x86: don't allow Dom0 (direct) access to port F0

This controls the driving of IGNNE# (if such emulation is enabled in
hardware), and hence would need proper handling in the hypervisor to be
safe to use by Dom0 (and fully emulating for PVH/HVM DomU-s).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>

xen/arch/x86/dom0_build.c

@@ -492,6 +492,9 @@ int __init dom0_setup_permissions(struct domain *d)
     /* INIT# and alternative A20M# control. */
     rc |= ioports_deny_access(d, 0x92, 0x92);
 
+    /* IGNNE# control. */
+    rc |= ioports_deny_access(d, 0xF0, 0xF0);
+
     /* ACPI PM Timer. */
     if ( pmtmr_ioport )
         rc |= ioports_deny_access(d, pmtmr_ioport, pmtmr_ioport + 3);