docs/system/replay.rst

4     Copyright (c) 2010-2022 Institute for System Programming
8     See the COPYING file in the top-level directory.
14 Execution recording writes a non-deterministic events log, which can be later
17 Execution replaying reads the log and replays all non-deterministic events
18 including external input, hardware clocks, and interrupts.
26  * Supports i386, x86_64, ARM, AArch64, Risc-V, MIPS, MIPS64, S390X, Alpha,
30    input devices, serial ports, and network.
36     .. parsed-literal::
38         -icount shift=auto,rr=record,rrfile=replay.bin \\
39         -drive file=disk.qcow2,if=none,snapshot,id=img-direct \\
40         -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay \\
41         -device ide-hd,drive=img-blkreplay \\
42         -netdev user,id=net1 -device rtl8139,netdev=net1 \\
43         -object filter-replay,id=replay,netdev=net1
47     .. parsed-literal::
49         -icount shift=auto,rr=replay,rrfile=replay.bin \\
50         -drive file=disk.qcow2,if=none,snapshot,id=img-direct \\
51         -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay \\
52         -device ide-hd,drive=img-blkreplay \\
53         -netdev user,id=net1 -device rtl8139,netdev=net1 \\
54         -object filter-replay,id=replay,netdev=net1
58  * Block device images are not actually changed in the recording mode,
61    for every enabled block device, as described in :ref:`block-label` section.
62  * ``-net none`` option should be specified when network is not used,
65    in :ref:`network-label` section.
70 ---------
72 Record/replay system is based on saving and replaying non-deterministic
73 events (e.g. keyboard input) and simulating deterministic ones (e.g. reading
74 from HDD or memory of the VM). Saving only non-deterministic events makes
77 The following non-deterministic data from peripheral devices is saved into
78 the log: mouse and keyboard input, network packets, audio controller input,
79 serial port input, and hardware clocks (they are non-deterministic
87 --------------------
89 QEMU should work in icount mode to use record/replay feature. icount was
91 of the virtual machine. Record/replay feature is enabled through ``-icount``
92 command-line option, making possible deterministic execution of the machine,
95 .. _block-label:
98 -------------
105 .. parsed-literal::
106     -drive file=disk.qcow2,if=none,snapshot,id=img-direct
107     -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay
108     -device ide-hd,drive=img-blkreplay
113 .. _snapshotting-label:
116 ------------
118 New VM snapshots may be created in replay mode. They can be used later
119 to recover the desired VM state. All VM states created in replay mode
126 .. parsed-literal::
127     -icount shift=auto,rr=record,rrfile=replay.bin,rrsnapshot=snapshot_name
136 .. parsed-literal::
137     -drive file=disk.ovl,if=none,id=img-direct
138     -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay
139     -device ide-hd,drive=img-blkreplay
151 .. parsed-literal::
153       -icount shift=auto,rr=replay,rrfile=record.bin,rrsnapshot=init \\
154       -net none -drive file=empty.qcow2,if=none,id=rr
159 .. _network-label:
162 ---------------
167 .. parsed-literal::
168     -netdev user,id=net1 -device rtl8139,netdev=net1
169     -object filter-replay,id=replay,netdev=net1
173 the outer world into the log. In replay mode packets from the log are
175 in replay mode are disabled.
178 -------------
183 .. parsed-literal::
184     -audio pa,model=ac97
187 ------------
189 Serial ports input is recorded and replay automatically. The command lines
192 E.g., ``-serial stdio`` in record mode, and ``-serial null`` in replay mode.
195 -----------------
208  - ``reverse-stepi`` (or ``rsi``) - step one instruction backwards
209  - ``reverse-continue`` (or ``rc``) - find last breakpoint in the past
232 See the :ref:`snapshotting-label` section to learn more about running record/replay