x86: Avoid check hlt for newer cpus

Check hlt instruction was targeted for some older CPUs. It is an expensive
operation in that it takes 4 ticks to break out the check.  We can avoid
such check completely for newer x86 cpus (family >= 5).

[ hpa: corrected family > 5 to family >= 5 ]

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
LKML-Reference: <1273269585-14346-1-git-send-email-jacob.jun.pan@linux.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 01a2652..c39576c 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -86,7 +86,7 @@ static void __init check_fpu(void)
 
 static void __init check_hlt(void)
 {
-       if (paravirt_enabled())
+       if (boot_cpu_data.x86 >= 5 || paravirt_enabled())
                return;
 
        printk(KERN_INFO "Checking 'hlt' instruction... ");