RE: [Xen-devel] EFER in HVM guests

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Jan Beulich
> Sent: 29 November 2006 13:07
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] EFER in HVM guests
> 
> Is it intentional that
> - under SVM, 32-bit guests can freely set EFER.LME

Ehm, I guess you mean "on 32-bit hypervisor", as it's impossible to
distinguish a 32-bit and 64-bit guest until the guest is setting LME...
;-). 

The correct reaction for a 32-bit hypervisor is to react like a
"non-64-bit capable processor", which means that EFER has the LME as a
mbz-bit. GP-fault if it's written as a one. We do prevent the long-mode
from being advertised by CPUID when HV is in 32-bit mode, so if the
guest is well-behaved, it shouldn't try to set this bit. 

--
Mats

> - under VMX, 32-bit guests can't access EFER at all?
> 
> Thanks, Jan
> 
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