> -----Original Message-----
> From: Koripella Srinivas [mailto:talkwithsrinivas@xxxxxxxxxxx]
> Sent: 09 May 2007 19:53
> To: Petersson, Mats
> Subject: Re: [Xen-devel] Xen on top of xen
>
> Can u throw more light on the non-nestability ??
Well, to put it simply, once you set up the SVM/VMX feature, it doesn't
allow another such setup on top of it. It would be technically possible
to support this in a processor designed to do so, but at the moment,
neither of AMD's or Intel's CPU's support this. It is clearly easier to
design a processor that only supports one level of "nesting" of
virtualization[1], and it is also debatable what the REAL benefit of
running nested virtual machines would be - I'm sure if it was a huge
benefit compared to the effort of implementing it[2], at least one of
the two producers of virtualizable x86 processors would have added such
fearures...
[1] Keeping one set of data for where to return to when the VMExit
happens, for example, is easier than having a "stack" of such.
[2] On top of the extra effort to design and test such feature, there is
also a potential performance penalty for nesting VM's, since there is
more logic involved. Depending on where that extra logic ends up, it may
be necessary to add a further clock-cycle to some operation.
--
Mats
>
>
> ----- Original Message ----
> From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
> To: pradeep singh rautela <rautelap@xxxxxxxxx>; Koripella
> Srinivas <talkwithsrinivas@xxxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx;
> xen-devel-request@xxxxxxxxxxxxxxxxxxx
> Sent: Wednesday, 9 May, 2007 4:33:57 PM
> Subject: RE: [Xen-devel] Xen on top of xen
>
>
>
>
> > -----Original Message-----
> > From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> > [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of
> > pradeep singh rautela
> > Sent: 09 May 2007 10:11
> > To: Koripella Srinivas
> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxx;
> > xen-devel-request@xxxxxxxxxxxxxxxxxxx
> > Subject: Re: [Xen-devel] Xen on top of xen
> >
> >
> >
> > On 5/9/07, pradeep singh rautela <rautelap@xxxxxxxxx> wrote:
> >
> >
> >
> > On 5/9/07, Koripella Srinivas <
> > talkwithsrinivas@xxxxxxxxxxx
> > <mailto:talkwithsrinivas@xxxxxxxxxxx> > wrote:
> >
> > Hi,
> > Is it possible to run xen in a hvm guest which
> > itself is running on xen?
> >
> >
> > Yes, you can.
> >
> >
> > Just to add only on hvm guests and not on pv guests.
>
> And you can't run HVM guests inside the "xen on top of xen",
> as the HVM
> feature is not (in current CPU's) nestable.
>
> --
> Mats
> >
> >
> >
> > Thanks
> > ~psr
> >
> >
> >
> >
> > Thanks
> >
> >
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> >
> >
> >
> >
> >
> >
> > --
> > ---
> > pradeep singh rautela
> >
> > "Genius is 1% inspiration, and 99% perspiration" - not me :)
> >
> >
> >
> >
> > --
> > ---
> > pradeep singh rautela
> >
> > "Genius is 1% inspiration, and 99% perspiration" - not me :)
> >
>
>
>
>
>
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