Commit c5bedc68 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/fpu: Get rid of PF_USED_MATH usage, convert it to fpu->fpstate_active 



Introduce a simple fpu->fpstate_active flag in the fpu context data structure
and use that instead of PF_USED_MATH in task->flags.

Testing for this flag byte should be slightly more efficient than
testing a bit in a bitmask, but the main advantage is that most
FPU functions can now be performed on a 'struct fpu' alone, they
don't need access to 'struct task_struct' anymore.

There's a slight linecount increase, mostly due to the 'fpu' local
variables and due to extra comments. The local variables will go away
once we move most of the FPU methods to pure 'struct fpu' parameters.

Reviewed-by: default avatarBorislav 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: default avatarIngo Molnar <mingo@kernel.org>
parent af7f8721

arch/x86/ia32/ia32_signal.c

+2 −1
Original line number Diff line number Diff line
@@ -307,6 +307,7 @@ static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs, 
				 size_t frame_size,

				 void __user **fpstate)

{

	struct fpu *fpu = &current->thread.fpu;

	unsigned long sp;



	/* Default to using normal stack */
@@ -321,7 +322,7 @@ 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 (current->flags & PF_USED_MATH) {

	if (fpu->fpstate_active) {

		unsigned long fx_aligned, math_size;



		sp = alloc_mathframe(sp, 1, &fx_aligned, &math_size);

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

+2 −2
Original line number Diff line number Diff line
@@ -375,7 +375,7 @@ static inline void drop_fpu(struct task_struct *tsk) 
		__thread_fpu_end(fpu);

	}



	tsk->flags &= ~PF_USED_MATH;

	fpu->fpstate_active = 0;



	preempt_enable();

}
@@ -424,7 +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 = (new->flags & PF_USED_MATH) &&

	fpu.preload = new_fpu->fpstate_active &&

		      (use_eager_fpu() || new->thread.fpu.counter > 5);



	if (old_fpu->has_fpu) {

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

+6 −0
Original line number Diff line number Diff line
@@ -137,6 +137,12 @@ struct fpu { 
	 * deal with bursty apps that only use the FPU for a short time:

	 */

	unsigned char			counter;

	/*

	 * This flag indicates whether this context is fpstate_active: if the task is

	 * not running then we can restore from this context, if the task

	 * is running then we should save into this context.

	 */

	unsigned char			fpstate_active;

};



#endif /* _ASM_X86_FPU_H */

arch/x86/include/asm/processor.h

+4 −2
Original line number Diff line number Diff line
@@ -385,6 +385,10 @@ struct thread_struct { 
	unsigned long		fs;

#endif

	unsigned long		gs;



	/* Floating point and extended processor state */

	struct fpu		fpu;



	/* Save middle states of ptrace breakpoints */

	struct perf_event	*ptrace_bps[HBP_NUM];

	/* Debug status used for traps, single steps, etc... */
@@ -395,8 +399,6 @@ struct thread_struct { 
	unsigned long		cr2;

	unsigned long		trap_nr;

	unsigned long		error_code;

	/* floating point and extended processor state */

	struct fpu		fpu;

#ifdef CONFIG_X86_32

	/* Virtual 86 mode info */

	struct vm86_struct __user *vm86_info;

arch/x86/kernel/fpu/core.c

+25 −13
Original line number Diff line number Diff line
@@ -236,14 +236,17 @@ static void fpu_copy(struct task_struct *dst, struct task_struct *src) 


int fpu__copy(struct task_struct *dst, struct task_struct *src)

{

	struct fpu *dst_fpu = &dst->thread.fpu;

	struct fpu *src_fpu = &src->thread.fpu;



	dst->thread.fpu.counter = 0;

	dst->thread.fpu.has_fpu = 0;

	dst->thread.fpu.state = NULL;



	task_disable_lazy_fpu_restore(dst);



	if (src->flags & PF_USED_MATH) {

		int err = fpstate_alloc(&dst->thread.fpu);

	if (src_fpu->fpstate_active) {

		int err = fpstate_alloc(dst_fpu);



		if (err)

			return err;
@@ -260,11 +263,12 @@ int fpu__copy(struct task_struct *dst, struct task_struct *src) 
 */

int fpstate_alloc_init(struct task_struct *curr)

