Re: [Xen-devel] [PATCH v4 2/4] x86/compat: Test both PV and PVH guests for compat mode

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 08/27/2015 12:01 PM, Jan Beulich wrote:
> > > > On 13.08.15 at 20:12, <boris.ostrovsky@xxxxxxxxxx> wrote:
> > @@ -777,7 +777,7 @@ int arch_set_info_guest(
> >   
> >       /* The context is a compat-mode one if the target domain is compat-mode;
> >        * we expect the tools to DTRT even in compat-mode callers. */
> > -    compat = is_pv_32bit_domain(d);
> > +    compat = is_pv_32bit_domain(d) || is_pvh_32bit_domain(d);
> I continue to think that this should include a v->domain ==
> current->domain check (to match behavior for HVM guests
> from the tool stack perspective). Having looked at patch 4, I also
> can't see how the tool stack is being made expect a non-native
> guest context record in the 32-bit PVH case (i.e. I'd appreciate
> if you could point out where that hides).
For vcpu 0 current->domain is dom0 so I am not sure how this check would 
work.
For a 32-bit PVH guest the toolstack will place data into 
vcpu_guest_context_x86_32_t (in vcpu_x86_32()) and so the hypervisor, 
knowing that the guest is a compat one (based on the test above), will 
access appropriate fields.
This is not how HVM guests are started --- "classic" PVH behaves very 
much like a PV guest, unlike what we are doing with no-dm PVH.
-boris



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