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Commit 36b544dc authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/fpu: Change fpu_owner_task to fpu_fpregs_owner_ctx 



Track the FPU owner context instead of the owner task: this change,
together with other changes, will allow in subsequent patches the
elimination of 'struct task_struct' usage in various FPU code:
we'll be able to use 'struct fpu' only.

There's no change in code size:

      text           data     bss      dec            hex filename
  13066467        2545248 1626112 17237827        1070743 vmlinux.before
  13066467        2545248 1626112 17237827        1070743 vmlinux.after

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 b0c050c5

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

+7 −7
Original line number Diff line number Diff line
@@ -37,7 +37,7 @@ extern unsigned int mxcsr_feature_mask; 
extern void fpu__cpu_init(void);

extern void eager_fpu_init(void);



DECLARE_PER_CPU(struct task_struct *, fpu_owner_task);

DECLARE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);



extern void convert_from_fxsr(struct user_i387_ia32_struct *env,

			      struct task_struct *tsk);
@@ -63,7 +63,7 @@ static inline void finit_soft_fpu(struct i387_soft_struct *soft) {} 
#endif



/*

 * Must be run with preemption disabled: this clears the fpu_owner_task,

 * Must be run with preemption disabled: this clears the fpu_fpregs_owner_ctx,

 * on this CPU.

 *

 * This will disable any lazy FPU state restore of the current FPU state,
@@ -71,7 +71,7 @@ static inline void finit_soft_fpu(struct i387_soft_struct *soft) {} 
 */

static inline void __cpu_disable_lazy_restore(unsigned int cpu)

{

	per_cpu(fpu_owner_task, cpu) = NULL;

	per_cpu(fpu_fpregs_owner_ctx, cpu) = NULL;

}



/*
@@ -86,7 +86,7 @@ static inline void task_disable_lazy_fpu_restore(struct task_struct *tsk) 


static inline int fpu_lazy_restore(struct task_struct *new, unsigned int cpu)

{

	return new == this_cpu_read_stable(fpu_owner_task) &&

	return &new->thread.fpu == this_cpu_read_stable(fpu_fpregs_owner_ctx) &&

		cpu == new->thread.fpu.last_cpu;

}
@@ -327,14 +327,14 @@ static inline int restore_fpu_checking(struct task_struct *tsk) 
static inline void __thread_clear_has_fpu(struct fpu *fpu)

{

	fpu->has_fpu = 0;

	this_cpu_write(fpu_owner_task, NULL);

	this_cpu_write(fpu_fpregs_owner_ctx, NULL);

}



/* Must be paired with a 'clts' before! */

static inline void __thread_set_has_fpu(struct task_struct *tsk)

{

	tsk->thread.fpu.has_fpu = 1;

	this_cpu_write(fpu_owner_task, tsk);

	this_cpu_write(fpu_fpregs_owner_ctx, &tsk->thread.fpu);

}



/*
@@ -431,7 +431,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta 
		else

			old->thread.fpu.last_cpu = cpu;



		/* But leave fpu_owner_task! */

		/* But leave fpu_fpregs_owner_ctx! */

		old->thread.fpu.has_fpu = 0;



		/* Don't change CR0.TS if we just switch! */

arch/x86/kernel/fpu/core.c

+4 −5
Original line number Diff line number Diff line
@@ -21,9 +21,9 @@ 
static DEFINE_PER_CPU(bool, in_kernel_fpu);



/*

 * Track which task is using the FPU on the CPU:

 * Track which context is using the FPU on the CPU:

 */

DEFINE_PER_CPU(struct task_struct *, fpu_owner_task);

DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);



static void kernel_fpu_disable(void)

{
@@ -96,15 +96,14 @@ EXPORT_SYMBOL(irq_fpu_usable); 


void __kernel_fpu_begin(void)

{

	struct task_struct *me = current;

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

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



	kernel_fpu_disable();



	if (fpu->has_fpu) {

		fpu_save_init(fpu);

	} else {

		this_cpu_write(fpu_owner_task, NULL);

		this_cpu_write(fpu_fpregs_owner_ctx, NULL);

		if (!use_eager_fpu())

			clts();

	}