{

	struct fpu *fpu = &curr->thread.fpu;

	int ret;



	if (WARN_ON_ONCE(curr != current))

		return -EINVAL;

	if (WARN_ON_ONCE(curr->flags & PF_USED_MATH))

	if (WARN_ON_ONCE(fpu->fpstate_active))

		return -EINVAL;



	/*
@@ -277,7 +281,7 @@ int fpstate_alloc_init(struct task_struct *curr) 
	fpstate_init(&curr->thread.fpu);



	/* Safe to do for the current task: */

	curr->flags |= PF_USED_MATH;

	fpu->fpstate_active = 1;



	return 0;

}
@@ -308,12 +312,13 @@ EXPORT_SYMBOL_GPL(fpstate_alloc_init); 
 */

static int fpu__unlazy_stopped(struct task_struct *child)

{

	struct fpu *child_fpu = &child->thread.fpu;

	int ret;



	if (WARN_ON_ONCE(child == current))

		return -EINVAL;



	if (child->flags & PF_USED_MATH) {

	if (child_fpu->fpstate_active) {

		task_disable_lazy_fpu_restore(child);

		return 0;

	}
@@ -328,7 +333,7 @@ static int fpu__unlazy_stopped(struct task_struct *child) 
	fpstate_init(&child->thread.fpu);



	/* Safe to do for stopped child tasks: */

	child->flags |= PF_USED_MATH;

	child_fpu->fpstate_active = 1;



	return 0;

}
@@ -348,7 +353,7 @@ void fpu__restore(void) 
	struct task_struct *tsk = current;

	struct fpu *fpu = &tsk->thread.fpu;



	if (!(tsk->flags & PF_USED_MATH)) {

	if (!fpu->fpstate_active) {

		local_irq_enable();

		/*

		 * does a slab alloc which can sleep
@@ -378,6 +383,8 @@ EXPORT_SYMBOL_GPL(fpu__restore); 


void fpu__flush_thread(struct task_struct *tsk)

{

	struct fpu *fpu = &tsk->thread.fpu;



	WARN_ON(tsk != current);



	if (!use_eager_fpu()) {
@@ -385,7 +392,7 @@ void fpu__flush_thread(struct task_struct *tsk) 
		drop_fpu(tsk);

		fpstate_free(&tsk->thread.fpu);

	} else {

		if (!(tsk->flags & PF_USED_MATH)) {

		if (!fpu->fpstate_active) {

			/* kthread execs. TODO: cleanup this horror. */

		if (WARN_ON(fpstate_alloc_init(tsk)))

				force_sig(SIGKILL, tsk);
@@ -402,12 +409,16 @@ void fpu__flush_thread(struct task_struct *tsk) 
 */

int fpregs_active(struct task_struct *target, const struct user_regset *regset)

{

	return (target->flags & PF_USED_MATH) ? regset->n : 0;

	struct fpu *target_fpu = &target->thread.fpu;



	return target_fpu->fpstate_active ? regset->n : 0;

}



int xfpregs_active(struct task_struct *target, const struct user_regset *regset)

{

	return (cpu_has_fxsr && (target->flags & PF_USED_MATH)) ? regset->n : 0;

	struct fpu *target_fpu = &target->thread.fpu;



	return (cpu_has_fxsr && target_fpu->fpstate_active) ? regset->n : 0;

}



int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
@@ -733,16 +744,17 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset, 
 * struct user_i387_struct) but is in fact only used for 32-bit

 * dumps, so on 64-bit it is really struct user_i387_ia32_struct.

 */

int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)

int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)

{

	struct task_struct *tsk = current;

	struct fpu *fpu = &tsk->thread.fpu;

	int fpvalid;



	fpvalid = !!(tsk->flags & PF_USED_MATH);

	fpvalid = fpu->fpstate_active;

	if (fpvalid)

		fpvalid = !fpregs_get(tsk, NULL,

				      0, sizeof(struct user_i387_ia32_struct),

				      fpu, NULL);

				      ufpu, NULL);



	return fpvalid;

}

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