernel.

        Enabling the group leader makes reading counters from it and the
        events under it possible.

        """
        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['ENABLE'], 0)

    def disable(self):
        """Disables the trace event in the kernel.

        Disabling the group leader makes reading all counters under it
        impossible.

        """
        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['DISABLE'], 0)

    def reset(self):
        """Resets the count of the trace event in the kernel."""
        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['RESET'], 0)


class Provider(object):
    """Encapsulates functionalities used by all providers."""
    def __init__(self, pid):
        self.child_events = False
        self.pid = pid

    @staticmethod
    def is_field_wanted(fields_filter, field):
        """Indicate whether field is valid according to fields_filter."""
        if not fields_filter:
            return True
        return re.match(fields_filter, field) is not None

    @staticmethod
    def walkdir(path):
        """Returns os.walk() data for specified directory.

        As it is only a wrapper it returns the same 3-tuple of (dirpath,
        dirnames, filenames).
        """
        return next(os.walk(path))


class TracepointProvider(Provider):
    """Data provider for the stats class.

    Manages the events/groups from which it acquires its data.

    """
    def __init__(self, pid, fields_filter):
        self.group_leaders = []
        self.filters = self._get_filters()
        self.update_fields(fields_filter)
        super(TracepointProvider, self).__init__(pid)

    @staticmethod
    def _get_filters():
        """Returns a dict of trace events, their filter ids and
        the values that can be filtered.

        Trace events can be filtered for special values by setting a
        filter string via an ioctl. The string normally has the format
        identifier==value. For each filter a new event will be created, to
        be able to distinguish the events.

        """
        filters = {}
        filters['kvm_userspace_exit'] = ('reason', USERSPACE_EXIT_REASONS)
        if ARCH.exit_reasons:
            filters['kvm_exit'] = ('exit_reason', ARCH.exit_reasons)
        return filters

    def _get_available_fields(self):
        """Returns a list of available events of format 'event name(filter
        name)'.

        All available events have directories under
        /sys/kernel/debug/tracing/events/ which export information
        about the specific event. Therefore, listing the dirs gives us
        a list of all available events.

        Some events like the vm exit reasons can be filtered for
        specific values. To take account for that, the routine below
        creates special fields with the following format:
        event name(filter name)

        """
        path = os.path.join(PATH_DEBUGFS_TRACING, 'events', 'kvm')
        fields = self.walkdir(path)[1]
        extra = []
        for field in fields:
            if field in self.filters:
                filter_name_, filter_dicts = self.filters[field]
                for name in filter_dicts:
                    extra.append(field + '(' + name + ')')
        fields += extra
        return fields

    def update_fields(self, fields_filter):
        """Refresh fields, applying fields_filter"""
        self.fields = [field for field in self._get_available_fields()
                       if self.is_field_wanted(fields_filter, field) or
                       ARCH.tracepoint_is_child(field)]

    @staticmethod
    def _get_online_cpus():
        """Returns a list of cpu id integers."""
        def parse_int_list(list_string):
            """Returns an int list from a string of comma separated integers and
            integer ranges."""
            integers = []
            members = list_string.split(',')

            for member in members:
                if '-' not in member:
                    integers.append(int(member))
                else:
                    int_range = member.split('-')
                    integers.extend(range(int(int_range[0]),
                                          int(int_range[1]) + 1))

            return integers

        with open('/sys/devices/system/cpu/online') as cpu_list:
            cpu_string = cpu_list.readline()
            return parse_int_list(cpu_string)

    def _setup_traces(self):
        """Creates all event and group objects needed to be able to retrieve
        data."""
        fields = self._get_available_fields()
        if self._pid > 0:
            # Fetch list of all threads of the monitored pid, as qemu
            # starts a thread for each vcpu.
            path = os.path.join('/proc', str(self._pid), 'task')
            groupids = self.walkdir(path)[1]
        else:
            groupids = self._get_online_cpus()

