x86/fpu: Remove fpu__current_fpstate_write_begin/end()

These functions are not used anymore, so remove them.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/20170923130016.21448-29-mingo@kernel.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

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

@@ -26,8 +26,6 @@
 extern void fpu__activate_curr(struct fpu *fpu);
 extern void fpu__activate_fpstate_read(struct fpu *fpu);
 extern void fpu__activate_fpstate_write(struct fpu *fpu);
-extern void fpu__current_fpstate_write_begin(void);
-extern void fpu__current_fpstate_write_end(void);
 extern void fpu__save(struct fpu *fpu);
 extern void fpu__restore(struct fpu *fpu);
 extern int  fpu__restore_sig(void __user *buf, int ia32_frame);

arch/x86/kernel/fpu/core.c

@@ -316,69 +316,6 @@ void fpu__activate_fpstate_write(struct fpu *fpu)
 	}
 }
 
-/*
- * This function must be called before we write the current
- * task's fpstate.
- *
- * This call gets the current FPU register state and moves
- * it in to the 'fpstate'.  Preemption is disabled so that
- * no writes to the 'fpstate' can occur from context
- * swiches.
- *
- * Must be followed by a fpu__current_fpstate_write_end().
- */
-void fpu__current_fpstate_write_begin(void)
-{
-	struct fpu *fpu = &current->thread.fpu;
-
-	/*
-	 * Ensure that the context-switching code does not write
-	 * over the fpstate while we are doing our update.
-	 */
-	preempt_disable();
-
-	/*
-	 * Move the fpregs in to the fpu's 'fpstate'.
-	 */
-	fpu__activate_fpstate_read(fpu);
-
-	/*
-	 * The caller is about to write to 'fpu'.  Ensure that no
-	 * CPU thinks that its fpregs match the fpstate.  This
-	 * ensures we will not be lazy and skip a XRSTOR in the
-	 * future.
-	 */
-	__fpu_invalidate_fpregs_state(fpu);
-}
-
-/*
- * This function must be paired with fpu__current_fpstate_write_begin()
- *
- * This will ensure that the modified fpstate gets placed back in
- * the fpregs if necessary.
- *
- * Note: This function may be called whether or not an _actual_
- * write to the fpstate occurred.
- */
-void fpu__current_fpstate_write_end(void)
-{
-	struct fpu *fpu = &current->thread.fpu;
-
-	/*
-	 * 'fpu' now has an updated copy of the state, but the
-	 * registers may still be out of date.  Update them with
-	 * an XRSTOR if they are active.
-	 */
-	if (fpu->fpstate_active)
-		copy_kernel_to_fpregs(&fpu->state);
-
-	/*
-	 * Our update is done and the fpregs/fpstate are in sync
-	 * if necessary.  Context switches can happen again.
-	 */
-	preempt_enable();
-}
-
 /*
  * 'fpu__restore()' is called to copy FPU registers from
  * the FPU fpstate to the live hw registers and to activate