x86: don't allow Dom0 access to port 92

Somewhat like port CF9 this may have a bit controlling the CPU's INIT#
signal, and it also may have a bit involved in the driving of A20M#.
Neither of these - just like CF9 - we want to allow Dom0 to drive.

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

xen/arch/x86/dom0_build.c

@@ -488,6 +488,10 @@ int __init dom0_setup_permissions(struct domain *d)
     rc |= ioports_deny_access(d, 0x40, 0x43);
     /* PIT Channel 2 / PC Speaker Control. */
     rc |= ioports_deny_access(d, 0x61, 0x61);
+
+    /* INIT# and alternative A20M# control. */
+    rc |= ioports_deny_access(d, 0x92, 0x92);
+
     /* ACPI PM Timer. */
     if ( pmtmr_ioport )
         rc |= ioports_deny_access(d, pmtmr_ioport, pmtmr_ioport + 3);