From 8ed1383fb7b6685968588141d5934e0e6715e954 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 22 Jul 2005 16:06:16 -0400 Subject: [PATCH] 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. --- arch/i386/kernel/i387.c | 11 ----------- include/asm-i386/i387.h | 13 ++++++++++++- 2 files changed, 12 insertions(+), 12 deletions(-) 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) -- 2.20.1