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Re: [Qemu-devel] [RFC PATCH v2 00/19] reverse debugging
From: |
Pavel Dovgalyuk |
Subject: |
Re: [Qemu-devel] [RFC PATCH v2 00/19] reverse debugging |
Date: |
Fri, 11 May 2018 11:32:01 +0300 |
> From: Ciro Santilli [mailto:address@hidden
> Did you manage to reproduce and solve the savevm and loadvm problems I
> mentioned at:
> http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg05219.html
> ?
I've tried to debug your scenario and found a bug in saving/loading PS/2
keyboard state.
Here is the patch for fixing it:
https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg02518.html
Maybe it will help for your debugging scenario.
Pavel Dovgalyuk
>
> I still observe them on the current patch.
>
> On Sat, Apr 28, 2018 at 1:36 PM, Pavel Dovgalyuk
> <address@hidden> wrote:
> > 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-180428
> >
> > 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 exitting
> > 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 | 8 +
> > 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, 695 insertions(+), 81 deletions(-)
> > create mode 100644 replay/replay-debugging.c
> >
> > --
> > Pavel Dovgalyuk
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