Re: [Qemu-devel] [PATCH v4 00/19] reverse debugging

[Pavel Dovgalyuk]

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На 28 Май 2018 г., 10:13, в 10:13, Pavel Dovgalyuk <address@hidden> 
написал:п>GDB remote protocol supports reverse debugging of the targets.
>It includes 'reverse step' and 'reverse continue' operations.
>The first one finds the previous step of the execution,
>and the second one is intended to stop at the last breakpoint that
>would happen when the program is executed normally.
>
>Reverse debugging is possible in the replay mode, when at least
>one snapshot was created at the record or replay phase.
>QEMU can use these snapshots for travelling back in time with GDB.
>
>Running the execution in replay mode allows using GDB reverse debugging
>commands:
> - reverse-stepi (or rsi): Steps one instruction to the past.
>   QEMU loads on of the prior snapshots and proceeds to the desired
>   instruction forward. When that step is reaches, execution stops.
> - reverse-continue (or rc): Runs execution "backwards".
>   QEMU tries to find breakpoint or watchpoint by loaded prior snapshot
>   and replaying the execution. Then QEMU loads snapshots again and
>   replays to the latest breakpoint. When there are no breakpoints in
>   the examined section of the execution, QEMU finds one more snapshot
>   and tries again. After the first snapshot is processed, execution
>   stops at this snapshot.
>
>The set of patches include the following modifications:
> - gdbstub update for reverse debugging support
> - functions that automatically perform reverse step and reverse
>   continue operations
> - hmp/qmp commands for manipulating the replay process
> - improvement of the snapshotting for saving the execution step
>   in the snapshot parameters
> - other record/replay fixes
>
>The patches are available in the repository:
>https://github.com/ispras/qemu/tree/rr-180524
>
>v4 changes:
>- changed 'since 2.13' to 'since 3.0' in json (as suggested by Eric
>Blake)
>
>v3 changes:
>- Fixed PS/2 bug with save/load vm, which caused failures of the
>replay.
>   The patch was sent separately.
> - Rebased to the new code base.
> - Minor fixes.
>
>v2 changes:
> - documented reverse debugging
> - fixed start vmstate loading in record mode
> - documented qcow2 changes (as suggested by Eric Blake)
> - made icount SnapshotInfo field optional (as suggested by Eric Blake)
> - renamed qmp commands (as suggested by Eric Blake)
> - minor changes
>
>---
>
>Pavel Dovgalyuk (19):
>      block: implement bdrv_snapshot_goto for blkreplay
>      replay: disable default snapshot for record/replay
>      replay: update docs for record/replay with block devices
>      replay: don't drain/flush bdrv queue while RR is working
>      replay: finish record/replay before closing the disks
>      qcow2: introduce icount field for snapshots
>      migration: introduce icount field for snapshots
>      replay: introduce info hmp/qmp command
>      replay: introduce breakpoint at the specified step
>   replay: implement replay-seek command to proceed to the desired step
>      replay: flush events when exiting
>      timer: remove replay clock probe in deadline calculation
>      replay: refine replay-time module
>      translator: fix breakpoint processing
>      replay: flush rr queue before loading the vmstate
>      gdbstub: add reverse step support in replay mode
>      gdbstub: add reverse continue support in replay mode
>      replay: describe reverse debugging in docs/replay.txt
>      replay: allow loading any snapshots before recording
>
>
> accel/tcg/translator.c    |    9 +
> block/blkreplay.c         |    8 +
> block/io.c                |   22 +++
> block/qapi.c              |   17 ++-
> block/qcow2-snapshot.c    |    9 +
> block/qcow2.h             |    2 
> blockdev.c                |   10 ++
> cpus.c                    |   19 ++-
> docs/interop/qcow2.txt    |    4 +
> docs/replay.txt           |   45 +++++++
> exec.c                    |    6 +
> gdbstub.c                 |   50 +++++++-
> hmp-commands-info.hx      |   14 ++
> hmp-commands.hx           |   30 +++++
> hmp.h                     |    3
> include/block/snapshot.h  |    1
> include/sysemu/replay.h   |   18 +++
> migration/savevm.c        |   15 +-
> qapi/block-core.json      |    5 +
> qapi/block.json           |    3
> qapi/misc.json            |   68 +++++++++++
> replay/Makefile.objs      |    3
>replay/replay-debugging.c |  287
>+++++++++++++++++++++++++++++++++++++++++++++
> replay/replay-events.c    |   14 --
> replay/replay-internal.h  |   10 +-
> replay/replay-snapshot.c  |   17 ++-
> replay/replay-time.c      |   27 ++--
> replay/replay.c           |   22 +++
> stubs/replay.c            |   10 ++
> util/qemu-timer.c         |   11 --
> vl.c                      |   18 ++-
> 31 files changed, 696 insertions(+), 81 deletions(-)
> create mode 100644 replay/replay-debugging.c
>
>--
>Pavel Dovgalyuk