        # The constant is needed as a buffer for python libs, std
        # streams and other files that the script opens.
        newlim = len(groupids) * len(fields) + 50
        try:
            softlim_, hardlim = resource.getrlimit(resource.RLIMIT_NOFILE)

            if hardlim < newlim:
                # Now we need CAP_SYS_RESOURCE, to increase the hard limit.
                resource.setrlimit(resource.RLIMIT_NOFILE, (newlim, newlim))
            else:
                # Raising the soft limit is sufficient.
                resource.setrlimit(resource.RLIMIT_NOFILE, (newlim, hardlim))

        except ValueError:
            sys.exit("NOFILE rlimit could not be raised to {0}".format(newlim))

        for groupid in groupids:
            group = Group()
            for name in fields:
                tracepoint = name
                tracefilter = None
                match = re.match(r'(.*)\((.*)\)', name)
                if match:
                    tracepoint, sub = match.groups()
                    tracefilter = ('%s==%d\0' %
                                   (self.filters[tracepoint][0],
                                    self.filters[tracepoint][1][sub]))

                # From perf_event_open(2):
                # pid > 0 and cpu == -1
                # This measures the specified process/thread on any CPU.
                #
                # pid == -1 and cpu >= 0
                # This measures all processes/threads on the specified CPU.
                trace_cpu = groupid if self._pid == 0 else -1
                trace_pid = int(groupid) if self._pid != 0 else -1

                group.add_event(Event(name=name,
                                      group=group,
                                      trace_cpu=trace_cpu,
                                      trace_pid=trace_pid,
                                      trace_point=tracepoint,
                                      trace_filter=tracefilter))

            self.group_leaders.append(group)

    @property
    def fields(self):
        return self._fields

    @fields.setter
    def fields(self, fields):
        """Enables/disables the (un)wanted events"""
        self._fields = fields
        for group in self.group_leaders:
            for index, event in enumerate(group.events):
                if event.name in fields:
                    event.reset()
                    event.enable()
                else:
                    # Do not disable the group leader.
                    # It would disable all of its events.
                    if index != 0:
                        event.disable()

    @property
    def pid(self):
        return self._pid

    @pid.setter
    def pid(self, pid):
        """Changes the monitored pid by setting new traces."""
        self._pid = pid
        # The garbage collector will get rid of all Event/Group
        # objects and open files after removing the references.
        self.group_leaders = []
        self._setup_traces()
        self.fields = self._fields

    def read(self, by_guest=0):
        """Returns 'event name: current value' for all enabled events."""
        ret = defaultdict(int)
        for group in self.group_leaders:
            for name, val in group.read().items():
                if name not in self._fields:
                    continue
                parent = ARCH.tracepoint_is_child(name)
                if parent:
                    name += ' ' + parent
                ret[name] += val
        return ret

    def reset(self):
        """Reset all field counters"""
        for group in self.group_leaders:
            for event in group.events:
                event.reset()


class DebugfsProvider(Provider):
    """Provides data from the files that KVM creates in the kvm debugfs
    folder."""
    def __init__(self, pid, fields_filter, include_past):
        self.update_fields(fields_filter)
        self._baseline = {}
        self.do_read = True
        self.paths = []
        super(DebugfsProvider, self).__init__(pid)
        if include_past:
            self._restore()

    def _get_available_fields(self):
        """"Returns a list of available fields.

        The fields are all available KVM debugfs files

        """
        return self.walkdir(PATH_DEBUGFS_KVM)[2]

    def update_fields(self, fields_filter):
        """Refresh fields, applying fields_filter"""
        self._fields = [field for field in self._get_available_fields()
                        if self.is_field_wanted(fields_filter, field) or
                        ARCH.debugfs_is_child(field)]

    @property
    def fields(self):
        return self._fields

    @fields.setter
    def fields(self, fields):
        self._fields = fields
        self.reset()

    @property
    def pid(self):
        return self._pid

    @pid.setter
    def pid(self, pid):
        self._pid = pid
        if pid != 0:
            vms = self.walkdir(PATH_DEBUGFS_KVM)[1]
            if len(vms) == 0:
                self.do_read = False

            self.paths = filter(lambda x: "{}-".format(pid) in x, vms)

        else:
            self.paths = []
            self.do_read = True
        self.reset()

    def read(self, reset=0, by_guest=0):
        """Returns a dict with format:'file name / field -> current value'.

