x86/of: Fix the APIC address registration

The device tree APIC parser tries to force-enable the local APIC when it is
not set in CPUID. apic_force_enable() registers the boot CPU apic on
success.

If that succeeds then dtb_lapic_setup() registers the local APIC again
eventually with a different address.

Rewrite the code so that it only registers it once.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Tested-by: Juergen Gross <jgross@suse.com> # Xen PV (dom0 and unpriv. guest)

arch/x86/kernel/devicetree.c

@@ -157,19 +157,15 @@ static void __init dtb_lapic_setup(void)
 
 	/* Did the boot loader setup the local APIC ? */
 	if (!boot_cpu_has(X86_FEATURE_APIC)) {
+		/* Try force enabling, which registers the APIC address */
 		if (apic_force_enable(lapic_addr))
 			return;
-	}
-	smp_found_config = 1;
-	if (of_property_read_bool(dn, "intel,virtual-wire-mode")) {
-		pr_info("Virtual Wire compatibility mode.\n");
-		pic_mode = 0;
 	} else {
-		pr_info("IMCR and PIC compatibility mode.\n");
-		pic_mode = 1;
+		register_lapic_address(lapic_addr);
 	}
-
-	register_lapic_address(lapic_addr);
+	smp_found_config = 1;
+	pic_mode = !of_property_read_bool(dn, "intel,virtual-wire-mode");
+	pr_info("%s compatibility mode.\n", pic_mode ? "IMCR and PIC" : "Virtual Wire");
 }
 
 #endif /* CONFIG_X86_LOCAL_APIC */