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Commit c9ad4882 authored by Avi Kivity's avatar Avi Kivity Committed by H. Peter Anvin
Browse files

x86: Eliminate TS_XSAVE 



The fpu code currently uses current->thread_info->status & TS_XSAVE as
a way to distinguish between XSAVE capable processors and older processors.
The decision is not really task specific; instead we use the task status to
avoid a global memory reference - the value should be the same across all
threads.

Eliminate this tie-in into the task structure by using an alternative
instruction keyed off the XSAVE cpu feature; this results in shorter and
faster code, without introducing a global memory reference.

[ hpa: in the future, this probably should use an asm jmp ]

Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
Acked-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1273135546-29690-2-git-send-email-avi@redhat.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 25082500

arch/x86/include/asm/i387.h

+16 −4
Original line number Diff line number Diff line
@@ -56,6 +56,18 @@ extern int restore_i387_xstate_ia32(void __user *buf); 


#define X87_FSW_ES (1 << 7)	/* Exception Summary */



static inline bool use_xsave(void)

{

	u8 has_xsave;



	alternative_io("mov $0, %0",

		       "mov $1, %0",

		       X86_FEATURE_XSAVE,

		       "=g"(has_xsave));



	return has_xsave;

}



#ifdef CONFIG_X86_64



/* Ignore delayed exceptions from user space */
@@ -99,7 +111,7 @@ static inline void clear_fpu_state(struct task_struct *tsk) 
	/*

	 * xsave header may indicate the init state of the FP.

	 */

	if ((task_thread_info(tsk)->status & TS_XSAVE) &&

	if (use_xsave() &&

	    !(xstate->xsave_hdr.xstate_bv & XSTATE_FP))

		return;
@@ -164,7 +176,7 @@ static inline void fxsave(struct task_struct *tsk) 


static inline void __save_init_fpu(struct task_struct *tsk)

{

	if (task_thread_info(tsk)->status & TS_XSAVE)

	if (use_xsave())

		xsave(tsk);

	else

		fxsave(tsk);
@@ -218,7 +230,7 @@ static inline int fxrstor_checking(struct i387_fxsave_struct *fx) 
 */

static inline void __save_init_fpu(struct task_struct *tsk)

{

	if (task_thread_info(tsk)->status & TS_XSAVE) {

	if (use_xsave()) {

		struct xsave_struct *xstate = &tsk->thread.xstate->xsave;

		struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
@@ -266,7 +278,7 @@ static inline void __save_init_fpu(struct task_struct *tsk) 


static inline int restore_fpu_checking(struct task_struct *tsk)

{

	if (task_thread_info(tsk)->status & TS_XSAVE)

	if (use_xsave())

		return xrstor_checking(&tsk->thread.xstate->xsave);

	else

		return fxrstor_checking(&tsk->thread.xstate->fxsave);

arch/x86/include/asm/thread_info.h

+0 −1
Original line number Diff line number Diff line
@@ -244,7 +244,6 @@ static inline struct thread_info *current_thread_info(void) 
#define TS_POLLING		0x0004	/* true if in idle loop

					   and not sleeping */

#define TS_RESTORE_SIGMASK	0x0008	/* restore signal mask in do_signal() */

#define TS_XSAVE		0x0010	/* Use xsave/xrstor */



#define tsk_is_polling(t) (task_thread_info(t)->status & TS_POLLING)

arch/x86/kernel/cpu/common.c

+1 −4
Original line number Diff line number Diff line
@@ -1243,9 +1243,6 @@ void __cpuinit cpu_init(void) 
	/*

	 * Force FPU initialization:

	 */

	if (cpu_has_xsave)

		current_thread_info()->status = TS_XSAVE;

	else

	current_thread_info()->status = 0;

	clear_used_math();

	mxcsr_feature_mask_init();

arch/x86/kernel/i387.c

+1 −4
Original line number Diff line number Diff line
@@ -102,9 +102,6 @@ void __cpuinit fpu_init(void) 


	mxcsr_feature_mask_init();

	/* clean state in init */

	if (cpu_has_xsave)

		current_thread_info()->status = TS_XSAVE;

	else

	current_thread_info()->status = 0;

	clear_used_math();

}

arch/x86/kernel/xsave.c

+3 −3
Original line number Diff line number Diff line
@@ -99,7 +99,7 @@ int save_i387_xstate(void __user *buf) 
		if (err)

			return err;



		if (task_thread_info(tsk)->status & TS_XSAVE)

		if (use_xsave())

			err = xsave_user(buf);

		else

			err = fxsave_user(buf);
@@ -116,7 +116,7 @@ int save_i387_xstate(void __user *buf) 


	clear_used_math(); /* trigger finit */



	if (task_thread_info(tsk)->status & TS_XSAVE) {

	if (use_xsave()) {

		struct _fpstate __user *fx = buf;

		struct _xstate __user *x = buf;

		u64 xstate_bv;
@@ -225,7 +225,7 @@ int restore_i387_xstate(void __user *buf) 
		clts();

		task_thread_info(current)->status |= TS_USEDFPU;

	}

	if (task_thread_info(tsk)->status & TS_XSAVE)

	if (use_xsave())

		err = restore_user_xstate(buf);

	else

		err = fxrstor_checking((__force struct i387_fxsave_struct *)