x86/fpu: Remove 'struct task_struct' usage from __thread_fpu_begin()

Migrate this function to pure 'struct fpu' usage.
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/include/asm/fpu-internal.h

@@ -351,11 +351,11 @@ static inline void __thread_fpu_end(struct fpu *fpu)
 		stts();
 }
 
-static inline void __thread_fpu_begin(struct task_struct *tsk)
+static inline void __thread_fpu_begin(struct fpu *fpu)
 {
 	if (!use_eager_fpu())
 		clts();
-	__thread_set_has_fpu(&tsk->thread.fpu);
+	__thread_set_has_fpu(fpu);
 }
 
 static inline void drop_fpu(struct task_struct *tsk)
@@ -451,7 +451,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
 				fpu.preload = 0;
 			else
 				prefetch(new->thread.fpu.state);
-			__thread_fpu_begin(new);
+			__thread_fpu_begin(new_fpu);
 		}
 	}
 	return fpu;
@@ -505,9 +505,11 @@ static inline int restore_xstate_sig(void __user *buf, int ia32_frame)
  */
 static inline void user_fpu_begin(void)
 {
+	struct fpu *fpu = &current->thread.fpu;
+
 	preempt_disable();
 	if (!user_has_fpu())
-		__thread_fpu_begin(current);
+		__thread_fpu_begin(fpu);
 	preempt_enable();
 }
 

arch/x86/kernel/fpu/core.c

@@ -329,6 +329,7 @@ static int fpu__unlazy_stopped(struct task_struct *child)
 void fpu__restore(void)
 {
 	struct task_struct *tsk = current;
+	struct fpu *fpu = &tsk->thread.fpu;
 
 	if (!tsk_used_math(tsk)) {
 		local_irq_enable();
@@ -347,7 +348,7 @@ void fpu__restore(void)
 
 	/* Avoid __kernel_fpu_begin() right after __thread_fpu_begin() */
 	kernel_fpu_disable();
-	__thread_fpu_begin(tsk);
+	__thread_fpu_begin(fpu);
 	if (unlikely(restore_fpu_checking(tsk))) {
 		fpu_reset_state(tsk);
 		force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);