Re: [Qemu-devel] [RFC PATCH v5 00/31] Deterministic replay and reverse execution

[Artyom Tarasenko <atar4qemu@gmail.com>]

On Wed, Nov 26, 2014 at 11:47 AM, Pavel Dovgaluk
<Pavel.Dovgaluk@ispras.ru> wrote:
> That covermail was wrong. Here is the correct one:
>
> 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.

This patch series is really impressive, hats off!

I wonder what would have to be done to add support for SPARC-64? Since
has a PCI bus, I guess the support in atapi and usb devices is already
there. Is anything beyond translate.c has to be adjusted?

Artyom

>  * 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:
>    '-record fname=replay.bin -icount 7 -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: '-replay fname=replay.bin -icount 7 -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
>
> v5 changes:
>  * Minor changes.
>  * Used fixed-width integer types for read/write functions (as suggested by Alex Bennee)
>  * Moved savevm-related code out of the core.
>  * Added new traced clock for deterministic virtual clock warping (as suggested by Paolo Bonzini)
>  * Fixed exception_index reset for user mode (as suggested by Paolo Bonzini)
>  * Adopted Paolo's icount patches
>  * Fixed hardware interrupts replaying
>
> v4 changes:
>  * Updated block drivers to support new bdrv_open interface.
>  * Moved migration patches into separate series (as suggested by Paolo Bonzini)
>  * Fixed a bug in replay_break operation.
>  * Fixed rtl8139 migration for replay.
>  * Fixed 'period' parameter processing for record mode.
>  * Fixed bug in 'reverse-stepi' implementation.
>  * Fixed replay without making any snapshots (even the starting one).
>  * Moved core replay patches into the separate series.
>  * Fixed reverse step and reverse continue support.
>  * Fixed several bugs in icount subsystem.
>  * Reusing native qemu icount for replay instructions counting.
>  * Separated core patches into their own series.
>
> v3 changes:
>  * Fixed bug with replay of the aio write operations.
>  * Added virtual clock based on replay icount.
>  * Removed duplicated saving of interrupt_request CPU field.
>  * Fixed some coding style issues.
>  * Renamed QMP commands for controlling reverse execution (as suggested by Eric Blake)
>  * Replay mode and submode implemented as QAPI enumerations (as suggested by Eric Blake)
>  * Added description and example for replay-info command (as suggested by Eric Blake)
>  * Added information about the current breakpoint to the output of replay-info (as suggested by Eric Blake)
>  * Updated version id for HPET vmstate (as suggested by Paolo Bonzini)
>  * Removed static fields from parallel vmstate (as suggested by Paolo Bonzini)
>  * New vmstate fields for mc146818rtc, pckbd, kvmapic, serial, fdc, rtl8139 moved to subsection (as suggested by Paolo Bonzini)
>  * Disabled textmode cursor blinking, when virtual machine is stopped (as suggested by Paolo Bonzini)
>  * Extracted saving of exception_index to separate patch (as suggested by Paolo Bonzini)
>
> v2 changes:
>  * Patches are split to be reviewable and bisectable (as suggested by Kirill Batuzov)
>  * Added QMP versions of replay commands (as suggested by Eric Blake)
>  * Removed some optional features of replay to make patches cleaner
>  * Minor changes and code cleanup were made
>
>
>



-- 
Regards,
Artyom Tarasenko

SPARC and PPC PReP under qemu blog: http://tyom.blogspot.com/search/label/qemu