Commit 4d164092 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/fpu: Factor out the FPU bug detection code into fpu__init_check_bugs() 



Move the boot-time FPU bug detection code to the other FPU boot time
init code in fpu/init.c.

No change in code size:

   text    data     bss     dec     hex filename
   13044568        1884440 1130496 16059504         f50c70 vmlinux.before
   13044568        1884440 1130496 16059504         f50c70 vmlinux.after

Reviewed-by: default avatarBorislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3a0aee48

arch/x86/include/asm/i387.h

+1 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ extern void fpu__flush_thread(struct task_struct *tsk); 


extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);

extern void fpu__restore(void);

extern void fpu__init_check_bugs(void);



extern bool irq_fpu_usable(void);

arch/x86/kernel/cpu/bugs.c

+1 −52
Original line number Diff line number Diff line
@@ -17,52 +17,6 @@ 
#include <asm/paravirt.h>

#include <asm/alternative.h>



static double __initdata x = 4195835.0;

static double __initdata y = 3145727.0;



/*

 * This used to check for exceptions..

 * However, it turns out that to support that,

 * the XMM trap handlers basically had to

 * be buggy. So let's have a correct XMM trap

 * handler, and forget about printing out

 * some status at boot.

 *

 * We should really only care about bugs here

 * anyway. Not features.

 */

static void __init check_fpu(void)

{

	s32 fdiv_bug;



	kernel_fpu_begin();



	/*

	 * trap_init() enabled FXSR and company _before_ testing for FP

	 * problems here.

	 *

	 * Test for the divl bug: http://en.wikipedia.org/wiki/Fdiv_bug

	 */

	__asm__("fninit\n\t"

		"fldl %1\n\t"

		"fdivl %2\n\t"

		"fmull %2\n\t"

		"fldl %1\n\t"

		"fsubp %%st,%%st(1)\n\t"

		"fistpl %0\n\t"

		"fwait\n\t"

		"fninit"

		: "=m" (*&fdiv_bug)

		: "m" (*&x), "m" (*&y));



	kernel_fpu_end();



	if (fdiv_bug) {

		set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV);

		pr_warn("Hmm, FPU with FDIV bug\n");

	}

}



void __init check_bugs(void)

{

	identify_boot_cpu();
@@ -85,10 +39,5 @@ void __init check_bugs(void) 
		'0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);

	alternative_instructions();



	/*

	 * kernel_fpu_begin/end() in check_fpu() relies on the patched

	 * alternative instructions.

	 */

	if (cpu_has_fpu)

		check_fpu();

	fpu__init_check_bugs();

}

arch/x86/kernel/fpu/init.c

+63 −0
Original line number Diff line number Diff line
@@ -4,6 +4,69 @@ 
#include <asm/fpu-internal.h>

#include <asm/tlbflush.h>



/*

 * Boot time CPU/FPU FDIV bug detection code:

 */



static double __initdata x = 4195835.0;

static double __initdata y = 3145727.0;



/*

 * This used to check for exceptions..

 * However, it turns out that to support that,

 * the XMM trap handlers basically had to

 * be buggy. So let's have a correct XMM trap

 * handler, and forget about printing out

 * some status at boot.

 *

 * We should really only care about bugs here

 * anyway. Not features.

 */

static void __init check_fpu(void)

{

	s32 fdiv_bug;



	kernel_fpu_begin();



	/*

	 * trap_init() enabled FXSR and company _before_ testing for FP

	 * problems here.

	 *

	 * Test for the divl bug: http://en.wikipedia.org/wiki/Fdiv_bug

	 */

	__asm__("fninit\n\t"

		"fldl %1\n\t"

		"fdivl %2\n\t"

		"fmull %2\n\t"

		"fldl %1\n\t"

		"fsubp %%st,%%st(1)\n\t"

		"fistpl %0\n\t"

		"fwait\n\t"

		"fninit"

		: "=m" (*&fdiv_bug)

		: "m" (*&x), "m" (*&y));



	kernel_fpu_end();



	if (fdiv_bug) {

		set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV);

		pr_warn("Hmm, FPU with FDIV bug\n");

	}

}



void fpu__init_check_bugs(void)

{

	/*

	 * kernel_fpu_begin/end() in check_fpu() relies on the patched

	 * alternative instructions.

	 */

	if (cpu_has_fpu)

		check_fpu();

}



/*

 * Boot time FPU feature detection code:

 */

unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;

unsigned int xstate_size;

EXPORT_SYMBOL_GPL(xstate_size);

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