vmfork in KVM

vmfork in KVM

[Hu Yaohui]

Hi all,
There are some vmfork features provided by Xen based on shadow page
table few years ago. I am wondering whether KVM provides the similar
feature on the same host.
By triggering vmfork, we can get a child VM which CPU and I/O status
is the same as the parent, and the memory is CoW shared with parent
VM.

Thanks,
Yaohui

Re: vmfork in KVM

[Zhi Yong Wu]

HI, all guys

Why does vmfork not get supported by KVM project? What is the
drawback? It's very cool if it's used in some scenario, e.g. HPC. It
will be appreciated for your comments, thanks.

On Fri, Oct 24, 2014 at 2:25 AM, Hu Yaohui <loki2441@gmail.com> wrote:
> Hi all,
> There are some vmfork features provided by Xen based on shadow page
> table few years ago. I am wondering whether KVM provides the similar
> feature on the same host.
> By triggering vmfork, we can get a child VM which CPU and I/O status
> is the same as the parent, and the memory is CoW shared with parent
> VM.
>
> Thanks,
> Yaohui
> --
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-- 
Regards,

Zhi Yong Wu

Re: vmfork in KVM

[Eric Blake]

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On 05/08/2015 03:55 AM, Zhi Yong Wu wrote:
> HI, all guys
> 
> Why does vmfork not get supported by KVM project? What is the
> drawback? It's very cool if it's used in some scenario, e.g. HPC. It
> will be appreciated for your comments, thanks.

In general, live cloning of a VM is a security nightmare - you have to
make sure that either both sides of the fork will never be exposed to
the same network, or that you figure out how to scrub everything such as
IP addresses and random number state so that the two VMs are independent
enough as to not be able to guess the behavior of one guest by observing
the other.  Offline cloning is a much more tractable problem.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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