        Parameter 'reset':
          0   plain read
          1   reset field counts to 0
          2   restore the original field counts

        """
        results = {}

        # If no debugfs filtering support is available, then don't read.
        if not self.do_read:
            return results

        paths = self.paths
        if self._pid == 0:
            paths = []
            for entry in os.walk(PATH_DEBUGFS_KVM):
                for dir in entry[1]:
                    paths.append(dir)
        for path in paths:
            for field in self._fields:
                value = self._read_field(field, path)
                key = path + field
                if reset == 1:
                    self._baseline[key] = value
                if reset == 2:
                    self._baseline[key] = 0
                if self._baseline.get(key, -1) == -1:
                    self._baseline[key] = value
                parent = ARCH.debugfs_is_child(field)
                if parent:
                    field = field + ' ' + parent
                else:
                    if by_guest:
                        field = key.split('-')[0]    # set 'field' to 'pid'
                increment = value - self._baseline.get(key, 0)
                if field in results:
                    results[field] += increment
                else:
                    results[field] = increment

        return results

    def _read_field(self, field, path):
        """Returns the value of a single field from a specific VM."""
        try:
            return int(open(os.path.join(PATH_DEBUGFS_KVM,
                                         path,
                                         field))
                       .read())
        except IOError:
            return 0

    def reset(self):
        """Reset field counters"""
        self._baseline = {}
        self.read(1)

    def _restore(self):
        """Reset field counters"""
        self._baseline = {}
        self.read(2)


EventStat = namedtuple('EventStat', ['value', 'delta'])


class Stats(object):
    """Manages the data providers and the data they provide.

    It is used to set filters on the provider's data and collect all
    provider data.

    """
    def __init__(self, options):
        self.providers = self._get_providers(options)
        self._pid_filter = options.pid
        self._fields_filter = options.fields
        self.values = {}
        self._child_events = False

    def _get_providers(self, options):
        """Returns a list of data providers depending on the passed options."""
        providers = []

        if options.debugfs:
            providers.append(DebugfsProvider(options.pid, options.fields,
                                             options.dbgfs_include_past))
        if options.tracepoints or not providers:
            providers.append(TracepointProvider(options.pid, options.fields))

        return providers

    def _update_provider_filters(self):
        """Propagates fields filters to providers."""
        # As we reset the counters when updating the fields we can
        # also clear the cache of old values.
        self.values = {}
        for provider in self.providers:
            provider.update_fields(self._fields_filter)

    def reset(self):
        self.values = {}
        for provider in self.providers:
            provider.reset()

    @property
    def fields_filter(self):
        return self._fields_filter

    @fields_filter.setter
    def fields_filter(self, fields_filter):
        if fields_filter != self._fields_filter:
            self._fields_filter = fields_filter
            self._update_provider_filters()

    @property
    def pid_filter(self):
        return self._pid_filter

    @pid_filter.setter
    def pid_filter(self, pid):
        if pid != self._pid_filter:
            self._pid_filter = pid
            self.values = {}
            for provider in self.providers:
                provider.pid = self._pid_filter

    @property
    def child_events(self):
        return self._child_events

    @child_events.setter
    def child_events(self, val):
        self._child_events = val
        for provider in self.providers:
            provider.child_events = val

    def get(self, by_guest=0):
        """Returns a dict with field -> (value, delta to last value) of all
        provider data.
        Key formats:
          * plain: 'key' is event name
          * child-parent: 'key' is in format '<child> <parent>'
          * pid: 'key' is the pid of the guest, and the record contains the
               aggregated event data
        These formats are generated by the providers, and handled in class TUI.
        """
        for provider in self.providers:
            new = provider.read(by_guest=by_guest)
            for key in new:
                oldval = self.values.get(key, EventStat(0, 0)).value
                newval = new.get(key, 0)
                newdelta = newval - oldval
                self.values[key] = EventStat(newval, newdelta)
        return self.values

    def toggle_display_guests(self, to_pid):
        """Toggle between collection of stats by individual event and by
        guest pid

        Events reported by DebugfsProvider change when switching to/from
        reading by guest values. Hence we have to remove the excess event
        names from self.values.

        """
        if any(isinstance(ins, TracepointProvider) for ins in self.providers):
            return 1
        if to_pid:
            for provider in self.providers:
                if isinstance(provider, DebugfsProvider):
                    for key in provider.fields:
                        if key in self.values.keys():
                            del self.values[key]
        else:
            oldvals = self.values.copy()
            for key in oldvals:
                if key.isdigit():
                    del self.values[key]
        # Update oldval (see get())
        self.get(to_pid)
        return 0


