Re: [Patch v5 1/4] Remove SMEP bit from CR4_RESERVED_BITS

[Ingo Molnar <mingo@elte.hu>]

* Avi Kivity <avi@redhat.com> wrote:

> On 05/30/2011 11:52 AM, Ingo Molnar wrote:
> >* Avi Kivity<avi@redhat.com>  wrote:
> >
> >>  >  Another option would be to try to set the SMEP bit *before* we
> >>  >  enable paging. In theory this should not confuse a Linux guest -
> >>  >  and while i have not tested it i *think* we let it survive in the
> >>  >  saved_cr4_features shadow variable. That would make guest
> >>  >  suspend/resume work out of box as well.
> >>
> >>  Is there any reason not to do it in a hidden way in kvm?  Why must
> >>  we play tricks?
> >
> > So do you have a suggestion of how to do this cleaner?
> >
> > Add an ioctl that allows a VCPU to be configured in a way to set 
> > a cr4 feature without the guest actually seeing that bit? 
> > [Assuming both cr4 reads and writes are fully captured by KVM and 
> > thus guest behavior is controllable.]
> 
> Yes, this was what I suggested before.  IIRC you liked it.

Oh, it wasn't clear to me that this was your preference as well - and 
i didnt see such a capability in this series [let me know if i 
blindly missed it] so i was wondering what the battle plan was fr 
that :-)

Thanks,

	Ingo