x86/fpu: Move restore_init_xstate() out of fpu/internal.h

Move restore_init_xstate() next to its sole caller.

Also rename it to copy_init_fpstate_to_fpregs() and add
some comments about what it does.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
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

@@ -341,14 +341,6 @@ static inline void fpregs_deactivate(struct fpu *fpu)
 	__fpregs_deactivate_hw();
 }
 
-static inline void restore_init_xstate(void)
-{
-	if (use_xsave())
-		xrstor_state(&init_fpstate.xsave, -1);
-	else
-		fxrstor_checking(&init_fpstate.fxsave);
-}
-
 /*
  * Definitions for the eXtended Control Register instructions
  */

arch/x86/kernel/fpu/core.c

@@ -391,6 +391,18 @@ void fpu__drop(struct fpu *fpu)
 	preempt_enable();
 }
 
+/*
+ * Clear FPU registers by setting them up from
+ * the init fpstate:
+ */
+static inline void copy_init_fpstate_to_fpregs(void)
+{
+	if (use_xsave())
+		xrstor_state(&init_fpstate.xsave, -1);
+	else
+		fxrstor_checking(&init_fpstate.fxsave);
+}
+
 /*
  * Clear the FPU state back to init state.
  *
@@ -409,7 +421,7 @@ void fpu__clear(struct fpu *fpu)
 			fpu__activate_curr(fpu);
 			user_fpu_begin();
 		}
-		restore_init_xstate();
+		copy_init_fpstate_to_fpregs();
 	}
 }