x86/fpu: Eliminate __save_fpu()

The current implementation of __save_fpu():

	if (use_xsave()) {
		xsave_state(&fpu->state.xsave);
	} else {
		fpu_fxsave(fpu);
	}

Is actually a simplified version of copy_fpregs_to_fpstate(),
if use_eager_fpu() is true.

But all call sites of __save_fpu() call it only it when use_eager_fpu()
is true.

So we can eliminate __save_fpu() altogether and use the standard
copy_fpregs_to_fpstate() function. This cleans up the code
by making it use fewer variants of FPU register saving.
Reviewed-by: NBorislav 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: NIngo Molnar <mingo@kernel.org>

arch/x86/kernel/fpu/core.c

@@ -169,15 +169,6 @@ void irq_ts_restore(int TS_state)
 }
 EXPORT_SYMBOL_GPL(irq_ts_restore);
 
-static void __save_fpu(struct fpu *fpu)
-{
-	if (use_xsave()) {
-		xsave_state(&fpu->state.xsave);
-	} else {
-		fpu_fxsave(fpu);
-	}
-}
-
 /*
  * Save the FPU state (initialize it if necessary):
  *
@@ -190,7 +181,7 @@ void fpu__save(struct fpu *fpu)
 	preempt_disable();
 	if (fpu->fpregs_active) {
 		if (use_eager_fpu()) {
-			__save_fpu(fpu);
+			copy_fpregs_to_fpstate(fpu);
 		} else {
 			copy_fpregs_to_fpstate(fpu);
 			fpregs_deactivate(fpu);
@@ -235,7 +226,7 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 
 	if (use_eager_fpu()) {
 		memset(&dst_fpu->state.xsave, 0, xstate_size);
-		__save_fpu(dst_fpu);
+		copy_fpregs_to_fpstate(dst_fpu);
 	} else {
 		fpu__save(src_fpu);
 		memcpy(&dst_fpu->state, &src_fpu->state, xstate_size);