/* * Copyright (C) 1994 Linus Torvalds * * Pentium III FXSR, SSE support * General FPU state handling cleanups * Gareth Hughes <gareth@valinux.com>, 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 */