DELAY_DEFAULT = 3.0
MAX_GUEST_NAME_LEN = 48
MAX_REGEX_LEN = 44
SORT_DEFAULT = 0


class Tui(object):
    """Instruments curses to draw a nice text ui."""
    def __init__(self, stats):
        self.stats = stats
        self.screen = None
        self._delay_initial = 0.25
        self._delay_regular = DELAY_DEFAULT
        self._sorting = SORT_DEFAULT
        self._display_guests = 0

    def __enter__(self):
        """Initialises curses for later use.  Based on curses.wrapper
           implementation from the Python standard library."""
        self.screen = curses.initscr()
        curses.noecho()
        curses.cbreak()

        # The try/catch works around a minor bit of
        # over-conscientiousness in the curses module, the error
        # return from C start_color() is ignorable.
        try:
            curses.start_color()
        except curses.error:
            pass

        # Hide cursor in extra statement as some monochrome terminals
        # might support hiding but not colors.
        try:
            curses.curs_set(0)
        except curses.error:
            pass

        curses.use_default_colors()
        return self

    def __exit__(self, *exception):
        """Resets the terminal to its normal state.  Based on curses.wrapper
           implementation from the Python standard library."""
        if self.screen:
            self.screen.keypad(0)
            curses.echo()
            curses.nocbreak()
            curses.endwin()

    @staticmethod
    def get_all_gnames():
        """Returns a list of (pid, gname) tuples of all running guests"""
        res = []
        try:
            child = subprocess.Popen(['ps', '-A', '--format', 'pid,args'],
                                     stdout=subprocess.PIPE)
        except:
            raise Exception
        for line in child.stdout:
            line = line.decode(ENCODING).lstrip().split(' ', 1)
            # perform a sanity check before calling the more expensive
            # function to possibly extract the guest name
            if ' -name ' in line[1]:
                res.append((line[0], Tui.get_gname_from_pid(line[0])))
        child.stdout.close()

        return res

    def _print_all_gnames(self, row):
        """Print a list of all running guests along with their pids."""
        self.screen.addstr(row, 2, '%8s  %-60s' %
                           ('Pid', 'Guest Name (fuzzy list, might be '
                            'inaccurate!)'),
                           curses.A_UNDERLINE)
        row += 1
        try:
            for line in self.get_all_gnames():
                self.screen.addstr(row, 2, '%8s  %-60s' % (line[0], line[1]))
                row += 1
                if row >= self.screen.getmaxyx()[0]:
                    break
        except Exception:
            self.screen.addstr(row + 1, 2, 'Not available')

    @staticmethod
    def get_pid_from_gname(gname):
        """Fuzzy function to convert guest name to QEMU process pid.

        Returns a list of potential pids, can be empty if no match found.
        Throws an exception on processing errors.

        """
        pids = []
        for line in Tui.get_all_gnames():
            if gname == line[1]:
                pids.append(int(line[0]))

        return pids

    @staticmethod
    def get_gname_from_pid(pid):
        """Returns the guest name for a QEMU process pid.

        Extracts the guest name from the QEMU comma line by processing the
        '-name' option. Will also handle names specified out of sequence.

        """
        name = ''
        try:
            line = open('/proc/{}/cmdline'
                        .format(pid), 'r').read().split('\0')
            parms = line[line.index('-name') + 1].split(',')
            while '' in parms:
                # commas are escaped (i.e. ',,'), hence e.g. 'foo,bar' results
                # in # ['foo', '', 'bar'], which we revert here
                idx = parms.index('')
                parms[idx - 1] += ',' + parms[idx + 1]
                del parms[idx:idx+2]
            # the '-name' switch allows for two ways to specify the guest name,
            # where the plain name overrides the name specified via 'guest='
            for arg in parms:
                if '=' not in arg:
                    name = arg
                    break
                if arg[:6] == 'guest=':
                    name = arg[6:]
        except (ValueError, IOError, IndexError):
            pass

        return name

    def _update_pid(self, pid):
        """Propagates pid selection to stats object."""
        self.screen.addstr(4, 1, 'Updating pid filter...')
        self.screen.refresh()
        self.stats.pid_filter = pid

