69 lines
2.0 KiB
C
69 lines
2.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _ASM_X86_FPU_SCHED_H
|
|
#define _ASM_X86_FPU_SCHED_H
|
|
|
|
#include <linux/sched.h>
|
|
|
|
#include <asm/cpufeature.h>
|
|
#include <asm/fpu/types.h>
|
|
|
|
#include <asm/trace/fpu.h>
|
|
|
|
extern void save_fpregs_to_fpstate(struct fpu *fpu);
|
|
extern void fpu__drop(struct fpu *fpu);
|
|
extern int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal);
|
|
extern void fpu_flush_thread(void);
|
|
|
|
/*
|
|
* FPU state switching for scheduling.
|
|
*
|
|
* This is a two-stage process:
|
|
*
|
|
* - switch_fpu_prepare() saves the old state.
|
|
* This is done within the context of the old process.
|
|
*
|
|
* - switch_fpu_finish() sets TIF_NEED_FPU_LOAD; the floating point state
|
|
* will get loaded on return to userspace, or when the kernel needs it.
|
|
*
|
|
* If TIF_NEED_FPU_LOAD is cleared then the CPU's FPU registers
|
|
* are saved in the current thread's FPU register state.
|
|
*
|
|
* If TIF_NEED_FPU_LOAD is set then CPU's FPU registers may not
|
|
* hold current()'s FPU registers. It is required to load the
|
|
* registers before returning to userland or using the content
|
|
* otherwise.
|
|
*
|
|
* The FPU context is only stored/restored for a user task and
|
|
* PF_KTHREAD is used to distinguish between kernel and user threads.
|
|
*/
|
|
static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)
|
|
{
|
|
if (cpu_feature_enabled(X86_FEATURE_FPU) &&
|
|
!(current->flags & (PF_KTHREAD | PF_IO_WORKER))) {
|
|
save_fpregs_to_fpstate(old_fpu);
|
|
/*
|
|
* The save operation preserved register state, so the
|
|
* fpu_fpregs_owner_ctx is still @old_fpu. Store the
|
|
* current CPU number in @old_fpu, so the next return
|
|
* to user space can avoid the FPU register restore
|
|
* when is returns on the same CPU and still owns the
|
|
* context.
|
|
*/
|
|
old_fpu->last_cpu = cpu;
|
|
|
|
trace_x86_fpu_regs_deactivated(old_fpu);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Delay loading of the complete FPU state until the return to userland.
|
|
* PKRU is handled separately.
|
|
*/
|
|
static inline void switch_fpu_finish(void)
|
|
{
|
|
if (cpu_feature_enabled(X86_FEATURE_FPU))
|
|
set_thread_flag(TIF_NEED_FPU_LOAD);
|
|
}
|
|
|
|
#endif /* _ASM_X86_FPU_SCHED_H */
|