x86/fpu: Use 'struct fpu' in fpu_lazy_restore()

Also rename it to fpu_want_lazy_restore(), to better indicate that
this function just tests whether we can do a lazy restore. (The old
name suggested that it was doing the lazy restore, which is not
the case.)
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

@@ -74,10 +74,9 @@ static inline void __cpu_disable_lazy_restore(unsigned int cpu)
 	per_cpu(fpu_fpregs_owner_ctx, cpu) = NULL;
 }
 
-static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)
+static inline int fpu_want_lazy_restore(struct fpu *fpu, unsigned int cpu)
 {
-	return &new->thread.fpu == this_cpu_read_stable(fpu_fpregs_owner_ctx) &&
-		cpu == new->thread.fpu.last_cpu;
+	return fpu == this_cpu_read_stable(fpu_fpregs_owner_ctx) && cpu == fpu->last_cpu;
 }
 
 static inline int is_ia32_compat_frame(void)
@@ -439,7 +438,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
 		old->thread.fpu.last_cpu = -1;
 		if (fpu.preload) {
 			new->thread.fpu.counter++;
-			if (fpu_lazy_restore(new, cpu))
+			if (fpu_want_lazy_restore(new_fpu, cpu))
 				fpu.preload = 0;
 			else
 				prefetch(new->thread.fpu.state);