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RE: [Xen-devel] Early test for Windows vs Linux hvm domain?

For my purposes, the definition of 'early' is before the launched guest
expects to be doing any (accurate) timekeeping.

I'm experimenting with the mechanisms in Xen for handling virtual time.
At this point, I'm looking for heuristics, not 100% accuracy, and want
to divine in hvm code whether Windows is running or Linux is running
(and, yes, I realize there are other possibilities :-)

Dan Magenheimer

If Xen could save time in a bottle / then clocks wouldn't virtually skew /
It would save every tick / for VMs that aren't quick /
and Xen then would send them anew
(by Dan Magenheimer... with apologies to the late great Jim Croce)

> -----Original Message-----
> From: James Harper [mailto:james.harper@xxxxxxxxxxxxxxxx]
> Sent: Wednesday, January 30, 2008 5:17 PM
> To: dan.magenheimer@xxxxxxxxxx; Xen-Devel (E-mail)
> Subject: RE: [Xen-devel] Early test for Windows vs Linux hvm domain?
> > 
> > Thanks to all for the 32-bit vs 64-bit ideas.  Keir's
> > EFER LME bit works like a charm.
> > 
> > Now a probably tougher (and more controversial) question:
> > 
> > Is there any algorithm or heuristic early in hvm launch that
> > can distinguish between a windows guest and a linux guest
> > (64-bit specifically, but if same or different test works
> > for 32-bit that would be useful too).
> > 
> You may have mentioned it in your other thread, but what 
> exactly is the
> problem you are trying to solve here?
> I would say that the answer is definitely no, depending on what your
> definition of 'early' is. A hvm domain could invoke grub, and then a
> user could then choose to run windows or Linux (or BSD, or another OS
> altogether). Does DOS work under HVM? If it does, a HVM domain could
> start DOS, the user could spend a bit of time in there, and then later
> on launch Linux from there.
> James

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