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 10:30:20 +0100
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Cc: Alexander Graf <agraf@suse.de>, Jan Kiszka <jan.kiszka@web.de>,
	kvm-devel list <kvm@vger.kernel.org>,
	Marcelo Tosatti <mtosatti@redhat.com>,
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To: Avi Kivity <avi@redhat.com>
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On Mon, Oct 26, 2009 at 11:21:12AM +0200, Avi Kivity wrote:
> On 10/26/2009 11:17 AM, Joerg Roedel wrote:
> >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.
> 
> Which host state?  As far as I can tell, it can all be regenerated.

The state which is loaded into the vcpu when a #vmexit is emulated. This
includes segments, control registers and the host rip for example.

	Joerg