Re: [RFC PATCH 03/13] kvm: Add XO memslot type

[Paolo Bonzini]

On 03/10/19 23:23, Rick Edgecombe wrote:
> Add XO memslot type to create execute-only guest physical memory based on
> the RO memslot. Like the RO memslot, disallow changing the memslot type
> to/from XO.
> 
> In the EPT case ACC_USER_MASK represents the readable bit, so add the
> ability for set_spte() to unset this.
> 
> This is based in part on a patch by Yu Zhang.
> 
> Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>

Instead of this, why not check the exit qualification gpa and, if it has
the XO bit set, mask away both the XO bit and the R bit?  It can be done
unconditionally for all memslots.  This should require no change to
userspace.

Paolo