[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH v3 09/15] replay: implement replay-seek command
From: |
Alex Bennée |
Subject: |
Re: [PATCH v3 09/15] replay: implement replay-seek command |
Date: |
Tue, 08 Sep 2020 12:10:34 +0100 |
User-agent: |
mu4e 1.5.5; emacs 28.0.50 |
Alex Bennée <alex.bennee@linaro.org> writes:
> Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes:
>
>> On 07.09.2020 19:25, Alex Bennée wrote:
>>>
>>> Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes:
>>>
>>>> On 07.09.2020 17:59, Alex Bennée wrote:
>>>>>
>>>>> Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes:
>>>>>
>>>>>> On 07.09.2020 15:58, Alex Bennée wrote:
>>>>>>>
>>>>>>> Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes:
>>>>>>>
>>>>>>>> From: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
>>>>>>>>
>>>>>>>> This patch adds hmp/qmp commands replay_seek/replay-seek that proceed
>>>>>>>> the execution to the specified instruction count.
>>>>>>>> The command automatically loads nearest snapshot and replays the
>>>>>>>> execution
>>>>>>>> to find the desired instruction count.
>>>>>>>
>>>>>>> Should there be an initial snapshot created at instruction 0? Using a
>>>>>>> separate monitor channel:
>>>>>>
>>>>>> Right, you can't go to the prior state, when there is no preceding
>>>>>> snapshot available.
>>>>>
>>>>> It seems creating an initial snapshot automatically would be more user
>>>>
>>>> Please take a look at 'Snapshotting' section of docs/replay.txt.
>>>> Reverse debugging is considered to be run with disk image (overlay)
>>>> and rrsnapshot option of icount, which allows creating an initial
>>>> VM snapshot.
>>>
>>> Given that I'm using the block device purely for VM snapshots I think it
>>> would be useful to document the minimal "no disk" approach - i.e. where
>>> the disk is only used for record/replay.
>>>
>>> However I'm still having trouble. I can record the trace with:
>>>
>>> ./qemu-system-aarch64 -cpu cortex-a53 -display none -serial stdio \
>>> -machine virt -kernel zephyr.elf -net none \
>>> -icount
>>> shift=6,align=off,sleep=off,rr=record,rrfile=record.out,rrsnapshot=rrstart
>>> \
>>> -drive file=record.qcow2,if=none,id=rr \
>>> -monitor telnet:127.0.0.1:4444 -S
>>
>> Can you provide your zephyr.elf image?
>>
>>>
>>> which shows:
>>>
>>> (qemu) info snapshots
>>> info snapshots
>>> List of snapshots present on all disks:
>>> ID TAG VM SIZE DATE VM CLOCK
>>> ICOUNT
>>> -- rrstart 653 KiB 2020-09-07 17:12:42 00:00:00.000
>>> 0
>>>
>>> but do I need a whole separate overlay in the replay case? I thought
>>> supplying snapshot to the drive would prevent the replay case
>>> overwriting what has been recorded but with:
>>>
>>> -icount shift=6,align=off,sleep=off,rr=replay,rrfile=record.out \
>>> -drive file=record.qcow2,if=none,id=rr,snapshot
>>
>> When you provide qcow2 (overlay or not) for snapshotting, you don't need
>> any 'snapshot' option on drive.
>>
>>>
>>> but I get:
>>>
>>> (qemu) info snapshots
>>> info snapshots
>>> There is no snapshot available.
>>>
>>> so if I drop the ,snapshot from the line I can at least see the snapshot
>>> but continue doesn't seem to work:
>>>
>>> (qemu) info snapshots
>>> info snapshots
>>> List of snapshots present on all disks:
>>> ID TAG VM SIZE DATE VM CLOCK
>>> ICOUNT
>>> -- rrstart 653 KiB 2020-09-07 17:12:42 00:00:00.000
>>> 0
>>> (qemu) replay_break 190505
>>> replay_break 190505
>>> (qemu) c
>>> c
>>> (qemu) info replay
>>> info replay
>>> Replaying execution 'record.out': instruction count = 0
>>
>> It seems, that replay hangs. Can you try removing '-S' in record command
>> line?
>
> That doesn't make any difference removing from both the record and
> replay cases. It seems to need a loadvm to start things off.
>
> I've sent you an image off list. Please let me know if you can
> replicate.
OK I can successfully use gdb to reverse debug the acceptance test (\o/)
so I suspect there are differences in the calling setup.
The first one is ensuring that rrsnapshot is set for both record and
replay. For this reason I think a more user friendly automatic snapshot
would be worth setting up when record/replay is being used.
-icount sleep=off definitely breaks things. Do we keep track of the
icount bias as save and restore state?
--
Alex Bennée
- Re: [PATCH v3 09/15] replay: implement replay-seek command, (continued)
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Alex Bennée, 2020/09/07
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Alex Bennée, 2020/09/07
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Pavel Dovgalyuk, 2020/09/07
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Alex Bennée, 2020/09/07
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Pavel Dovgalyuk, 2020/09/07
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Alex Bennée, 2020/09/07
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Pavel Dovgalyuk, 2020/09/08
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Alex Bennée, 2020/09/08
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Pavel Dovgalyuk, 2020/09/08
- Re: [PATCH v3 09/15] replay: implement replay-seek command,
Alex Bennée <=
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Pavel Dovgalyuk, 2020/09/08
- Re: [PATCH v3 09/15] replay: implement replay-seek command, Pavel Dovgalyuk, 2020/09/08
[PATCH v3 10/15] replay: flush rr queue before loading the vmstate, Pavel Dovgalyuk, 2020/09/02
[PATCH v3 11/15] gdbstub: add reverse step support in replay mode, Pavel Dovgalyuk, 2020/09/02
[PATCH v3 12/15] gdbstub: add reverse continue support in replay mode, Pavel Dovgalyuk, 2020/09/02
[PATCH v3 13/15] replay: describe reverse debugging in docs/replay.txt, Pavel Dovgalyuk, 2020/09/02