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RE: [Xen-devel] Save/restore, migration of HVM-guest's

To: "Mark Williamson" <mark.williamson@xxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Save/restore, migration of HVM-guest's
From: "Nakajima, Jun" <jun.nakajima@xxxxxxxxx>
Date: Wed, 26 Apr 2006 16:43:44 -0700
Cc: Thorolf Godawa <nospam@xxxxxxxxx>
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Thread-topic: [Xen-devel] Save/restore, migration of HVM-guest's
Mark Williamson wrote:
>> can s.b. tell me what the actual status for save/restore and
>> migration of unmodified HVM-guest's is? Are there any news since Xen
>> 3.0.1, any timeframe when it could be available?
> Since memory is fully virtualised a fair bit of the infrastructure
> necessary is already there.  I don't know to what extent page
> dirtying is exported to userspace for an HVM domain, which is an
> important part of live migration (although not necessary for suspend
> / resume). 
> Somebody might in principle be able to hack the Qemu device models to
> suspend their state, at which point almost all the pieces will be in
> place. 

We are working on save/restore. Once it's done we'll work on live

> However, the primary plan (I believe) is to move the device emulator
> into a paravirtualised domain that runs alongside the HVM domain. 
> This encapsulates all the state of the device models in an opaque way
> and migration can be achieved by migrating the device model emulator
> along with the domain in question.

The prototype is based on the current model as the qemu already has the
save/restore feature. There are many issues to resolve, such as handling
of in-flight I/O requests, and most of them are also applicable to the
mini-guest based I/O device emulation. 

> There was recently a call for help on implementing this new model
> (which should also improve emulation performance), but I'm not sure
> anyone is working directly on it yet.  Since the emulator domain is
> likely to be based on mini-os, a number of people are working on
> cleaning up its code base and making it run on 64-bit x86.

We are thinking which code should be in the mini-guest first to get I/O
device emulation working. Such works on the mini-os would be

> Cheers,
> Mark

Intel Open Source Technology Center

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