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xen-devel
RE: [Xen-devel] Different instruction stream for PV OS on VT/Pacifica?
> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of
> Magenheimer, Dan (HP Labs Fort Collins)
> Sent: 28 April 2006 17:27
> To: xen-devel
> Subject: [Xen-devel] Different instruction stream for PV OS
> on VT/Pacifica?
>
> I was asked a question and I think I know the answer for
> Xen/ia64 but am not sure I know the answer for Xen/x86 -- or
> if there is a different answer for VT vs Pacifica.
>
> In the three scenarios:
> A. Paravirtualized (PV) OS running on a pre-HVM processor
> using a virtualization-capable Xen
> B. PV OS running on a VT (or Pacifica) processor using a
> virtualization-capable Xen but NOT running any fully
> virtualized (FV) OS
> C. PV OS running on a VT (or Pacifica) processor using a
> virtualization-capable Xen which is sharing the processor
> with a FV OS
>
> is the sequence of instructions executed by the processor on
> behalf of the PV OS -- including instructions in firmware and
> in Xen -- identical or different/faster/slower? (Ignoring
> irrelevant factors such as domain switch, non-virtualization-
> related processor differences, etc.)
>
> On Xen/ia64, a PV OS should always execute the same sequence
> of instructions, whether or not it is on a VT-capable processor.
>
> Can experts for the others (VT-x and Pacifica) comment?
I'd say that this answer applies to AMD processors (and as far as I know
it applies to Intel too - but I'm not really a spokesperson for AMD, and
even less so for Intel.)
There's been some thinking that we could use HVM (VT/SVM (pacifica)) to
enhance PV guest too, but so far nothing has been implemented [and I
guess once it does get implemented, IA64 will follow shortly afterwards,
assuming it's generally useful and not specific to x86].
--
Mats
>
> Thanks,
> Dan
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
>
>
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