x86/fpu: Rename unlazy_fpu() to fpu__save()

This function is a misnomer on two levels:

1) it doesn't really manipulate TS on modern CPUs anymore, its
   primary purpose is to save FPU state, used:

      - when executing fork()/clone(): to copy current FPU state
        to the child's FPU state.

      - when handling math exceptions: to generate the math error
        si_code in the signal frame.

2) even on legacy CPUs it doesn't actually 'unlazy', if then
   it lazies the FPU state: as a side effect of the old FNSAVE
   instruction which clears (destroys) FPU state it's necessary
   to set CR0::TS.

So rename it to fpu__save() to better reflect its purpose.

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/fpu-internal.h

@@ -602,7 +602,7 @@ static inline void fpu_copy(struct task_struct *dst, struct task_struct *src)
 		struct fpu *dfpu = &dst->thread.fpu;
 		struct fpu *sfpu = &src->thread.fpu;
 
-		unlazy_fpu(src);
+		fpu__save(src);
 		memcpy(dfpu->state, sfpu->state, xstate_size);
 	}
 }

arch/x86/include/asm/i387.h

@@ -101,7 +101,7 @@ static inline int user_has_fpu(void)
 	return current->thread.fpu.has_fpu;
 }
 
-extern void unlazy_fpu(struct task_struct *tsk);
+extern void fpu__save(struct task_struct *tsk);
 
 #endif /* __ASSEMBLY__ */
 

arch/x86/kernel/i387.c

@@ -117,7 +117,7 @@ void __kernel_fpu_end(void)
 }
 EXPORT_SYMBOL(__kernel_fpu_end);
 
-void unlazy_fpu(struct task_struct *tsk)
+void fpu__save(struct task_struct *tsk)
 {
 	preempt_disable();
 	if (__thread_has_fpu(tsk)) {
@@ -130,7 +130,7 @@ void unlazy_fpu(struct task_struct *tsk)
 	}
 	preempt_enable();
 }
-EXPORT_SYMBOL(unlazy_fpu);
+EXPORT_SYMBOL(fpu__save);
 
 unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
 unsigned int xstate_size;
@@ -251,7 +251,7 @@ int init_fpu(struct task_struct *tsk)
 
 	if (tsk_used_math(tsk)) {
 		if (cpu_has_fpu && tsk == current)
-			unlazy_fpu(tsk);
+			fpu__save(tsk);
 		task_disable_lazy_fpu_restore(tsk);
 		return 0;
 	}

arch/x86/kernel/traps.c

@@ -731,7 +731,7 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
 	/*
 	 * Save the info for the exception handler and clear the error.
 	 */
-	unlazy_fpu(task);
+	fpu__save(task);
 	task->thread.trap_nr = trapnr;
 	task->thread.error_code = error_code;
 	info.si_signo = SIGFPE;