On 27/02/2015 10:23, Pavel Dovgaluk wrote: >> From: Paolo Bonzini [mailto:[email protected]] On Behalf Of Paolo >> Bonzini >> On 18/02/2015 12:55, Pavel Dovgalyuk wrote: >>> This set of patches is related to the reverse execution and deterministic >>> replay of qemu execution. This implementation of deterministic replay can >>> be used for deterministic debugging of guest code through gdb remote >>> interface. >>> >>> These patches include only core function of the replay, >>> excluding the support for replaying serial, audio, network, and USB devices' >>> operations. Reverse debugging and monitor commands were also excluded to >>> be submitted later as separate patches. >>> >>> Execution recording writes non-deterministic events log, which can be later >>> used for replaying the execution anywhere and for unlimited number of times. >>> It also supports checkpointing for faster rewinding during reverse >>> debugging. >>> Execution replaying reads the log and replays all non-deterministic events >>> including external input, hardware clocks, and interrupts. >>> >>> Deterministic replay has the following features: >>> * Deterministically replays whole system execution and all contents of the >>> memory, >>> state of the hadrware devices, clocks, and screen of the VM. >>> * Writes execution log into the file for latter replaying for multiple >>> times >>> on different machines. >>> * Supports i386, x86_64, and ARM hardware platforms. >>> * Performs deterministic replay of all operations with keyboard and mouse >>> input devices. >>> * Supports auto-checkpointing for convenient reverse debugging. >>> >>> Usage of the record/replay: >>> * First, record the execution, by adding the following string to the >>> command line: >>> '-icount shift=7,rr=record,rrfile=replay.bin -net none'. >>> Block devices' images are not actually changed in the recording mode, >>> because all of the changes are written to the temporary overlay file. >>> * Then you can replay it for the multiple times by using another command >>> line option: '-icount shift=7,rr=replay,rrfile=replay.bin -net none' >>> * '-net none' option should also be specified if network replay patches >>> are not applied. >>> >>> Paper with short description of deterministic replay implementation: >>> http://www.computer.org/csdl/proceedings/csmr/2012/4666/00/4666a553-abs.html >>> >>> Modifications of qemu include: >>> * wrappers for clock and time functions to save their return values in the >>> log >>> * saving different asynchronous events (e.g. system shutdown) into the log >>> * synchronization of the bottom halves execution >>> * synchronization of the threads from thread pool >>> * recording/replaying user input (mouse and keyboard) >>> * adding internal events for cpu and io synchronization >>> >>> v9 changes: >>> * Replaced fwrite/fread with putc/getc (as suggested by Paolo Bonzini) >>> * Stopping virtual machine in case of replay file end (as suggested by >>> Paolo Bonzini) >>> * Removed one of the replay mutexes (as suggested by Paolo Bonzini) >>> * Fixed RCU queue for bottom halves (as suggested by Paolo Bonzini) >>> * Updated command line options' names (as suggested by Paolo Bonzini) >>> * Added design document for record/replay (as suggested by Paolo Bonzini) >>> * Simplified checkpoints for the timers >>> * Added cloning InputEvent objects for replay (as suggested by Paolo >>> Bonzini) >>> * Added replay blockers instead of checking the command line (as suggested >>> by Paolo >> Bonzini) >>> * Some functions renaming and extracting. >> >> I haven't yet reviewed patch 23 completely, and I have to think (a lot >> :)) more about block devices. In the meanwhile I understand the replay >> code much better so I had some suggestions. > > Do you have more comments? I'm ready to submit a new version.
23 is fine. Block devices probably are best left as is for now. Paolo >> >> In general, the handling of replay_has_unread_data / replay_data_kind is >> a bit messy. It would be nice if you could call >> replay_fetch_data_kind() only when replay_has_unread_data == 0. Or, >> even, remove replay_has_unread_data altogether: just call >> replay_fetch_data_kind() when you'd set it to zero. That would simplify >> a lot the code for readers. > > Fixed. > > Pavel Dovgalyuk >
