Re: [V10 PATCH 09/23] PVH xen: introduce pvh_set_vcpu_info() and vmx_pvh_set_vcpu_info()

[Mukesh Rathor <mukesh.rathor@oracle.com>]

On Wed, 7 Aug 2013 11:01:21 +0100
Tim Deegan <tim@xen.org> wrote:

> At 18:53 -0700 on 06 Aug (1375815193), Mukesh Rathor wrote:
> > On Mon, 5 Aug 2013 18:34:36 -0700
> > Mukesh Rathor <mukesh.rathor@oracle.com> wrote:
> > 
> > > On Mon, 05 Aug 2013 12:08:50 +0100
> > > "Jan Beulich" <JBeulich@suse.com> wrote:
> > > 
> > > > >>> On 26.07.13 at 02:58, Mukesh Rathor
> > > > >>> <mukesh.rathor@oracle.com> wrote:
> > > > > On Thu, 25 Jul 2013 14:47:55 +0100
> > > > > Tim Deegan <tim@xen.org> wrote:
> > ....... > > 
> > > > >> At 18:59 -0700 on 23 Jul (1374605957), Mukesh Rathor wrote:
> > > > > That was an option discussed with Jan, walking and reading
> > > > > the GDT entries from the gdtaddr the guest provided to load
> > > > > the hidden parts. But, I agree with him, that for the initial
> > > > > cpu boot we can restrict the ABI to say: 0 base addr, ~0
> > > > > limit, and "read/write, accessed" default attributes for the
> > > > > hidden part (64bit guest). 
> > > > 
> > > > That must be a misunderstanding then (also see my other reply)
> > > > - I always meant to require that you either properly load the
> > > > hidden register portions from the descriptor tables, or at
> > > > least verify that the descriptor table entries referenced match
> > > > the defaults you enforce.
> > > 
> > > Ok, I thought you just wanted to be documented, If I'm gonna write
> > > the code to verify, i might as well just write the hidden
> > > porions, an option I'd proposed. That way there are no
> > > constraints. I'm currently working on just doing that, and will
> > > be in the next version of the patch.
> > 
> > Ok, I've mostly got code to set the hidden fields, but the more I
> > think about it, the more I feel that the right/better thing to do
> > is to just not set any selectors at all, instead default them in
> > the VMCS.
> 
> Why do you think that's better?  Why on earth wouldn't a VCPU
> context-setting hypercall that takes segment selectors as arguments
> just DTRT?  The principle of least astonishment should apply here.

Ok. looks like the common denometer is to just set the hidden fields,
so I'll just do that.

thanks,
mukesh