[Xen-devel] Different instruction stream for PV OS on VT/Pacifica?

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

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?

Thanks,
Dan


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