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 >
