| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org> |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify it |
| 5 | * under the terms of the GNU General Public License version 2 as published |
| 6 | * by the Free Software Foundation. |
| 7 | */ |
| 8 | |
| 9 | #ifndef __ASM_SIMD_H |
| 10 | #define __ASM_SIMD_H |
| 11 | |
| 12 | #include <linux/compiler.h> |
| 13 | #include <linux/irqflags.h> |
| 14 | #include <linux/percpu.h> |
| 15 | #include <linux/preempt.h> |
| 16 | #include <linux/types.h> |
| 17 | |
| 18 | #ifdef CONFIG_KERNEL_MODE_NEON |
| 19 | |
| 20 | DECLARE_PER_CPU(bool, kernel_neon_busy); |
| 21 | |
| 22 | /* |
| 23 | * may_use_simd - whether it is allowable at this time to issue SIMD |
| 24 | * instructions or access the SIMD register file |
| 25 | * |
| 26 | * Callers must not assume that the result remains true beyond the next |
| 27 | * preempt_enable() or return from softirq context. |
| 28 | */ |
| 29 | static __must_check inline bool may_use_simd(void) |
| 30 | { |
| 31 | /* |
| 32 | * kernel_neon_busy is only set while preemption is disabled, |
| 33 | * and is clear whenever preemption is enabled. Since |
| 34 | * this_cpu_read() is atomic w.r.t. preemption, kernel_neon_busy |
| 35 | * cannot change under our feet -- if it's set we cannot be |
| 36 | * migrated, and if it's clear we cannot be migrated to a CPU |
| 37 | * where it is set. |
| 38 | */ |
| 39 | return !in_irq() && !irqs_disabled() && !in_nmi() && |
| 40 | !this_cpu_read(kernel_neon_busy); |
| 41 | } |
| 42 | |
| 43 | #else /* ! CONFIG_KERNEL_MODE_NEON */ |
| 44 | |
| 45 | static __must_check inline bool may_use_simd(void) { |
| 46 | return false; |
| 47 | } |
| 48 | |
| 49 | #endif /* ! CONFIG_KERNEL_MODE_NEON */ |
| 50 | |
| 51 | #endif |