x2apic: fix reserved APIC register accesses in print_local_APIC()

APIC_ARBPRI is a reserved register for XAPIC and beyond.
APIC_RRR is a reserved register except for 82489DX, APIC for Pentium processors.
APIC_EOI is a write only register.
APIC_DFR is reserved in x2apic mode.

Access to these registers in x2apic will result in #GP fault. Fix these
apic register accesses.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 14 insertions, 0 deletions

diff --git a/include/asm-x86/apic.h b/include/asm-x86/apic.h
index 2d970f6bc2a1..ef1d72dbdfe0 100644
--- a/include/asm-x86/apic.h
+++ b/include/asm-x86/apic.h
@@ -98,6 +98,20 @@ extern void check_x2apic(void);
 extern void enable_x2apic(void);
 extern void enable_IR_x2apic(void);
 extern void x2apic_icr_write(u32 low, u32 id);
+static inline int x2apic_enabled(void)
+{
+        int msr, msr2;
+
+        if (!cpu_has_x2apic)
+                return 0;
+
+        rdmsr(MSR_IA32_APICBASE, msr, msr2);
+        if (msr & X2APIC_ENABLE)
+                return 1;
+        return 0;
+}
+#else
+#define x2apic_enabled()        0
 #endif
 
 struct apic_ops {