Linux kernel mirror (for testing)
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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
4 */
5
6#ifndef __ASM_SIMD_H
7#define __ASM_SIMD_H
8
9#include <linux/compiler.h>
10#include <linux/irqflags.h>
11#include <linux/percpu.h>
12#include <linux/preempt.h>
13#include <linux/types.h>
14
15DECLARE_PER_CPU(bool, fpsimd_context_busy);
16
17#ifdef CONFIG_KERNEL_MODE_NEON
18
19/*
20 * may_use_simd - whether it is allowable at this time to issue SIMD
21 * instructions or access the SIMD register file
22 *
23 * Callers must not assume that the result remains true beyond the next
24 * preempt_enable() or return from softirq context.
25 */
26static __must_check inline bool may_use_simd(void)
27{
28 /*
29 * We must make sure that the SVE has been initialized properly
30 * before using the SIMD in kernel.
31 * fpsimd_context_busy is only set while preemption is disabled,
32 * and is clear whenever preemption is enabled. Since
33 * this_cpu_read() is atomic w.r.t. preemption, fpsimd_context_busy
34 * cannot change under our feet -- if it's set we cannot be
35 * migrated, and if it's clear we cannot be migrated to a CPU
36 * where it is set.
37 */
38 return !WARN_ON(!system_capabilities_finalized()) &&
39 system_supports_fpsimd() &&
40 !in_hardirq() && !irqs_disabled() && !in_nmi() &&
41 !this_cpu_read(fpsimd_context_busy);
42}
43
44#else /* ! CONFIG_KERNEL_MODE_NEON */
45
46static __must_check inline bool may_use_simd(void) {
47 return false;
48}
49
50#endif /* ! CONFIG_KERNEL_MODE_NEON */
51
52#endif