x86/fpu: Rename fpu->has_fpu to fpu->fpregs_active

So the current code uses fpu->has_cpu to determine whether a given
user FPU context is actively loaded into the FPU's registers [*] and
that those registers represent the task's current FPU state.

But this term is not unambiguous: especially the distinction between
fpu->has_fpu, PF_USED_MATH and fpu_fpregs_owner_ctx is not clear.

Increase clarity by unambigously signalling that it's about
hardware registers being active right now, by renaming it to
fpu->fpregs_active.

( In later patches we'll use more of the 'fpregs' naming, which will
  make it easier to grep for as well. )

[*] There's the kernel_fpu_begin()/end() primitive that also
    activates FPU hw registers as well and uses them, without
    touching the fpu->fpregs_active flag.
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/api.h

@@ -96,7 +96,7 @@ static inline void irq_ts_restore(int TS_state)
  */
 static inline int user_has_fpu(void)
 {
-	return current->thread.fpu.has_fpu;
+	return current->thread.fpu.fpregs_active;
 }
 
 extern void fpu__save(struct fpu *fpu);

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

@@ -308,7 +308,7 @@ static inline int restore_fpu_checking(struct fpu *fpu)
 			"fnclex\n\t"
 			"emms\n\t"
 			"fildl %P[addr]"	/* set F?P to defined value */
-			: : [addr] "m" (fpu->has_fpu));
+			: : [addr] "m" (fpu->fpregs_active));
 	}
 
 	return fpu_restore_checking(fpu);
@@ -317,14 +317,14 @@ static inline int restore_fpu_checking(struct fpu *fpu)
 /* Must be paired with an 'stts' after! */
 static inline void __thread_clear_has_fpu(struct fpu *fpu)
 {
-	fpu->has_fpu = 0;
+	fpu->fpregs_active = 0;
 	this_cpu_write(fpu_fpregs_owner_ctx, NULL);
 }
 
 /* Must be paired with a 'clts' before! */
 static inline void __thread_set_has_fpu(struct fpu *fpu)
 {
-	fpu->has_fpu = 1;
+	fpu->fpregs_active = 1;
 	this_cpu_write(fpu_fpregs_owner_ctx, fpu);
 }
 
@@ -357,7 +357,7 @@ static inline void drop_fpu(struct fpu *fpu)
 	preempt_disable();
 	fpu->counter = 0;
 
-	if (fpu->has_fpu) {
+	if (fpu->fpregs_active) {
 		/* Ignore delayed exceptions from user space */
 		asm volatile("1: fwait\n"
 			     "2:\n"
@@ -416,14 +416,14 @@ switch_fpu_prepare(struct fpu *old_fpu, struct fpu *new_fpu, int cpu)
 	fpu.preload = new_fpu->fpstate_active &&
 		      (use_eager_fpu() || new_fpu->counter > 5);
 
-	if (old_fpu->has_fpu) {
+	if (old_fpu->fpregs_active) {
 		if (!fpu_save_init(old_fpu))
 			old_fpu->last_cpu = -1;
 		else
 			old_fpu->last_cpu = cpu;
 
 		/* But leave fpu_fpregs_owner_ctx! */
-		old_fpu->has_fpu = 0;
+		old_fpu->fpregs_active = 0;
 
 		/* Don't change CR0.TS if we just switch! */
 		if (fpu.preload) {

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

@@ -142,7 +142,7 @@ struct fpu {
 	 */
 	unsigned int			last_cpu;
 
-	unsigned int			has_fpu;
+	unsigned int			fpregs_active;
 	union thread_xstate		*state;
 	/*
 	 * This counter contains the number of consecutive context switches

arch/x86/kernel/fpu/core.c

@@ -62,7 +62,7 @@ static bool interrupted_kernel_fpu_idle(void)
 	if (use_eager_fpu())
 		return true;
 
-	return !current->thread.fpu.has_fpu && (read_cr0() & X86_CR0_TS);
+	return !current->thread.fpu.fpregs_active && (read_cr0() & X86_CR0_TS);
 }
 
 /*
@@ -100,7 +100,7 @@ void __kernel_fpu_begin(void)
 
 	kernel_fpu_disable();
 
-	if (fpu->has_fpu) {
+	if (fpu->fpregs_active) {
 		fpu_save_init(fpu);
 	} else {
 		this_cpu_write(fpu_fpregs_owner_ctx, NULL);
@@ -114,7 +114,7 @@ void __kernel_fpu_end(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
-	if (fpu->has_fpu) {
+	if (fpu->fpregs_active) {
 		if (WARN_ON(restore_fpu_checking(fpu)))
 			fpu_reset_state(fpu);
 	} else if (!use_eager_fpu()) {
@@ -147,7 +147,7 @@ void fpu__save(struct fpu *fpu)
 	WARN_ON(fpu != &current->thread.fpu);
 
 	preempt_disable();
-	if (fpu->has_fpu) {
+	if (fpu->fpregs_active) {
 		if (use_eager_fpu()) {
 			__save_fpu(fpu);
 		} else {
@@ -243,7 +243,7 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 {
 	dst_fpu->counter = 0;
-	dst_fpu->has_fpu = 0;
+	dst_fpu->fpregs_active = 0;
 	dst_fpu->state = NULL;
 	dst_fpu->last_cpu = -1;