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author | Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru> | 2018-02-27 12:52:20 +0300 |
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committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-03-12 16:12:50 +0100 |
commit | bb040e006f0245ca376b45dc5ea247f6e1f02648 (patch) | |
tree | 0626655f86b9dab17f36b7a609aff02adb4985af /docs/replay.txt | |
parent | 377b21ccea1755a8b0dae822c29567c58dda6939 (diff) | |
download | qemu-bb040e006f0245ca376b45dc5ea247f6e1f02648.zip qemu-bb040e006f0245ca376b45dc5ea247f6e1f02648.tar.gz qemu-bb040e006f0245ca376b45dc5ea247f6e1f02648.tar.bz2 |
replay: added replay log format description
This patch adds description of the replay log file format
into the docs/replay.txt.
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20180227095220.1060.58759.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'docs/replay.txt')
-rw-r--r-- | docs/replay.txt | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/docs/replay.txt b/docs/replay.txt index 486c1e0..c52407f 100644 --- a/docs/replay.txt +++ b/docs/replay.txt @@ -232,3 +232,72 @@ Audio devices Audio data is recorded and replay automatically. The command line for recording and replaying must contain identical specifications of audio hardware, e.g.: -soundhw ac97 + +Replay log format +----------------- + +Record/replay log consits of the header and the sequence of execution +events. The header includes 4-byte replay version id and 8-byte reserved +field. Version is updated every time replay log format changes to prevent +using replay log created by another build of qemu. + +The sequence of the events describes virtual machine state changes. +It includes all non-deterministic inputs of VM, synchronization marks and +instruction counts used to correctly inject inputs at replay. + +Synchronization marks (checkpoints) are used for synchronizing qemu threads +that perform operations with virtual hardware. These operations may change +system's state (e.g., change some register or generate interrupt) and +therefore should execute synchronously with CPU thread. + +Every event in the log includes 1-byte event id and optional arguments. +When argument is an array, it is stored as 4-byte array length +and corresponding number of bytes with data. +Here is the list of events that are written into the log: + + - EVENT_INSTRUCTION. Instructions executed since last event. + Argument: 4-byte number of executed instructions. + - EVENT_INTERRUPT. Used to synchronize interrupt processing. + - EVENT_EXCEPTION. Used to synchronize exception handling. + - EVENT_ASYNC. This is a group of events. They are always processed + together with checkpoints. When such an event is generated, it is + stored in the queue and processed only when checkpoint occurs. + Every such event is followed by 1-byte checkpoint id and 1-byte + async event id from the following list: + - REPLAY_ASYNC_EVENT_BH. Bottom-half callback. This event synchronizes + callbacks that affect virtual machine state, but normally called + asyncronously. + Argument: 8-byte operation id. + - REPLAY_ASYNC_EVENT_INPUT. Input device event. Contains + parameters of keyboard and mouse input operations + (key press/release, mouse pointer movement). + Arguments: 9-16 bytes depending of input event. + - REPLAY_ASYNC_EVENT_INPUT_SYNC. Internal input synchronization event. + - REPLAY_ASYNC_EVENT_CHAR_READ. Character (e.g., serial port) device input + initiated by the sender. + Arguments: 1-byte character device id. + Array with bytes were read. + - REPLAY_ASYNC_EVENT_BLOCK. Block device operation. Used to synchronize + operations with disk and flash drives with CPU. + Argument: 8-byte operation id. + - REPLAY_ASYNC_EVENT_NET. Incoming network packet. + Arguments: 1-byte network adapter id. + 4-byte packet flags. + Array with packet bytes. + - EVENT_SHUTDOWN. Occurs when user sends shutdown event to qemu, + e.g., by closing the window. + - EVENT_CHAR_WRITE. Used to synchronize character output operations. + Arguments: 4-byte output function return value. + 4-byte offset in the output array. + - EVENT_CHAR_READ_ALL. Used to synchronize character input operations, + initiated by qemu. + Argument: Array with bytes that were read. + - EVENT_CHAR_READ_ALL_ERROR. Unsuccessful character input operation, + initiated by qemu. + Argument: 4-byte error code. + - EVENT_CLOCK + clock_id. Group of events for host clock read operations. + Argument: 8-byte clock value. + - EVENT_CHECKPOINT + checkpoint_id. Checkpoint for synchronization of + CPU, internal threads, and asynchronous input events. May be followed + by one or more EVENT_ASYNC events. + - EVENT_END. Last event in the log. |