x86: x2apic, IR: Clean up panic() with nox2apic boot option

Instead of panic() ignore the "nox2apic" boot option when BIOS
has already enabled x2apic prior to OS handover.

[ Impact: printk warning instead of panic() when BIOS has enabled x2apic already ]
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Cc: dwmw2@infradead.org
Cc: Weidong Han <weidong.han@intel.com>
LKML-Reference: <20090420200450.425091000@linux-os.sc.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/apic/apic.c

@@ -141,8 +141,12 @@ static int x2apic_preenabled;
 static int disable_x2apic;
 static __init int setup_nox2apic(char *str)
 {
-	if (x2apic_enabled())
-		panic("Bios already enabled x2apic, can't enforce nox2apic");
+	if (x2apic_enabled()) {
+		pr_warning("Bios already enabled x2apic, "
+			   "can't enforce nox2apic");
+		return 0;
+	}
+
 	disable_x2apic = 1;
 	setup_clear_cpu_cap(X86_FEATURE_X2APIC);
 	return 0;