x86: select x2apic ops in early apic probe only if x2apic mode is enabled

If BIOS hands over the control to OS in legacy xapic mode, select
legacy xapic related ops in the early apic probe and shift to x2apic
ops later in the boot sequence, only after enabling x2apic mode.

If BIOS hands over the control in x2apic mode, select x2apic related
ops in the early apic probe.

This fixes the early boot panic, where we were selecting x2apic ops,
while the cpu is still in legacy xapic mode.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 3 deletions

diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c
index 70935dd904db..e7c163661c77 100644
--- a/arch/x86/kernel/apic/probe_64.c
+++ b/arch/x86/kernel/apic/probe_64.c
@@ -50,9 +50,16 @@ static struct apic *apic_probe[] __initdata = {
 void __init default_setup_apic_routing(void)
 {
 #ifdef CONFIG_X86_X2APIC
-        if (apic == &apic_x2apic_phys || apic == &apic_x2apic_cluster) {
-                if (!intr_remapping_enabled)
-                        apic = &apic_flat;
+        if (x2apic && (apic != &apic_x2apic_phys &&
+#ifdef CONFIG_X86_UV
+                       apic != &apic_x2apic_uv_x &&
+#endif
+                       apic != &apic_x2apic_cluster)) {
+                if (x2apic_phys)
+                        apic = &apic_x2apic_phys;
+                else
+                        apic = &apic_x2apic_cluster;
+                printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
         }
 #endif