blob: ed8089d69094066985794cf4db39c04ecd545379 [file] [log] [blame]
* Copyright (C) 1994 Linus Torvalds
* Pentium III FXSR, SSE support
* General FPU state handling cleanups
* Gareth Hughes <>, 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)
static inline void kernel_fpu_end(void)
* 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) {
return 1;
return 0;
static inline void irq_ts_restore(int TS_state)
if (TS_state)
* 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 */