x86/fpu: Merge fpu__reset() and fpu__clear()

With recent cleanups and fixes the fpu__reset() and fpu__clear()
functions have become almost identical in functionality: the only
difference is that fpu__reset() assumed that the fpstate
was already active in the eagerfpu case, while fpu__clear()
activated it if it was inactive.

This distinction almost never matters, the only case where such
fpstate activation happens if if the init thread (PID 1) gets exec()-ed
for the first time.

So keep fpu__clear() and change all fpu__reset() uses to
fpu__clear() to simpify the logic.

( In a later patch we'll further simplify fpu__clear() by making
  sure that all contexts it is called on are already active. )

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: NIngo Molnar <mingo@kernel.org>

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

@@ -56,7 +56,6 @@ extern void fpu__restore(void);
 extern int  fpu__restore_sig(void __user *buf, int ia32_frame);
 extern void fpu__drop(struct fpu *fpu);
 extern int  fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu);
-extern void fpu__reset(struct fpu *fpu);
 extern void fpu__clear(struct fpu *fpu);
 
 extern void fpu__init_check_bugs(void);
@@ -490,7 +489,7 @@ static inline void switch_fpu_finish(struct fpu *new_fpu, fpu_switch_t fpu_switc
 {
 	if (fpu_switch.preload) {
 		if (unlikely(copy_fpstate_to_fpregs(new_fpu)))
-			fpu__reset(new_fpu);
+			fpu__clear(new_fpu);
 	}
 }
 

arch/x86/kernel/fpu/core.c

@@ -116,7 +116,7 @@ void __kernel_fpu_end(void)
 
 	if (fpu->fpregs_active) {
 		if (WARN_ON(copy_fpstate_to_fpregs(fpu)))
-			fpu__reset(fpu);
+			fpu__clear(fpu);
 	} else {
 		__fpregs_deactivate_hw();
 	}
@@ -339,7 +339,7 @@ void fpu__restore(void)
 	kernel_fpu_disable();
 	fpregs_activate(fpu);
 	if (unlikely(copy_fpstate_to_fpregs(fpu))) {
-		fpu__reset(fpu);
+		fpu__clear(fpu);
 		force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
 	} else {
 		tsk->thread.fpu.counter++;
@@ -376,19 +376,10 @@ void fpu__drop(struct fpu *fpu)
 }
 
 /*
- * Reset the FPU state back to init state:
- */
-void fpu__reset(struct fpu *fpu)
-{
-	if (!use_eager_fpu())
-		fpu__drop(fpu);
-	else
-		restore_init_xstate();
-}
-
-/*
- * Called by sys_execve() to clear the FPU fpregs, so that FPU state
- * of the previous binary does not leak over into the exec()ed binary:
+ * Clear the FPU state back to init state.
+ *
+ * Called by sys_execve(), by the signal handler code and by various
+ * error paths.
  */
 void fpu__clear(struct fpu *fpu)
 {

arch/x86/kernel/fpu/xstate.c

@@ -401,7 +401,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 			 config_enabled(CONFIG_IA32_EMULATION));
 
 	if (!buf) {
-		fpu__reset(fpu);
+		fpu__clear(fpu);
 		return 0;
 	}
 
@@ -474,7 +474,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		 */
 		user_fpu_begin();
 		if (restore_user_xstate(buf_fx, xfeatures, fx_only)) {
-			fpu__reset(fpu);
+			fpu__clear(fpu);
 			return -1;
 		}
 	}

arch/x86/kernel/signal.c

@@ -667,7 +667,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 		 * Ensure the signal handler starts with the new fpu state.
 		 */
 		if (fpu->fpstate_active)
-			fpu__reset(fpu);
+			fpu__clear(fpu);
 	}
 	signal_setup_done(failed, ksig, stepping);
 }