x86/apic: Avoid open coded x2apic detection

enable_IR_x2apic() grew a open coded x2apic detection. Implement a
proper helper function which shares the code with the already existing
x2apic_enabled().

Made it use rdmsrl_safe as suggested by Boris.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/20150115211702.285038186@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 1 insertions, 4 deletions

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 35e6d09294ed..7ecfce13be05 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1625,10 +1625,7 @@ void __init enable_IR_x2apic(void)
         int ret, ir_stat;
 
         if (!IS_ENABLED(CONFIG_X86_X2APIC)) {
-                u64 msr;
-
-                rdmsrl(MSR_IA32_APICBASE, msr);
-                if (msr & X2APIC_ENABLE)
+                if (apic_is_x2apic_enabled())
                         panic("BIOS has enabled x2apic but kernel doesn't support x2apic, please disable x2apic in BIOS.\n");
         }