Re: [PATCH] kvm_para_available() should check hypervisor bit before accessing hypervisor cpuid leaf.

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On Tue, May 01, 2012 at 03:59:33PM +0300, Avi Kivity wrote:
> On 05/01/2012 03:55 PM, Gleb Natapov wrote:
> > On Tue, May 01, 2012 at 03:50:44PM +0300, Avi Kivity wrote:
> > > On 04/30/2012 02:45 PM, Gleb Natapov wrote:
> > > > This couid range does not exist on real HW and Intel spec says that
> > > > "Information returned for highest basic information leaf" will be
> > > > returned. Not very well defined. 
> > > >
> > > 
> > > Correct in principle.  But IIRC some old qemus supported the kvm cpuid
> > > range without setting the hypervisor bit.
> > > 
> > How old?
> 
> commit e19967a0e00c7af4efd2f2db12a7d5d7f0b387f7
> Author: Avi Kivity <avi@xxxxxxxxxxxx>
> Date:   Tue Apr 22 11:44:19 2008 +0300
> 
>     Set "hypervisor present" cpuid bit
>    
>     This tells Microsoft guests that they are running under a hypervisor.
>    
>     Signed-off-by: Avi Kivity <avi@xxxxxxxxxxxx
> 
> $ git describe --contains e19967a0e00c
> kvm-80rc2~489
> 
Since latest Windowses will not run on such old version correctly (may
use tsc for QPC) may be dropping support for Linuxes past 3.4 is a
possibility too?

--
			Gleb.
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