    def _refresh_header(self, pid=None):
        """Refreshes the header."""
        if pid is None:
            pid = self.stats.pid_filter
        self.screen.erase()
        gname = self.get_gname_from_pid(pid)
        if gname:
            gname = ('({})'.format(gname[:MAX_GUEST_NAME_LEN] + '...'
                                   if len(gname) > MAX_GUEST_NAME_LEN
                                   else gname))
        if pid > 0:
            self.screen.addstr(0, 0, 'kvm statistics - pid {0} {1}'
                               .format(pid, gname), curses.A_BOLD)
        else:
            self.screen.addstr(0, 0, 'kvm statistics - summary', curses.A_BOLD)
        if self.stats.fields_filter:
            regex = self.stats.fields_filter
            if len(regex) > MAX_REGEX_LEN:
                regex = regex[:MAX_REGEX_LEN] + '...'
            self.screen.addstr(1, 17, 'regex filter: {0}'.format(regex))
        if self._display_guests:
            col_name = 'Guest Name'
        else:
            col_name = 'Event'
        self.screen.addstr(2, 1, '%-40s %10s%7s %8s' %
                           (col_name, 'Total', '%Total', 'CurAvg/s'),
                           curses.A_STANDOUT)
        self.screen.addstr(4, 1, 'Collecting data...')
        self.screen.refresh()

    def _refresh_body(self, sleeptime):
        def insert_child(sorted_items, child, values, parent):
            num = len(sorted_items)
            for i in range(0, num):
                # only add child if parent is present
                if parent.startswith(sorted_items[i][0]):
                    sorted_items.insert(i + 1, ('  ' + child, values))

        def get_sorted_events(self, stats):
            """ separate parent and child events """
            if self._sorting == SORT_DEFAULT:
                def sortkey(pair):
                    # sort by (delta value, overall value)
                    v = pair[1]
                    return (v.delta, v.value)
            else:
                def sortkey(pair):
                    # sort by overall value
                    v = pair[1]
                    return v.value

            childs = []
            sorted_items = []
            # we can't rule out child events to appear prior to parents even
            # when sorted - separate out all children first, and add in later
            for key, values in sorted(stats.items(), key=sortkey,
                                      reverse=True):
                if values == (0, 0):
                    continue
                if key.find(' ') != -1:
                    if not self.stats.child_events:
                        continue
                    childs.insert(0, (key, values))
                else:
                    sorted_items.append((key, values))
            if self.stats.child_events:
                for key, values in childs:
                    (child, parent) = key.split(' ')
                    insert_child(sorted_items, child, values, parent)

            return sorted_items

        row = 3
        self.screen.move(row, 0)
        self.screen.clrtobot()
        stats = self.stats.get(self._display_guests)
        total = 0.
        ctotal = 0.
        for key, values in stats.items():
            if self._display_guests:
                if self.get_gname_from_pid(key):
                    total += values.value
                continue
            if not key.find(' ') != -1:
                total += values.value
            else:
                ctotal += values.value
        if total == 0.:
            # we don't have any fields, or all non-child events are filtered
            total = ctotal

        # print events
        tavg = 0
        tcur = 0
        for key, values in get_sorted_events(self, stats):
            if row >= self.screen.getmaxyx()[0] - 1 or values == (0, 0):
                break
            if self._display_guests:
                key = self.get_gname_from_pid(key)
                if not key:
                    continue
            cur = int(round(values.delta / sleeptime)) if values.delta else ''
            if key[0] != ' ':
                if values.delta:
                    tcur += values.delta
                ptotal = values.value
                ltotal = total
            else:
                ltotal = ptotal
            self.screen.addstr(row, 1, '%-40s %10d%7.1f %8s' % (key,
                               values.value,
                               values.value * 100 / float(ltotal), cur))
            row += 1
        if row == 3:
            self.screen.addstr(4, 1, 'No matching events reported yet')
        if row > 4:
            tavg = int(round(tcur / sleeptime)) if tcur > 0 else ''
            self.screen.addstr(row, 1, '%-40s %10d        %8s' %
                               ('Total', total, tavg), curses.A_BOLD)
        self.screen.refresh()

    def _show_msg(self, text):
        """Display message centered text and exit on key press"""
        hint = 'Press any key to continue'
        curses.cbreak()
        self.screen.erase()
        (x, term_width) = self.screen.getmaxyx()
        row = 2
        for line in text:
            start = (term_width - len(line)) / 2
            self.screen.addstr(row, start, line)
            row += 1
        self.screen.addstr(row + 1, (term_width - len(hint)) / 2, hint,
                           curses.A_STANDOUT)
        self.screen.getkey()

