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, 1 insertions, 8 deletions

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index c12823eb55b5..47c2d12e5cf5 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1265,14 +1265,7 @@ void __cpuinit end_local_APIC_setup(void)
 #ifdef CONFIG_X86_X2APIC
 void check_x2apic(void)
 {
-        int msr, msr2;
-
-        if (!cpu_has_x2apic)
-                return;
-
-        rdmsr(MSR_IA32_APICBASE, msr, msr2);
-
-        if (msr & X2APIC_ENABLE) {
+        if (x2apic_enabled()) {
                 pr_info("x2apic enabled by BIOS, switching to x2apic ops\n");
                 x2apic_preenabled = x2apic = 1;
         }