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

Migrate this function to pure 'struct fpu' usage.

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

@@ -358,14 +358,13 @@ static inline void __thread_fpu_begin(struct fpu *fpu)
 	__thread_set_has_fpu(fpu);
 }
 
-static inline void drop_fpu(struct task_struct *tsk)
+static inline void drop_fpu(struct fpu *fpu)
 {
-	struct fpu *fpu = &tsk->thread.fpu;
 	/*
 	 * Forget coprocessor state..
 	 */
 	preempt_disable();
-	tsk->thread.fpu.counter = 0;
+	fpu->counter = 0;
 
 	if (fpu->has_fpu) {
 		/* Ignore delayed exceptions from user space */
@@ -394,8 +393,10 @@ static inline void restore_init_xstate(void)
  */
 static inline void fpu_reset_state(struct task_struct *tsk)
 {
+	struct fpu *fpu = &tsk->thread.fpu;
+
 	if (!use_eager_fpu())
-		drop_fpu(tsk);
+		drop_fpu(fpu);
 	else
 		restore_init_xstate();
 }

arch/x86/kernel/fpu/core.c

@@ -389,7 +389,7 @@ void fpu__flush_thread(struct task_struct *tsk)
 
 	if (!use_eager_fpu()) {
 		/* FPU state will be reallocated lazily at the first use. */
-		drop_fpu(tsk);
+		drop_fpu(fpu);
 		fpstate_free(&tsk->thread.fpu);
 	} else {
 		if (!fpu->fpstate_active) {

arch/x86/kernel/fpu/xsave.c

@@ -392,7 +392,7 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 		 * We will be ready to restore/save the state only after
 		 * fpu->fpstate_active is again set.
 		 */
-		drop_fpu(tsk);
+		drop_fpu(fpu);
 
 		if (__copy_from_user(&fpu->state->xsave, buf_fx, state_size) ||
 		    __copy_from_user(&env, buf, sizeof(env))) {

arch/x86/kernel/process.c

@@ -104,6 +104,7 @@ void exit_thread(void)
 	struct task_struct *me = current;
 	struct thread_struct *t = &me->thread;
 	unsigned long *bp = t->io_bitmap_ptr;
+	struct fpu *fpu = &t->fpu;
 
 	if (bp) {
 		struct tss_struct *tss = &per_cpu(cpu_tss, get_cpu());
@@ -119,7 +120,7 @@ void exit_thread(void)
 		kfree(bp);
 	}
 
-	drop_fpu(me);
+	drop_fpu(fpu);
 }
 
 void flush_thread(void)