docs/devel/replay.rst

13 execution. Execution recording writes a non-deterministic events log, which
16 non-deterministic events including external input, hardware clocks,
21 Devices' models that have non-deterministic input from external devices were
26 All non-deterministic events are coming from these devices. But to
33 …th Multi-target QEMU Simulator for Dynamic Analysis and Reverse Debugging <https://www.computer.or…
50 --------------------
55 non-deterministic events. The number of instructions elapsed from the last event
60 ----------------------------------
68 another lock to keep things in lock-step. This role is now handled by
71 in a deterministic ping-pong between the two main threads.
82 -----------
85 non-determinism. These are inputs from clock and peripheral devices,
87 from timers, asynchronous input-output, and bottom halves.
90 of the virtual machine. Reads produce non-deterministic data taken from
127 ------
140    of non-determinism. Host clock read operations should be logged to
144    sleeping. Due to its nature it is also non-deterministic as the host clock
159 -------------
171 -------------
203 -----------------------------
214 the dependencies that may make restoring the VM state non-deterministic.
217 ---------------
228 events. The header includes 4-byte replay version id and 8-byte reserved
233 It includes all non-deterministic inputs of VM, synchronization marks and
241 Every event in the log includes 1-byte event id and optional arguments.
242 When argument is an array, it is stored as 4-byte array length
246  - EVENT_INSTRUCTION. Instructions executed since last event. Followed by:
248    - 4-byte number of executed instructions.
250  - EVENT_INTERRUPT. Used to synchronize interrupt processing.
251  - EVENT_EXCEPTION. Used to synchronize exception handling.
252  - EVENT_ASYNC. This is a group of events. When such an event is generated,
256      - REPLAY_ASYNC_EVENT_BH. Bottom-half callback. This event synchronizes
260         - 8-byte operation id.
262      - REPLAY_ASYNC_EVENT_INPUT. Input device event. Contains
266         - 9-16 bytes depending of input event.
268      - REPLAY_ASYNC_EVENT_INPUT_SYNC. Internal input synchronization event.
269      - REPLAY_ASYNC_EVENT_CHAR_READ. Character (e.g., serial port) device input
272         - 1-byte character device id.
273         - Array with bytes were read.
275      - REPLAY_ASYNC_EVENT_BLOCK. Block device operation. Used to synchronize
278         - 8-byte operation id.
280      - REPLAY_ASYNC_EVENT_NET. Incoming network packet. Followed by:
282         - 1-byte network adapter id.
283         - 4-byte packet flags.
284         - Array with packet bytes.
286  - EVENT_SHUTDOWN. Occurs when user sends shutdown event to qemu,
288  - EVENT_CHAR_WRITE. Used to synchronize character output operations. Followed by:
290     - 4-byte output function return value.
291     - 4-byte offset in the output array.
293  - EVENT_CHAR_READ_ALL. Used to synchronize character input operations,
296     - Array with bytes that were read.
298  - EVENT_CHAR_READ_ALL_ERROR. Unsuccessful character input operation,
301     - 4-byte error code.
303  - EVENT_CLOCK + clock_id. Group of events for host clock read operations. Followed by:
305     - 8-byte clock value.
307  - EVENT_CHECKPOINT + checkpoint_id. Checkpoint for synchronization of
309  - EVENT_END. Last event in the log.