From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joerg Roedel <joerg.roedel@amd.com>
Subject: Re: List of unaccessible x86 states
Date: Mon, 26 Oct 2009 10:17:31 +0100
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Cc: Alexander Graf <agraf@suse.de>, Jan Kiszka <jan.kiszka@web.de>,
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	Marcelo Tosatti <mtosatti@redhat.com>,
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To: Avi Kivity <avi@redhat.com>
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On Sun, Oct 25, 2009 at 11:49:35AM +0200, Avi Kivity wrote:
> On 10/24/2009 12:35 PM, Alexander Graf wrote:
> >
> >Hm, thinking about this again, it might be useful to have an
> >"currently in nested VM" flag here. That way userspace can decide
> >if it needs to get out of the nested state (for migration) or if
> >it just doesn't care.
> 
> Getting out of nested state involves modifying state (both memory
> and registers).  Nor can we in the general case force it.  The guest
> can set up a situation where it is impossible to #vmexit.

There is actually more than that. If the guest runs in guest mode itself
we also need to report the host state to be able to do an #vmexit after
migration.
In nested SVM the host state is not saved in the guest memory to prevent
the guest from modifying it and break out of its virtualization jail.

	Joerg