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RE: [Xen-users] No Full Virtualisation with Intel Core 2 Duo T5500 Mobil

To: "Otavio Salvador" <otavio@xxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] No Full Virtualisation with Intel Core 2 Duo T5500 Mobile CPU?
From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
Date: Wed, 14 Feb 2007 11:41:00 +0100
Cc: Falko Tesch <falko.tesch@xxxxxxxxxxx>, Karl Stevens <karl@xxxxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
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Thread-topic: [Xen-users] No Full Virtualisation with Intel Core 2 Duo T5500 Mobile CPU?

> -----Original Message-----
> From: Otavio Salvador [mailto:otavio@xxxxxxxxxxxxxxxx] 
> Sent: 13 February 2007 18:20
> To: Petersson, Mats
> Cc: Karl Stevens; Falko Tesch; xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] No Full Virtualisation with Intel 
> Core 2 Duo T5500 Mobile CPU?
> "Petersson, Mats" <Mats.Petersson@xxxxxxx> writes:
> > It's worth noting also that there are BIOS's that don't 
> allow this bit
> > to be turned on/off - they just lock it without giving the user any
> > options to change the setting. 
> Current, there's any way to workaround those "broken" BIOS? Are XEN or
> Intel pushing the vendors to fix them?

If the BIOS is "broken", then there's nothing other than replacing the
BIOS with one that isn't "broken"... This is because the bit is
"sticky", as in you can only set it once, and then it stays set whatever
you do until you power-down the processor. [Technically, I think it's
sufficient to pulse the hard-reset pin, aka pwrgood, but since there's
usually no other way than to turn the power off and on again to cause
that pin to pulse, it's no good knowing how it actually works!]

I don't know if Xen is working with motherboard/laptop manufacturers to
fix the problem. I would think that the Intel recommendation is to have
a switch in the BIOS. Whether each and every motherboard vendor
implements that is a different story - and of course "old" motherboards
may not get the attention of BIOS development beyond what's absolutely
necessary to sell the motherboards. New boards are more likely to get
more development work to make them "good". 

Finally, it turns out that the particular model of processor doesn't
have VT - in which case the discussion of a switch becomes meaningless. 


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