x86/fpu: Open code PF_USED_MATH usages

PF_USED_MATH is used directly, but also in a handful of helper inlines.

To ease the elimination of PF_USED_MATH, convert all inline helpers
to open-coded PF_USED_MATH 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/ia32/ia32_signal.c

@@ -321,7 +321,7 @@ static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
 		 ksig->ka.sa.sa_restorer)
 		sp = (unsigned long) ksig->ka.sa.sa_restorer;
 
-	if (used_math()) {
+	if (current->flags & PF_USED_MATH) {
 		unsigned long fx_aligned, math_size;
 
 		sp = alloc_mathframe(sp, 1, &fx_aligned, &math_size);

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

@@ -375,7 +375,8 @@ static inline void drop_fpu(struct task_struct *tsk)
 		__thread_fpu_end(fpu);
 	}
 
-	clear_stopped_child_used_math(tsk);
+	tsk->flags &= ~PF_USED_MATH;
+
 	preempt_enable();
 }
 
@@ -423,7 +424,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
 	 * If the task has used the math, pre-load the FPU on xsave processors
 	 * or if the past 5 consecutive context-switches used math.
 	 */
-	fpu.preload = tsk_used_math(new) &&
+	fpu.preload = (new->flags & PF_USED_MATH) &&
 		      (use_eager_fpu() || new->thread.fpu.counter > 5);
 
 	if (old_fpu->has_fpu) {

arch/x86/kernel/fpu/core.c

@@ -242,7 +242,7 @@ int fpu__copy(struct task_struct *dst, struct task_struct *src)
 
 	task_disable_lazy_fpu_restore(dst);
 
-	if (tsk_used_math(src)) {
+	if (src->flags & PF_USED_MATH) {
 		int err = fpstate_alloc(&dst->thread.fpu);
 
 		if (err)
@@ -331,7 +331,7 @@ void fpu__restore(void)
 	struct task_struct *tsk = current;
 	struct fpu *fpu = &tsk->thread.fpu;
 
-	if (!tsk_used_math(tsk)) {
+	if (!(tsk->flags & PF_USED_MATH)) {
 		local_irq_enable();
 		/*
 		 * does a slab alloc which can sleep
@@ -361,12 +361,14 @@ EXPORT_SYMBOL_GPL(fpu__restore);
 
 void fpu__flush_thread(struct task_struct *tsk)
 {
+	WARN_ON(tsk != current);
+
 	if (!use_eager_fpu()) {
 		/* FPU state will be reallocated lazily at the first use. */
 		drop_fpu(tsk);
 		fpstate_free(&tsk->thread.fpu);
 	} else {
-		if (!tsk_used_math(tsk)) {
+		if (!(tsk->flags & PF_USED_MATH)) {
 			/* kthread execs. TODO: cleanup this horror. */
 		if (WARN_ON(fpstate_alloc_init(tsk)))
 				force_sig(SIGKILL, tsk);
@@ -383,12 +385,12 @@ void fpu__flush_thread(struct task_struct *tsk)
  */
 int fpregs_active(struct task_struct *target, const struct user_regset *regset)
 {
-	return tsk_used_math(target) ? regset->n : 0;
+	return (target->flags & PF_USED_MATH) ? regset->n : 0;
 }
 
 int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
 {
-	return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
+	return (cpu_has_fxsr && (target->flags & PF_USED_MATH)) ? regset->n : 0;
 }
 
 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
@@ -719,7 +721,7 @@ int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
 	struct task_struct *tsk = current;
 	int fpvalid;
 
-	fpvalid = !!used_math();
+	fpvalid = !!(tsk->flags & PF_USED_MATH);
 	if (fpvalid)
 		fpvalid = !fpregs_get(tsk, NULL,
 				      0, sizeof(struct user_i387_ia32_struct),

arch/x86/kernel/fpu/xsave.c

@@ -349,7 +349,7 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 	if (!access_ok(VERIFY_READ, buf, size))
 		return -EACCES;
 
-	if (!used_math() && fpstate_alloc_init(tsk))
+	if (!(tsk->flags & PF_USED_MATH) && fpstate_alloc_init(tsk))
 		return -1;
 
 	if (!static_cpu_has(X86_FEATURE_FPU))
@@ -384,12 +384,12 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 		int err = 0;
 
 		/*
-		 * Drop the current fpu which clears used_math(). This ensures
+		 * Drop the current fpu which clears PF_USED_MATH. This ensures
 		 * that any context-switch during the copy of the new state,
 		 * avoids the intermediate state from getting restored/saved.
 		 * Thus avoiding the new restored state from getting corrupted.
 		 * We will be ready to restore/save the state only after
-		 * set_used_math() is again set.
+		 * PF_USED_MATH is again set.
 		 */
 		drop_fpu(tsk);
 
@@ -401,7 +401,7 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 			sanitize_restored_xstate(tsk, &env, xstate_bv, fx_only);
 		}
 
-		set_used_math();
+		tsk->flags |= PF_USED_MATH;
 		if (use_eager_fpu()) {
 			preempt_disable();
 			fpu__restore();
@@ -685,7 +685,7 @@ void xsave_init(void)
  */
 void __init_refok eager_fpu_init(void)
 {
-	WARN_ON(used_math());
+	WARN_ON(current->flags & PF_USED_MATH);
 	current_thread_info()->status = 0;
 
 	if (eagerfpu == ENABLE)

arch/x86/kernel/signal.c

@@ -217,7 +217,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 		}
 	}
 
-	if (used_math()) {
+	if (current->flags & PF_USED_MATH) {
 		sp = alloc_mathframe(sp, config_enabled(CONFIG_X86_32),
 				     &buf_fx, &math_size);
 		*fpstate = (void __user *)sp;
@@ -233,7 +233,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 		return (void __user *)-1L;
 
 	/* save i387 and extended state */
-	if (used_math() &&
+	if ((current->flags & PF_USED_MATH) &&
 	    save_xstate_sig(*fpstate, (void __user *)buf_fx, math_size) < 0)
 		return (void __user *)-1L;
 
@@ -664,7 +664,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 		/*
 		 * Ensure the signal handler starts with the new fpu state.
 		 */
-		if (used_math())
+		if (current->flags & PF_USED_MATH)
 			fpu_reset_state(current);
 	}
 	signal_setup_done(failed, ksig, stepping);

arch/x86/kvm/x86.c

@@ -6600,7 +6600,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	int r;
 	sigset_t sigsaved;
 
-	if (!tsk_used_math(current) && fpstate_alloc_init(current))
+	if (!(current->flags & PF_USED_MATH) && fpstate_alloc_init(current))
 		return -ENOMEM;
 
 	if (vcpu->sigset_active)

arch/x86/math-emu/fpu_entry.c

@@ -148,7 +148,7 @@ void math_emulate(struct math_emu_info *info)
 	unsigned long code_limit = 0;	/* Initialized to stop compiler warnings */
 	struct desc_struct code_descriptor;
 
-	if (!used_math()) {
+	if (!(current->flags & PF_USED_MATH)) {
 		if (fpstate_alloc_init(current)) {
 			do_group_exit(SIGKILL);
 			return;