Re: [Qemu-devel] Running Qemu in discrete time/step by step

[Matt]

I did not know about Qemu's record/replay mode which is an interesting
feature but unneeded if a  2nd qemu run with the same inputs generated
the same outputs (as it's the case with DCE).
@nutaro Thanks for the updated patch. I will have a look at adevs. On
a related note https://github.com/qemu/qemu/blob/master/docs/replay.txt
enumerates different sources of indeterminism
==
Replaying of the execution of virtual machine is bound by sources of
non-determinism. These are inputs from clock and peripheral devices,
and QEMU thread scheduling. Thread scheduling affect on processing events
from timers, asynchronous input-output, and bottom halves.
==

Do you manage to achieve perfect reproducibility with adevs + qemu ?
If yes, is there any publication describing how you achieve this ?

Best regards
matt

2017-10-21 0:02 GMT+09:00 Nutaro, James J. <address@hidden>:
> Thanks for taking a look at the patch. The most recent version of the patch 
> will also work with KVM if you need to speed things up. You can find it here:
>
> https://patchwork.kernel.org/patch/9960369/
>
> Somehow I messed up that post and it shows V8 when it should be V9.
>
> You can get the simulator that it works with at
>
> https://sourceforge.net/projects/adevs/
>
> If nothing else, this simulator would give you a blue print for integration 
> with another tool.
>
> Jim
>
> -----Original Message-----
> From: Emilio G. Cota [mailto:address@hidden
> Sent: Thursday, October 19, 2017 4:54 PM
> To: Matt
> Cc: address@hidden; Hajime Tazaki; Nutaro, James J.
> Subject: Re: [Qemu-devel] Running Qemu in discrete time/step by step
>
> On Thu, Oct 19, 2017 at 14:14:12 +0900, Matt wrote:
> (snip)
>> - VMSimint does nearly that, it runs Qemu in discrete time but
>> interface it with a JAVA simulator
>> http://www.ikr.uni-stuttgart.de/Content/Publications/Archive/We_SIMUTools_2014_40209.pdf
>> (with the code http://www.ikr.uni-stuttgart.de/Content/IKRSimLib/Download/)
>> - http://web.ornl.gov/~nutarojj/adevs/ does sthg similar too
>
> Nutaro's work to interface with QEMU has been posted on the list:
>   https://patchwork.kernel.org/patch/9572497/
> I'm Cc'ing him in case he's not subscribed to the list.
>
>
>> My questions would be:
>> 1/ do you know of any other related work ?
>
> Is QEMU's record/replay mode of any use to you? Note that as is the
> case with Nutaro's patch, you'll need icount mode (i.e. single-core)
> enabled.
>
>> 2/ I believe there is interest from the research side but would it be
>> possible to merge either approach or a similar one (adevs patch
>> doesn't seem too big ~500 lines), would that be of interest for the
>> Qemu comminity too ?
>> 3/ if yes to 2. How to proceed, which one would be favorite ? if no,
>> what should be improved ? or would that be a definitive no ?
>
> I think the adevs approach is reasonable. The patch hasn't gotten much
> attention I guess because not many people care about this feature.
> But if you could review the patch and certify that it works for you
> (i.e. it works with simulators other than adevs), that could only help
> the patch getting in.
>
> That said, I make no merging decisions so take this as just my opinion.
>
> Cheers,
>
>                 Emilio
>