Within the context of a simulator, qemu runs with a limited set of devices so that removes some indeterminism but not all I guess.
VMsimint boasts exact reproducibility because they control all outputs/inputs. I tried to look into their patch but the patch is empty and instead there seems to be the partial (full ?) tree of qemu 1.6. I suspect this might be quite some work to port this to the latest qemu. It's sad because I really like the approach :) (qemu changes in the latest archive of http://www.ikr.uni-stuttgart.de/Content/IKRSimLib/Download/) I guess I will stick to DCE with the hope that qemu considers the usecase and make it easier. Cheers 2017-10-24 6:33 GMT+09:00 Nutaro, James J. <nutar...@ornl.gov>: > I don't expect exact repeatability, but I haven't tested for it either. The > machinery that prevents repeatability with replay will probably have the same > effect in the adevs/qemu simulator. > > -----Original Message----- > From: Matt [mailto:matta...@gmail.com] > Sent: Monday, October 23, 2017 5:38 AM > To: Nutaro, James J. > Cc: Emilio G. Cota; qemu-devel@nongnu.org; Hajime Tazaki > Subject: Re: [Qemu-devel] Running Qemu in discrete time/step by step > > 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. <nutar...@ornl.gov>: >> 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:c...@braap.org] >> Sent: Thursday, October 19, 2017 4:54 PM >> To: Matt >> Cc: qemu-devel@nongnu.org; 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 >> >
