Re: [PATCH 11/24] Implement VMPTRST

["Nadav Har'El" <nyh@math.technion.ac.il>]

On Wed, Jun 16, 2010, Gleb Natapov wrote about "Re: [PATCH 11/24] Implement VMPTRST":
> On Mon, Jun 14, 2010 at 12:15:10PM +0300, Avi Kivity wrote:
> > write_guest_virt_system() is used by writes which need to ignore the
> > cpl, for example when a cpl 3 instruction loads a segment, the
> > processor needs to update the accessed flag even though it is only
> > accessible to cpl 0.  That's not your case, you need the ordinary
> > write_guest_virt().
> > 
> > Um, I see there is no kvm_write_guest_virt(), you'll have to introduce it.
> > 
> the code uses this function after checking cpl to be zero, so may be it
> is ok, not to pretty though. I was actually hoping to get rid of all
> kvm_(read|write)_guest_virt* and replace existing uses with
> emulator_(read|write)_emulated, but this patch series adds more users
> that will be hard to replace :(

If I remember the history correctly, this is exactly what happened in this
code. We used to use kvm_write_guest_virt(), until a few months ago it
disappeared. I thought it to be fine to call write_guest_virt_system()
because, like you said, we only already check above that cpl=0, so it is fine
to assume we have cpl 0 privileges.

So while it might look a bit strange at first, I think it should be fine and
there's no need to create more functions.

-- 
Nadav Har'El                        |    Wednesday, Jun 16 2010, 4 Tammuz 5770
nyh@math.technion.ac.il             |-----------------------------------------
Phone +972-523-790466, ICQ 13349191 |Amateurs built the ark - professionals
http://nadav.harel.org.il           |built the Titanic.