Re: [Xen-devel] [PATCH v3 04/16] hypervisor part of add vmware_port to xl.cfg

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 09/08/2014 11:32 AM, Andrew Cooper wrote:
> On 08/09/14 16:22, Jan Beulich wrote:
> > > > > On 08.09.14 at 17:01, <boris.ostrovsky@xxxxxxxxxx> wrote:
> > > I wonder whether we should enable #GP intercepts only when we know that
> > > the guest is VMware-aware (which we do as far as I can tell since we
> > > have a config option).
> > I didn't look at the patches themselves yes, but I very much expected
> > this to now be the case considering discussion on the earlier version.
> > If it's not, I'm not even sure looking at the new version is going to be
> > of much use...
> >
> > Jan
> I find it incredibly hard to believe that VMWare do unconditional #GP
> exits, and looking at the Intel manual, you do not actually need to
> intercept #GP faults.
>
> The "unconditional I/O exiting" control can be used to cherry-pick
> specific IO ports in combination with the IO port bitmap, ahead of the
> #GP fault due to a failure of IOPL.  I would expect AMD has a similar
> option.
Yes, it does. However, I believe #GP intercept has been added so that IO 
access can be made from guest's ring 3 as well, not to handle IO access 
in general.
Having said that, I don't remember seeing updates to IO permissions map 
in the patch.
-boris


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel