/*
* Copyright (C) 1994 Linus Torvalds
*
* Pentium III FXSR, SSE support
* General FPU state handling cleanups
* Gareth Hughes <[email protected]>, May 2000
* x86-64 work by Andi Kleen 2002
*/

#ifndef _ASM_X86_I387_H
#define _ASM_X86_I387_H

#ifndef __ASSEMBLY__

#include <linux/sched.h>
#include <linux/hardirq.h>

struct pt_regs;
struct user_i387_struct;

extern int init_fpu(struct task_struct *child);
extern void fpu_finit(struct fpu *fpu);
extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
extern void math_state_restore(void);

extern bool irq_fpu_usable(void);

/*
* Careful: __kernel_fpu_begin/end() must be called with preempt disabled
* and they don't touch the preempt state on their own.
* If you enable preemption after __kernel_fpu_begin(), preempt notifier
* should call the __kernel_fpu_end() to prevent the kernel/user FPU
* state from getting corrupted. KVM for example uses this model.
*
* All other cases use kernel_fpu_begin/end() which disable preemption
* during kernel FPU usage.
*/
extern void __kernel_fpu_begin(void);
extern void __kernel_fpu_end(void);

static inline void kernel_fpu_begin(void)
{
WARN_ON_ONCE(!irq_fpu_usable());
preempt_disable();
__kernel_fpu_begin();
}

static inline void kernel_fpu_end(void)
{
__kernel_fpu_end();
preempt_enable();
}

/*
* Some instructions like VIA's padlock instructions generate a spurious
* DNA fault but don't modify SSE registers. And these instructions
* get used from interrupt context as well. To prevent these kernel instructions
* in interrupt context interacting wrongly with other user/kernel fpu usage, we
* should use them only in the context of irq_ts_save/restore()
*/
static inline int irq_ts_save(void)
{
/*
* If in process context and not atomic, we can take a spurious DNA fault.
* Otherwise, doing clts() in process context requires disabling preemption
* or some heavy lifting like kernel_fpu_begin()
*/
if (!in_atomic())
return 0;

if (read_cr0() & X86_CR0_TS) {
clts();
return 1;
}

return 0;
}

static inline void irq_ts_restore(int TS_state)
{
if (TS_state)
stts();
}

/*
* The question "does this thread have fpu access?"
* is slightly racy, since preemption could come in
* and revoke it immediately after the test.
*
* However, even in that very unlikely scenario,
* we can just assume we have FPU access - typically
* to save the FP state - we'll just take a #NM
* fault and get the FPU access back.
*/
static inline int user_has_fpu(void)
{
return current->thread.fpu.has_fpu;
}

extern void unlazy_fpu(struct task_struct *tsk);

#endif /* __ASSEMBLY__ */

#endif /* _ASM_X86_I387_H */