    def _show_help_interactive(self):
        """Display help with list of interactive commands"""
        msg = ('   b     toggle events by guests (debugfs only, honors'
               ' filters)',
               '   c     clear filter',
               '   f     filter by regular expression',
               '   g     filter by guest name/PID',
               '   h     display interactive commands reference',
               '   o     toggle sorting order (Total vs CurAvg/s)',
               '   p     filter by guest name/PID',
               '   q     quit',
               '   r     reset stats',
               '   s     set update interval',
               '   x     toggle reporting of stats for individual child trace'
               ' events',
               'Any other key refreshes statistics immediately')
        curses.cbreak()
        self.screen.erase()
        self.screen.addstr(0, 0, "Interactive commands reference",
                           curses.A_BOLD)
        self.screen.addstr(2, 0, "Press any key to exit", curses.A_STANDOUT)
        row = 4
        for line in msg:
            self.screen.addstr(row, 0, line)
            row += 1
        self.screen.getkey()
        self._refresh_header()

    def _show_filter_selection(self):
        """Draws filter selection mask.

        Asks for a valid regex and sets the fields filter accordingly.

        """
        msg = ''
        while True:
            self.screen.erase()
            self.screen.addstr(0, 0,
                               "Show statistics for events matching a regex.",
                               curses.A_BOLD)
            self.screen.addstr(2, 0,
                               "Current regex: {0}"
                               .format(self.stats.fields_filter))
            self.screen.addstr(5, 0, msg)
            self.screen.addstr(3, 0, "New regex: ")
            curses.echo()
            regex = self.screen.getstr().decode(ENCODING)
            curses.noecho()
            if len(regex) == 0:
                self.stats.fields_filter = ''
                self._refresh_header()
                return
            try:
                re.compile(regex)
                self.stats.fields_filter = regex
                self._refresh_header()
                return
            except re.error:
                msg = '"' + regex + '": Not a valid regular expression'
                continue

    def _show_set_update_interval(self):
        """Draws update interval selection mask."""
        msg = ''
        while True:
            self.screen.erase()
            self.screen.addstr(0, 0, 'Set update interval (defaults to %fs).' %
                               DELAY_DEFAULT, curses.A_BOLD)
            self.screen.addstr(4, 0, msg)
            self.screen.addstr(2, 0, 'Change delay from %.1fs to ' %
                               self._delay_regular)
            curses.echo()
            val = self.screen.getstr().decode(ENCODING)
            curses.noecho()

            try:
                if len(val) > 0:
                    delay = float(val)
                    if delay < 0.1:
                        msg = '"' + str(val) + '": Value must be >=0.1'
                        continue
                    if delay > 25.5:
                        msg = '"' + str(val) + '": Value must be <=25.5'
                        continue
                else:
                    delay = DELAY_DEFAULT
                self._delay_regular = delay
                break

            except ValueError:
                msg = '"' + str(val) + '": Invalid value'
        self._refresh_header()

    def _show_vm_selection_by_guest(self):
        """Draws guest selection mask.

        Asks for a guest name or pid until a valid guest name or '' is entered.

        """
        msg = ''
        while True:
            self.screen.erase()
            self.screen.addstr(0, 0,
                               'Show statistics for specific guest or pid.',
                               curses.A_BOLD)
            self.screen.addstr(1, 0,
                               'This might limit the shown data to the trace '
                               'statistics.')
            self.screen.addstr(5, 0, msg)
            self._print_all_gnames(7)
            curses.echo()
            curses.curs_set(1)
            self.screen.addstr(3, 0, "Guest or pid [ENTER exits]: ")
            guest = self.screen.getstr().decode(ENCODING)
            curses.noecho()

            pid = 0
            if not guest or guest == '0':
                break
            if guest.isdigit():
                if not os.path.isdir(os.path.join('/proc/', guest)):
                    msg = '"' + guest + '": Not a running process'
                    continue
                pid = int(guest)
                break
            pids = []
            try:
                pids = self.get_pid_from_gname(guest)
            except:
                msg = '"' + guest + '": Internal error while searching, ' \
                      'use pid filter instead'
                continue
            if len(pids) == 0:
                msg = '"' + guest + '": Not an active guest'
                continue
            if len(pids) > 1:
                msg = '"' + guest + '": Multiple matches found, use pid ' \
                      'filter instead'
                continue
            pid = pids[0]
            break
        curses.curs_set(0)
        self._refresh_header(pid)
        self._update_pid(pid)

