On Fri, Nov 25, 2016 at 09:17:08AM +0000, Dong, Eddie wrote: > > On Thu, Nov 24, 2016 at 08:44:06AM +0000, Dong, Eddie wrote: > > > Under certain situation, we have a requirement to apply the > > virtual DMA event in a deterministic way. Current Qemu uses asynchronous > > approach to emulate the virtual IO events since quite long time ago. I am > > wondering if we still have an option to choose the synchronous emulation > > solution. > > > > Please explain exactly what you mean. > > > The usage is to construct a secondary hot standby VM (SVM), identical with > the primary VM (PVM). > When an virtual DMA happens in PVM side, we need to know at which instruction > boundary the virtual DMA is delivered, so that we can replay the virtual DMA > event at the 2nd VM side, to keep them identical at any time. > > Asynchronous IO emulations seems to be a little bit more complicate to be > deterministic... > I might be wrong.
There is a record-replay mode that might be worth investigating. See docs/replay.txt. It sounds like you are not using live migration for micro-checkpoints? The live migration mechanism would keep memory in sync at each checkpoint. Is this work releated to the COLO effort? Stefan
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