x86/platform/UV: Add UV MMR Illegal Access Function

This new function is generated by the UV MMR generation script to
identify MMR registers and fields that are not defined for a specific
UV architecture.  With this switch, the immediate panic can be replaced
with a message and a bad return value allowing either hardware or the
emulator to diagnose the problem.  It allows functions common to some
UV arches to use common defines that might not be fully defined for all
arches, as long as they do not reference them on the unsupported arches.

Tested-by: John Estabrook <estabrook@sgi.com>
Tested-by: Gary Kroening <gfk@sgi.com>
Tested-by: Nathan Zimmer <nzimmer@sgi.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Cc: Andrew Banman <abanman@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russ Anderson <rja@sgi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160429215403.231926687@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/apic/x2apic_uv_x.c

@@ -55,6 +55,18 @@ EXPORT_SYMBOL_GPL(uv_apicid_hibits);
 
 static struct apic apic_x2apic_uv_x;
 
+/* Set this to use hardware error handler instead of kernel panic */
+static int disable_uv_undefined_panic = 1;
+unsigned long uv_undefined(char *str)
+{
+	if (likely(!disable_uv_undefined_panic))
+		panic("UV: error: undefined MMR: %s\n", str);
+	else
+		pr_crit("UV: error: undefined MMR: %s\n", str);
+	return ~0ul;	/* cause a machine fault  */
+}
+EXPORT_SYMBOL(uv_undefined);
+
 static unsigned long __init uv_early_read_mmr(unsigned long addr)
 {
 	unsigned long val, *mmr;