    def show_stats(self):
        """Refreshes the screen and processes user input."""
        sleeptime = self._delay_initial
        self._refresh_header()
        start = 0.0  # result based on init value never appears on screen
        while True:
            self._refresh_body(time.time() - start)
            curses.halfdelay(int(sleeptime * 10))
            start = time.time()
            sleeptime = self._delay_regular
            try:
                char = self.screen.getkey()
                if char == 'b':
                    self._display_guests = not self._display_guests
                    if self.stats.toggle_display_guests(self._display_guests):
                        self._show_msg(['Command not available with '
                                        'tracepoints enabled', 'Restart with '
                                        'debugfs only (see option \'-d\') and '
                                        'try again!'])
                        self._display_guests = not self._display_guests
                    self._refresh_header()
                if char == 'c':
                    self.stats.fields_filter = ''
                    self._refresh_header(0)
                    self._update_pid(0)
                if char == 'f':
                    curses.curs_set(1)
                    self._show_filter_selection()
                    curses.curs_set(0)
                    sleeptime = self._delay_initial
                if char == 'g' or char == 'p':
                    self._show_vm_selection_by_guest()
                    sleeptime = self._delay_initial
                if char == 'h':
                    self._show_help_interactive()
                if char == 'o':
                    self._sorting = not self._sorting
                if char == 'q':
                    break
                if char == 'r':
                    self.stats.reset()
                if char == 's':
                    curses.curs_set(1)
                    self._show_set_update_interval()
                    curses.curs_set(0)
                    sleeptime = self._delay_initial
                if char == 'x':
                    self.stats.child_events = not self.stats.child_events
            except KeyboardInterrupt:
                break
            except curses.error:
                continue


def batch(stats):
    """Prints statistics in a key, value format."""
    try:
        s = stats.get()
        time.sleep(1)
        s = stats.get()
        for key, values in sorted(s.items()):
            print('%-42s%10d%10d' % (key.split(' ')[0], values.value,
                  values.delta))
    except KeyboardInterrupt:
        pass


def log(stats):
    """Prints statistics as reiterating key block, multiple value blocks."""
    keys = sorted(stats.get().keys())

    def banner():
        for key in keys:
            print(key.split(' ')[0], end=' ')
        print()

    def statline():
        s = stats.get()
        for key in keys:
            print(' %9d' % s[key].delta, end=' ')
        print()
    line = 0
    banner_repeat = 20
    while True:
        try:
            time.sleep(1)
            if line % banner_repeat == 0:
                banner()
            statline()
            line += 1
        except KeyboardInterrupt:
            break


def get_options():
    """Returns processed program arguments."""
    description_text = """
This script displays various statistics about VMs running under KVM.
The statistics are gathered from the KVM debugfs entries and / or the
currently available perf traces.

The monitoring takes additional cpu cycles and might affect the VM's
performance.

Requirements:
- Access to:
    %s
    %s/events/*
    /proc/pid/task
- /proc/sys/kernel/perf_event_paranoid < 1 if user has no
  CAP_SYS_ADMIN and perf events are used.
- CAP_SYS_RESOURCE if the hard limit is not high enough to allow
  the large number of files that are possibly opened.

Interactive Commands:
   b     toggle events by guests (debugfs only, honors filters)
   c     clear filter
   f     filter by regular expression
   g     filter by guest name
   h     display interactive commands reference
   o     toggle sorting order (Total vs CurAvg/s)
   p     filter by PID
   q     quit
   r     reset stats
   s     set update interval
   x     toggle reporting of stats for individual child trace events
Press any other key to refresh statistics immediately.
""" % (PATH_DEBUGFS_KVM, PATH_DEBUGFS_TRACING)

    class PlainHelpFormatter(optparse.IndentedHelpFormatter):
        def format_description(self, description):
            if description:
                return description + "\n"
            else:
                return ""

    def cb_guest_to_pid(option, opt, val, parser):
        try:
            pids = Tui.get_pid_from_gname(val)
        except:
            sys.exit('Error while searching for guest "{}". Use "-p" to '
                     'specify a pid instead?'.format(val))
        if len(pids) == 0:
            sys.exit('Error: No guest by the name "{}" found'.format(val))
        if len(pids) > 1:
            sys.exit('Error: Multiple processes found (pids: {}). Use "-p" '
                     'to specify the desired pid'.format(" ".join(pids)))
        parser.values.pid = pids[0]

