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Commit 037f0eed authored by Kevin Hao's avatar Kevin Hao Committed by Benjamin Herrenschmidt
Browse files

powerpc: Make flush_fp_to_thread() nop when CONFIG_PPC_FPU is disabled 



In the current kernel, the function flush_fp_to_thread() is not
dependent on CONFIG_PPC_FPU. So most invocations of this function
is not wrapped by CONFIG_PPC_FPU. Even through we don't really
save the FPRs to the thread struct if CONFIG_PPC_FPU is not enabled,
but there does have some runtime overhead such as the check for
tsk->thread.regs and preempt disable and enable. It really make
no sense to do that. So make it a nop when CONFIG_PPC_FPU is
disabled. Also remove the wrapped #ifdef CONFIG_PPC_FPU
when invoking this function.

Signed-off-by: default avatarKevin Hao <haokexin@gmail.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 662499d0

arch/powerpc/include/asm/switch_to.h

+6 −1
Original line number Diff line number Diff line
@@ -19,7 +19,6 @@ extern struct task_struct *_switch(struct thread_struct *prev, 
extern void giveup_fpu(struct task_struct *);

extern void load_up_fpu(void);

extern void enable_kernel_fp(void);

extern void flush_fp_to_thread(struct task_struct *);

extern void enable_kernel_altivec(void);

extern void load_up_altivec(struct task_struct *);

extern int emulate_altivec(struct pt_regs *);
@@ -37,6 +36,12 @@ static inline void discard_lazy_cpu_state(void) 
}

#endif



#ifdef CONFIG_PPC_FPU

extern void flush_fp_to_thread(struct task_struct *);

#else

static inline void flush_fp_to_thread(struct task_struct *t) { }

#endif



#ifdef CONFIG_ALTIVEC

extern void flush_altivec_to_thread(struct task_struct *);

extern void giveup_altivec(struct task_struct *);

arch/powerpc/kernel/process.c

+2 −0
Original line number Diff line number Diff line
@@ -74,6 +74,7 @@ struct task_struct *last_task_used_vsx = NULL; 
struct task_struct *last_task_used_spe = NULL;

#endif



#ifdef CONFIG_PPC_FPU

/*

 * Make sure the floating-point register state in the

 * the thread_struct is up to date for task tsk.
@@ -107,6 +108,7 @@ void flush_fp_to_thread(struct task_struct *tsk) 
	}

}

EXPORT_SYMBOL_GPL(flush_fp_to_thread);

#endif



void enable_kernel_fp(void)

{

arch/powerpc/math-emu/math.c

+1 −2
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 


#include <asm/uaccess.h>

#include <asm/reg.h>

#include <asm/switch_to.h>



#include <asm/sfp-machine.h>

#include <math-emu/double.h>
@@ -433,9 +434,7 @@ do_mathemu(struct pt_regs *regs) 
	 * is flushed into the thread_struct before attempting

	 * emulation

	 */

#ifdef CONFIG_PPC_FPU

	flush_fp_to_thread(current);

#endif



	eflag = func(op0, op1, op2, op3);