Re: [Xen-devel] Intermittent fatal page fault with XEN 4.3.1 (Centos 6.3 DOM0 with linux kernel 3.10.16.)

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-11-07 at 09:10 +0000, Jan Beulich wrote:
> >>> On 06.11.13 at 18:07, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> > On 06/11/13 17:06, Ian Campbell wrote:
> >> On Wed, 2013-11-06 at 16:54 +0000, Andrew Cooper wrote:
> >>> I looked over the xl code and thought that nestedhvm should default to
> >>> false, but I would prefer someone more familar with libxl and the idl to
> >>> confirm what the default should be.
> >> libxl thinks the default is false and will set HVM_PARAM_NESTEDHVM to 0
> >> in that case. Is there some way to query the hypervisor for what it
> >> thinks the setting is?
> > 
> > A get hvmparam hypercall will retrieve the value, but it is initialised
> > to 0 and only ever set by a set hvmparam hypercall.
> 
> Which makes me start suspecting that the guest might be deriving
> its information on VMX being available from something other than
> CPUID. Of course we ought to confirm that we don't unintentionally
> return the VMX flag set (and that the config file doesn't override it
> in this way - I think we shouldn't be suppressing user overrides
> here, but I didn't go check whether we do).

I was also wondering about the behaviour of using vmx instructions in a
guest despite vmx not being visible in cpuid...

Ian.



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