From: "Gregory Haskins" <ghaskins-Et1tbQHTxzrQT0dZR+AlfA@public.gmane.org>
To: "Casey Jeffery"
<kcjeffery-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
<kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
Subject: Re: Recursive virtualization
Date: Wed, 04 Apr 2007 12:53:55 -0400 [thread overview]
Message-ID: <461391C9.BA47.005A.0@novell.com> (raw)
In-Reply-To: <cb6aceaa0704040936j62354e99vb49108040ff79d4e-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
It seems from cursory inspection that this is possible in theory, even on HVM hardware. My thoughts are as follows (Intel oriented, which I know better):
*) The hypervisor sets to trap on VMX type operations (VMXON/OFF/START/RESUME, etc) and provide emulation of them as follows:
*) When a VMXON instruction is encountered, mark the guest as a nested hypervisor and setup any necessary structures for tracking
*) when a VMXSTART/RESUME instruction is encountered, launch the new guest as a subordinate guest of the owning hypervisor guest. When a VMEXIT occurs, VMXRESUME the hypervisor guest.
etc etc
This in theory could work to any degree of nesting, as long as the VMX operations are emulated. Note that each subordinate hypervisor would think it was emulating the VMX operations too, even though it is really only the bottom hypervisor which does so. This is kind of mind bending ;)
-Greg
>>> On Wed, Apr 4, 2007 at 12:36 PM, in message
<cb6aceaa0704040936j62354e99vb49108040ff79d4e-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>, "Casey Jeffery"
<kcjeffery-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> I swear this has been brought up before in this forum, but I can't
> find it. I'm curious what the virtualization gurus in this forum think
> of the possibilities for recursive virtualization. I know vbox claims
> to support it, but I haven't come across many details on how they do
> it and I don't think they really use the hvm hardware. Is it something
> that should be possible without an "enlightened" guest hypervisor and
> by basically just virtualizing the VMCS/VMCB structures?
>
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prev parent reply other threads:[~2007-04-04 16:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-04 16:36 Recursive virtualization Casey Jeffery
[not found] ` <cb6aceaa0704040936j62354e99vb49108040ff79d4e-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2007-04-04 16:48 ` Dor Laor
[not found] ` <64F9B87B6B770947A9F8391472E032160B318F00-yEcIvxbTEBqsx+V+t5oei8rau4O3wl8o3fe8/T/H7NteoWH0uzbU5w@public.gmane.org>
2007-04-04 16:57 ` Casey Jeffery
[not found] ` <cb6aceaa0704040957r7ff6dc2dycc626e7079deceef-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2007-04-04 21:30 ` Dor Laor
2007-04-04 16:53 ` Gregory Haskins [this message]
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