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>

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 465b309af25425dce160848ab8c32df14058ef35..1a8ba26c2fbdac9a2305529898e0111fe0ea7219 100644 (file)
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -108,6 +108,15 @@ extern u64 native_apic_icr_read(void);
 
 extern int x2apic_mode;
 
+static inline bool apic_is_x2apic_enabled(void)
+{
+       u64 msr;
+
+       if (rdmsrl_safe(MSR_IA32_APICBASE, &msr))
+               return false;
+       return msr & X2APIC_ENABLE;
+}
+
 #ifdef CONFIG_X86_X2APIC
 /*
  * Make previous memory operations globally visible before
@@ -175,15 +184,7 @@ extern void check_x2apic(void);
 extern void enable_x2apic(void);
 static inline int x2apic_enabled(void)
 {
-       u64 msr;
-
-       if (!cpu_has_x2apic)
-               return 0;
-
-       rdmsrl(MSR_IA32_APICBASE, msr);
-       if (msr & X2APIC_ENABLE)
-               return 1;
-       return 0;
+       return cpu_has_x2apic && apic_is_x2apic_enabled();
 }
 
 #define x2apic_supported()     (cpu_has_x2apic)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 35e6d09294ed06598568438ac40138d4587bd02c..7ecfce13be05b399c4233a656b33ac01c098eda0 100644 (file)
--- 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");
        }