From: Stefan Hajnoczi <stefanha@gmail.com>
To: "Dong, Eddie" <eddie.dong@intel.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
zhanghailiang <zhang.zhanghailiang@huawei.com>,
dgilbert@redhat.com
Subject: Re: [Qemu-devel] Asynchronous / synchronous IO emulation
Date: Fri, 25 Nov 2016 12:01:10 +0000 [thread overview]
Message-ID: <20161125120110.GE4939@stefanha-x1.localdomain> (raw)
In-Reply-To: <A12AC9D104E08D47BAF23C492F83C53B546260D4@SHSMSX104.ccr.corp.intel.com>
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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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next prev parent reply other threads:[~2016-11-25 12:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-24 8:44 [Qemu-devel] Asynchronous / synchronous IO emulation Dong, Eddie
2016-11-24 11:16 ` Stefan Hajnoczi
2016-11-25 9:17 ` Dong, Eddie
2016-11-25 12:01 ` Stefan Hajnoczi [this message]
2016-11-26 7:27 ` Dong, Eddie
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