x86-32, fpu: Fix DNA exception during check_fpu()

Before check_fpu() is called, we have cr0.TS bit set and hence the floating
point code to check the FDIV bug was generating a DNA exception.

Use kernel_fpu_begin()/kernel_fpu_end() around the floating point
code to avoid this unnecessary device not available exception during
boot.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1309479572.2665.1372.camel@sbsiddha-MOBL3.sc.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/kernel/cpu/bugs.c

@@ -62,6 +62,8 @@ static void __init check_fpu(void)
 		return;
 	}
 
+	kernel_fpu_begin();
+
 	/*
 	 * trap_init() enabled FXSR and company _before_ testing for FP
 	 * problems here.
@@ -80,6 +82,8 @@ static void __init check_fpu(void)
 		: "=m" (*&fdiv_bug)
 		: "m" (*&x), "m" (*&y));
 
+	kernel_fpu_end();
+
 	boot_cpu_data.fdiv_bug = fdiv_bug;
 	if (boot_cpu_data.fdiv_bug)
 		printk(KERN_WARNING "Hmm, FPU with FDIV bug.\n");