    optparser = optparse.OptionParser(description=description_text,
                                      formatter=PlainHelpFormatter())
    optparser.add_option('-1', '--once', '--batch',
                         action='store_true',
                         default=False,
                         dest='once',
                         help='run in batch mode for one second',
                         )
    optparser.add_option('-i', '--debugfs-include-past',
                         action='store_true',
                         default=False,
                         dest='dbgfs_include_past',
                         help='include all available data on past events for '
                              'debugfs',
                         )
    optparser.add_option('-l', '--log',
                         action='store_true',
                         default=False,
                         dest='log',
                         help='run in logging mode (like vmstat)',
                         )
    optparser.add_option('-t', '--tracepoints',
                         action='store_true',
                         default=False,
                         dest='tracepoints',
                         help='retrieve statistics from tracepoints',
                         )
    optparser.add_option('-d', '--debugfs',
                         action='store_true',
                         default=False,
                         dest='debugfs',
                         help='retrieve statistics from debugfs',
                         )
    optparser.add_option('-f', '--fields',
                         action='store',
                         default='',
                         dest='fields',
                         help='''fields to display (regex)
                                 "-f help" for a list of available events''',
                         )
    optparser.add_option('-p', '--pid',
                         action='store',
                         default=0,
                         type='int',
                         dest='pid',
                         help='restrict statistics to pid',
                         )
    optparser.add_option('-g', '--guest',
                         action='callback',
                         type='string',
                         dest='pid',
                         metavar='GUEST',
                         help='restrict statistics to guest by name',
                         callback=cb_guest_to_pid,
                         )
    options, unkn = optparser.parse_args(sys.argv)
    if len(unkn) != 1:
        sys.exit('Error: Extra argument(s): ' + ' '.join(unkn[1:]))
    try:
        # verify that we were passed a valid regex up front
        re.compile(options.fields)
    except re.error:
        sys.exit('Error: "' + options.fields + '" is not a valid regular '
                 'expression')

    return options


def check_access(options):
    """Exits if the current user can't access all needed directories."""
    if not os.path.exists(PATH_DEBUGFS_TRACING) and (options.tracepoints or
                                                     not options.debugfs):
        sys.stderr.write("Please enable CONFIG_TRACING in your kernel "
                         "when using the option -t (default).\n"
                         "If it is enabled, make {0} readable by the "
                         "current user.\n"
                         .format(PATH_DEBUGFS_TRACING))
        if options.tracepoints:
            sys.exit(1)

        sys.stderr.write("Falling back to debugfs statistics!\n")
        options.debugfs = True
        time.sleep(5)

    return options


def assign_globals():
    global PATH_DEBUGFS_KVM
    global PATH_DEBUGFS_TRACING

    debugfs = ''
    for line in open('/proc/mounts'):
        if line.split(' ')[0] == 'debugfs':
            debugfs = line.split(' ')[1]
            break
    if debugfs == '':
        sys.stderr.write("Please make sure that CONFIG_DEBUG_FS is enabled in "
                         "your kernel, mounted and\nreadable by the current "
                         "user:\n"
                         "('mount -t debugfs debugfs /sys/kernel/debug')\n")
        sys.exit(1)

    PATH_DEBUGFS_KVM = os.path.join(debugfs, 'kvm')
    PATH_DEBUGFS_TRACING = os.path.join(debugfs, 'tracing')

    if not os.path.exists(PATH_DEBUGFS_KVM):
        sys.stderr.write("Please make sure that CONFIG_KVM is enabled in "
                         "your kernel and that the modules are loaded.\n")
        sys.exit(1)


def main():
    assign_globals()
    options = get_options()
    options = check_access(options)

    if (options.pid > 0 and
        not os.path.isdir(os.path.join('/proc/',
                                       str(options.pid)))):
        sys.stderr.write('Did you use a (unsupported) tid instead of a pid?\n')
        sys.exit('Specified pid does not exist.')

    stats = Stats(options)

    if options.fields == 'help':
        stats.fields_filter = None
        event_list = []
        for key in stats.get().keys():
            event_list.append(key.split('(', 1)[0])
        sys.stdout.write('  ' + '\n  '.join(sorted(set(event_list))) + '\n')
        sys.exit(0)

    if options.log:
        log(stats)
    elif not options.once:
        with Tui(stats) as tui:
            tui.show_stats()
    else:
        batch(stats)

if __name__ == "__main__":
    main()