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x86: make restore_fpu() use alternative assembler instructions 

It's really just a single instruction, conditional on whether the CPU
supports FXSR or not, so implement it as such instead of making it a
function that queries FXSR dynamically.

This means that the instruction just gets automatically rewritten to the
correct one at boot-time.
This commit is contained in:
Linus Torvalds 2005-07-22 16:06:16 -04:00
parent b339a18b81
commit 8ed1383fb7
2 changed files with 12 additions and 12 deletions
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11
arch/i386/kernel/i387.c
View File

@ -82,17 +82,6 @@ void kernel_fpu_begin(void)
}
EXPORT_SYMBOL_GPL(kernel_fpu_begin);
void restore_fpu( struct task_struct *tsk )
{
if ( cpu_has_fxsr ) {
asm volatile( "fxrstor %0"
: : "m" (tsk->thread.i387.fxsave) );
} else {
asm volatile( "frstor %0"
: : "m" (tsk->thread.i387.fsave) );
}
}
/*
* FPU tag word conversions.
*/

13
include/asm-i386/i387.h
View File

@ -19,10 +19,21 @@
extern void mxcsr_feature_mask_init(void);
extern void init_fpu(struct task_struct *);
/*
* FPU lazy state save handling...
*/
extern void restore_fpu( struct task_struct *tsk );
/*
* The "nop" is needed to make the instructions the same
* length.
*/
#define restore_fpu(tsk) \
alternative_input( \
"nop ; frstor %1", \
"fxrstor %1", \
X86_FEATURE_FXSR, \
"m" ((tsk)->thread.i387.fsave))
extern void kernel_fpu_begin(void);
#define kernel_fpu_end() do { stts(); preempt_enable(); } while(0)