80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
/*
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* Copyright (C) 1994 Linus Torvalds
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*
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* Pentium III FXSR, SSE support
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* General FPU state handling cleanups
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* Gareth Hughes <gareth@valinux.com>, May 2000
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* x86-64 work by Andi Kleen 2002
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*/
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#ifndef _ASM_X86_I387_H
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#define _ASM_X86_I387_H
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#ifndef __ASSEMBLY__
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#include <linux/sched.h>
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#include <linux/hardirq.h>
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struct pt_regs;
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struct user_i387_struct;
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extern int init_fpu(struct task_struct *child);
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extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
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extern void math_state_restore(void);
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extern bool irq_fpu_usable(void);
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extern void kernel_fpu_begin(void);
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extern void kernel_fpu_end(void);
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/*
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* Some instructions like VIA's padlock instructions generate a spurious
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* DNA fault but don't modify SSE registers. And these instructions
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* get used from interrupt context as well. To prevent these kernel instructions
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* in interrupt context interacting wrongly with other user/kernel fpu usage, we
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* should use them only in the context of irq_ts_save/restore()
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*/
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static inline int irq_ts_save(void)
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{
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/*
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* If in process context and not atomic, we can take a spurious DNA fault.
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* Otherwise, doing clts() in process context requires disabling preemption
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* or some heavy lifting like kernel_fpu_begin()
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*/
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if (!in_atomic())
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return 0;
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if (read_cr0() & X86_CR0_TS) {
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clts();
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return 1;
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}
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return 0;
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}
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static inline void irq_ts_restore(int TS_state)
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{
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if (TS_state)
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stts();
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}
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/*
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* The question "does this thread have fpu access?"
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* is slightly racy, since preemption could come in
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* and revoke it immediately after the test.
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*
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* However, even in that very unlikely scenario,
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* we can just assume we have FPU access - typically
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* to save the FP state - we'll just take a #NM
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* fault and get the FPU access back.
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*/
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static inline int user_has_fpu(void)
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{
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return current->thread.fpu.has_fpu;
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}
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extern void unlazy_fpu(struct task_struct *tsk);
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_X86_I387_H */
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