Re: [Qemu-devel] [PATCH for-4.1 00/24] Fix record/replay and add reverse debugging

["Pavel Dovgalyuk" <dovgaluk@ispras.ru>]

Ping.


Pavel Dovgalyuk

> -----Original Message-----
> From: dovgaluk [mailto:dovgaluk@ispras.ru]
> Sent: Thursday, June 27, 2019 8:49 PM
> To: pbonzini@redhat.com
> Cc: qemu-devel@nongnu.org; kwolf@redhat.com; peter.maydell@linaro.org;
> crosthwaite.peter@gmail.com; boost.lists@gmail.com; artem.k.pisarenko@gmail.com;
> quintela@redhat.com; ciro.santilli@gmail.com; jasowang@redhat.com; mst@redhat.com;
> armbru@redhat.com; mreitz@redhat.com; maria.klimushenkova@ispras.ru; kraxel@redhat.com;
> pavel.dovgaluk@ispras.ru; thomas.dullien@googlemail.com; pbonzini@redhat.com;
> alex.bennee@linaro.org; dgilbert@redhat.com; rth@twiddle.net
> Subject: Re: [PATCH for-4.1 00/24] Fix record/replay and add reverse debugging
> 
> Paolo,
> 
> what about merging reviewed and acked patches before the soft freeze?
> 
> 
> 
> Pavel Dovgalyuk
> 
> Pavel Dovgalyuk писал 2019-06-21 11:20:
> > 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-190419
> >
> > v17 changes:
> >  - updated gdbstub patches according to the latest changes
> >
> > v16 changes:
> >  - rebased to 4.0
> >
> > v15 changes:
> >  - rebased to the new master
> >  - removed obsolete rtc patch
> >  - fixed misprint in the test
> >
> > v14 changes:
> >  - rebased to the new master
> >
> > v13 changes:
> >  - rebased to make QAPI stuff applicable
> >  - minor reverse step/reverse continue fix
> >
> > v12 changes:
> >  - style fixes
> >
> > v11 changes:
> >  - added can_do_io resetting before jumping to the next block in the
> > chain
> >  - rebase to the latest master
> >
> > v10 changes:
> >  - added patch for correct deadline calculation with external timers
> >  - updated icount-related documentation in json files
> >    (suggested by Markus Armbruster)
> >  - fixed replay shutdown
> >  - renamed some functions and variables to make them consistent with
> >    the documentation and displayed messages
> >  - minor changes
> >
> > v9 changes:
> >  - moved rr qapi stuff to the separate file (suggested by Markus
> > Armbruster)
> >  - minor coding style fixes
> >
> > v8 changes:
> >  - rebased to the new master
> >  - added missing fix for prior rr patch
> >  - updated 'since' version number in json-related patches
> >
> > v7 changes:
> >  - rebased to the new master with upstreamed patches from the series
> >  - several improvements in hmp/qmp commands handling (suggested by
> > Markus Armbruster)
> >  - fixed record/replay with '-rtc base' option enabled
> >  - added document with virtual hardware requirements
> >
> > v6 changes:
> >  - rebased to the new version of master
> >  - fixed build of linux-user configurations
> >  - added new clock for slirp and vnc timers
> >
> > v5 changes:
> >  - multiple fixes of record/replay bugs appeared after QEMU core update
> >  - changed reverse debugging to 'since 3.1'
> >
> > 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.
> >  - 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 (23):
> >       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: provide an accessor for rr filename
> >       qapi: introduce replay.json for record/replay-related stuff
> >       replay: introduce info hmp/qmp command
> >       replay: introduce breakpoint at the specified step
> >       replay: implement replay-seek command
> >       replay: refine replay-time module
> >       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: add BH oneshot event for block layer
> >       replay: document development rules
> >       util/qemu-timer: refactor deadline calculation for external
> > timers
> >       replay: fix replay shutdown
> >       replay: rename step-related variables and functions
> >       icount: clean up cpu_can_io before jumping to the next block
> >
> > pbonzini@redhat.com (1):
> >       replay: add missing fix for internal function
> >
> >
> >  MAINTAINERS               |    1
> >  accel/tcg/tcg-runtime.c   |    2
> >  accel/tcg/translator.c    |    1
> >  block/blkreplay.c         |    8 +
> >  block/block-backend.c     |    8 +
> >  block/io.c                |   32 ++++
> >  block/iscsi.c             |    5 -
> >  block/nfs.c               |    5 -
> >  block/null.c              |    4 -
> >  block/nvme.c              |    6 +
> >  block/qapi.c              |   18 ++
> >  block/qcow2-snapshot.c    |    9 +
> >  block/qcow2.h             |    2
> >  block/rbd.c               |    5 -
> >  block/vxhs.c              |    5 -
> >  blockdev.c                |   10 +
> >  cpus.c                    |   30 +++-
> >  docs/devel/replay.txt     |   46 ++++++
> >  docs/interop/qcow2.txt    |    4 +
> >  docs/replay.txt           |   45 ++++++
> >  exec.c                    |    8 +
> >  gdbstub.c                 |   63 ++++++++-
> >  hmp-commands-info.hx      |   14 ++
> >  hmp-commands.hx           |   53 +++++++
> >  hmp.h                     |    4 +
> >  include/block/snapshot.h  |    1
> >  include/qemu/timer.h      |    7 -
> >  include/sysemu/replay.h   |   30 ++++
> >  migration/savevm.c        |   11 ++
> >  qapi/Makefile.objs        |    2
> >  qapi/block-core.json      |    8 +
> >  qapi/block.json           |    3
> >  qapi/misc.json            |   18 --
> >  qapi/qapi-schema.json     |    1
> >  qapi/replay.json          |  121 +++++++++++++++++
> >  qtest.c                   |    2
> >  replay/Makefile.objs      |    3
> >  replay/replay-debugging.c |  327
> > +++++++++++++++++++++++++++++++++++++++++++++
> >  replay/replay-events.c    |   18 ++
> >  replay/replay-internal.c  |   10 +
> >  replay/replay-internal.h  |   17 +-
> >  replay/replay-snapshot.c  |    6 -
> >  replay/replay-time.c      |   36 ++---
> >  replay/replay.c           |   56 ++++++--
> >  stubs/Makefile.objs       |    1
> >  stubs/replay-user.c       |    9 +
> >  stubs/replay.c            |   10 +
> >  tests/ptimer-test-stubs.c |    4 -
> >  tests/ptimer-test.c       |    4 -
> >  util/qemu-timer.c         |   41 +++++-
> >  vl.c                      |   11 +-
> >  51 files changed, 1014 insertions(+), 131 deletions(-)
> >  create mode 100644 docs/devel/replay.txt
> >  create mode 100644 qapi/replay.json
> >  create mode 100644 replay/replay-debugging.c
> >  create mode 100644 stubs/replay-user.c