x86/fpu: Eliminate the __thread_has_fpu() wrapper

Start migrating FPU methods towards using 'struct fpu *fpu'
directly. __thread_has_fpu() is just a trivial wrapper around
fpu->has_fpu, eliminate it.

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

@@ -323,16 +323,6 @@ static inline int restore_fpu_checking(struct task_struct *tsk)
 	return fpu_restore_checking(&tsk->thread.fpu);
 }
 
-/*
- * Software FPU state helpers. Careful: these need to
- * be preemption protection *and* they need to be
- * properly paired with the CR0.TS changes!
- */
-static inline int __thread_has_fpu(struct task_struct *tsk)
-{
-	return tsk->thread.fpu.has_fpu;
-}
-
 /* Must be paired with an 'stts' after! */
 static inline void __thread_clear_has_fpu(struct task_struct *tsk)
 {
@@ -370,13 +360,14 @@ static inline void __thread_fpu_begin(struct task_struct *tsk)
 
 static inline void drop_fpu(struct task_struct *tsk)
 {
+	struct fpu *fpu = &tsk->thread.fpu;
 	/*
 	 * Forget coprocessor state..
 	 */
 	preempt_disable();
 	tsk->thread.fpu.counter = 0;
 
-	if (__thread_has_fpu(tsk)) {
+	if (fpu->has_fpu) {
 		/* Ignore delayed exceptions from user space */
 		asm volatile("1: fwait\n"
 			     "2:\n"
@@ -424,6 +415,7 @@ typedef struct { int preload; } fpu_switch_t;
 
 static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct task_struct *new, int cpu)
 {
+	struct fpu *old_fpu = &old->thread.fpu;
 	fpu_switch_t fpu;
 
 	/*
@@ -433,7 +425,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
 	fpu.preload = tsk_used_math(new) &&
 		      (use_eager_fpu() || new->thread.fpu.counter > 5);
 
-	if (__thread_has_fpu(old)) {
+	if (old_fpu->has_fpu) {
 		if (!fpu_save_init(&old->thread.fpu))
 			task_disable_lazy_fpu_restore(old);
 		else

arch/x86/kernel/fpu/core.c

@@ -57,8 +57,7 @@ static bool interrupted_kernel_fpu_idle(void)
 	if (use_eager_fpu())
 		return true;
 
-	return !__thread_has_fpu(current) &&
-		(read_cr0() & X86_CR0_TS);
+	return !current->thread.fpu.has_fpu && (read_cr0() & X86_CR0_TS);
 }
 
 /*
@@ -93,11 +92,12 @@ EXPORT_SYMBOL(irq_fpu_usable);
 void __kernel_fpu_begin(void)
 {
 	struct task_struct *me = current;
+	struct fpu *fpu = &me->thread.fpu;
 
 	kernel_fpu_disable();
 
-	if (__thread_has_fpu(me)) {
-		fpu_save_init(&me->thread.fpu);
+	if (fpu->has_fpu) {
+		fpu_save_init(fpu);
 	} else {
 		this_cpu_write(fpu_owner_task, NULL);
 		if (!use_eager_fpu())
@@ -109,8 +109,9 @@ EXPORT_SYMBOL(__kernel_fpu_begin);
 void __kernel_fpu_end(void)
 {
 	struct task_struct *me = current;
+	struct fpu *fpu = &me->thread.fpu;
 
-	if (__thread_has_fpu(me)) {
+	if (fpu->has_fpu) {
 		if (WARN_ON(restore_fpu_checking(me)))
 			fpu_reset_state(me);
 	} else if (!use_eager_fpu()) {
@@ -128,14 +129,16 @@ EXPORT_SYMBOL(__kernel_fpu_end);
  */
 void fpu__save(struct task_struct *tsk)
 {
+	struct fpu *fpu = &tsk->thread.fpu;
+
 	WARN_ON(tsk != current);
 
 	preempt_disable();
-	if (__thread_has_fpu(tsk)) {
+	if (fpu->has_fpu) {
 		if (use_eager_fpu()) {
 			__save_fpu(tsk);
 		} else {
-			fpu_save_init(&tsk->thread.fpu);
+			fpu_save_init(fpu);
 			__thread_fpu_end(tsk);
 		}
 	}