xen/pvh: Setup up shared_info.

For PVHVM the shared_info structure is provided via the same way
as for normal PV guests (see include/xen/interface/xen.h).

That is during bootup we get 'xen_start_info' via the %esi register
in startup_xen. Then later we extract the 'shared_info' from said
structure (in xen_setup_shared_info) and start using it.

The 'xen_setup_shared_info' is all setup to work with auto-xlat
guests, but there are two functions which it calls that are not:
xen_setup_mfn_list_list and xen_setup_vcpu_info_placement.
This patch modifies the P2M code (xen_setup_mfn_list_list)
while the "Piggyback on PVHVM for event channels" modifies
the xen_setup_vcpu_info_placement.
Signed-off-by: Mukesh Rathor <mukesh.rathor@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

arch/x86/xen/p2m.c

@@ -339,6 +339,9 @@ void __ref xen_build_mfn_list_list(void)
 
 void xen_setup_mfn_list_list(void)
 {
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return;
+
 	BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
 
 	HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =