From: Linus Torvalds Date: Fri, 22 Jul 2005 20:06:16 +0000 (-0400) Subject: x86: make restore_fpu() use alternative assembler instructions X-Git-Tag: v2.6.13-rc4~85 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=8ed1383fb7b6685968588141d5934e0e6715e954;p=linux-2.6-omap-h63xx.git 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. --- diff --git a/arch/i386/kernel/i387.c b/arch/i386/kernel/i387.c index b817168d9c6..d75524758da 100644 --- a/arch/i386/kernel/i387.c +++ b/arch/i386/kernel/i387.c @@ -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. */ diff --git a/include/asm-i386/i387.h b/include/asm-i386/i387.h index f6feb98a939..e678609bb57 100644 --- a/include/asm-i386/i387.h +++ b/include/asm-i386/i387.h @@ -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)