blob: c2d6cd78ed0c2986181217a184e8d52f7e72c534 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
|
/* 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 */
|
