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
15 DECLARE_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 */
26 static __must_check inline bool may_use_simd(void)
27 {
28 /*
29 * fpsimd_context_busy is only set while preemption is disabled,
30 * and is clear whenever preemption is enabled. Since
31 * this_cpu_read() is atomic w.r.t. preemption, fpsimd_context_busy
32 * cannot change under our feet -- if it's set we cannot be
33 * migrated, and if it's clear we cannot be migrated to a CPU
34 * where it is set.
35 */
36 return !in_irq() && !irqs_disabled() && !in_nmi() &&
37 !this_cpu_read(fpsimd_context_busy);
38 }
39
40 #else /* ! CONFIG_KERNEL_MODE_NEON */
41
42 static __must_check inline bool may_use_simd(void) {
43 return false;
44 }
45
46 #endif /* ! CONFIG_KERNEL_MODE_NEON */
47
48 #endif