Re: [Xen-devel] [PATCH 04/16] vmx: nest: nested control structure

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On Wednesday 15 September 2010 15:46:24 Dong, Eddie wrote:
> >>>>>  #ifdef __x86_64__
> >>>>>      struct vmx_msr_state msr_state;
> >>>>>      unsigned long        shadow_gs;
> >>>>
> >>>> I think, the structure should be allocated in the
> >>>> nestedhvm_vcpu_initialise() function hook and assigned to the
> >>>> nh_arch pointer in struct nestedhvm.
> >>>
> >>> Well, the structure itself is pretty small, so dynamic allocation is
> >>> really not a good idea.
> >
> > It's not a question of size. The point is that it is opaque to
> > non-vmx code.
>
> I think it is anyway recycling again, that is not necessary.
> Outside of VMX should not access those VMX specific code in theory.

Also practically. The point is if that mistake happens then gcc will complain
when the data structure is opaque to non-vmx code.

I already discussed exactly that point with Keir when he suggested
me to go your way but then agreed.
See:
http://lists.xensource.com/archives/html/xen-devel/2010-08/msg01024.html
http://lists.xensource.com/archives/html/xen-devel/2010-08/msg01028.html

Christoph


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